The Flat Residual

The star was called TEV-9 on the sensor manifest, which meant nothing except that it was the ninth object logged by the Tertiary External Verification array, and that the array had been Cleo Anselm's responsibility for eleven years.

She found it again at 0217 ship-time, which was the middle of nothing, the dead trough of third shift when the corridors dimmed to amber and the recyclers ran their loud cycle because nobody was awake to complain. She was up on the spine, in the crawl above Frame 44, wedged in the space between the hull's inner skin and the coolant run, breathing the smell of hot dust and old solder. She had come up to reseat a bracket. She had brought her slate to log the work and the slate had, out of habit, pulled the array feed.

TEV-9 flickered.

It did that. It was a variable, some kind of pulsating subdwarf that nobody in Astro cared about because it wasn't on any of the navigation triads. Cleo cared about it because four years and two months ago she had spent nine hours in this same crawlspace realigning the sensor that watched it, and during those nine hours she had watched TEV-9 blink at her with the peculiar rhythm of a thing that wasn't trying to communicate but looked like it was: long, long, short, short, long, a stutter, then a gap of forty-one seconds, then the whole phrase again with the stutter one beat earlier.

She had liked it. She had memorized it the way you memorize a song you hear during a bad week. She had even, God help her, hummed it.

Now, four years later, she watched the slate render the flicker in its little grey waveform box, and she heard the song.

Long, long, short, short, long. Stutter. Forty-one seconds.

She sat very still with her shoulder against the coolant pipe, and the pipe was warm, and somewhere below her eleven thousand people were asleep in a ship that had been moving at eight percent of light for eighty years.

It should have shifted, she thought.

That was all, at first. Not a conspiracy, not a horror. A technician's small objection. Eighty years into a two-century crossing, the Ambit had crossed a great deal of space. Four years alone was almost eleven light-months of travel. TEV-9's phase — its position in its own private cycle of brightening and dimming, and the light-travel time from it to the ship's eye — should not present the same face. The pattern's phase should have crept. Not much. But measurably. That was the entire point of variable stars; they were the ship's clocks, cross-checked against the drift of the navigation triads, and a clock that read the same time four years later was not a clock.

Unless the light had a shorter distance to travel than it should. Unless you had not gone as far as you thought.

Cleo looked at the number: 41.00 seconds. She had written it in her personal log four years ago as 41s, call it 41 exactly, cute.

Cute.

She unwedged herself, banged her elbow on the bracket she'd come to fix, said a word her mother would have disliked, and fixed the bracket. Then she sat in the crawl with her knees up and ran a phase fit on eleven years of TEV-9 data, which the slate could do badly in about forty seconds.

The fit came back and the residuals were flat.

Flat. Not creeping. Eleven years of a variable star's light arriving at a ship travelling eight percent of light, and the phase had not moved by a hair beyond the sensor's own noise. As though the Ambit had been sitting still. As though the Ambit had been sitting still for at least eleven years, and the great bright numbers on the bridge display, the ones they showed on Progress Day with the children's choir, were a story.

Cleo Anselm, thirty-nine, third-shift maintenance, hull and thermal, put her hand flat against the inner skin of the ship she'd been born on and felt exactly the same faint hum she'd felt every day of her life, and understood for the first time that she had never in her life felt acceleration, or the absence of it, or anything at all that could tell her which was true.

She did not tell anyone that night. She went and cleaned a filter in Ag-3, because it was on her list, and the filter was a filter, and the air in Ag-3 smelled like wet green things and the false dawn was starting to come up in the grow-lamps. Two of the night crop crew were arguing quietly about whether beans counted as a vegetable. Cleo said, "Beans are a legume," which nobody had asked, and they laughed, and one of them, Turi, threw her a cherry tomato and she ate it standing under the lamps.

Eleven thousand people. Nine hundred and something children.

She thought: If I'm wrong, I'm an idiot who can't run a phase fit.

She thought: If I'm right, then somebody already knows.

That second thought was the one that kept her from talking. Because eleven years of flat residuals was not something you hid by accident. Astro ran cross-checks on the navigation triads every watch. It was the single most instrumented fact aboard: where are we, how fast, how long left. If the phase of a variable star had been flat for eleven years, then either every instrument aboard was broken in the same direction, which was not how broken worked, or somebody had gone into the numbers with intent.

And if somebody had gone into the numbers with intent, then the question was not what is true. The question was what happens to the person who says it out loud.

The Ambit had a Morale Directorate. That was not a euphemism; it was a department, with a budget line and a director and a public mandate, and nobody found it sinister, because on a generation ship morale was not a mood. It was a resource. It was tracked like water and air and nitrogen. There was a morale reserve the way there was a water reserve, and it could be drawn down, and it could be spent, and it could run out, and there was a whole shelf of history explaining what happened when it ran out on ships that had gone before.

The Ambit schoolchildren learned about the Kestrel in year four. The Kestrel had run out. The details were softened for year four and less softened in year nine and by the time you were an adult you knew that on the Kestrel four hundred people had opened a cargo lock from the inside.

So: Morale Directorate. Public mandate. And a doctrine everyone knew by the name of the woman who wrote it, Ilsa Verrat, whose Managed Disclosure Framework was required reading for anybody above grade six. Not all true things are load-bearing. That was the famous line. The purpose of a fact aboard a closed vessel is not to be known but to be useful. A fact which is not load-bearing, and which reduces the reserve, may be retired.

Retired. That was the word. Not hidden, not suppressed — retired, like a pump, like a person, like something that had done its work and could be set aside with honour.

Cleo had read it at twenty-two in a training module and thought it was reasonable. She had thought: of course you don't tell everyone every fault code. She had spent seventeen years not telling people fault codes. Last year she had spent six days repairing a bearing in the main gyro without telling anyone that for eleven of those hours the Ambit had been a single failure away from losing attitude control, and she had not lost a minute's sleep, because telling would have done nothing but hurt.

She thought about that now, lying in her bunk at 0640 with the light off and the wake-shift starting to bang around out in the corridor. She thought: I am a person who is very good at not telling. And she thought: That is exactly why they'd have picked someone like me to be the one who never checks.

She checked four more things over the next nine days, working the edges of her clearance, doing it slow.

The first was the obvious one and it was closed to her: the navigation triads, the primary parallax baselines, all Astro-locked. Requesting them logged a request. She did not request them.

The second was the neutron star. There was a pulsar the ship used as a timing reference, PSR-something, and the raw arrival times were archived in an engineering datastore because the timing feed also drove the master clock, which was a thermal problem, which made it hers. She pulled six months of raw arrival times, which she was entitled to do, and looked at the Doppler.

The pulse period was shifted. Blue-shifted, consistent with the ship moving toward it at — she worked it out twice — eight point zero one percent of light.

Which was correct. Which was what the bridge said.

Cleo sat back and felt a lightness in her chest so sudden it made her laugh out loud, one bark, alone in a service closet on Deck 6.

Wrong. I was wrong. Something's wrong with the TEV array and I'll fix it and go to sleep.

She spent the next two shifts happy. On the third she went up to Frame 44 and put a calibration source in front of the TEV-9 sensor and it read the source perfectly, and she pulled the sensor and bench-tested it and it was fine, and she looked again at eleven years of flat residuals and the happiness went out of her like water out of a cracked tank.

Because both things could not be true. You could not be moving at eight percent of light toward a pulsar and be stationary relative to a variable star. Not unless the star and the pulsar were in wildly different directions and — no. She checked. TEV-9 was nineteen degrees off the ship's velocity vector. The pulsar was thirty-one degrees off, the other side. If you were moving, TEV-9's phase would creep. It would creep by roughly forty minutes' worth of light-time per year, which would show up in the phase as an enormous, unmissable, unarguable drift.

So one of the two feeds was lying.

And that was the third thing she checked, and it took her six days, and it broke something in her that never quite set again afterward.

The pulsar timing feed came into the engineering datastore through a preprocessor. Of course it did; the raw photon arrival times were a firehose and something had to fold them into pulse phases. The preprocessor was a black-box module with a version number and a signed hash and no source code available at her clearance, which was normal, which was true of eighty modules she used daily.

But every module aboard had a thermal profile, because everything aboard had a thermal profile, because heat was the one thing you could not hide on a ship whose entire existence was a war against heat. Cleo Anselm had eleven years of radiator logs.

She looked at the compute cluster in Bay 7 that ran, among other things, the pulsar preprocessor. And she found, buried in eleven years of heat, a periodic load spike with a period of exactly 41.00 seconds.

The number sat there on her slate looking back at her.

Somewhere in Bay 7, forty-one seconds at a time, a process woke up and did a little work and went back to sleep, and it had been doing that for at least eleven years, and it was synchronised to the phase of a star.

Not a lie about the star. A lie built on the star. Somebody had needed a coherent fake and had used the real sky as a metronome so the fake would stay in phase with itself forever, and they had chosen TEV-9 because TEV-9 was on nobody's triad, TEV-9 was junk, TEV-9 was a variable that a maintenance engineer had once found cute.

Cleo put the slate face-down on the bench.

Not moving. Eleven years at minimum. Possibly longer. Possibly — and here her mind went white and had to be pushed — possibly the Ambit had never moved at all.

The fourth thing she checked was the water.

This was the one nobody would have predicted, and it was the one that decided her, because it was the one that meant the lie wasn't just a lie. It meant somebody had made a choice about eleven thousand people's lives on the basis of it.

The Ambit had a fuel budget. Deuterium and helium-3, laid in at Sol, tanked in the great cold spine. The mission profile was: burn for eleven years to reach eight percent, coast for a hundred and seventy-eight, burn for eleven to decelerate. The coast phase used almost nothing. The margin on the deceleration fuel was fourteen percent, which everybody knew, which was in the year-nine curriculum, which was a source of quiet pride: fourteen percent, we're not cutting it close, they built us right.

Cleo had thermal access to the cryo tanks because their boil-off ran through her radiators.

Boil-off scaled with surface area and fill fraction, and she had eleven years of it, and any tank engineer alive could invert it to a mass estimate. She did it three times over two nights with a pencil, on paper, because she had stopped trusting anything with a processor in it.

The tanks were at sixty-one percent.

They should have been at ninety-four. Coast phase used almost nothing. Sixty-one percent meant somebody had spent thirty-three percent of the ship's entire fuel load, which was more than the whole deceleration burn, which was —

Which was consistent with a ship that had accelerated to eight percent of light, and then decelerated, and then done something else with what was left.

Which was consistent with a ship that had stopped.

Cleo Anselm sat on the floor of a service closet on Deck 6 with a paper covered in pencil and understood that the Ambit had gone somewhere, and arrived, and stopped, and stayed, and had been staying for at least eleven years, and that everyone aboard except some number of people had gone on eating tomatoes and arguing about legumes and singing on Progress Day and dying of ordinary old age in the belief that they were crossing.

Arrived where?

She looked at the number sixty-one percent for a long time.

And if you arrived, and you're still sitting there, then you couldn't get out of the car.

She was thirty-nine and she had been born in Bay 4 and she had buried her mother in the recycler like everybody buried everybody, and she had a brother in Hydroponics who thought she was a bit strange and a lover on second shift she saw twice a week and no children because she'd never wanted them and had never had to explain that to anyone but her mother.

She had, by her own count, four people she could tell.

Turi Achebe, night crop, Ag-3, who had thrown her a tomato. Turi was thirty-one and kind and would believe her instantly and completely and would then tell six people by dinner because Turi could not hold a thing in her hands without showing it to someone. Telling Turi was the same as telling the ship. Cleo put Turi at the bottom.

Mattias Anselm, her brother, Hydroponics section lead, grade seven. Mattias would not believe her. Mattias would take the slate out of her hands and look at her the way he'd looked at their mother in her last month and say, gently, Cleo, you're on third shift, you don't see people, this is what third shift does. And then, because he was a good section lead who followed procedure, he would file a wellness flag. Cleo put her brother second from the bottom, and hated the arithmetic that put him there.

Ovid Reyes, seventy-four, retired Astro, who taught the year-nine navigation module and who had, twenty years ago, taught her orbital mechanics in a room that smelled of chalk. Ovid would understand the phase argument in four minutes. Ovid was old enough to have been in Astro when whatever happened, happened. Which made him the best person aboard to ask and the most dangerous.

Sub-Director Idra Vaan, Morale Directorate, forty-six, who ran the Disclosure Review Board and who Cleo knew because Vaan had personally approved the no announcement on the gyro bearing last year, and who had come down to the bay afterward — actually come down, in Directorate whites, into the grease — and said: Thank you. I know it cost you. If it goes bad, it goes bad on me, not you. Cleo had thought about that sentence for a year.

Four people. And the fifth option, which was no person: the Common Channel, an open-comm request any resident could file, which put your statement in front of the whole ship in the 1800 bulletin. It had been used forty-some times in eighty years. Every use went through Disclosure Review first.

Cleo sat with her four names and one channel and she thought about the Kestrel and the cargo lock, and she thought about the tomato, and she thought: whoever did this was also sitting somewhere making a list like this.

She went to Ovid Reyes.

She went at 1400 on her off-day, which meant being awake at a time her body hated, and she went to the school because he was still allowed a room there, a little office off the year-nine lab with a window onto the Ag-2 dome so the kids could see something green while they learned about parallax. He was grading. He had a real pencil, which was where she'd gotten the habit.

"Anselm," he said, without looking up. "You've aged."

"You haven't."

"I've hollowed. It's different." He set the pencil down and looked at her, and his eyes were still the eyes of a man who had spent forty years finding faint things against a bright background, and they went over her face and found something. His hand moved, very slightly, toward the door panel, and he tapped it, and the door slid shut.

That gesture — that small, immediate, unsurprised gesture — told Cleo more than the next hour of conversation.

She laid it out. She'd rehearsed it as an engineering brief, because that was the only voice she trusted: TEV-9 phase, eleven years, flat residuals, sensor bench-tested good, pulsar Doppler nominal, incompatibility of the two, the 41.00-second load spike in Bay 7, the boil-off inversion, sixty-one percent.

Ovid Reyes listened without interrupting, with his hands folded, and when she was done he sat for a while and looked out the window at the green.

"Sixty-one," he said. "I'd wondered. I never had thermal."

Cleo's ears rang.

"You knew."

"No." He turned back. "I want to be exact, because you're going to make decisions off what I say. I did not know. I suspected, for about nineteen years, and then I stopped suspecting, because suspecting alone will eat a man, and I'd already lost my wife and I had a hundred children a year to teach. That's not knowing. That's cowardice with a good filing system." He picked the pencil up again and held it like a cigarette. "But yes. I noticed things. And when I noticed them, I was moved."

"Moved."

"Out of Astro. Twenty-two years ago. Lateral, they called it — a promotion with a nicer office and no data access. Educational Outreach." He smiled at the wall. "It was very well done. I was flattered. I remember being flattered."

"What did you notice?"

"The burn." He set the pencil down again. "In year sixty-eight, ship-time — twelve years ago, near enough your eleven — there was a Class Four thermal event. Do you remember it?"

"I was twenty-seven. Everybody was confined to quarters for nine days. Radiator anomaly."

"Radiator anomaly." Ovid nodded slowly. "The radiators were fine, Anselm, and I know that because a young thermal engineer I taught once told me at a funeral that the radiators had run at a hundred and forty percent of design for six days and she couldn't understand why nobody would tell her what was making the heat."

"That was me. That was —" Cleo stopped. She had said that. At her mother's memorial. Nine years ago. She had drunk three cups of the Ag-3 wine and complained to her old teacher about a work mystery from three years before that.

"It was you." Ovid's voice was very gentle. "I don't think it went further than me. But I want you to hold in your mind, Cleo, that you have been saying this out loud, in fragments, for a decade, to anyone who'd listen. And nothing happened to you. Consider what that means."

"That nobody was listening."

"Or that somebody was, and decided you weren't load-bearing either." He let that sit. "The heat was a burn. A long, hard burn, mostly on the shadow side so the sky sensors wouldn't see the plume, which is why your radiators screamed. Nine days confined. Nobody felt a thing because they ran it with the habitat gimballed, and I'd bet everything I own that the accelerometer logs from those nine days are missing or clean."

"They're clean." She'd looked. Two nights ago. "Perfectly clean."

"Perfectly clean." He laughed, one dry note. "Nobody's ever perfectly clean. Not in eighty years of a real machine."

Cleo found she had to hold the edge of his desk.

"So where are we?"

"I don't know."

"Guess."

"No." Sharply, for the first time. "No, and listen to why, because it matters. If I guess and I'm wrong and you carry my guess out of this room, you will be a woman with a wrong story, and a wrong story is the easiest thing in the universe to kill. Your case is not where are we. Your case is the number on the wall is false. That case is made of four measurements a competent fifteen-year-old could check, and it does not require you to know a single thing about what's actually out there. Keep it that small. Small is armour."

She let go of the desk.

"They'll say I'm ill."

"They'll say you're tired, and they'll be right, you look like a dredged filter." He rubbed his face. "Then they'll say you're mistaken, and offer to show you the triads, and the triads will be beautiful. Then, if you hold, they will say something worse."

"What?"

Ovid Reyes looked at her for a long moment.

"They'll say: yes. And here is why, and here is what happens to eleven thousand people if you say it in the bulletin, and now it's yours too." He nodded slowly. "That's the one to be afraid of, Anselm. Not the denial. The invitation."

She thought about that for two days while she cleaned filters.

The invitation. Because that was the shape of it, wasn't it. Whoever had done this had not done it out of malice; you did not burn a third of your fuel and gimbal a habitat and build a forty-one-second metronome for the fun of hurting people. Somebody had faced a thing and made a decision and had been carrying it, presumably, for twelve years, and had built the whole apparatus of forgetting because they had looked at the alternative and found it worse.

She wanted very badly to believe that. It was so much more comfortable than the other options.

The Kestrel. Four hundred people. A cargo lock from the inside.

On the second day she was in the crawl above Frame 44 again, not because there was work but because it was the only place she could think, and she looked at TEV-9 flickering its little song, and she thought about the fact that they'd chosen it because it was junk, and about how nothing on a ship is junk, only unwatched.

And she thought about the year-nine curriculum. Fourteen percent margin. They built us right. Nine hundred children learning a number that was a lie about a tank she could read from the outside.

And she found that she could accept a lot of things — she could accept the burn, the gimbal, the preprocessor, even the invitation — but she could not accept the children's choir. She could not accept Progress Day. She could not accept that someone had looked at the situation and decided that the correct response was not merely to withhold the truth but to manufacture a celebration of its opposite, every year, with singing.

That was not a retired fact. That was a fact that had been killed and replaced with an actor.

She requested a meeting with Sub-Director Idra Vaan.

She did it properly, through the system, subject line Thermal anomaly, historical, request private consult, which was true in every word. She did it because Ovid, when she'd asked him what he'd do, had said: If you go to the Common Channel cold, they will have you in a wellness suite in twenty minutes and a very kind announcement about you in the bulletin by 1800, and it will be the last thing anyone ever hears about it. You need someone inside the wall to have to look at your numbers with their own eyes. Make them decide in front of you. Then at least there is a witness inside, and inside is where witnesses matter.

The meeting came back approved in ninety minutes, which was fast. Room 6 of the Directorate suite, 0300 ship-time, which was Cleo's shift and which she noticed was also the hour when nobody would see her go in.

She spent the intervening day copying her work onto paper. Nineteen pages, pencil, in her own hand, with the plots drawn by ruler. She made two copies. One she put in her coverall. The other she took up to Frame 44 and taped inside the crawl behind the coolant run where she had reseated a bracket eleven days ago and where nobody but a thermal engineer on third shift would ever have reason to put a hand.

Then she went and sat with Turi Achebe under the grow-lamps for twenty minutes and talked about nothing, about beans, about Turi's daughter who was six and had decided to be a doctor, and Cleo laughed and ate two tomatoes and did not tell her a single thing, and understood as she walked away that she had just done a thing that Idra Vaan did every day of her life, and that it had felt, to her surprise, like love.

Room 6 of the Directorate suite was small and warm and had a real wooden table, one of the six real wooden things aboard, and a bowl of the good apples. Idra Vaan was already there in a soft grey off-duty jacket, not the whites, with her hair down, drinking something that steamed.

"Anselm. Sit. Have an apple, they're from the Ag-1 trial trees, they're extraordinary and there are forty of them in existence."

Cleo sat and did not take an apple.

Vaan looked at that, and at Cleo's face, and set her cup down, and the room changed.

"All right," she said. "How much do you have?"

And there it was. No preamble. No what seems to be the trouble. Cleo felt the floor of her chest drop away, and then, immediately underneath it, a strange fierce gladness, because the alternative — an hour of gentle theatre, a tour of the beautiful triads — would have been worse.

"You knew I'd come."

"I knew someone would, eventually, and I've read your file, and if you want the truth I've had a marker on your name for nine years." Vaan's mouth twitched. "You told an old man at a funeral that your radiators had run at a hundred and forty percent in year sixty-eight."

"You had my mother's memorial monitored?"

"I had everything monitored, that's my job, don't make it a horror." She said it without heat. "Eleven thousand people, one air supply, and a history that includes the Kestrel. Yes. I know who's sad. I know who's angry. I know who drinks. And I knew there was a thermal engineer who had one loose thread and had never pulled it, and I decided — I, personally, twelve years into this — that moving you or watching you would be more dangerous than leaving you alone, because you were happy and useful and quiet, and Cleo, I want you to hear this, I have thought about you a great deal and I never once considered doing you harm."

"Nine years," Cleo said. "You watched me for nine years."

"Yes."

"Waiting for me to pull it."

"Hoping you wouldn't." Vaan folded her hands. "How much do you have?"

Cleo put the nineteen pages on the wooden table.

She watched Idra Vaan read them. It took eleven minutes. Vaan read like an engineer, which Cleo hadn't expected, going back two pages, checking a number, tracing a plot with one finger. When she got to the boil-off inversion she stopped and closed her eyes for a moment.

"Sixty-one percent," she said.

"Sixty-one point four, plus or minus two."

"Sixty-one point one." Vaan opened her eyes. "You're good. You did that from radiator logs."

"I did it with a pencil."

"You did it with a pencil." Vaan pushed the pages back across the table, all nineteen, which Cleo also had not expected. "Keep those. If I wanted them I'd have had them out of your bunk a week ago, and I'd rather you knew I didn't."

"Where are we?"

Idra Vaan took an apple, and turned it in her hands, and did not eat it.

"We're eleven light-years from Sol," she said, "and we have been for twelve years. We stopped at a place called — well, it was HD something, it's called Kesh in the classified docs, somebody's grandmother's name. It has four planets. One of them is in the band. That's where we were going."

Cleo had prepared herself for many things. She had not prepared for that.

"We arrived."

"We arrived twelve years ago, forty years early." Vaan's voice was flat and level, the voice of a woman who had said this before, to a small number of people, and had made her peace with the saying. "The original profile was wrong. Not wrong — conservative. Fuel was better than modelled, the drive ran cleaner than the engineers dared promise, and by year thirty they knew, and by year forty they were certain, and the Council of that generation made a decision that we have all been living inside ever since. They ran the burn hot. We got here in sixty-eight years instead of two hundred."

"Then why —" Cleo's voice failed and she had to start again. "Then why are we still here? Why is nobody down there? Why is my brother growing beans in a tin can eleven light-years from anywhere with a habitable planet out the window?"

"Because you can't land," Idra Vaan said.

She set the apple down.

"Because Kesh-3 has an atmosphere, and water, and a biosphere, and the biosphere is a hundred and ten million years older than ours and it is not compatible. Not hostile. Worse. Indifferent and porous. The first survey team went down in year sixty-nine. Nine people. They came back up clean through every protocol we had, and eleven weeks later the first of them started to — " Vaan stopped, and for the first time something moved in her face. "There's a class of pseudo-prion, it isn't a prion, we don't have a word. It doesn't infect. It catalyses. It gets into a certain kind of protein fold and it teaches the fold a new shape and the shape spreads and it isn't alive so you cannot kill it, and it was in the air, and it was in the water, and it was in the rock, and we did not find it in nine weeks of quarantine because it takes eleven weeks to show and we were so happy, Cleo, we were so happy, they took the helmets off on day sixty and everyone cheered."

The room was very quiet. Somewhere behind the wall, a pump ran.

"Nine people," Cleo said.

"Nine went down. Four hundred and six died." Vaan said the number without flinching, which meant she had said it to herself a very great number of times. "It got into Bay 2 before we understood. They sealed Bay 2 from the outside, on order, with two hundred and forty living people inside it, and they vented it, and then they vented the six compartments around it. That was the Class Four thermal event. That's what your radiators were dumping. Not a burn — the burn was two months earlier. Your hundred and forty percent was the sterilisation. They ran the inner hull of nine compartments at four hundred degrees for six days."

Cleo thought about being twenty-seven, confined to quarters, nine days, playing cards with her mother, complaining about radiators.

"I don't remember four hundred people dying."

"No," said Idra Vaan. "You don't."

And Cleo understood, then, the full size of the thing, and it was so much larger than a false number on a wall.

"You retired four hundred people."

"Four hundred and six." Vaan's hands were perfectly still on the table. "I was thirty-four. I was a junior analyst. I did not make the decision and I have implemented it for twelve years and I will not tell you I was ordered, because I agreed. I want that on the record between us, whatever you do next. I agreed."

"How." It came out of Cleo as barely a word. "How do you make eleven thousand people forget four hundred?"

"You don't. You make eleven thousand people never know." Vaan turned her cup a quarter-circle. "It was a generation ship, Cleo, and Bay 2 was a mostly-endogamous residential bay, and we were forty years ahead of a schedule nobody had ever seen except on a screen. There was no outside. There was no news. Every fact aboard this ship arrives through a system, and the systems were ours, and the people who could check were nine hundred and sixty and every one of them was in Astro or Medical or Council. It was — " She exhaled. "It was appallingly easy. That's the thing I'd want you to write down if you write anything. It was not a feat. It took forty people and eight months and it was easy, and the ease of it is the horror, not the malice, because there wasn't any malice, there were forty exhausted people in a room with four hundred and six dead and a planet we could not touch and a hundred and thirty years of return trip that we did not have the fuel for, and somebody said what if they simply keep going."

"Keep going where?"

"Nowhere. That's the point." Vaan looked up. "There is nowhere. Kesh-3 is closed. Kesh-4 is a rock with no volatiles. We cannot go home; you did the boil-off, you know what sixty-one percent buys, it buys a deceleration burn we already did and about four light-years of nothing. We are a closed vessel at a dead end with a working ecology and eleven thousand people and a hundred and twenty years of consumables, and the only thing we have to give anyone is time. So we gave them the voyage. We gave them the schedule. We gave them Progress Day and the choir and fourteen percent margin and a landfall in the year two hundred that nobody now alive will see, and Cleo — " and here, at last, her voice went, one crack, quickly mended — "and they have been happy. Eighty years in and the reserve is the highest it's been in the mission. Fertility's stable. Violence is nil. Your brother's daughter — sorry, your brother's section — the year-nine class last month scored the best navigation results in mission history. On a fake sky. They love it. They love the crossing. It's the best thing anyone's ever built and it's made of nothing but a lie and forty-one seconds."

Cleo found she was crying, which annoyed her, and she wiped her face with the back of her wrist like a woman clearing a work surface.

"What happens in a hundred and twenty years?"

"Then it's someone else's problem, and the honest answer is that the Council of year sixty-eight decided that a hundred and thirty years of peace was worth more than the truth, and that a future generation with better science might crack the Kesh problem and land, and if they can't, then the Ambit dies out here in about a hundred and fifty years, quietly, in stages, believing right up to the last decade that it is about to arrive." Vaan's mouth moved. "There's a Directorate plan for the last decade. I've read it. It's forty pages and it is the single most obscene document ever produced by a human being."

"And you want me to help."

"No." Idra Vaan sat back. "That's not why I let you in the door."

"Then what?"

"Because you're going to do something," Vaan said, "and I would rather it happened in front of me than behind me. And because —" She stopped. Started again, and something in her posture came down, some load-bearing member removed. "Because I am forty-six years old and I have been the only person under sixty who knows this for four years, since Weir died, and I am so tired, Cleo, I am so tired of the apples."

She gestured at the bowl.

"Forty apples in existence and I get them because I'm the woman who keeps everyone happy. I've eaten maybe six. I keep them out for guests. Nobody ever takes one." She laughed, and it was an ugly sound, and she let it be ugly. "You didn't take one. Do you know how many people have sat in that chair in twelve years and not taken an apple?"

"How many?"

"You," said Idra Vaan. Cleo reached out and took an apple.

She did not eat it. She set it down on top of her nineteen pages, where it sat like a paperweight, and the two of them looked at it.

"There it is," Cleo said. "That's the invitation."

"Is that what he called it?"

"He said the denial wasn't the dangerous part. He said the dangerous part was when you said yes, and now it's yours too."

"Reyes was always the smartest man in Astro and it did him no good at all." Vaan rubbed her eyes with two fingers. "He's right, though. It's yours now. I can't unsay it. That's not a threat, it's just physics. You walked in here a woman with four measurements and you'll walk out a woman with four hundred and six dead people, and there's no procedure for giving them back."

"I'm not going to the Common Channel."

Vaan went very still, and Cleo watched a thing happen in her face that she would think about for years afterward: not triumph. Not relief, exactly. Something more like grief arriving on schedule.

"Say the rest of it," Vaan said.

"Not because you've convinced me. Because you're right about the Kestrel and I'm not willing to be the woman who finds out whether you're right." Cleo turned the apple a quarter-circle, mirroring, without meaning to, the way Vaan had turned her cup. "Eleven thousand people at 1800 in the bulletin, cold. Turi Achebe hears it while she's picking, with her daughter in the next row. No. I've thought about it for eleven days and I can't get to a version of that where nobody opens a lock."

"Thank you."

"Don't." It came out harder than she meant. "Don't thank me. You've been thanking people for twelve years. Last year you came down into my bay in whites and thanked me for a gyro bearing, and I thought about that sentence for a year, and now I understand it was a procedure. You have a procedure for people who hold something for you."

Idra Vaan considered that.

"Yes," she said. "I do. It works. It worked on you. I also meant it. Both of those are true and I've stopped finding it interesting that they are."

"Fine." Cleo took her hands off the apple. "Then here's mine. I have three conditions and they're not negotiable in kind, only in schedule, and I'd like you to hear all three before you start telling me why they're impossible."

"Go on."

"One. The metronome stops."

Vaan's chin came up.

"Not the announcement," Cleo said. "I'm not asking you to tell anybody anything. I'm asking you to stop making it. The preprocessor in Bay 7 dies. The pulsar feed goes raw. The triads get unlocked to grade six. And from that day forward this ship's instruments say what they see, and anyone who checks — anyone at all, a fifteen-year-old in the year-nine lab with a pencil — finds it in an afternoon."

"That's not disclosure," Vaan said. "That's detonation with extra steps. Morning watch in Astro is three people. The Doppler goes to zero at 0600 and by 0630 it's in the section leads and by noon it's in Ag and by 1800 I am not managing anything, I'm just a woman in a room watching it happen, and the Kestrel took nine days from first rumour to the lock."

"Then don't do it at 0600 on a Tuesday. Do it properly. Build the ground first, spend a year, spend two — but do it, and give me a date, and after that date this ship stops lying forward."

"Why does that matter more to you than the truth?"

"Because it is the truth," Cleo said. "Not the whole of it. The load-bearing part. Your framework says a fact's purpose is to be useful, and fine, I'll grant you the framework for one minute. Here's what isn't useful: a lie with no author." She leaned in. "You're forty-six. You said three others and they're all over seventy. In fifteen years, twenty, you're all dead, and the preprocessor is still running, and the choir is still singing, and there is nobody left alive who chose it. It just runs. It becomes weather. And then it isn't a managed disclosure any more, Sub-Director, it's a haunted house, and every soul aboard is a hundred and twenty years from a wall they can't see, being steered by forty exhausted people who died before their grandparents were born." She sat back. "You didn't build a lie. You built a machine that tells one, and you forgot to give it an off switch, and now you're the switch and you're going to stop working."

Vaan looked at the table for a long moment.

"That's the argument," she said quietly. "That's the actual argument. In twelve years nobody's made it to me, and I've made it to myself perhaps four thousand times."

"Two. The fourteen percent comes out of the curriculum."

"Cleo —"

"They teach nine hundred children a number about a tank I can read from the outside with a radiator log." Cleo's voice did something she didn't authorise. "That's what I couldn't get past. Not the burn, not Bay 2 — I can understand Bay 2, I understand people in a room with four hundred dead. But somebody sat down afterward with a lesson plan. Somebody wrote fourteen percent, they built us right, and put it in front of children, and taught them to be proud of it. You didn't retire a fact. You killed it and hired an actor."

"And what do I teach instead?"

"Teach them to read the tanks. Teach them the boil-off inversion in year nine — it's four lines of arithmetic, it's easier than parallax. Let them measure the real number every year and write it on the wall themselves." Cleo spread her hands. "You want a reserve? Build a generation that knows how to check. Then when the day comes, it isn't a betrayal arriving out of nowhere. It's a thing they already half-knew and had the tools for. That's the only version of your last-decade document that isn't obscene, and you know it, because you've read the obscene one."

Vaan's fingers had gone white on the cup.

"Three," Cleo said.

"The names."

"The names."

"Four hundred and six," Vaan said. "In the ledger."

"With dates. No cause. Nobody has to say what happened in Bay 2. But they died and they are not in the book, and there are people alive on this ship with holes in their families that they've been told are something else, and that has to stop being true." Cleo's throat closed and she pushed through it. "My mother's in that book. Whoever they were, they get to be in the same book as my mother. That one isn't negotiable in schedule either."

Somewhere behind the wall the pump ran, and stopped, and the room was so quiet Cleo could hear the apple's own faint sound of being an apple.

"The ledger I can do in a month," Vaan said at last. "Quietly. Ledger revisions are archival housekeeping, nobody reads them, and the ones who'd notice are the ones who'd cry and say nothing. The curriculum is two years because it goes through Education and Council and I'll have to lose an argument on purpose somewhere to win it." She looked up. "The first one is the one that ends me."

"Yes."

"Give me ten years."

"No."

"Five. Cleo, five years to build a population that can hear it. I know how to do this — this is the one thing in the universe I actually know how to do. There are ways. You seed it. You put a variable star in a children's book. You let a rumour run and don't kill it. You make it so that when the number goes to zero, four thousand people say I've been wondering about that instead of eleven thousand people saying they lied. Five years."

"Two hundred and nine days," Cleo said. "The next Progress Day."

Vaan laughed, one shocked note. "You've dated it."

"I want it to be that day. I want the last Progress Day to be the day it stops. Because that's the obscene part, that's the singing, and if you can't undo the singing then at least let it be the last time." Cleo stood up. "Two hundred and nine days. You can have the ledger and the curriculum on your own schedule and I'll never mention them again. But on Progress Day the preprocessor dies, and you tell them, however you want, in whatever words you've spent twelve years writing — and I'll stand next to you when you do it, if that helps, a maintenance engineer with nineteen pages, so it doesn't look like the Directorate confessing to a crime nobody can check. It looks like two people who checked."

"And if I don't?"

"Then I do it," Cleo said. "I have thermal access to Bay 7, and a wrench, and I know exactly which cabinet."

"You'd be in a wellness suite in an hour."

"Yes. And the pulsar would still read zero." She let that sit until she saw Vaan understand that it was not a bluff, because it did not require Cleo to survive it. "I'm not brave, Sub-Director. I'd rather do it your way, with a year and a half of your seeding and your children's books and your rumours you don't kill. I think your way is better. I think it might even be good. But I'm not the only lock on the door any more and I want you to go to sleep knowing that."

Idra Vaan sat back in her chair and looked at Cleo Anselm for a long time, and then she nodded, once, the way you nod at a survey result you dislike and cannot fault.

"You left a copy somewhere," she said.

"Yes."

"Don't tell me where."

"I wasn't going to."

"Good." Vaan reached over and moved the bowl an inch, aligning it with nothing. "Reyes. If you ever go back to him — and you will — understand that he was moved once and men do not survive being moved twice at seventy-four. Be careful what you make him carry."

"He's carried it for nineteen years alone."

"So have I," said Idra Vaan.

Cleo picked up her nineteen pages. She folded them into the chest pocket of her coverall, and then, deliberately, she picked up the apple and put it in the other pocket, and watched Vaan's face come apart very slightly at the seams.

"That's for Turi Achebe's daughter," Cleo said. "She's six and she's decided to be a doctor and she has never eaten an apple. If you want it back you'll have to come and take it out of a child's hand in Ag-3 in front of the night crop crew."

Vaan's eyes were bright and furious and something else.

"Get out," she said, "before I like you," and Cleo did.

At 0217 she was up on the spine again, above Frame 44, wedged between the inner skin and the coolant run, breathing hot dust and old solder. There was no work to do. She had reseated the bracket twelve days ago and it was fine and it would be fine for years.

She pulled the array feed anyway.

TEV-9 flickered in its little grey waveform box. Long, long, short, short, long. The stutter. Then the gap, forty-one seconds exactly, and the whole phrase again with the stutter one beat earlier, the same song it had been singing since before her mother was born, eleven light-years away and utterly indifferent, having been made a clock and then a metronome and then, tonight, a deadline.

Cleo put her palm flat on the hull and hummed it.

Somewhere below her, eleven thousand people slept in a ship that had arrived, and been happy, and would go on being happy for two hundred and nine more days, and she was one of them now in the way she had not been before: not a woman who hadn't been told, but a woman who was not telling. She'd been good at that her whole working life. She had a whole shelf of fault codes she'd never mentioned to anyone.

The difference — the only difference, and she held onto it in the dark like a bracket in a socket — was that this one had a date on it.

She logged the visit as inspection, no fault found, which was true in every word, and climbed down to go clean a filter in Ag-3, where the false dawn was starting to come up in the grow-lamps, and where she had an apple to deliver.

The apple went to Sefi Achebe at 0455, under the grow-lamps in Ag-3, in a room that smelled of wet green things.

Sefi was six and had been brought to third shift because her mother had swapped a rota and there was nobody to sit with her, and she was asleep in a nest of empty seedling flats with her boots off, which was against four separate regulations that nobody in Ag-3 had ever once enforced. Cleo crouched down and put the apple on the flat beside her head, and then sat on an upturned crate and waited, because you did not wake a child to give her something; you let her find it.

Turi came down the row with a harvest tray on her hip and saw the apple and stopped walking.

"Cleo."

"It's real."

"I know it's real, I can smell it from here, where in the name of —" Turi set the tray down very carefully, the way you set down something when your hands have stopped being reliable. "Those are the Ag-1 trials. There are forty of those. Forty, in the whole —"

"Thirty-nine," Cleo said.

Turi looked at her for a long moment. She was thirty-one and kind and she was also, Cleo remembered too late, not stupid.

"Who gave you an apple?"

"Somebody who owed me."

"Nobody owes a thermal engineer an apple." Turi crouched, and her hand hovered over it, and did not touch it. "Nobody on this ship owes anybody an apple. That's — Cleo, that's a Directorate thing. That's a plaque-and-a-handshake thing."

"It was a plaque-and-a-handshake thing." Cleo made herself shrug with the correct number of muscles. "Historical thermal work. There was a review. It went well."

The lie came out clean and unhurried, and she heard it come out that way, and noted the fact with a kind of cold professional interest, the way you note that a bearing has begun to sing.

Sefi woke because the lamps were coming up, the false dawn ramping through its amber into white, and she sat up with the print of a flat's ribbing on her cheek and saw the apple and did not shout. She looked at it. She looked at her mother. She looked at Cleo.

"Is it for everybody?"

"It's for you," Cleo said.

Sefi picked it up in two hands. She turned it over the way Idra Vaan had turned it over, exactly the same gesture, which nearly undid Cleo entirely, and then she said, "Can I have a knife?"

Turi gave her a knife. Sefi cut the apple into eight pieces on the surface of a seedling flat, badly, and gave one to her mother and one to Cleo and one to each of the three night crop crew who had drifted over, and one to old Bakri who was only there because he could not sleep and came to Ag-3 to sit among the beans, and kept two for herself, and ate one, and put the other in her pocket.

For the piece in her pocket she gave no reason, and nobody asked, because everyone in the room understood that some things are kept.

Cleo ate her eighth of an apple standing under the lamps. It was extraordinary. It tasted like a place with weather. It tasted like something the human race had spent nine thousand years arguing into existence and then loaded onto a ship as a rumour of itself, and around her six people were laughing at nothing, at the sheer ridiculousness of apple at five in the morning, and Bakri had tears going down into his collar and was pretending it was the lamps.

I have just spent one apple, Cleo thought, and bought about eleven person-days of morale.

She thought: that's the arithmetic. That's the whole discipline. It works.

She thought: this is how you become her.

The second meeting was not in Room 6. It was in a stores annex off the Directorate suite, a windowless room with racked chairs and a wall of archive crates, and Idra Vaan was in whites this time and had brought nothing to drink.

"Sit. There are no apples. I want you to notice that I noticed."

Cleo sat.

"Two hundred and six days," Vaan said. "You'll forgive me for keeping count out loud, I find it steadies me. Here's the position. I have three people to move and one machine, and I want to talk to you about the machine first, because you're going to be more use to me there than anywhere and because it's worse than I told you."

"Bay 7."

"Bay 7 is a cabinet. Bay 7 is a hand." Vaan pulled a chair off the rack and sat down facing her, close, knees almost touching, which Cleo recognised after a second as a technique and could not make herself resent. "The preprocessor was built by Paavo Lund. He was Chief Astrogator in year sixty-eight. He is eighty-one and he lives in the low-grav annex on Deck 2 and he is the third person alive who knows, and he did not build a program, Cleo, he built an institution. You found a forty-one second load spike. Good. That's the metronome. Now ask me where the metronome lives."

"Bay 7."

"Bay 7 today. It lived in Bay 9 for four years before that and it has been in the reactor telemetry cluster and it has been, for eight months in year seventy-four, running on the laundry scheduler." Vaan's mouth did something without humour in it. "It migrates. It's got a nursery. There's a set of watchdogs — Paavo calls them the vergers, he's a religious man in a very old-fashioned way — that check the coherence of the nav story across nine datastores every three hours, and if the story stops being coherent they rebuild it from the sky. From TEV-9. That's why he used a real star. You worked that out on your own and I want you to know that in twelve years you're the only one who has."

Cleo sat with that.

"You're telling me the lie repairs itself."

"I'm telling you that if I walk into Bay 7 on Progress Day with your wrench, the ship notices a fault, and by 0300 the following morning the numbers on the wall are beautiful again and there's an incident report about a maintenance error in the timing chain, and the report writes itself, and it names you." Vaan let that arrive. "It's very good work. I want you to appreciate that I'm not describing a villain. I'm describing an eighty-one-year-old man who was told to make something that would outlive him and did the job properly."

"Then he can turn it off."

"He can. He won't."

"Have you asked him?"

"Four times in eleven years, in a general sort of way, the way you ask a man about his will." Vaan looked at the archive crates. "The last time was after Weir died. He said: Idra, you're describing a door and I've spent my life describing a wall, and if you find you can't tell the difference any more you should stop coming."

"So we're stuck."

"No. We're engineering," Vaan said, "which is a thing I don't know how to do and you do, and it's why I let you into Room 6 instead of into a wellness suite, and I'd rather be honest about that than have you find out later and think I was warm at you on purpose." She counted on her fingers. "Three tracks. One: I move Paavo. That's mine, and it's slow, and it may fail. Two: the seeding. Also mine, and it's started, and I'll show you because you'll see it anyway and I'd rather you saw it from inside than caught me at it. Three: you find the vergers. All of them. Every nest. Because on Progress Day I don't need the metronome broken, I need it dead in nine places at once and unable to reseed, and that is not a wrench job, that's eleven years of thermal logs and a woman who can read a load spike through a radiator."

"And if I find them all and Lund still says no?"

"Then you and I will have a very difficult conversation about whether we do it anyway," Vaan said, "and I would like to postpone that conversation until we've earned it."

Cleo looked at her hands. There was solder under the left thumbnail. There always was.

"Ledger," she said.

"Started. Ledger revision 44-B, four hundred and six entries, dates only, filed as reconciliation of pre-consolidation residential records." Vaan pulled a slate from her coat and turned it around and slid it across, and there they were, four hundred and six names in an ordinary archival table with an ordinary revision header, and Cleo read eleven of them before she had to stop, because the fourth was a family name she knew from Ag and the ninth was a family name she knew from her own school year.

"Okonwe," she said.

"Two. Sisters. There's a nephew in Fabrication who was told they transferred to the Bay 2 consolidation and stopped answering. He's fifty-eight. He still files a locator query on their birthdays." Vaan took the slate back. "That's why I can do the ledger in a month, Cleo. Because I've been holding a list of people like him for twelve years and every single one of them is a leak I have chosen not to plug. The ledger isn't a concession to you. It's the thing I've wanted most and could never justify, and you handed me a justification, and I'd be lying if I said I didn't take the meeting hoping you'd do exactly that."

"You're doing it now," Cleo said. "Aren't you. On me."

"Yes."

"Just — say when you are."

"I can't always tell," said Idra Vaan. "That's the honest answer and it's the worst thing about the job. After twelve years I cannot reliably distinguish between what I mean and what I've decided to mean." She stood and racked her chair, and at the door she stopped. "The curriculum. Education won't have it inside two years, I told you that. But Reyes has a room and a year-nine lab and no oversight worth the name, because he's a retired old man doing outreach and nobody reads his lesson plans. If you were going to teach nine hundred children to read a fuel tank, you would not start with Education."

Cleo said nothing.

"I'm not asking you to do it. I'm telling you where the door isn't locked." Vaan's hand was on the frame. "That's the last favour I'll do you as a person instead of as a department. After today I'm the Directorate again, and if this goes wrong I will process you, and you should assume I'll be good at it."

Ovid Reyes had a class at 0900 on the fourth day, and Cleo waited outside the year-nine lab and watched fifteen-year-olds do parallax on a fake sky.

There were nineteen of them. They worked in threes off a shared plate, arguing about baselines, one boy laughing so hard at his own error that he had to put his head on the bench, and a girl at the back with her hair scraped up in a clip taking notes with a pencil, which almost nobody did, which meant Ovid had got to her. Cleo watched the girl for some time before she registered the shape of the jaw and the set of the shoulders and understood that she was looking at Noor, her brother's daughter, who she saw at four family dinners a year and could not remember ever having had a conversation with.

Fifteen. Noor had been eleven the last time Cleo had properly looked at her.

When the room emptied Ovid stayed at his bench, wiping the plate with the flat of his hand.

"You went to Vaan," he said.

"How do you —"

"Because you're here, and you have the face of a woman who's been given the whole thing, and there's only one place aboard that could have given it to you." He didn't look up. "I've had nineteen years to imagine that face. It's worse in person."

She told him. She told him all of it, standing up, in the smell of chalk and warm electronics, and it took twenty minutes because she had to stop twice, and Ovid Reyes heard about Kesh-3 and the pseudo-prion and the sixty days and the helmets and everyone cheering, and the sealing of Bay 2 from the outside, and the four hundred and six, and the four hundred degrees for six days, and he did not move at all except that at some point he sat down on a lab stool as though his hip had been switched off.

When she finished he said, "Kesia Ferreira is still alive."

"Vaan says there are three. Lund, and a Council member, and someone in Medical."

"Ferreira chaired the Council in year sixty-eight." Ovid's voice was strange and light. "She came to my wedding. She's ninety-one, she's in the Deck 2 annex, she can't hold a cup. I visit her." He laughed, one dry note, the same note as before. "I visit her every ninth day and read her the sports."

"Ovid —"

"Twenty-two years ago they moved me out of Astro and gave me an office with a window, and I have spent every year since then telling myself that I was a coward with a good filing system, and I built quite a comfortable little life inside that sentence." He put his hands on his knees. "Now you tell me the thing I was too cowardly to find, and it is four hundred and six people vented from a compartment, and Anselm, I find I would rather have gone on being a coward. That's the news from in here. I'd rather not have known. Please write that down somewhere and use it when they tell you people can bear anything."

Cleo pulled a stool over and sat, which put them at the same height, which she had learned four days ago was a technique, and she used it anyway.

"I need to ask you for something."

"Ask."

"Two hundred and two days from now the pulsar feed goes raw and the sky starts telling the truth. Vaan is seeding — children's books, rumours she doesn't kill, whatever she does. But the curriculum's two years and I don't have two years, and I want the year-nine class to be able to check the tanks before the announcement instead of after."

"You want me to teach the boil-off inversion."

"It's four lines of arithmetic."

"It's four lines of arithmetic and a radiator log," Ovid said, "and the radiator logs are unclassified because nobody ever imagined that a fuel state could be read out of a heat curve, and it would take a fifteen-year-old about ninety minutes." He was already looking at the plate on the bench, and his hand had begun, unconsciously, to sketch on it with one finger. "You understand what you're asking. You're asking me to hand nineteen children a lit match and trust the seeding to have wet the floor."

"I'm asking you to teach them to check. That's all I've ever asked anyone."

"No, that isn't all, and you should be exact with me because I'm going to make decisions off what you say." He turned and his eyes were wet and absolutely steady. "You're asking me to arrange for the truth to be discovered by a child rather than confessed by a directorate, because you have decided — correctly, I think — that a ship can survive finding something out and cannot survive being told it has been managed. That's not education, Cleo. That's stagecraft. That's Verrat's framework with the polarity reversed. Say it in those words and I'll do it."

Cleo felt the floor of her chest drop, the way it had in Room 6.

"That's what it is," she said. "I'm doing to them what she did to me, only forwards."

"Yes."

"Is that better?"

"Immeasurably," said Ovid Reyes. "And you should be frightened of how easily you got here, and you should do it anyway, and you should never once let yourself believe that the two of you are different in kind. You're different in direction, which is everything, and it is not the same as being clean." He picked up his pencil. "Now. The lesson has to be honest work or they'll smell it. I'll do it as a thermal audit exercise — measurement of an inaccessible quantity by proxy, three worked examples, one of which happens to be a cryogenic tank, and I'll leave the ship's own logs in the resource set because they've always been in the resource set, and if a child pulls them that's a child pulling a public document." He wrote four lines and looked at them. "And when one of them comes to me with sixty-one percent and a white face, I'll say: interesting, check it again, bring me your working. Because that's what a teacher says."

"And then?"

"And then I do the most dangerous thing available to a seventy-four-year-old man," Ovid said. "I don't kill the rumour."

Paavo Lund's rooms in the Deck 2 low-grav annex smelled of pipe smoke, which was impossible, and Cleo spent the first minute of the visit working out that it was a synthetic — an old man's licensed indulgence, four grams a month, run through a filter that dumped its heat into a radiator loop she maintained.

He was in a chair by the window. The Deck 2 annex had real windows, three of them, the ship's only unmediated view, small and thick and set into the hull for reasons that were medical rather than romantic: the old and the dying were permitted to look out. Beyond the glass, stars. A great deal of nothing, and stars, and Cleo could not stop herself from doing the geometry and locating, off to the left, nineteen degrees off the axis that no longer meant anything, a dim thing that might have been TEV-9.

"You'll be Anselm," Lund said. "Sit where I can see you. My neck's finished."

He was very thin and very clean and his hands lay on the arms of the chair like tools set down at the end of a shift. He had ordered tea and forgotten it.

"Sub-Director Vaan didn't send me," Cleo said.

"No. She wouldn't. She'd have come herself and been kind at me for an hour." He turned his head with visible cost. "You're the thermal. You read the boil-off with a pencil."

"Yes."

"Good." He said it flatly, as a mark on a report. "That was always the flaw. I told them in year sixty-nine, I said, you can lock every instrument on this ship and you cannot lock the heat, heat is a public fact, heat is the one thing that leaves. They didn't understand me. Ferreira asked whether we could classify the radiator logs." A dry click of a laugh. "Classify the radiators. You'd have had a thousand engineers with a grievance and a stopwatch inside a month."

"So you left them open."

"I left them open, and I built the story out of a star instead of a number, and I calculated that in eighty years perhaps four people would ever have the access and the arithmetic and the reason at the same time." His eyes came round to her. "Four was my estimate. You're the second. The first was a woman in Fabrication in year seventy-three who got to within a whisker and then died of an aneurysm, which I want you to know I had nothing to do with and which nearly killed me too, because for six weeks I could not decide whether I was relieved, and a man who cannot decide that about a stranger's death has already lost something."

Cleo had come with a speech. She discarded it.

"I want the vergers," she said.

"Of course you do."

"Not the source. Not the keys. Just the list. Every nest, every host, every reseed path. I'll do the rest."

Paavo Lund looked at her for a while, and outside the window the stars did not move, had not moved in twelve years, would not move.

"No," he said.

"Sir —"

"Let me do you the courtesy of the actual argument, girl, since Idra never lets me finish one." He shifted in the chair. "You believe you're asking for an off switch. You aren't. You're asking me to put out the only light in a room with eleven thousand people standing in it, on the promise that Idra Vaan has spent two hundred days teaching them where the walls are. Now. Do you know what the reserve was in year seventy?"

"No."

"Thirty-one," he said. "The scale runs to a hundred. It sat at thirty-one for fourteen months after the sterilisation, when nobody knew anything, when all they'd been told was that there'd been a Class Four and nine compartments were sealed and rebuilding, and we had four suicides that year in a population that averages one every three years, and there were two nights — I'm going to tell you this because you're the second person in eighty years to earn it — two nights when Ferreira had armed crew standing at every cargo lock on the ship, because we had run the model and the model said nine days from first rumour." He raised one hand a few centimetres off the chair arm and let it fall. "Then we gave them the crossing. Do you know what it went to?"

"She said the reserve's the highest it's been in the mission."

"Eighty-eight, last quarter. Eighty-eight." Lund's voice did not gloat; it was worse than gloating, it was tired and exact. "I built a lie and it has produced twelve years of the happiest, healthiest, most productive human population in the recorded history of closed-vessel operation, and there are nine hundred children aboard this ship who are alive because their parents believed in a landfall, and you would like a list so you can switch it off on a holiday."

"So they can know."

"Know what? Say the sentence you'd have them know." He leaned forward. "Go on. Say it out loud in this room where the walls are eight centimetres from vacuum. We are eleven light-years from anywhere, we cannot land, we cannot go home, our great-grandchildren will die here, and everyone you ever trusted arranged for you not to find out. Which part of that is load-bearing, Anselm? Which part of it holds anything up?"

"The part where it's true."

"Truth doesn't hold things up. Truth is a measurement," Lund said. "I spent sixty years taking measurements. I never once met a measurement that fed anybody."

Cleo found she was very calm, and that the calm had a floor under it, and that the floor was nineteen pages of pencil.

"Then let me tell you what I know that you don't," she said. "You're eighty-one. Ferreira's ninety-one and can't hold a cup. Tal is seventy-six. Vaan is forty-six and she's the last, and when she goes there will be nobody alive who chose this. The vergers will keep rebuilding the sky out of TEV-9 for a hundred and twenty years and nobody will be able to read them, because you didn't leave source and you didn't leave documentation and you deliberately didn't leave an off switch, and so the last generation aboard — the one in the forty-page document Vaan says is the most obscene thing a human being ever wrote — that generation will be steered into a wall by a machine built by four dead people, and nobody will even be lying to them. It'll just be weather." She leaned in to meet him. "You didn't build a light in a dark room, sir. You built a haunted house and then you died in it."

Paavo Lund's face did not change. But his right hand closed, slowly, on the arm of the chair, and did not open again.

"That's Idra's argument," he said. "She's been circling it for four years."

"It's mine. She said nobody had made it to her in twelve years."

"Did she." Something that might have been amusement crossed him and left. "Well. She's better at her job than I am at mine."

"Give me the list."

"No." He unclosed the hand, deliberately, finger by finger. "But I'll tell you a true thing, and you may make what use of it you like, and you will note that I am doing you the immense favour of not knowing whether I'm doing it out of conscience or out of vanity, because a man my age is entitled to one unexamined act." He looked out the window. "The vergers reseed from the array. From TEV-9. That is their only external reference and their only source of truth, and I chose it because it's junk and nobody watches junk. But it means that everything that machine believes about where we are, it believes because of one sensor on Frame 44, mounted eleven years ago by a woman with a pencil." His head came round again, slowly, at cost. "It is a very clean architecture. And every clean architecture has exactly one throat."

Cleo sat absolutely still.

"You're telling me where the door isn't locked."

"I'm telling you," said Paavo Lund, "that I am eighty-one, and that I would like, on the whole, for someone else to have made the decision. I imagine that disgusts you."

"No," Cleo said. "It's the most honest thing anyone's said to me in three weeks."

She stood. At the door she stopped, because there was one more thing and she had promised herself she'd ask it while he was alive to answer.

"Why forty-one seconds? You could have used any interval."

Lund's eyes had gone back to the window.

"Because it was already there," he said. "I didn't choose it. The star did. I have never, in twelve years, been able to make myself feel that I chose any of it, and I know precisely how convenient that is."

The seeding began, and Cleo watched it the way she'd once watched an unfamiliar system come up: with her hand near the cut-off and her whole attention on the noises.

Day 19: a new title in the year-two library queue, The Star That Kept Time, forty pages, illustrated, about a lonely little star that blinked long-long-short-short-long and a girl who wrote the pattern down and used it to find her way home. Cleo read it standing in the school corridor and had to go and be alone in a service closet afterward.

Day 26: the ledger. Revision 44-B went into the archive at 0400 on a Fifthday with nine other housekeeping revisions, and for eleven days nothing happened, and on the twelfth day a man in Fabrication named Osei Okonwe filed a query about two names and got, for the first time in twelve years, a date. He did not go to the Common Channel. He went to the memorial wall on Deck 5 with a stylus and wrote two names on it in the blank space at the bottom, where there was always blank space, and then he sat down under them, and by evening there were forty people there, and by the next evening there were eleven more names on the wall in eleven different hands, and no announcement, and no explanation, and nobody in the Directorate said a single word about it.

Cleo went on the fourth night. There were two hundred people in the corridor, quiet, some of them crying, most of them not. Somebody had brought lamps. There were ninety-odd names now. A woman about Cleo's age was explaining to a teenager, patiently, that the Bay 2 consolidation records had always been a mess, that people had been listed as transferred who had actually died in the Class Four, that the Directorate was finally reconciling it, that it was about time.

That's not a rumour she didn't kill, Cleo thought. That's a rumour she wrote.

She looked down the corridor and found, sixty metres away in the shadow past the lamps, a woman in a soft grey off-duty jacket standing with her arms folded, watching two hundred people mourn on schedule.

Cleo did not go over. Later she was not sure whether that was mercy or cowardice, and she suspected there was no difference at that range.

Day 34: the fourth name in a queue of unattributed maintenance faults in the timing chain, filed by C. Anselm, thermal — nine sub-nests located, three of them in places that made her admire Lund almost unbearably. The reactor telemetry cluster. The laundry scheduler, still, a vestigial copy sitting there for eight years doing nothing but agreeing with itself. And one in the medical archive, in the module that indexed cause-of-death codes, which she looked at for a long time.

Day 40: Halim ended it, on second shift, in his own quarters, kindly.

"You've gone somewhere," he said. Halim Osei was fifty-one and drove a machine shop and had never in six years asked her a question she couldn't answer in one sentence, which was most of why it had worked. He had made the tea. He had made the tea before she arrived, which meant he had decided before she arrived, and Cleo sat down on the end of his bunk and understood that she was going to lose this and that there was nothing available to her that would stop it.

"I'm tired," she said. "There's a historical thermal review, it's eating me."

"Cleo."

"It's real. There's a review. I can show you the file."

"I don't want the file." He turned his cup a quarter-circle and she nearly laughed out loud, because everyone did it, everyone in the world turned a cup a quarter-circle when they were about to say a hard thing, and she had begun to see the mechanism in people the way she saw the mechanism in bulkheads, and that was new, and it was Vaan's, and she had caught it like a cough. "Eleven weeks ago you laughed at things. Now you look at me while I'm talking and you're somewhere doing arithmetic. And I've decided I'm not going to ask, because if I ask twice more you'll lie twice more and then I'll know something about you that I can't put down."

"That's very fair of you," she said. "I hate it."

"I know." He didn't move to touch her. "Is anyone hurting you?"

"No."

"Is it something you did?"

"It's something I found."

Halim sat with that, and to his enormous credit he did not ask what, and Cleo felt the shape of the space where he would have fitted, if she had been a woman with nothing in her pockets.

"Then I hope you put it down eventually," he said. "Come to the shop when you do. I'll still be there. I'm not leaving in any way that matters, I'm just — not going to sit in a room with the back of your head."

She walked the eleven decks home instead of taking the lift, and somewhere around Deck 5 she stopped at the memorial wall, where there were now a hundred and forty names in eleven different hands and someone had begun ruling faint pencil lines to keep the columns straight, and she thought: that's the price. Halim's the price, and it's a small one, and I've paid it, and I'd have paid twice.

Then she thought: listen to yourself doing the arithmetic.

Day 71. Ovid Reyes sent her a single line on the internal, unencrypted, exactly the sort of thing a retired teacher sends a former student: Come and look at some good work.

The year-nine lab at 1700 was empty except for the two of them and a plate on the bench with a plot on it, and the plot was a boil-off curve, and next to it in a fifteen-year-old's careful hand was a fill-fraction inversion, four lines, with the units written out in full because she hadn't yet learned to be lazy about units.

61.6%.

"Noor," Cleo said.

"Noor Anselm." Ovid was not smiling. "Three of them got to within four percent. She got to within half. She did the surface-area term properly, which I did not teach, which she went and found."

"What did she say?"

"She said: sir, this can't be right, the tanks are supposed to be at ninety-four, it's in the year-nine text." He had his hands in his coat pockets and was looking at the plate. "And I said what I told you I'd say. Interesting. Check it again. Bring me your working."

"And?"

"She came back in two days with it checked, and a second method using the radiator duty cycle, and a written note asking whether the year-nine text might be using a design figure rather than a measured one." Ovid's mouth twisted. "Which is a fifteen-year-old handing an old man a way out. She built me a door, Cleo. She helped me. And I said: that's a very good question and I don't know the answer, and I think you should go and ask someone in Fuels."

"You sent her to Fuels."

"There is nobody in Fuels who knows anything," Ovid said. "There are eleven people in Fuels who will look at her working and go pale and start checking their own tanks, because Lund was right about heat, heat is public, and I have spent seventy days deciding whether I am a teacher or an arsonist and the answer is that at my age they use the same room."

Cleo looked at the plot for a long moment. Sixty-one point six. She had gotten sixty-one point four with a pencil in a service closet and had thought, at the time, that she was alone in the universe.

"Vaan will know by tomorrow," she said.

"Vaan has known for nine days," said Ovid, "and has done nothing, which tells you everything about what she's decided, and should frighten you more than anything Lund said to you. Because it means she isn't managing this any more. She's riding it."

Mattias came to her quarters on day 76, at 0700, at the end of her shift, which meant he had waited outside for the shift bell so as not to wake her, which was so exactly her brother that she wanted to sit down on the deck.

He had Noor's working in his hand. Printed. On paper.

"Explain this to me," he said.

"Come in."

"No, I want to stand in the corridor and be told my daughter is confused, and then I want to go to work." He was grey. Section leads did not go grey; section leads ran twelve people and a hundred tonnes of biomass and complained about pump seals. "She brought it to dinner, Cleo. She put it next to the bowl and said, Papa, I think the fuel margin in the curriculum is wrong by thirty points, and eleven people in Fuels agree with me, and Sub-Director Vaan's office has scheduled a review."

"Then it's started," Cleo said.

Mattias stopped.

The corridor at 0700 was full of the noise of the wake-shift, doors, boots, someone's music, the smell of the protein line coming up through the grating, and her brother stood in it and looked at her and did the thing she had been dreading for seventy-six days, which was to be, immediately and without any evidence, entirely correct.

"You knew," he said. "You've known. That's why you look like that."

"Come inside."

"You let my daughter find it."

"Come inside, Mattias, or I'll say it here."

He came inside.

She told him. She had not planned to; she had run the arithmetic eleven weeks ago and put him second from the bottom of a list of four and hated the arithmetic and kept it anyway. But he was sitting on her one chair with his daughter's homework in his fist, and she found that the arithmetic had changed, or that she had, and that the new number was: he is going to hear this from a bulletin in a hundred and thirty-three days with nine hundred children in the room, or he is going to hear it now from his sister with a wall to lean on.

It took forty minutes. He did not interrupt except twice, once to say "the Class Four" in a voice like a man identifying a body, and once, at the sealing of Bay 2, to stand up and walk four steps and put his forehead against her cupboard door and stay there.

At the end he said: "Okonwe. In Fabrication. He's been filing locator queries on birthdays for twelve years, we all knew, we all thought he was —" He stopped. "We thought he was ill."

"Yes."

"There's a hundred and forty names on that wall."

"Four hundred and six," Cleo said. "The wall's got a hundred and forty because that's how many families have gone looking so far."

Mattias sat back down. He was thirty-four hours from his next rest cycle and he had twelve people and a hundred tonnes of biomass, and Cleo watched him arrive, with total predictability and total legitimacy, at the question she had asked Ovid Reyes.

"Why now?" he said. "You've known for eleven weeks. It's held for twelve years. It's working, Cleo, the reserve's the best it's ever been, I sat on the section leads' briefing last quarter and they showed us the curve and we were proud — " He heard himself. "God. That's the choir, isn't it. I'm the choir."

"You're not the choir."

"I'm the choir. I've been singing it at my own daughter." He put the paper down on the table very flat, and smoothed it, and it was such an Anselm gesture — their mother's gesture, over a bill, over a bad diagnosis — that Cleo had to look away. "So. Progress Day."

"Progress Day."

"You could have not told me. You had a hundred and thirty-three days of me not knowing available, and you spent it."

"Yes."

"Why?"

"Because I'm not going to stand next to a Sub-Director on a stage in front of eleven thousand people and have you look up at me from the fourth row," Cleo said, "and see me finding out at the same time as you. That's all. It isn't principle. It's that I couldn't stand it."

Mattias Anselm looked at his sister for a while.

"Then I want a job," he said. "Whatever it is. Something on the day. Don't put me in the fourth row with my hands empty, I'll come apart. Give me twelve people and something to do."

She thought about that afterward for a long time, and about how much of everything came down to it. Nobody had ever needed the truth. They had needed a job on the day the truth arrived.

Paavo Lund died on day 158, in the chair by the window, at some point in the second half of third shift. The annex staff found him at 0540 with a cold cup of tea beside him and his hands on the arms of the chair like tools set down at the end of a shift.

Cleo heard at 0600 and went up, and was not allowed in, and stood in the corridor outside with four other people who had also come at six in the morning to stand in a corridor: two annex orderlies, a woman from Astro in her forties who had no idea who she was mourning, and Kesia Ferreira in a chair, ninety-one, who could not hold a cup, who had chaired the Council of year sixty-eight, and who looked up at Cleo with absolute lucidity and said, "You're the thermal."

"Yes."

"He said there'd be four. He said you'd be second."

"There's a third now," Cleo said. "She's fifteen and she found it in ninety minutes with a pencil, and she wasn't looking for it, she was doing her homework."

Ferreira's face moved. It was hard to read what through the slack of it, but Cleo thought, later, that it might have been relief.

"Good," the old woman said. "Good. We were always going to lose to the arithmetic. I told them that. I said, we're not building a wall, we're building a delay, and the only question is whether we're honest about the difference." Her hand twitched on the blanket. "We weren't. Twelve years. I could have written it down for whoever came, and I didn't, because I was ashamed, and shame is not a plan, girl, don't ever let it stand in for one — "

They took her away then, because she had begun to tire, and Cleo went back to her shift.

Lund's effects came to her on day 161, because he had left instructions with the annex, and the instructions said: the paper in the pipe tin to C. Anselm, thermal, third shift, personally.

The pipe tin held four grams of synthetic and a single sheet folded twice. On it, in a very old man's very steady hand, was a list of nests. Ten of them. Nine she had found. The tenth was in the water-quality telemetry for Bay 4, which was where she had been born, and which she would never have looked at in a hundred years.

At the bottom, dated year seventy-four — eight years before he died, eight years before she had ever knocked on his door — was a note.

If you are reading this you are the one who came. I could not decide, and I have therefore arranged, in the only way available to a coward, for the decision to be made by whoever cared enough to knock. Note that this is itself a decision and that I have been careful not to notice it for eight years.

The vergers do not verify the story. They verify its coherence with the array. Do not attack the machine. Correct its reference. It will then defend the truth with the same diligence with which it has defended the lie, and no one — not you, not Idra, not any Council — will be able to reverse it without doing to the truth what I did to the truth, which will take them eight months and forty people and I do not believe they will find forty.

I am sorry about the singing. That was not mine. I told them not to.

P. Lund

The throat was a sensor the size of her thumb on Frame 44, and correcting its reference took Cleo Anselm nine weeks, forty-one hours of crawlspace, and a piece of engineering she was never able to explain to anyone but Noor.

She did not touch the star. That was the elegance of it and the thing that let her sleep. TEV-9 went on flickering long, long, short, short, long, stutter, forty-one seconds, indifferent, and the sensor went on reporting it truthfully. What she built was underneath: a translation layer between the array and the datastore, four hundred lines, hers, commented in plain language so that a fifteen-year-old could read it, which took twice as long as writing it. Where Lund's architecture asked is the story coherent with the sky, her layer answered with the sky as it actually was for a vessel at rest eleven light-years from Sol — flat phase, no creep, no motion — and the vergers, in nine places and then ten, woke on their forty-one-second heartbeat and found the ship's position incoherent with their reference and did precisely what they had been built to do.

They repaired it.

They repaired it toward the truth, all ten of them, patiently, over eleven days, migrating and cross-checking and rebuilding, and Cleo sat in the crawl above Frame 44 and watched a machine that four dead people had built to hide a graveyard turn slowly around and begin to tell eleven thousand people where they were.

The last thing she did was write the off switch. Six lines, documented, published in the open maintenance archive under her own name and staff number as a thermal timing-chain revision, along with the location of every nest, and Lund's sheet scanned in his own handwriting.

She had promised a machine with an off switch. She was not going to be the second person to break that promise.

Then she went to Room 6 and told Idra Vaan what she had done.

Vaan listened without moving. When it was finished she put her hands flat on the wooden table and looked at them for a while.

"It's running now," she said. "It's rebuilding. Today."

"Eleven days. It'll be coherent by day one hundred and ninety-six."

"And the display on the bridge?"

"Reads the datastore. The datastore reads the vergers." Cleo swallowed. "Day one ninety-six, the distance-to-target number stops advancing. Day one ninety-eight, the Doppler goes flat. Astro's morning watch will see it inside a shift."

"Eleven days before Progress Day."

"Yes."

Idra Vaan began, very quietly, to laugh, and then stopped herself with an effort that Cleo could see cost her something.

"You've taken the schedule," she said.

"I've given you eleven days of it leaking before you stand up. Astro finds it. Fuels are already writing a review nobody asked for. There's a hundred and eighty names on the wall on Deck 5 and a rumour you seeded yourself walking around saying the Class Four killed more people than they told us." Cleo made herself hold the woman's eyes. "By Progress Day, four thousand people will have been wondering. You said that. You said you needed four thousand people saying I've been wondering about that instead of eleven thousand saying they lied. So I built you the wondering."

Vaan sat back.

"You've become extremely good at this," she said, "in two hundred days, and I want you to hear that as the diagnosis it is."

"I know."

"Do you? Because in twelve years I never once did anything as effective as what you did in nine weeks in a crawlspace, and you did it by deciding what eleven thousand people would find out and when, and by seeding a schoolroom, and by using an old man's guilt, and by not telling your lover a single true thing until he left you." Vaan's voice was not cruel. It was worse than cruel; it was collegial. "Welcome. There's no ceremony. Nobody takes an apple."

Cleo looked at the bowl, which had thirty-eight apples in it now, or looked as though it did.

"Different in direction," she said. "Not in kind. Reyes told me. I've been carrying it for a hundred and seventy days."

"Keep carrying it," said Idra Vaan. "It's the only load-bearing thing either of us has got."

The two hundred and ninth day was a Fourthday and it began, as Progress Day had begun for eighty years, with the children's choir in the Long Gallery at 0900 under the great bright display, and eleven thousand people at their stations or in the corridors or crowded on the mezzanines with their families, and the smell of the good bread they baked twice a year.

The number on the display read 11.02 light-years travelled, 5.31 remaining, and it had not moved in thirteen days, and by 0900 on the two hundred and ninth day approximately six thousand people knew it.

Nobody had announced anything. That was the terrible, brilliant, unrepeatable thing about it, and Cleo understood as she stood in the wings with her nineteen pages that this was Vaan's actual craft and that she had never really seen it before: thirteen days of no denial. Astro's morning watch had reported an anomaly and been told, in writing, acknowledged, under investigation, do not speculate publicly, which every adult aboard could read as what it was. Fuels had published their tank review — sixty-one point one percent — on the open archive on day two hundred and three, unblocked, with a covering note that said only figures confirmed by three independent methods, discrepancy with curriculum noted, no explanation available at this level. Noor Anselm's four lines of arithmetic had been copied into eleven hundred slates by children.

By day two hundred and six there were queues at the three real windows in the Deck 2 annex.

The choir sang anyway. Nine- and ten-year-olds, forty of them, in the blue, and they sang the Crossing Song, which was ninety years old and had been written on Earth by a woman who never went anywhere, and Cleo stood in the wings with her heart going like a pump in cavitation and listened to eleven thousand people not sing along.

That was the sound she remembered afterward. Not the announcement. The sound of a hall where the audience always sang the third verse and, this year, didn't.

When the children filed off, Idra Vaan walked out in the whites.

She did not go to the lectern. She stopped at the front of the stage in the wash of the display, eleven light-years and five point three one, and she stood there until the Gallery was completely silent, and then she said:

"You already know. Most of you. So I'm not going to tell you as though it's news, because it isn't news any more, it's arithmetic, and it's been on the open archive for six days and half of you have checked it with your children."

Somebody in the middle distance made a noise. It was not a shout. It was more like a man being told a diagnosis he had already booked the appointment for.

"The number behind me is false," said Idra Vaan. "It has been false for twelve years. I have known that for twelve years. I helped maintain it, I approved it every quarter, and I want that said in my own voice before anything else is said, because there will be a great deal said in the next year and I would like the record to start with the plainest available sentence. My name is Idra Vaan, I am Sub-Director of the Morale Directorate, and I have lied to every person in this room, including the children who just sang."

She let it stand. She did not soften it. Cleo, four metres away in the wings, watched her not soften it and understood that this, this one thing, was Vaan's own — not managed, not modelled, not seeded. A woman spending herself.

"The Ambit arrived at its destination in mission year sixty-eight. We are at rest eleven light-years from Sol, at a system the classified record calls Kesh. There are four planets. One of them has air and water and an ocean, and in year sixty-nine we sent nine people down to it, and in the eleven weeks that followed four hundred and six people aboard this ship died, and Bay 2 was sealed from the outside with two hundred and forty living people inside it on the order of the Council of that year, and then nine compartments were sterilised at four hundred degrees for six days, and that is what you were told was a Class Four thermal event. Their names have been on the ledger since day twenty-six of this year and some of you have already written them on the wall on Deck 5. There are four hundred and six. Two hundred and eighty-one are still not on the wall. I would ask you to finish it."

The Gallery had gone past silence into something with a pressure to it.

"We cannot land. I will not tell you it is impossible for ever; I'll tell you that in year sixty-nine it killed four hundred and six of us in eleven weeks and that nothing we have learned since has changed it. We cannot return to Sol; the tanks are at sixty-one percent and a child in the year-nine class can show you what that buys and it does not buy a hundred and thirty years. What we have is this ship, which is sound, and an ecology which is thriving, and a hundred and twenty years of consumables, and eleven thousand people, and one hundred and thirty-one years in which to become the kind of people who can solve Kesh." Vaan's hands were at her sides. "The Council of year sixty-eight decided you could not survive knowing that. They were not monsters. They had four hundred and six dead and a model that said nine days, and they chose to give you a voyage instead, and it worked — it worked better than anything the Directorate has ever built. Your grandparents were happy. You have been happy. I have the curves, and I will publish them, and they are the most damning documents I possess."

She looked out at them.

"Here is what I have to say for myself, and then I'm going to stand aside for someone who does not work for me. It was easy. That is the part I would beg you to remember when you decide what to do with me. It did not take genius or cruelty. It took forty tired people, eight months, one small sensor, and the fact that every fact aboard this ship reached you through a system that belonged to us. I have spent twelve years believing I was holding a wall up. I was standing in a doorway. And the reason you are hearing this today from a woman in whites instead of from a machine in a hundred years is not that I found courage. It's that a third-shift maintenance engineer took a phase fit in a crawlspace on her own time and would not put it down."

She stood aside.

Cleo Anselm walked out onto the stage with nineteen pages of pencil in her hand, into the light of a false number, in her working coverall because she had refused twice to be given anything else, and eleven thousand faces turned up at her, and in the fourth row on the left her brother Mattias stood with twelve people from Hydroponics who had a job to do afterward, and further back under the mezzanine Turi Achebe held her daughter's hand and looked up at Cleo with an expression Cleo would be a long time reading, and beyond her Ovid Reyes sat with his hands on his knees, and beside him a fifteen-year-old girl with her hair scraped up in a clip and a pencil behind her ear.

She had written a speech. She had written eleven of them. She put the pages down on the boards at her feet, unread, and left them there where anyone could come up and take them.

"My name is Cleo Anselm," she said. "Third shift, hull and thermal. I found this with four measurements and any of you can check every one of them by Thirdday, and I'd like to teach you how, because that's the only part of this that's actually mine."

She held up one hand and counted.

"One. There's a star out there called TEV-9, and it flickers, and it's been flickering the same way for eleven years, and it shouldn't have."

Somewhere above her, in the crawl above Frame 44, behind a coolant run, taped to the inner skin of a ship that had arrived and stopped and stayed, a second copy of nineteen pages went on quietly not being needed.

"Long, long, short, short, long," Cleo said. "Then a gap of forty-one seconds. I want to show you what that means."

She taught them the phase argument for nineteen minutes.

She had not planned nineteen minutes. She had planned four, and then the woman from Fuels in the eleventh row asked her to go back and do the light-travel term again, and a man on the mezzanine shouted that he couldn't see the waveform, and somebody in the technical gallery patched the TEV array feed onto the great display, so that the false number went away and was replaced by a small grey box in which a star nobody had ever heard of blinked long, long, short, short, long, and eleven thousand people watched it in silence and counted forty-one seconds along with her.

That was the strangest thing she would carry out of the Long Gallery: the counting. Eleven thousand people counting under their breath, and at thirty-nine a sort of pressure gathering in the hall, and at forty-one the stutter arriving on time, and a sound going up that was not applause and not a groan but the noise a crowd makes when a prediction is fulfilled and they wish it had not been.

"Again," said the woman from Fuels.

They did it again. Cleo drew the geometry on the boards with a stylus and the display mirrored her hand: the ship, the star nineteen degrees off the old velocity vector, the light coming in. She explained that a variable star is a clock and that the clock's face turns as you approach it, and that eleven years of approach at eight percent of light should have turned this one through an angle so gross that a child could see it, and that it had not turned at all.

"Any of you can check it," she said. "The array logs are open. They have always been open. Nobody hid them; they hid the meaning, which is cheaper."

Then a man stood up in the lower left, and he was very old, and Cleo knew him.

Bakri Amse had been coming to Ag-3 on third shift for as long as she had been on third shift, an old man in a good coat who could not sleep and who sat among the bean rows because the smell was the smell. He had cried into his collar over an eighth of an apple a hundred and ninety-nine days ago and had pretended it was the lamps.

"Engineer," he said. His voice was thin and it carried anyway, because eleven thousand people had gone quiet for him. "How do we know you are not lying now?"

Idra Vaan, standing at the side of the stage with her hands at her sides, did not move a muscle. Cleo felt the whole hall arrive at the question and understood that it was the only question, that everything else was housekeeping, and that if she got it wrong the next four hundred and six were on her.

"You don't," she said.

Somebody laughed, one shocked bark, the way Vaan had laughed in Room 6.

"You don't, and you never will, and neither do I. That's what I want to say more than anything else and then I'll get out of your way." Cleo put both hands out, palms up, empty. "I checked four things. It took me nineteen days and I got two of them wrong the first time. I was wrong about the sensor for three shifts and I was very happy for three shifts and then I bench-tested it and the happiness went away. That's the whole method. There isn't a better one. Nobody is coming to tell you the truth, and if somebody does come and tell you the truth you should thank them and then go and check it, and if they mind you checking, that is the entire information you need about them."

"I am eighty years old," said Bakri Amse.

"Yes."

"I do not have nineteen days."

The hall held its breath, and Cleo Anselm, who had lain awake for two hundred and nine nights writing eleven speeches, found she had nothing prepared for an old man in a good coat.

"Then take mine," she said. "There are nineteen pages on the floor at my feet in pencil. They're not a document, they're arithmetic. Come up and take them and get someone you trust to walk you through them. That is the honest best I have."

Bakri looked at her for a long moment and sat down.

And then a girl of perhaps twelve, up on the second mezzanine, with the absolute clarity of a person who has not yet learned which questions are permitted, called out:

"Can we see it?"

There was a silence of a different quality.

"The planet," she said. "You said there's a planet with an ocean. Is it out there? Can we see it out the window?"

Cleo had been ready for rage, for the lock, for the Kestrel, for a hundred people rushing the stage. She had not been ready for that, and it went through her like a coolant surge.

"There are three windows on this ship," she said, "and they are all in the low-grav annex on Deck 2, and they are eleven centimetres across, and they were put there so that the old and the dying could look out." Her voice was not entirely under her control. "But there are eleven survey telescopes on the forward truss and they have been pointed at Kesh-3 for twelve years, and the imagery exists, and it is beautiful, and I have seen four frames of it and I have wanted for two hundred days to put it on this wall."

She turned to look at Idra Vaan.

"I don't have the authority," Cleo said.

Vaan crossed the stage. She did not go to the lectern either. She stopped at the front, in the wash of the grey waveform box where the false number used to be, and she said, to a room of eleven thousand people who half an hour ago had been sung to by children:

"Technical gallery. Put up the survey feed."

There was a pause of about eleven seconds, which Cleo later learned was a duty officer named Fen Adeyemi arguing with a classification lock and then, on his own authority, breaking it.

Then the wall went blue.

Nobody remembered the rest of the ceremony because there wasn't any. There was a wall four storeys high with a world on it, half in shadow, banded with white weather, an ocean going out of the terminator into night, one continent like a hand, and eleven thousand people standing up out of their seats without any of them deciding to.

The disc was eleven arcseconds wide from where the Ambit sat and the telescopes made it four storeys tall, and it turned. That was the thing that broke people: it turned. Weather moved on it. It was not a picture, it was a live feed with a nineteen-minute light delay, and a storm the size of a sea was walking east across the hand-shaped continent at that moment, and had been walking there for twelve years while the choir sang.

Cleo stood in the wing with her back against a stanchion and watched a hall full of people look at a place.

Grief needs an object, she thought. She had worked that out in a service closet on day one hundred and eighty and had not been sure enough of it to say it to Vaan. A voyage gives you a future, which is a very thin thing and can be taken away by arithmetic. A window gives you a place, and a place cannot be taken away by arithmetic, and a place can be hated and mourned and studied and painted by children, and none of those things open a cargo lock.

Somewhere in the middle of the hall her brother's twelve people from Hydroponics were passing out the good bread they baked twice a year, going along the rows with the trays, because Mattias Anselm had asked for a job and had been given four hundred loaves, and it turned out that four hundred loaves distributed by hand in the first fifteen minutes was worth more than any words available to any human being.

The model said nine days.

That number was in the Directorate's archive, written in year seventy by four exhausted people, and it said that on a closed vessel the interval between the arrival of an unmanaged catastrophic disclosure and the first mass irrational act was nine days, plus or minus two, and that the Kestrel had gone in nine.

In year seventy Kesia Ferreira had put armed crew at every cargo lock on the ship, and there had been four suicides.

Cleo had read that document on day one hundred and forty-one and had gone to Vaan and said: no guards.

"You cannot be serious."

"They didn't work. You have the numbers. You put crew with weapons at every lock and four people died anyway, and the crew were the ones who found them, and two of those crew are on your long-term care list."

"Then what."

"Chairs," Cleo had said. "Chairs and a kettle."

So on the two hundred and ninth day, in the corridor outside every cargo lock and every EVA hatch and every maintenance airlock on eleven decks — forty-one of them, and she had laughed for a long time when she counted them — there was a chair, and a small folding table, and a kettle, and a tin of the third-shift tea that nobody liked, and a person sitting there.

The chairs came out of Halim Osei's machine shop.

He had built them in nine days, three hundred and eighteen of them, in laminate and offcut tube, and he had never once asked her a question about why, and when she came down to the shop on day two hundred and one he had straightened up from the jig with his hands full of shavings and said only:

"Are they to be comfortable, or are they to be uncomfortable?"

"Comfortable. Somebody's going to sit in one for six hours at a time."

"Then I'll do arms." He wiped his hands. "You look better."

"I put it down," Cleo said. "It's got a date on it. Nine days from now."

"Then you haven't put it down, you've scheduled it." He turned back to the jig. "Come when you have, Cleo. I've six years of tea to make."

Third shift ran the watch. That had been Cleo's second condition and Vaan had not argued: not Directorate, not crew, not medical. Third shift — hull, thermal, recyclers, night crop, laundry, the people who were awake at 0300 anyway and who were, as a class, extremely comfortable with sitting in a corridor doing nothing for hours in the amber light.

Cleo took the Deck 9 aft cargo lock, because it was the biggest, and because it was the one the Kestrel people would have used if the Kestrel had been the Ambit.

Nobody came for three nights.

On the fourth night, at 0140, a woman came down the corridor at a normal walking pace with her hands in her pockets and stopped when she saw the chair.

"Oh," she said. "There's a person."

"There's a person. There's tea, and it's bad."

"I know it's bad, I'm forty-four, I've had it." She stood there. She was in Astro blues, off duty, and she had the grey face of someone eleven days past the end of her sleep. "Sanne Baro. Morning watch."

Cleo stood up out of the chair, which she had not expected to do, and it took her a second to understand why. "You're the one who reported the anomaly."

"Day one hundred and ninety-six. 0611." Sanne Baro laughed with no humour in it at all. "I called the Duty Astrogator and I said, sir, the distance-to-target hasn't advanced in a watch and a half, and he said, put it in writing, and I put it in writing, and at 0900 I got a note back that said acknowledged, under investigation, do not speculate publicly, and I sat with that for thirteen days." She took her hands out of her pockets. "Thirteen days, engineer. I knew for thirteen days and there was nobody I could say it to, and so what I did was I checked it four hundred times."

"That's what I did."

"I know. I watched you on the stage saying you got it wrong for three shifts and were happy, and I sat in the fifth row and I thought, she knows," Sanne said. "I wasn't coming here for the lock. I want that on the record because you'll have to write a log."

"I'll write that you came for the tea."

"Write that I came because I wanted to see whether they'd really put chairs out." She sat down on the deck instead of in the chair, with her back to the bulkhead, and Cleo sat down beside her, and they drank the bad tea, and at some point Sanne Baro cried for about ninety seconds in a businesslike way and then stopped and said, "Right," and Cleo said nothing at all, which was the entire skill the job required.

Nine days came and went. There were, in the Directorate's later accounting, eleven hundred and six visits to the forty-one chairs in the first fourteen days. Most were like Sanne's. Some were people who came to shout, and a few of those shouted at whoever was in the chair for an hour, and Cleo herself was shouted at twice, once by a Fabrication foreman who wanted her retired, actually retired, in front of the whole ship, and once by a woman of twenty-six who wanted to know why, if you could see the planet, you couldn't just go, and who had to be told about the eleven weeks and the four hundred and six and who then sat down on the deck and asked to be told again slowly.

On day six a man from Hydroponics called Ivo Merrick stood in front of the Deck 11 EVA hatch for nine minutes with his hand on the manual override, and the person in the chair was one of Mattias's twelve, a woman called Prisca who had known him for twenty years and who did not stand up and did not raise her voice and simply talked to him about a pump they had rebuilt together in year seventy-three, and at the end of the nine minutes he took his hand off the override and sat down on the floor and she got him tea.

That was the one they used afterward, in the training. Cleo hated that it became a piece of training.

Because on day eight, at 0347, the thermal panel in Cleo's own hand pinged an unexplained transient in the Bay 9 forward maintenance airlock — a small one, a two-man EVA hatch that had not been cycled in six years, that was on the manifest as sealed, that nobody had put a chair in front of because nobody had counted it as a lock.

Bakri Amse was eighty years old. He had been two at launch. He was, and this was in his file and nobody aboard had noticed it in decades because it had stopped being interesting, the last living person aboard the Ambit who had been born on Earth.

He had left his good coat folded on the deck outside the inner door, and on top of it, a note.

I have been in a corridor for seventy-eight years and they told me I was going somewhere. Please do not make a thing of it. The beans were good.

Do not blame the engineer. She gave me an eighth of an apple in the middle of the night and never asked for anything.

Cleo Anselm read that at 0402 standing in the Bay 9 access with two medical crew and a hull tech behind her, and then she went and sat in the crawl above Frame 44 with her knees up and her forehead against the coolant run for two hours and did not cry, and could not afterward account for the two hours in any way at all.

Idra Vaan published the curves on day fourteen, unabridged, as she had promised: eighty years of the morale reserve, quarter by quarter, with the mission events annotated, including the ones that had never been announced.

The reserve had been at eighty-eight in the last quarter of year seventy-nine.

It was at thirty-four eleven weeks after Progress Day. It went to twenty-nine in the second quarter and sat there, and everyone in the Directorate who had ever seen the year-seventy trace knew what twenty-nine meant, and the graph in the open archive was consulted, in the first year, by nine thousand four hundred residents, which was a number Vaan put in her own report with a note beside it that said: this is the only figure in this document I regard as good news.

In the first year after the disclosure, nineteen people aboard the Ambit died by their own hand.

Cleo learned each one within an hour, because the chairs reported to third shift and third shift reported to her, and on the last day of the mission year Vaan sent her a plain file with nineteen names, dates, no cause, no commentary, and no covering note.

She took it to the memorial wall on Deck 5, where four hundred and six names were now written in something like ninety different hands, in pencil, in stylus, in one case in what looked like beetroot, and where somebody had ruled columns and somebody else had come along and ruled them straighter.

There was already an argument in progress about the nineteen. A man was saying that they didn't belong on this wall, that this wall was for Bay 2, that it would be an insult to the vented to have them mixed in with people who had chosen it.

"Whoever they were," Cleo said, "they get to be in the same book as my mother."

The man turned round. He had never seen her in person, only on a stage four storeys under a planet, and she watched him work out who she was, and she watched him decide, with an effort that she respected, not to say to her the thing he had been carrying for eleven weeks.

"It's not a book," he said instead. "It's a wall."

"The ledger's the book. The wall's what the book looks like when people are angry." She held out the slate. "Nineteen. Some of them have got nobody to write them up, so if you're going to stand here all afternoon arguing you may as well hold the light."

He held the light. She wrote nineteen names on the wall on Deck 5, and Bakri Amse's was the fourth, and it took her a long time because her hand was not good that day.

Turi Achebe did not speak to her for a hundred and six days.

Cleo went on cleaning the filter in Ag-3 on her rota because it was on her list and because she was not going to make Turi do the thing of asking for a different technician. They worked in the same room, four metres apart, under the lamps. The night crop crew went from unbearable to merely careful in about a month. Cleo cleaned the filter and went away and said nothing and it was the most sustained act of discipline of her life.

On the hundred and sixth day Turi came down the row with a harvest tray on her hip and set it down and said:

"The apple."

Cleo stopped what she was doing and straightened up.

"You'd already found it. When you gave Sefi that apple you'd already worked out the whole thing, you'd already been to the Directorate, you had — what did you have, nineteen pages? — in your pocket." Turi's voice was perfectly level and her hands were shaking. "And you sat on that crate and you watched my daughter cut it into eight pieces and give one to you."

"Yes."

"Why?"

"You want the true answer or the one that makes me look better?"

"Don't," said Turi. "Don't do the thing where you offer me a choice about what you tell me. That's them. That's the whites."

Cleo put down the filter housing.

"I wanted to see whether it worked," she said. "That's the true answer. Idra Vaan gave me an apple to buy me and I refused it, and then I took it, and I gave it to a six-year-old, and I stood in this room and watched eleven person-days of morale come out of a single piece of fruit, and I thought: that's the arithmetic, and it works, and this is how you become her. And then I went and became her anyway, for two hundred and nine days, on purpose, and it worked, and that is why nine thousand people found out from arithmetic instead of from a bulletin, and that is why the reserve is at twenty-nine instead of at four, and I would do all of it again tomorrow." She made herself keep her eyes on Turi's. "And I used your kitchen table to test my method on your child. Both of those are true and I've stopped finding it interesting that they are."

Turi Achebe looked at her for a long moment.

"That's her sentence," she said. "That's Vaan's sentence, I've heard it in the bulletin."

"Yes. I caught it like a cough."

Turi sat down on the upturned crate, which was the same crate.

"Sefi kept a piece," she said. "You know that. She kept a piece in her pocket for two days and then it went brown and she cried and I said, that's what happens to apples, and she said, then why did she give me an apple instead of a tree."

Cleo said nothing.

"Six years old." Turi wiped her face with the back of her wrist. "So that's what I've been sitting with for a hundred and six days, engineer. Not the lie. Not the planet, I've looked at the planet, I take her to look at the planet, half of Ag goes and looks at it on rest-day like it's a lake. I've been sitting with the fact that a woman I would have given a kidney to came into my room and dosed me, kindly, with fruit."

"Then I'll come off the Ag-3 rota."

"No you won't." Turi stood up. "You'll teach me the four measurements."

Cleo blinked.

"Not the story. Not the pages, everyone's got the pages, they're in the year-nine text now, my mother's got a copy and she can't read a pressure gauge." Turi's chin came up. "The measurements. I want to be able to do them. I want to be one of the people who can walk up to whatever comes next and check it before they've finished telling me. That's what you said on the stage, that was the only useful thing anybody said that day, and you said it and then you went off and became a department."

"I'm not a department."

"Cleo." Turi picked up her tray. "There's forty-one chairs and eleven hundred visits and a training document with Prisca's pump in it, and third shift reports to you, and you've got a room. What do you think a department is?"

The Council inquiry sat for eleven months.

It was open. That was the single largest structural change of the first year and it had happened almost by accident, because on the fourth day a Fabrication delegation had asked to observe and nobody had felt able to say no, and by the ninth day the sessions were carried live on the internal and watched, at peak, by six thousand people.

Kesia Ferreira gave evidence on the thirty-first day, from a chair, with an orderly beside her and a cup she could not hold.

She was ninety-one. She had chaired the Council of year sixty-eight. She had ordered Bay 2 sealed from the outside with two hundred and forty living people inside it, and she had ordered the sterilisation, and she had approved the Managed Disclosure Framework extension that had created, in eight months, a voyage that did not exist.

They had prepared a procedure for her: written questions, a recess every twenty minutes, an option to submit in writing.

She refused all of it.

"I will say it in my own voice," she said, "while I still have one, and you will not be kind at me, and I would ask the chair to instruct the room not to make any noise, because I cannot start again."

The room made no noise.

"I sealed Bay 2," she said. "I gave that order at 0340 on the eleventh of the ninth, year sixty-nine, and I gave it in the knowledge that there were two hundred and forty people alive inside it, and I would give it again, and if this ship needs to hang someone for it then I am here and I am ninety-one and it will be the cheapest justice you ever bought." A long pause for breath. "That is not what I have come to say. I have come to say that the sealing was a decision, and it was mine, and I have carried it, and it was not the crime. The crime came afterward and it was quieter. The crime was that in the eleventh month of that year I sat in a room with thirty-nine people and someone said what if they simply keep going, and I said: how long can we hold it. Not: should we. Not: what do we owe them. How long can we hold it. And somebody said eighty years, and I said, make it a hundred and thirty." "How long can we hold it," Kesia Ferreira said again, "and somebody said eighty years, and I said, make it a hundred and thirty. And then we broke for a meal. I remember the meal. There was fish."

The orderly moved the cup an inch closer and she ignored it.

"I want the room to understand the sequence, because the sequence is the whole of it. We did not decide to deceive you and then work out how. We worked out that we could, and the ease of it did the deciding. Thirty-nine people and eight months and one small sensor. Nobody in that room was a monster. Every one of them had been awake for two days and had helped carry bodies, and I could give you the name of every single one and tell you a good thing about them, and I have written those down and you'll have the file." A breath. "The Sub-Director said on Progress Day that the ease of it is the horror and not the malice. She learned that sentence from me. I have had twelve years to improve on it and I cannot."

Somebody in the fourth row of the public gallery stood up. The chair moved to rule him out of order and Ferreira lifted one hand two centimetres off the blanket, which stopped the room.

"Let him."

Osei Okonwe was fifty-eight and worked in Fabrication and had filed a locator query on two birthdays every year for twelve years, and he had been the first person to write a name on the wall on Deck 5.

"Faridah and Amaka Okonwe," he said. "Bay 2. Did you know their names when you gave the order?"

"No."

"Do you know them now?"

"Yes," said Kesia Ferreira. "I have known all four hundred and six for twelve years and I could not say them out loud to anyone, and I want to be exact about that, because there is a version of me that would like you to hear it as suffering. It was not suffering. It was bookkeeping. I kept the list because keeping the list let me feel like a woman who had not done something unforgivable, and I never gave it to anyone who might have used it, and that is the difference between grief and shame, and shame is not a plan." Her head turned, slowly, at cost. "Your sisters were nineteen and twenty-three and they worked the Bay 2 laundry, and the younger one had put in for a transfer to Ag."

Osei Okonwe stood in the gallery for a moment longer, and then sat down, and put both hands over his face, and nobody in that room ever afterwards agreed on whether Ferreira had done him a kindness or a violence, including Cleo, who watched it from the technical bench with her hands flat on the table.

Ferreira died four months later. There was no inquiry finding against her, because the inquiry, in the end, declined to find against anybody, which enraged nine hundred people and was, Cleo thought, the only survivable outcome. The finding ran to two hundred pages and its load-bearing sentence was four lines long:

The Council of year sixty-eight faced a decision without precedent and made it badly. The Council of year sixty-nine institutionalised that decision, which was worse. No living person aboard can be punished in a manner proportionate to four hundred and six deaths and eighty years of manufactured belief, and this body declines to perform a punishment which is not proportionate and call it justice. We instead recommend the following structural changes, and we note that the ship will be able to check whether we have made them.

There were forty-one recommendations. Cleo counted them and laughed until she had to sit down.

They did not retire Idra Vaan.

That was the thing nobody outside the Directorate ever quite forgave, and the thing Cleo defended for the rest of her life, in a voice that got flatter each year.

The Morale Directorate was dissolved as a directorate in the third quarter and reconstituted as a bureau with no classification authority and a standing obligation to publish its own reserve curves quarterly, and its first Bureau Chief was a Hydroponics section lead called Mattias Anselm, who had asked for a job on the day and got one for eleven years. The whites were abolished. Vaan herself was reduced two grades, barred permanently from disclosure decisions, and assigned — by the inquiry, over her own objection, and Cleo believed to the end that this was somebody's deliberate cruelty and somebody else's deliberate mercy — to the Kesh Programme, as an archivist.

"Archivist," she said, in the stores annex off what used to be the Directorate suite, which had chairs on a rack and a wall of crates and no apples in it because Cleo had told her once to notice.

"You know where everything is."

"I know where everything is because I put it there in order to make sure nobody found it." Vaan turned her cup a quarter-circle. She was forty-eight now and had gone grey in eleven months in a way that looked less like ageing than like a load coming off a member and the member relaxing into its real shape. "Do you know what they've got me doing? Reconciling the year-sixty-nine survey logs. All of it. Every hour of the nine, every sample, every reading off the landers, and cross-indexing it into a form a fifteen-year-old can query."

"That's the whole Kesh problem," Cleo said. "That's the only Kesh problem. Nobody's looked at that data with fresh eyes in twelve years because nobody was allowed to know it existed."

"I'm aware. I've been reading it for four months and I have to stop every second day because of the personal logs, they kept personal logs, there's a woman called Iyabo Sarr who spent day fifty-nine of her quarantine writing down what she was going to plant." Vaan set the cup down. "Eleven thousand people, Cleo, and now nine hundred children have the whole thing, and last week a boy of sixteen in Bio sent me a query asking whether anybody had ever tried the catalysis assay at four degrees, because his reading of the fold kinetics suggests the propagation might be thermally gated, and the answer is that no, nobody had, because in year sixty-nine there were four biologists left alive who had access and three of them were on the sterilisation crew."

Cleo sat with that.

"Is he right?"

"I have absolutely no idea. Neither has he. That's not the point and you know it isn't." Vaan almost smiled. "The point is there are now four hundred people looking, instead of four, and one of them is sixteen, and one hundred and thirty-one years is a very long time, and I am not permitted to tell anyone that I have hope because it is exactly the sort of thing I would have manufactured."

"Then I'll say it," Cleo said. "You can quote me. It's checkable."

The Bureau of Verification was three people and a room for the first year and eleven people and a room for the next thirty.

Cleo had not wanted it. She had wanted to clean filters and reseat brackets and go up to Frame 44 at 0217, and she said so, at length, to a Council subcommittee, and the subcommittee listened politely and then pointed out that third shift already reported to her, that there were forty-one chairs, that eleven hundred people had come to sit in them, and that she had personally published the off switch to the largest lie in human history under her own staff number in the open maintenance archive, which was, they said, the founding document of the thing they were asking her to run.

"It's six lines," Cleo said.

"Six lines, documented, in plain language, so a fifteen-year-old could read it," said the chair, who had it in front of her. "We've had eighty years of policy on this ship and none of it did that. Take the room, engineer."

So she took the room, and the room's mandate was one sentence long, and she wrote it herself and it never changed:

The Bureau exists to ensure that any resident of the Ambit may, without permission, check any load-bearing fact about the vessel, and to teach them how.

It did the four measurements. That was the whole curriculum for the first eleven years and later it was nineteen measurements and by the time Cleo was seventy it was sixty-four, one for every quantity aboard that could kill you or lie to you: tank fill by boil-off inversion, hull integrity by thermal gradient, reactor state by radiator duty cycle, air by four independent chemistries in four independent labs run by four groups of people who were forbidden to share instruments, and, always, first on the list, taught to every child in year nine with a pencil and a plot: position and motion, by the phase of a variable star.

Turi Achebe took the course in the second year and got a distinction and then took it again as an instructor in the fourth, and ran the Ag-side teaching for twenty-two years, and was the person who insisted — over Cleo's objection, and Cleo lost, publicly, in a meeting minuted and published — that the Bureau also teach people how to check the Bureau.

"You'll be dead," Turi said. "You'll be dead and there'll be a room with your name on it and eleven people in it who nobody can audit, and Lund built a haunted house and so will you, you'll just build it out of good intentions and better documentation."

"Fine," Cleo said. "Write it."

Turi wrote it. It was nine pages. It is why the Bureau's own instruments were, from year eighty-four onward, duplicated in Ag-3 under a beans rota, by people who were not permitted to be engineers, and it is why in year one hundred and nineteen, when a Bureau technician was found to have quietly smoothed eleven months of hull-stress data to avoid a panic about Frame 12, it was a night crop crew that caught him inside a fortnight.

Cleo was sixty-eight then. She read the report and went and sat in Ag-3 under the lamps for an hour among the bean rows, and thought about an old man in a good coat, and did not cry, and went home and slept better than she had in years.

Ovid Reyes lived another nine years and taught until the last of them.

He never fully forgave himself for the lesson, and he never once said he regretted it, and Cleo came to understand that these were not in conflict and that this was, in fact, the only honest posture available to any of them. In year eighty-three the year-nine navigation module was formally rewritten and the boil-off inversion went into it on page four, and he was asked to write the preface, and what he wrote was two sentences:

This module will teach you to measure the ship you live in. Everything in it was known to somebody eighty years before it was taught to you, and the reason it is now taught to you is that a woman on third shift did not put down a thing she found, and a class of fifteen-year-olds checked her working.

He would not take his own name out of the acknowledgements and he would not let anyone put it in the preface, and Noor Anselm, who was by then twenty-four and in Fuels, told Cleo that the old man's exact words on the matter had been: I was moved once, and I stood still for twenty-two years, and I would rather the record showed the standing still.

He died in the low-grav annex on Deck 2 in year eighty-nine, in a chair by one of the three windows, and it was Cleo who was with him, and the last thing he said to her that made sense was:

"Different in direction."

"Not in kind," she said.

"No." His eyes were on the glass. "But direction is everything, Anselm. I've done the geometry."

There is a photograph, or rather there is a frame of internal-log imagery that a laundry technician pulled and printed in year ninety-one and which ended up on a wall.

It shows the Ag-1 trial orchard in its ninth year: eleven rows of dwarf apple under long lamps, four hundred and six trees.

The number was not deliberate at first. There had been forty trees in year eighty, and the trial had been a curiosity — Ag-1's private hobby, four decades of grafting, forty apples a year that went to the Directorate for guests who never ate them. In the second year after the disclosure a girl of eight named Sefi Achebe stood up at an open Ag section meeting, which children were now permitted to attend and to speak at, which was itself recommendation nineteen, and asked why there were forty trees instead of a lot of trees.

The section lead said, honestly, that nobody had ever asked for a lot of trees.

Sefi Achebe said: "Then I'm asking."

It took nine years, because grafting takes nine years, and it took eleven hundred square metres of floor that had to come out of protein and a two-year argument about it that was conducted in the open and lost twice before it was won. When the count passed four hundred somebody suggested stopping at four hundred and six, and nobody argued, and nobody put up a plaque, because Ag-3 had opinions about plaques.

The trees came into bearing in year eighty-nine and by year ninety-two the Ambit had, for the first time in its history, apples in the ordinary autumn ration. Not forty. Nine thousand.

Cleo was fifty-one that year. She ate one standing up in Ag-1 with juice on her wrist, and beside her Idra Vaan, sixty, archivist, two grades reduced, with her sleeves rolled, ate hers with the concentration of a woman doing sums.

"Nine thousand," Vaan said.

"There'll be forty thousand by year one hundred."

"Nine thousand." Vaan looked at the core in her hand as though it had insulted her. "Do you know what I could have bought with nine thousand apples?"

"Yes," said Cleo. "So do they. That's the difference."

Vaan laughed, and it was not the ugly sound; it was some other sound, one Cleo had heard perhaps four times in thirty years, and she let it be.

Sefi Achebe was seventeen and had not become a doctor. She had become an orchardist, which she said was worse hours and better company, and she was three rows over with a pruning hook, arguing with somebody about rootstock.

Cleo Anselm went up to Frame 44 for the last time in the ninety-fourth year of the voyage, which was to say the twenty-sixth year at Kesh, at 0217, because she was sixty-two and had stopped pretending she'd ever adjust to a day shift.

The crawl was the same. The coolant run was warm. It smelled of hot dust and old solder, and the bracket she had reseated in year eighty was fine, and would be fine for years, and had outlasted three of the four people who had ever known why she'd been up there.

She had brought Noor's daughter, who was eleven and called Bakri, which had become a common name on the Ambit in a way that nobody had planned and nobody had prevented.

"Wedge yourself in. Feet against that. Not the pipe — that. Good." Cleo passed over the slate. "Pull the array feed."

"Which array?"

"Tertiary External Verification. Ninth object."

The girl found it in about eleven seconds, because children now grew up with the array feed the way they grew up with the water report, and the little grey waveform box opened, and TEV-9 flickered.

Long, long, short, short, long. Stutter. Gap.

"Count it," Cleo said.

"Forty-one," said Bakri, at forty-one.

"Forty-one point zero zero. It hasn't changed since before my mother was born." Cleo leaned back against the inner skin. "Now. What does it mean that it hasn't changed?"

"That we're not moving."

"Say it properly."

The girl rolled her eyes, which was the single most reassuring thing that had happened to Cleo all week, and said, in the singsong of a child reciting the year-nine text: "That our distance to TEV-9 is not changing measurably, therefore our velocity component along the line to TEV-9 is approximately zero, and since TEV-9 is nineteen degrees off the old vector, and since the pulsar timing is flat, and since the tanks are at fifty-eight point four —"

"Fifty-eight point one."

"— fifty-eight point one, we are at rest at Kesh." She looked up. "Everybody knows that."

"Everybody knows it," Cleo said. "That isn't the same as everybody being able to check it, and the difference between those two things killed four hundred and twenty-five people, and if you can only remember one sentence from an old woman in a crawlspace, remember that one."

Bakri considered this with the seriousness of eleven.

"Great-aunt Cleo."

"Mm."

"What happens if it changes?"

Cleo Anselm turned her head. Below them, through eight centimetres of hull, eleven thousand four hundred people were asleep, or awake and arguing about legumes, or sitting at one of forty-one chairs with a kettle, or standing at one of the nineteen windows they had cut into the Deck 2 annex in year eighty-six because it turned out that being able to look at the place you were was worth more than any number on any wall.

"Then somebody will have moved us," she said. "And that'll be a decision, and it'll be an enormous one, and it will get made in the open by people who are alive, in front of everyone, and argued about for four years, and there'll be a vote, and eleven hundred people will hate it." She smiled in the dark. "And on the first night of the burn, the phase will start to creep. About forty minutes of light-time a year. And whoever's on third shift will see it move for the first time in a hundred and thirty years, and they'll come up here and sit exactly where you're sitting and watch the song change."

"Will it be me?"

"It might be you. It won't be me." Cleo put her palm flat against the inner skin, the way she had done at thirty-nine, and felt the same faint hum she had felt every day of her life. "Log the visit. Inspection, no fault found. It's true in every word."

Behind them, taped to the inner skin behind the coolant run where nobody but a thermal engineer on third shift would ever have reason to put a hand, nineteen pages of pencil went on quietly not being needed, and had done for twenty-six years, and Cleo had never once taken them down.

She hummed the song on the way out. Long, long, short, short, long, a stutter, then a gap of forty-one seconds, then the whole phrase again with the stutter one beat earlier — indifferent, eleven light-years away, a clock that had been made a metronome and then a deadline and was now, at last, simply what it had always been.

A star, keeping its own time, where anyone could see it.

By year ninety-seven the great display in the Long Gallery no longer showed a distance.

It showed four things on a nine-minute cycle, and the order had been argued about in open session for two years before anyone was satisfied. First the planet, live, nineteen minutes stale, half in shadow, weather walking east. Then the phase box: TEV-9 in grey, flickering long, long, short, short, long, with the residual plotted underneath it flat as a shelf. Then the four air chemistries, four numbers from four labs that were forbidden to share instruments. And then, last, because Turi Achebe had insisted it go last where the eye rested, the tank fraction.

57.4%.

It went down. That was the thing about it. It went down by roughly a quarter of a percent a year, and it had gone down by a quarter of a percent a year for ninety-seven years, and it would go on going down whatever anybody did, because you cannot insulate a cryogenic tank perfectly and heat is the one thing that always arrives. The Ambit was a ship parked at a dead end with its fuel evaporating into the dark at a rate that a child in year nine could compute with a pencil, and nine hundred children in year nine did compute it, every year, and wrote the number on the wall themselves as Cleo Anselm had once demanded.

Fifty-seven point four. At year one hundred and thirty it would be forty-nine. At year one hundred and sixty it would be forty-one and would buy nothing at all but the slow, sensible use of a tank as ballast.

The ship called it the window. Nobody had decided to call it that; it had simply arrived in the language the way words do, and the Bureau of Verification had eventually put it in the year-nine text: the window is the interval during which the vessel retains the capacity to change its state. The window closes. This is not a policy. It is a boil-off curve.

Cleo was sixty-five that year and had a room with eleven people in it and had not reseated a bracket with her own hands in four years, which she mentioned to people more often than was strictly interesting.

Her brother's daughter came to see her about it on a Fifthday.

Noor Anselm was thirty-two and worked Fuels, which was where Ovid Reyes had sent her at fifteen with four lines of arithmetic and a white face, and she had gone into it the way people go into the thing that happened to them. She came into the Bureau room without knocking, because family, and she put a slate down on Cleo's bench and said:

"Where's the comet catalogue?"

"The what?"

"The comet catalogue. Aunt, we've been parked in a stellar system for twenty-nine years." Noor was already pacing, which she did in a room the size of a cupboard, four steps and turn. "There's a star. There's four planets. There is therefore, unless the entire physics of accretion is wrong, a population of cometary bodies out past the fourth orbit, and cometary bodies are water and ammonia and methane and — and deuterium, Cleo, deuterium at a hundred and fifty parts per million in ordinary cometary ice, and we have a working ecology and a hundred and twenty years of consumables and eleven telescopes on the forward truss, and I went to look up the survey this morning for a student, and there isn't one."

Cleo sat very still.

"There's a partial," she said. "Approach imagery. Year sixty-six through sixty-eight."

"There's four hundred hours of approach imagery that nobody has ever reduced." Noor stopped pacing. "Nobody has ever reduced it. It's sitting in the Kesh archive in raw frames. I put in a query and it came back unreduced, no analysis on file, and I sat there for a minute and I thought it was an error, and then I understood, and then I had to go and stand in the corridor."

She had gone grey around the mouth, the way her father did.

"Twenty-nine years," she said. "Nobody surveyed the system for volatiles. Nobody even catalogued it. Because for the first twelve years the answer to why are you looking out there was a thing you couldn't be told, and for the eleven years after that everybody was busy having a nervous breakdown, and after that everyone assumed it had been done in year sixty-nine by people who knew what they were doing." Noor's hands opened. "We might have been sitting on a tanker programme for thirty years. We might have been sitting on fuel."

"Or on nothing," Cleo said. "There are systems with almost no cometary population at all. It's not common but it happens."

"Then let's know."

Cleo looked at her niece for a while, and then at the slate, and then at the small window her Bureau room had onto the Ag-2 dome, which she had asked for and got and had never once admitted was sentimental.

"Yes," she said. "Let's know."

She went to see Idra Vaan in the archive, which was on Deck 8 in what had been the Directorate stores annex and was now four rooms of racking and one desk under a lamp.

Vaan was seventy-five. She had been an archivist for twenty-seven years, longer than she had been a Sub-Director, and she had never once complained about it in Cleo's hearing, and Cleo had come to understand somewhere around year ninety that this was not humility but appetite: the woman had spent twelve years being the only person who knew everything, and had then been given the job of making everything knowable, and it had turned out to be the same skill pointed the other way.

She was in a cardigan the colour of oatmeal with her reading lenses down and a stack of physical printout at her elbow, and she said, without looking up, "The comets."

"How long have you known?"

"That there was no reduction? Since year eighty-three." Vaan took the lenses off. "It's item four hundred and eleven."

"Of what?"

Vaan put both hands flat on the desk, which was a tell Cleo had learned in the first year and had never told her about.

"There's a document," she said. "I've been keeping it since the inquiry. It has a working title and the working title is Register of Consequential Omissions, which is the most cowardly phrase I have ever constructed and I constructed a great many. It is a list of things that were not done, not asked, not tried, and not looked at, between year sixty-nine and year eighty, because the fact that would have motivated them was classified." She turned her cup a quarter-circle. "It has, at last count, six hundred and nineteen entries."

Cleo sat down on the stores crate that served as a visitor's chair.

"Read me four."

"No."

"Idra."

"You'll want them and then you'll have them." Vaan looked at the ceiling, and then said, in the flat voice of a woman reciting something she had recited to herself in the dark: "Item nine. No exobiological training cohort was recruited in years seventy to eighty; the ship therefore entered the disclosure period with four qualified biologists over sixty and no one under forty who had ever handled a Kesh sample. Item forty-one. Iyabo Sarr's quarantine notebooks, containing eleven weeks of first-hand observation of the onset in nine subjects, were sealed and were read for the first time by a working scientist in year eighty-two, thirteen years after her death. Item two hundred and six. The catalysis assay at reduced temperature, proposed by Sarr herself on day fifty-one of the quarantine, was not performed, because by the time anyone was free to perform it the entire subject had become a classified matter with four people in it and three of them were administrators." A breath. "Item four hundred and eleven. No reduction of approach-phase outer-system imagery. No cometary catalogue. Reason given in the year-seventy-one work plan: no operational requirement."

The pump ran behind the wall and stopped.

"Publish it," Cleo said.

"No."

"Idra —"

"You don't understand what it is." Vaan's voice went up, which happened perhaps once every three years. "The disclosure was survivable because it was about the dead and about a decision made by people in a room with four hundred and six bodies. This is not that. This is six hundred and nineteen entries of what it cost afterward, every single one of them a door that was standing open the whole time, and the reserve is at fifty-one, which took us seventeen years to claw back from twenty-nine, and I have watched every quarter of that curve, and I am telling you as the only living person who has ever managed a population through a disclosure that this document is a weapon and I do not want to be the one who fires it at nine thousand people who have just started planting trees."

"That's the argument," Cleo said. "That's the actual argument. In twenty-seven years nobody's made it to me and I've made it to myself perhaps four thousand times."

Vaan stopped.

"Oh, you petty —"

"You had it coming for twenty-seven years." Cleo leaned forward, elbows on knees. "Listen to me. Item four hundred and eleven is going to come out in about nine weeks whatever either of us does, because Noor Anselm is going to reduce four hundred hours of approach imagery and she's going to publish whatever's in it and somebody in the Long Gallery is going to say why did nobody do this thirty years ago, and the answer is going to be found by a fifteen-year-old in an afternoon, because they're all fifteen-year-olds who can find things in an afternoon now, because we did that, deliberately, on purpose." She let that sit. "You can publish six hundred and nineteen entries as a document with your name on it and a preface explaining exactly how each one happened. Or the ship can discover them one at a time for the next forty years, each one arriving alone, each one looking like a fresh betrayal. Which of those two do you think costs more reserve?"

Vaan sat with her hands flat on the desk for a long moment.

"The second," she said. "Obviously the second. I've known that since year eighty-three."

"Then what stopped you?"

"Shame," said Idra Vaan. "Which is not a plan. Kesia told me that in a corridor and I've had twenty-seven years to improve on it and I cannot."

She published it in the ninth month of year ninety-seven, six hundred and nineteen entries, with a four-page preface that Cleo read three times and could never get through the second page of without stopping. The reserve fell four points in a quarter and was back inside two years. There were eleven weeks of ferocious, granular, extremely boring argument in the open sessions, and out of it came recommendation forty-two, which required every classified holding aboard to carry a public index line stating its existence, its class, and the name of the person who could be petitioned about it — and which was, Vaan observed drily at the time, the only piece of legislation in human history to be produced by an act of literary criticism.

Noor Anselm reduced the approach imagery in fourteen months with eleven volunteers and a borrowed cluster.

There were comets. There was a substantial cometary population, sparse and cold and ordinary, and the nearest workable concentration was a loose family of nine bodies in a low-inclination group at eight point six astronomical units, and the largest of them was four kilometres across and was, on the spectra, sixty percent water ice.

They named it Sarr. They named it Sarr, and then they spent four years discovering what it was worth, which was very nearly nothing and not quite nothing, and the difference between those two quantities became the largest argument in the ship's history.

Cleo learned the arithmetic the way she had learned everything, badly and twice, from a Fuels engineer half her age with a stylus and a wall.

"Four kilometres, sixty percent water ice by mass, call it density point six and you get eleven point five times ten to the twelve tonnes of usable volatile," Noor said. "Which sounds like the answer to everything. Now watch me take it away from you."

She took it away in nine steps. You could not move a four-kilometre body; you went to it and cut. You could not cut with anything the Ambit had; you would have to build a tug, and the only hulls aboard capable of being made into one were the two surviving survey landers, which had sat in Bay 11 under seal for thirty years because everyone who had ever touched the first three was dead. A round trip to eight point six astronomical units on a chemical-plus-ion profile was four years. Each trip could bring back nine hundred tonnes of water ice, optimistically, in fabricated tankage that would itself have to be built out of hull stock the ship could not spare and would argue about for a year. And of nine hundred tonnes of water you got, after electrolysis and eleven stages of isotope separation that would run for two years off reactor power, about twenty-six tonnes of deuterium.

"Twenty-six tonnes," Noor said. "Against a mission load of nine hundred and forty thousand. Do the division."

"Point zero zero three of a percent."

"Point zero zero two eight." Noor put the stylus down. "Per trip. Per four years."

Cleo sat back on the bench and laughed, one bark, alone in a room with her niece.

"Then it's nothing."

"That's what I said for eleven weeks. Then I did the thing you taught nine hundred children to do, which is check it again." Noor turned to the wall and drew a line, sloping gently down, and Cleo recognised her own tank curve, the quarter-percent-a-year of a cryogenic tank losing to physics. "That's the boil-off. That's the window closing. Now put four tugs on it, running continuously, staggered, forever."

She drew a second line, and the second line was almost the first line, and then it was flatter than the first line, and then, somewhere out past year one hundred and sixty, it stopped going down.

"Four tugs, eleven trips each per forty-four years, that's point one two percent a year of new deuterium against a quarter percent of loss, so it doesn't reverse anything. It halves the slope." Noor's voice had gone very flat and careful, which in an Anselm meant the opposite. "And if you build eleven tugs, which is a fifty-year fabrication programme and about a tenth of Fabrication's whole output, it goes up."

"By how much?"

"By nothing. By point zero four percent a year. By a number so small that the year-nine class will spend the rest of history arguing about whether it's real." Noor turned round. "Aunt, it doesn't get us anywhere. It doesn't buy Sol and it doesn't buy landfall and it doesn't buy any single thing that anybody alive today would call an outcome. All it does is stop the window shutting."

Cleo looked at the two lines for a long time.

"Cost," she said.

"Four percent of the tank to build and boost the first tug, spent in the first nine years, gone, irrecoverable, and no return on it until year one hundred and eleven at the earliest." Noor said it without softening, which was the house style now, everywhere, in everything, and had been for twenty years. "We spend four percent of what's left of the Ambit's ability to ever go anywhere, on a machine that will pay it back forty years after the last person who voted for it is dead. That's the proposal. That's the whole proposal. I've published it."

The argument took four years and two months, which Cleo noted privately was the interval between her two visits to TEV-9, and she never told anyone she had noticed, because at seventy she had grown suspicious of the way her mind reached for patterns.

It was conducted in the open, because everything was now, and the open turned out to be slow and ugly and repetitive and entirely worth it. There were eleven public sessions in the Long Gallery and four hundred and some in section halls and one, in the third year, in Ag-3 among the bean rows, which Cleo attended and at which an eighty-year-old woman from Recyclers said the sentence that everybody afterwards agreed had turned it.

The case against was not stupid. Cleo made herself say that out loud, at least once a month, to whoever was in the room.

The case against was: four percent is real and the return is a promise. Four percent is nine years of Fabrication's spare capacity, which is nine years of not replacing the Frame 12 stress members, nine years of no new lab space, nine years of the protein line running on the old plant. Four percent is a burn we can do today and cannot do in a hundred years. And the return is a curve drawn by a thirty-six-year-old on a wall, extrapolated over sixty years, dependent on eleven consecutive four-year missions succeeding with hardware nobody has flown in thirty years. And we have been here before, said the case against; we have been asked before to accept a sacrifice today for a landfall in the year two hundred, and we sang about it, and there were nine hundred children in the choir.

That was the argument that could not be answered and was made in nearly every session by somebody, usually somebody young, and it was correct.

"It's the same shape," said a Fabrication delegate called Ines Roque, in the fourth session, twenty-four years old and very good. "Spend now, receive later, trust the curve. That is exactly the shape of the crossing. The only difference is that this time you're showing us the working."

"That's not a small difference," Cleo said.

"No. It's an enormous difference and it isn't a disproof, engineer, and you of all people should be careful about the moment when your own project becomes the thing that everybody's proud of."

Cleo went home and lay awake and, at some point in the amber hours, wrote that sentence down in pencil and put it in the drawer with the other things she kept.

What answered it, in the end, was not an argument. It was the woman from Recyclers in Ag-3, whose name was Delphine Ouma and who had been fifty-one on Progress Day and had come to a chair on Deck 7 in the ninth night and shouted at a laundry technician for an hour and then apologised and then come back every night for a week.

She stood up among the bean rows and said: "I don't care about the curve. I want to know what we tell the year-nine class."

Somebody said that was not the question.

"It is the only question," said Delphine Ouma. "In year eighty they were taught fourteen percent and it was a lie and it broke this ship in half. Now we teach them fifty-seven point four and it's true and it goes down every year, and I have watched three of them write it on the wall, and last year the girl who wrote it stood there afterwards with the stylus in her hand and asked me what happens when it gets to nothing, and I told her the truth, which is: nothing happens, we just stop being a ship and become a house. And she said, oh." Ouma's chin came up. "So I would like to know whether we are going to be a ship that teaches its children a number that goes down forever, or a ship that teaches them a number that goes down more slowly because we did something. Because those are two different kinds of people, and we get to choose which kind we make, and it costs four percent."

Cleo Anselm, sixty-nine, sat on an upturned crate in Ag-3 with her hands on her knees and thought: that is the load-bearing sentence, and it took a recycler to find it, and it is not an engineering argument at all.

She thought: and it is still not a disproof of Ines Roque, and I will be dead before anybody knows which of them was right, and that is now simply how this ship works.

The ballot ran for eleven days in the fifth year. Turnout was ninety-four percent of adult residents, which nobody had expected, and the tug programme passed with sixty-one point four percent in favour.

Cleo read the number four times on the Bureau slate before she understood why her chest had gone tight, and then she laughed until she had to sit on the floor, and eleven people in the Bureau room stood around her with the expressions of staff who suspect their director has finally gone, and she could not explain it to any of them except Vaan, who, when told, put down her cup and said:

"Sixty-one point four. Well. Of course it was."

"You'd have engineered that if you could."

"I'd have engineered it, I'd have leaked it to Ag first, I'd have put a variable star in a children's book about it," said Idra Vaan, "and it would have been worse, and I'd have got fifty-eight percent, and I want you to know that at eighty-one I am finally certain of that and it took me a very long time."

Vaan died in year one hundred and four, in her own bed on Deck 8, at eighty-two, of a heart that had been listed as a long-term watch item for nineteen years.

Cleo was with her for the last two days, along with a Kesh Programme archivist of thirty called Fen who had been Vaan's assistant for six years and who cried openly and constantly and apologised for it, and whom Vaan liked enormously and referred to, in her last coherent hour, as "the best filing system I ever had, and I include myself."

The Register had run to eleven hundred and forty entries by then. Vaan had gone on adding to it after publication, which had been Cleo's suggestion and Vaan's private joy: a public document, indexed, revised in the open, with a line at the top that said entries invited from any resident and a footer that said this document is a confession and will not be closed while I am alive. Three hundred of the last four hundred entries had come in from other people. Nine had come in from children.

Somewhere in the second day she surfaced and was entirely herself for about eleven minutes.

"The apples," she said.

Cleo had brought one. She had brought it in her coverall pocket out of Ag-1's ordinary autumn ration, one of eleven thousand, unremarkable, slightly bruised on one shoulder because she had knelt down in a crawl on the way over out of habit, and she had not decided whether she was going to give it to her.

She put it on the blanket.

Idra Vaan looked at it for a long moment.

"It's got a bruise," she said.

"There were nine thousand in the bin. I didn't pick."

"You didn't pick." Vaan's hand came out and closed on it, and it took her some effort, and Cleo did not help her, because she had learned that in a corridor outside Paavo Lund's rooms forty years ago. "Do you know what I have wanted, Cleo? For sixty years. Not to be forgiven. I've never once wanted that and I'd have distrusted anybody who offered."

"I know."

"I wanted an ordinary apple. One with a mark on it, out of a bin, from a place that had too many." She got it up to her mouth, and she ate it, all of it, slowly, over about nine minutes, with the concentration of a woman doing sums. Then she gave the core to Fen, who took it as though it were an instrument being handed over at the end of a shift, and who kept it, and who — Cleo learned decades later — had it dried and put in the Kesh archive under an index line, class open, petitionable, described as: organic material, one apple core, I. Vaan, year 104. Retained for no operational reason.

She went under again in the evening and did not come back except once, near 0300, when Cleo was the only one awake, and she said, very clearly, into the amber dark:

"Different in direction."

"Not in kind," Cleo said.

"No." A long pause; the pump ran behind the wall and stopped. "But it's everything. I've done the geometry."

Cleo Anselm sat in the dark and understood that she had just been quoted a dead man by a dying woman who had never met him except across an inquiry table, and that this was what a culture was, and she put her head down on the edge of the bed and stayed there until the wake-shift bell.

They wrote her name on the wall on Deck 5, because that argument had been settled in year eighty-two: the wall was for everybody, in the order they went, in whatever hand was holding the stylus. She went in between a machinist of twenty-six and a child of four, and eleven hundred people came, and Mattias Anselm, seventy-two and eleven years into being a Bureau Chief that had been made out of the thing that had killed four hundred and six people, read out the four lines of the inquiry finding because nobody could think of anything better and because they were true.

Someone, later that year, put a small brass plate under the ninth row of the Ag-1 orchard, and Ag-3 had opinions about plaques, and it stayed anyway.

The Kesh Programme did not solve Kesh.

Cleo wanted that written down plainly, in the record, and she wrote it herself in the Bureau's year one hundred and ten report, because by then there was a generation aboard who had grown up with the survey feed on the Long Gallery wall and had begun, in the way of the young, to talk about landfall as a thing that was being worked on.

What the Programme found, in forty-one years, was this.

The boy from Bio — Idris Achebe-Roque, no relation to Ines, who had sent Vaan a query at sixteen about thermal gating — was partly right, which is the most that anybody was ever right about Kesh. The catalysis was gated. Below about four degrees the fold propagation rate fell by three orders of magnitude and above thirty-one it rose sharply, which was consistent with Iyabo Sarr's eleventh-week notebook observation that two of the nine had declined more slowly than the rest and that both of them had been the ones running the cold-store inventory, an observation she had recorded on day sixty-six of her quarantine in a hand that was already beginning to change.

It did not save anybody. It meant that the agent was not, as year sixty-nine had believed, an absolute; it meant it was a rate, and rates can be fought, and a fight against a rate takes instruments and cohorts and decades and a population willing to fund a programme that will produce its first useful result after most of its founders are dead.

By year one hundred and nineteen they could reverse the fold in vitro, in a solution, in nine hours, using a catalytic scaffold that took nineteen years to design and that could not be introduced into a living human being without killing them in about four minutes.

By year one hundred and thirty-one they had four candidate approaches, three of which were understood to be wrong, and a Programme of eleven hundred people, and a standing estimate — published quarterly, revised in the open, the most consulted document aboard after the tank fraction — that placed a survivable landing on Kesh-3 at somewhere between eighty and four hundred years away, with the honest note appended that the interval had been eighty to four hundred years for the last nineteen years and had not moved.

Cleo, who was eighty-nine when she read that revision, thought it was the most beautiful sentence the Ambit had ever produced, and said so, and was widely misunderstood.

The first tug flew in year one hundred and eleven and was called Ouma, over the objection of Delphine Ouma, who was ninety-six and had to be argued down by her own great-grandson.

It came back in year one hundred and fifteen with eight hundred and forty tonnes of dirty ice and a cracked secondary radiator, and Cleo Anselm, eighty, retired from the Bureau for three years and formally forbidden to enter Bay 11, stood in the observation gallery with eleven hundred other people and watched a tank of frozen water come alongside a ship that had been parked for forty-seven years, and heard the noise the crowd made, which was not applause and not a groan, and was the noise a crowd makes when a prediction is fulfilled and they had not entirely dared believe it.

The second tug flew in year one hundred and seventeen. The fourth in year one hundred and twenty-six. The seventh in year one hundred and thirty-four, three years after the tank fraction, published on the Long Gallery wall in the fourth position where the eye rested, went from 52.8 to 52.9.

It went up.

There is a frame of internal-log imagery from that day that ended up on a wall, as these things do: a year-nine class in the Long Gallery, nineteen of them, and a girl of fifteen with a stylus writing the fourth digit, and every one of the other eighteen watching her hand.

The number had gone down every year for one hundred and thirty-four years, in a ship that had spent eighty of them being lied to about it and fifty-four being told the truth about it, and it went up by one part in a thousand, and it was checkable by anybody with a radiator log and four lines of arithmetic, and Cleo was told afterwards by three separate people that the Long Gallery had been unusable for an hour because of the crowd.

She was not there. She was eighty-eight and had had a bad winter and was in the low-grav annex on Deck 2, in a chair, by one of the nineteen windows, being read the sports.

Turi Achebe died in year one hundred and twenty-nine at ninety-one, having taught the four measurements, and then the nineteen, and then the sixty-four, to something on the order of six thousand people over fifty-three years, and having twice caught the Bureau of Verification lying — once about hull stress in year one hundred and nineteen, once about its own instrument calibration in year one hundred and twenty-six, both times with a night crop crew and a duplicate set of instruments kept under a beans rota, exactly as she had written it in nine pages that Cleo had lost an argument about, publicly, in a minuted meeting, sixty years earlier.

At the second catch she had come to Cleo's quarters at 0700, at the end of Cleo's shift, because Cleo was eighty-two and still kept third-shift hours out of pure stubbornness, and she had stood in the corridor and said: "Your lot are drifting."

"They're not my lot."

"There's a room with your name on it, Cleo."

"There's a room with my name on it because a subcommittee out-argued me in year eighty-one and I have regretted it for fifty years." Cleo had leaned on the door frame, which she did now. "Come in. Show me."

Turi had shown her, and it had been nothing, and it had been exactly the sort of nothing that becomes weather: a calibration drift on the Bureau's own reference cell, known about for eleven months, unpublished because the correction was small and the paperwork was tedious and the technician responsible had genuinely intended to get to it.

"That's how it starts," Turi said. "That's literally how it starts. Not forty people in a room with four hundred bodies. One woman with a tedious form."

"Yes."

"Say it in the session. Not me. You."

So Cleo Anselm, eighty-two, had gone to the open session and said it, and it had cost the Bureau three points of public confidence in the quarterly survey and had produced recommendation two hundred and six, which required the Bureau's reference instruments to be calibrated annually by a body that was not the Bureau, and which was, everyone agreed, tedious.

At the memorial they wrote Turi's name on the wall on Deck 5 in the ordinary way, and Sefi Achebe, sixty-three, orchardist, put a single apple on the deck underneath it, and then, because she was her mother's daughter, took out a knife and cut it into eight pieces and gave one to each of the seven people standing nearest, and kept one, and did not eat it, and put it in her pocket.

Nobody asked why. Everyone in the corridor understood that some things are kept.

The vote to burn came in year one hundred and forty-one, and Cleo Anselm did not live to see it.

She lived to see the argument begin, which she said afterwards — in the annex, in a chair, to whoever would sit — was the better half anyway.

The target was TEV-4.

That was the thing that delighted her beyond all reason in the last decade of her life, and she told it to every child brought to the annex to be polite to an old woman: that the Tertiary External Verification array had been a junk catalogue, a set of objects logged for no reason except that a sensor needed something to look at, and that the ninth of them had held up a lie for twelve years and brought it down in nine weeks, and that the fourth of them was an orange dwarf four point four light-years off the Ambit's old dead vector with two candidate worlds in the band, and had sat in the manifest for a hundred and forty years being nothing, because nobody had ever needed a destination.

"Nothing on a ship is junk," she would say. "Only unwatched."

Four point four light-years. At the speed a refuelled Ambit could reach it was one hundred and nineteen years, which was to say: nobody in the room, nobody in the room's children, and possibly nobody in the room's grandchildren. It required the tank at seventy-one percent minimum to fly it with any margin at all, and the tank was at fifty-four point six in year one hundred and forty-one and rising by one part in a thousand a year, which put the earliest honest departure somewhere out past year three hundred.

Which meant that the vote in year one hundred and forty-one was not a vote to go.

It was a vote to commit — to write a destination on the wall, to point the Kesh Programme and Fabrication and the tug fleet and the year-nine curriculum at a thing a hundred and sixty years away, to spend eleven generations building a ship that could leave, in the full knowledge that the generation which could actually leave might look at Kesh-3 by then and decide to stay and fight the rate instead, and would be entitled to.

Ines Roque was one hundred and four in the year the argument began and gave evidence to the second session from a chair, and Cleo, ninety-nine, watched it on the internal from the annex with a blanket over her knees.

"I said sixty years ago that the tug programme was the same shape as the crossing," said Ines Roque. "Spend now, receive later, trust the curve. I was right about the shape and I voted against it and I was wrong, and I've had sixty years to work out why, and here it is." She had a wire-thin voice by then and the session gave her silence for it. "The crossing asked us to trust a curve we could not check. This asks us to trust a curve we check every autumn on the wall in the Long Gallery with a stylus, in front of nine hundred children, and it went up." A pause for breath. "That is not a small difference. I have said in this hall that showing the working is not a disproof, and it isn't, and I stand by it, and I want the record to show that a woman who said that for sixty years has now had the working shown to her for sixty years and has changed her mind, because that is what the working is for."

Cleo watched the whole of it and then sat for a long time with the feed off.

Fen — who was seventy-one by then, and had been Vaan's filing system, and had taken over the Kesh archive, and who came to the annex on ninth days to read the sports because that was a thing people did on this ship and nobody remembered why — asked her, that evening, whether she was going to give evidence.

"No," Cleo said.

"They'd hear you."

"That's precisely why not." She had her hand flat on the arm of the chair. "Fen. I found a flicker in a crawlspace when I was thirty-nine and I have been a load-bearing member for sixty years and it has been, on the whole, a good life and I have done four things I'm ashamed of and I did them all in the first two hundred and nine days. But there is a version of this session where an old woman is wheeled in and says a sentence and eleven thousand people vote for it because she is the one who found the star." She turned her head, slowly, at cost. "That's not checking. That's a choir. I've heard one."

She went up to Frame 44 for the last time in year one hundred and forty-two, which was to say the seventy-fourth year at Kesh, and she did not get there on her own and was not supposed to be there at all.

Bakri Anselm was fifty-nine and worked hull and thermal on third shift, which had surprised nobody, and had been the Bureau's phase instructor for eleven years, and carried her great-aunt up the spine ladder in a harness rig she had built in Halim Osei's old shop over four evenings without telling anybody, and which she filed afterwards as a fabrication test, which was true in every word.

The crawl was the same. The coolant run was warm. It smelled of hot dust and old solder, and there was a bracket at Frame 44 that had been reseated in year eighty by a woman who had been thirty-nine and had brought her slate up out of habit.

"You'll have to wedge me," Cleo said. "There's nothing left of me to wedge with."

They got her in with her shoulder against the pipe and her knees up, which took nine minutes and hurt a great deal and which she did not mention.

"Feet against that," she said. "Not the pipe. That."

"I know, Aunt. You taught me here."

"I taught you at eleven and you've had forty-eight years to get sloppy." Cleo put out her hand and Bakri put the slate into it, and the old woman's fingers were bad now and it took her three tries to open the array feed, and Bakri watched her do it three times and did not help.

The little grey waveform box opened.

TEV-9 flickered. Long, long, short, short, long. The stutter. Then the gap.

"Count it," Cleo said.

"Forty-one," said Bakri, at forty-one.

"Forty-one point zero zero." Cleo leaned her head back against the inner skin. "It has not changed since before my mother was born, and my mother was born in year forty-one, which I have never once mentioned to anybody in a hundred and three years because they'd have thought I was making it up."

Bakri laughed.

"Residual," Cleo said.

Bakri pulled it. A hundred and thirty-one years of phase residual on a junk variable, flat as a shelf, with a hair of sensor noise on it and one small step in year eighty where a thermal engineer had put a translation layer underneath an architecture built by a man who had wanted, on the whole, for somebody else to have made the decision.

"Flat," Bakri said.

"Flat." Cleo Anselm put her palm against the hull, and felt the same faint hum she had felt every day of her life, and closed her eyes. "Now. Tell me what happens."

"When?"

"When they vote it through. They will; it'll be sixty-one percent, it's always sixty-one percent, this ship has a number and doesn't know it." Her mouth moved. "Not this year. Not in mine. Say it anyway."

Bakri Anselm sat in the crawl above Frame 44 with her feet braced against a stringer and said it the way you say a thing you have said to nineteen classes:

"They'll spend a hundred and sixty years filling the tank. Then they'll argue for four years about whether to go at all, and somebody will want to stay and fight the rate, and they'll be right too, and it'll be settled in the open with a ballot and eleven hundred people will hate it. And then one night

—"

"Stop," Cleo said. "That's the Gallery version. That's the one with the singing in it. Give me the true one."

Bakri Anselm was quiet for a moment, and the coolant run ticked as it always ticked, and somewhere four decks below them the recyclers went into their loud cycle because nobody was awake to complain.

"The true one is that on the first night you see nothing," she said. "You'll feel it. That's the part nobody's ready for — a hundred and seventy years and not one person aboard has ever felt weight that wasn't spin, and there'll be about a twentieth of a gravity in the long axis and it'll come on over four hours and everybody will be sick. But the slate will show nothing. TEV-9's forty-one seconds won't move, because on the first night we'll be doing about eleven metres a second and the light-time changes by nothing you could measure with a hundred sensors."

"Good," Cleo said. "Go on."

"Eleven days in, you can start to fit a slope. Not see it — fit it. The residual comes off zero by about a hair and a half and it's inside the noise and anybody honest calls it nothing." Bakri had her chin on her knees. "A month in, it's outside the noise. Two months and it's a line. And then it just keeps going, forever, and nobody ever gets to see the flat shelf again, and that's the thing I'd want to be up here for. Not the first night. Not the tilt. The moment the shelf stops existing."

"And they'll come up here on the first night anyway."

"Of course they will," said Bakri. "It's a ritual. It's got a chair and a kettle in it somewhere, knowing this ship."

Cleo Anselm laughed until it hurt her, which at a hundred and three did not take long, and she lay against the inner skin with her eyes shut and let it pass.

"There are nineteen pages behind you," she said. "Taped to the skin behind the run. Pencil. Mine. I put them there in year eighty in case somebody came for the first copy, and I never took them down."

"I know."

Cleo opened her eyes.

"Aunt." Bakri's voice had gone careful, the way you go careful with an old woman when you are about to hand her something. "Third shift has known about those for about forty years. Everybody knows. There's a — " She stopped and started again. "Put your hand out. Not there. Left. Further."

Cleo put her hand out, along the inner skin, behind the coolant run, into a space she had reached into perhaps four hundred times in sixty years and had stopped reaching into when her shoulder went.

Paper. A great deal of paper. Sheaves of it, taped and re-taped, layered, some of it soft as cloth with age, running away from her fingers along the curve of the hull further than she could follow.

"How much?"

"I don't know. Nobody's ever counted." Bakri sounded, suddenly, about eleven. "It started with people coming up to read yours. Then somebody left their own working next to it — I think it was a laundry tech in the nineties who'd done the hull-stress the hard way and didn't trust the Bureau. Then it was everybody. Anyone who ever checked something and wanted it somewhere that wasn't a filing system. There's four generations of it up there. There's a boy's parallax homework from year one hundred and four with his mother's corrections on it. There's a whole set of Halim Osei's chair drawings. There's a note from somebody who worked the chairs in the first year and never told anyone what she heard and wrote it all out on nine pages and taped it up here in the dark instead."

"Has the Bureau catalogued it?"

"The Bureau has a standing rule about it," Bakri said. "You may come up and read anything. You may leave anything. You may not take anything down, and you may not index it. It's in the year-nine text as an example of a holding that is open and uncatalogued, and there's an argument about it every eleven years or so, and the argument always ends the same way."

"How?"

"Somebody says: it's a crawlspace, and nine hundred children a year know exactly where it is, and if you can find it and read it then it isn't hidden, and if you make it a document somebody will eventually have to be in charge of it." Bakri shrugged in the dark. "Ag-3 has opinions about plaques."

Cleo Anselm lay with her hand in a hundred and sixty years of other people's arithmetic and found that she could not speak for some time, and that this was fine, because the coolant run ticked and the slate glowed grey and TEV-9 went on flickering long, long, short, short, long into a box that nobody needed to be told how to read.

"Log the visit," she said at last.

Bakri took the slate. "What am I logging?"

"Inspection, no fault found."

"There isn't an inspection, Aunt. There's an old woman and a fabrication test I filed a lie about."

"Then log the fabrication test as a fabrication test, and log the inspection as an inspection," Cleo said, "because I looked at a bracket I reseated a hundred and twenty-two years ago and it's fine, and I looked at a residual and it's flat, and I looked at a wall of paper I didn't know existed and there's no fault in any of it. It's true in every word."

She died in year one hundred and forty-three, at a hundred and four, in the low-grav annex on Deck 2, in a chair, at 0250 on a Fourthday.

Not at 0217. She would have liked 0217 and she did not get it, and Bakri, who was with her, spent a while afterwards being irrationally annoyed about it on her behalf.

The last coherent thing she said was not about the star. It was about a filter in Ag-3, which had been off her rota for thirty-one years and which she was worried had not been done, and Bakri said, "It's done, I did it," which was a lie and the only one she ever told her, and Cleo said, "Good. It's on the list," and went to sleep.

There were nineteen windows in the annex by then. She was by the fourth one, which looked out along the spine at nothing in particular: a great deal of dark, and stars, and off to one side, if you had the geometry, a dim thing nineteen degrees off a vector that had not meant anything for seventy-five years.

They wrote her name on the wall on Deck 5, in the ordinary way, in whatever hand was holding the stylus, which turned out to be a machinist's apprentice of seventeen who had been passing and was handed it and who wrote C. ANSELM between a hydroponics technician of forty-one and a stillborn child with one name, and who was, she told an interviewer sixty years later, sick with fright the whole time and got the S slightly wrong.

Fourteen hundred people came. Sefi Achebe was seventy-seven and could not stand for long, and had a chair brought, one of Halim Osei's with the arms on it, of which there were still a hundred and forty in service, and she cut an apple into eight pieces on her knee and gave one to each of the seven people standing nearest and kept the last, and put it in her pocket, and nobody asked.

The Bureau of Verification declined to hold a ceremony. There were four separate proposals to rename it the Anselm Bureau and all four were voted down in open session, twice by very large margins, and on the fourth occasion a Fabrication delegate read out the minute of a meeting from year one hundred and twenty-nine in which Cleo Anselm had said, on the record, that a room with a name on it is a room that has stopped being audited, and that if anybody ever put her name on the door she would come back and take it off with a wrench, and that she had thermal access and knew exactly which cabinet.

They put her name on the year-nine text instead, on page four, at the bottom, in the six-point line where the derivation of a method is credited, next to Sarr and next to a laundry technician from year ninety-one, and that stayed.

The vote came fourteen months later.

It ran for eleven days, as ballots did. The question was two sentences long and had been argued into that shape over four years and two months:

Shall the Ambit adopt TEV-4 as its declared destination, and direct its fabrication, propulsion, and educational programmes toward departure at a tank fraction of not less than seventy-one percent, on the understanding that the generation which becomes able to depart is not bound by this vote and may resolve to remain?

Shall the Kesh Programme continue at not less than its present establishment, irrespective of the foregoing?

You voted yes or no to each, separately, and eleven thousand nine hundred people did.

Two things happened in the eleven days that were afterwards taught, and both of them were about a number.

The first was that somebody found the pencil.

Cleo Anselm had left one small effect that was not disposed of by rota, and it was a drawer: a shallow steel drawer out of a service bench, taped shut, marked THINGS I KEEP — C.A. — NOT LOAD-BEARING, which the Bureau opened four months after her death because the estate procedure required a holding index line.

There were forty-one items in it. Nine were bolts. One was a dried apple core in a twist of paper, which caused an archivist of thirty to have to leave the room and which was, when Fen's successor cross-indexed it, the second such object in the Kesh archive. One was an eighth of a printed sheet with a young engineer's handwriting on it: It's the same shape. The only difference is that this time you're showing us the working — I. Roque, yr 93. And one was a scrap of pencil in Cleo's own hand, undated, in the shaky letters of her last decade:

They will vote it through and it will be sixty-one percent. It is always sixty-one percent. This ship has a number and does not know it. I have watched four ballots and three of them came in between sixty-one and sixty-two and nobody has ever mentioned it and I have decided that I am not going to be the one, because I do not know what saying it out loud would do and that is exactly the reason people give.

The Bureau put it in front of an open session eleven days before the ballot opened and asked what to do with it.

It took nine hours. A statistician of twenty-six argued, correctly and at length, that publishing an observed anchor of that kind during a live ballot could not fail to bias it; that a voter who reads it is always sixty-one percent is a voter who has been handed an expectation; that they would be, in effect, running an experiment on eleven thousand nine hundred people without consent, and that the honest course was to seal it until after the count.

A recycler of eighty answered her. Nobody remembered her name for certain afterwards, which the record notes with some embarrassment.

"Sealed until after," she said. "Right. Who holds it?"

"The Bureau holds it."

"So eleven people know a thing about how this ship decides, and eleven thousand nine hundred don't, for eleven days, for our own good." The old woman let that sit. "I was nine years old on Progress Day. My mother held my hand in the fourth row. You publish it tonight."

They published it that night, with the statistician's objection attached in full at her own insistence, and a note in Bureau plain language explaining what an anchor was and how a person might guard against being one.

The second thing that happened was that it did not work.

Turnout was ninety-six percent. The first question passed with sixty-eight point two percent in favour. The second passed with ninety-one point four.

Bakri Anselm was sixty-one and read the number in the Bureau room at 0400 on the twelfth day, off the same slate her great-aunt had once used to run a bad phase fit in forty seconds, and she laughed out loud, one bark, alone.

Sixty-eight point two. Not sixty-one. Seven points clear of the ship's superstition about itself, in the first ballot ever held in which the superstition had been written down and handed out.

"She'd have been furious," Bakri told the session, when they asked her to say something, which she had not wanted. "I want to be clear that she would have been delighted and that the delight would have come second, at least a day later. She was wrong about the number for a hundred years and the reason she was wrong is that she published it. That's — " and here, in the record, there is a pause of some seconds — "that's the whole of it, isn't it. That's the entire hundred and forty-three years. You cannot check a thing without changing it and you must check it anyway."

TEV-4 went on the wall in the Long Gallery in the fifth position, after the tank fraction, in a new box that showed a dim orange dot at four point four light-years and, under it, in figures a child could check, the distance and the rate of change of the distance.

The rate of change of the distance read 0.000.

It read 0.000 for one hundred and sixty-one years.

That is the part of the story that cannot be told at the speed of a life, and the Ambit solved the problem the way it solved everything after year eighty, which was to hand it to the year-nine class.

The tank fraction went up by one part in a thousand, and then two, and then — when the eleventh tug flew in year one hundred and ninety-four and the fabrication programme finally caught the boil-off and passed it — by four parts in a thousand, and then by six. It was written on the wall every autumn by a fifteen-year-old with a stylus while eighteen others watched her hand, and the ship kept the frames of it, and there is a sequence of two hundred and eleven such frames in the archive, class open, and in it you can watch the number rise and the hands change and the handwriting go from careful to confident to careful again in the years when things went badly.

Things went badly four times.

In year one hundred and sixty-six a bearing failure in the third tug killed nine people at eight point six astronomical units, and their names went on the wall on Deck 5, and the programme stopped for four years while eleven thousand people argued about whether they had just reinvented the crossing — spend the living for a landfall nobody will see — and the vote to resume was fifty-one point eight percent, the narrowest in the ship's history, and it is taught as the year the Ambit nearly stopped.

In year one hundred and eighty-nine the Kesh Programme's fourth candidate approach failed in a way that closed the other three, and the published interval to a survivable landing went from eighty-to-four-hundred years to no defensible estimate, and stayed there for nineteen years, and the reserve fell to thirty-nine and was clawed back at four points a decade by nothing anybody could identify except apples and chairs.

In year two hundred and four a Bureau technician was found to have concealed the failure of a reference cell for eleven months, exactly as one had in year one hundred and nineteen, and a night crop crew caught him in nine days with instruments kept under a beans rota, and Turi Achebe's nine pages were read out in open session for the fourth time in eighty years.

And in year two hundred and thirty-one Frame 12 finally went, as everyone had always known it would, and took nine compartments out of service and four hundred people out of their homes and eleven years of Fabrication's output out of the tug programme, and the tank fraction went down for six consecutive years, and a girl of fifteen wrote a lower number than the year before on the wall for the first time in a lifetime, and there is a frame of that too, and her hand is perfectly steady.

The number was 70.4 in year two hundred and ninety-nine.

It was 71.1 in year three hundred and four.

The last argument took four years, as they all did, and it was not about whether to go.

It was about what to leave.

There was no dispute by then that the Ambit would leave: the generation that could depart had been raised on a destination for a hundred and sixty years and had, in a preliminary indicative ballot, gone eighty-one percent in favour, and the small determined minority who held that the ship's business was Kesh and only Kesh had lost the technical argument in year two hundred and eighty-eight when the Programme published, with its usual flatness, that the fold-reversal problem was not soluble by any method presently conceivable within the instrument capability of this vessel and that the interval to a survivable landing was best estimated at four hundred to two thousand years, and had not moved in ninety.

You could not leave people. That had been settled early and painfully; there was nowhere to leave them, and the ship was one ship, and a colony of the willing on a world that killed in eleven weeks was not a colony but a queue.

So the question was the cairn.

They built it in Bay 11, out of a survey lander that had sat under seal for two hundred and thirty-five years and had been made into a tug and then made back, and it took nine years, and there was an argument about every single thing that went into it, and the argument was minuted and published and is four thousand pages long and is, to this day, the single most consulted holding in the archive.

They put it in a two-hundred-year orbit around Kesh-3, high and cold and stable.

Inside it went: the ledger, entire, all four hundred and six names of Bay 2 with their dates, and the nineteen from the first year after the disclosure, and every name written on the wall on Deck 5 in two hundred and forty years, in the order they went, in facsimile of the hands that wrote them. The Register of Consequential Omissions, eleven hundred and ninety-one entries, unclosed, with Idra Vaan's four-page preface and her instruction that entries were invited from any resident, which the drafting committee argued about for eleven months and left in. Iyabo Sarr's quarantine notebooks, all nine weeks of them, in facsimile, including the pages where the hand begins to change. The complete Kesh Programme record: two hundred and thirty-five years of samples, spectra, assays, failures, and the four candidate approaches with the reasons each was wrong. The two hundred and eleven frames of a number being written on a wall by children.

And, at the front, on the outermost surface where a hand would fall first, a plate with four lines on it, which had been the inquiry finding of year eighty-one and which the committee could not improve upon and did not try:

The Council of year sixty-eight faced a decision without precedent and made it badly. The Council of year sixty-nine institutionalised that decision, which was worse. No living person aboard can be punished in a manner proportionate to four hundred and six deaths and eighty years of manufactured belief, and this body declines to perform a punishment which is not proportionate and call it justice.

Under it, in smaller letters, added by amendment on the floor of the Long Gallery by a majority of nine votes:

This world is beautiful and it is closed. We could not open it. We have written down everything we tried, including the things we did not try and why. Check us.

Ag-3 had opinions about plaques. The plate went on anyway.

The first night of the burn was 0217 on a Fourthday in year three hundred and thirteen, ship-time, which was to say the two hundred and forty-fifth year at Kesh, and there was a queue at the crawl above Frame 44 that began forming eleven hours before ignition and that ran, in the end, to two hundred and six people.

Yara Amse had put her name on it four months earlier and had drawn the fourth slot, which was luck, and she had traded it away, which was not.

She was thirty-nine. She worked hull and thermal on third shift, which meant she had been awake at 0217 for eleven years and would be tonight regardless, and she had traded her fourth slot to an eighty-eight-year-old man from Recyclers who had wanted the first hour and had nothing to give her for it, and she had taken the last slot instead: 0403, when the queue was gone and the corridors were amber and everybody who had come up to see history would have gone back down to be sick in their own quarters.

Because it was going to be a twentieth of a gravity along the long axis, and it was going to come on over four hours, and the Bureau had been publishing the sickness estimate for nine years and the estimate was that eleven thousand of eleven thousand nine hundred people would vomit at least once.

Yara vomited at 0140, before ignition, out of pure anticipation, which she chose not to mention to anyone.

The burn lit at 0217 exactly, because Astro had a sense of occasion that four hundred years of institutional humility had failed to kill, and there was no noise. That was the thing nobody had been ready for, in a ship where everybody had been raised on two hundred and forty-five years of expectation: no noise, no shudder, nothing but a slow and profoundly wrong sensation in the fluid of the inner ear, as though every deck in the ship had been very slightly tilted by a person of enormous strength and infinite patience.

Things began to fall over. Not fast. A cup left on a bench at 0300 was against the bulkhead by 0700. There was a great deal of laughter in the corridors, the ugly kind, the kind that comes out of people who are frightened and delighted and have nothing to do with their hands.

Yara Amse worked her shift. There were forty-one items on her list and thirty-nine of them were the same item, which was: go and look at a bracket, because in a ship that has not accelerated in two hundred and forty-five years every single fastener in the hull is now being asked a question it has never been asked, and third shift had spent nine years drawing up the list of which questions to check first.

She found four faults. One was real: a stringer clip at Frame 31 that had been fine for three hundred and thirteen years and was now, under a twentieth of a gravity, singing at eleven hertz, and she shimmed it and logged it and put it up for a proper repair on second shift.

At 0403 she went up the spine ladder to Frame 44.

The queue was gone. There was a chair at the bottom of the ladder with a kettle on the folding table beside it and a woman from Ag-3 sitting in it, because there had been a chair at the bottom of that ladder every night of the burn's first fortnight by decision of the Bureau and the Ag section jointly, and there would be one for two hundred more nights, and the woman said, "You're the last one," and Yara said, "I'm third shift, I'm not the last one, I'm just the one who has to be here anyway," and the woman laughed and poured her a cup of the tea that nobody liked, and Yara drank it and went up.

The crawl was the same.

That is a sentence with two hundred and forty-five years in it, and Yara Amse thought about it as she wedged herself in between the inner skin and the coolant run, feet against the stringer, not the pipe — not the pipe, that — because that was the first thing anyone was taught up here and nobody could tell you any more who had taught it first.

Hot dust. Old solder. The coolant run warm against her shoulder, ticking as it warmed, and behind her, in the dark along the curve of the hull, an uncatalogued and unclassified holding of pencil and printout and a boy's parallax homework and forty-one drawings of a chair, going away out of reach further than anyone had ever followed it.

She had brought her slate. She had brought it out of habit, because she logged her work on it, and because the array feed was the first thing on her home screen the way it was on the home screen of everybody on this ship who had ever been fifteen.

She pulled the feed.

TEV-9 flickered in its little grey waveform box.

Long, long, short, short, long. The stutter. Then the gap, and Yara counted it under her breath the way eleven thousand people had once counted it in a hall four storeys under a planet, and at forty-one the phrase came round again with the stutter one beat earlier, and it was exactly, precisely, to the resolution of the sensor, the same song it had been singing since before anybody.

Nothing.

She had known there would be nothing. Everybody had known; it was in the year-nine text, on page nine, in the section on the burn, with the arithmetic worked out in four lines: on the first night the vessel's velocity will be approximately eleven metres per second. The change in light-travel time from TEV-9 over one night is therefore approximately four microseconds. The sensor's timing resolution is eleven milliseconds. You will see nothing. Go up anyway.

Go up anyway. That line had been in the text for eighty years and nobody now knew who had put it there.

Yara Amse sat in the crawl above Frame 44 with a slate showing her a flat shelf and put her palm flat against the inner skin of a ship that was, for the first time in two hundred and forty-five years, going somewhere, and felt the hum, which was the same hum, and under the hum, faint and wrong and utterly new, a direction.

She sat there for eleven minutes and did not think anything she could afterwards reconstruct.

Then she logged the visit, inspection, no fault found, which was true in every word, and went down the ladder past the chair and the kettle, and said goodnight to the woman from Ag-3, and went and cleaned a filter.

The off switch was thrown on the ninth day.

It had to be, and the fact that it had to be was itself a piece of housekeeping that eleven people had spent four years preparing and that no more than a few hundred residents ever fully understood, and it is taught now in year nine as the last act of the oldest machine aboard. It had been running for two hundred and forty-four years.

That was the plain fact of it, and the drafting committee had put the plain fact at the top of the public note, because the plain fact was the whole of the argument. Paavo Lund had built the vergers in year sixty-nine out of nine nests and a nursery and a forty-one-second heartbeat, and they had defended a lie for eleven years, and then in year eighty a thermal engineer had gone up to Frame 44 and, without touching the star, changed what the machine believed the sky to mean. And from that day the vergers had defended the truth with exactly the same diligence: waking every forty-one seconds in ten places, asking is the ship's stated position coherent with the array, and, when it was not, patiently, over eleven days, making it so.

They had caught things. That was the part nobody expected and everybody afterwards found difficult. In year one hundred and forty-two a corrupted datastore in Bay 9 had put the ship four light-hours from where it was, and the vergers had repaired it in a night and filed a fault code under a dead man's build number. In year two hundred and four, when the Bureau technician concealed his reference cell, it had been a verger's coherence flag, not the night crop crew, that had first put a mark against the file, eleven months before anybody read it.

They had also, for two hundred and forty-four years, been the only thing aboard that could not be voted on. You could petition the index line. You could read the source, because Cleo Anselm had rewritten four hundred lines of it in plain language so a fifteen-year-old could, and generations of fifteen-year-olds had. But the machine did not consult anyone. It woke, and checked, and repaired.

And on the ninth day of the burn, at the rate the Ambit was then accelerating, the ship's true position would begin to diverge from at rest at Kesh by more than the vergers' coherence tolerance.

Whereupon they would repair it.

Faithfully. Diligently. In ten places at once. Back to a flat shelf and a ship that had never moved — because that was the reference Cleo had given them, and she had given it to them precisely so that no Council could ever reverse it without doing to the truth what Lund had done to the truth, and had noted in her own commentary, in year eighty, in a line that four hundred years of schoolchildren had read and mostly skipped over:

Note that this makes the machine an obstacle to any future change of state. That is deliberate. If this ship ever moves again it should have to switch me off on purpose, in public, and say why.

There was a proposal to update the reference instead. It was a good proposal. It would have taken nine weeks, it would have kept the fault-catching, and it would have meant that the Ambit went on being audited every forty-one seconds by an incorruptible thing that no one could bribe or tire.

It lost, in open session, by four hundred and eleven votes out of nine thousand cast, and the sentence that beat it was said by a Bureau instructor of twenty-six whose name is in the minute and who never held another office in her life.

"Then who writes the new reference?" she said. "Eleven of us, in a room. And in three hundred years nobody alive will have chosen it, and it will just run, and it will become weather." She let it sit. "There is a whole book about this. It's in the crawl above Frame 44 in pencil and it's on page four of the year-nine text. We are not doing it again because it would be convenient. We're big enough to check ourselves now. We had to be taught how by a machine and by a woman with a pencil, and I'd like to be the generation that says thank you and turns it off."

They did it in the Long Gallery at 0900 on the ninth day, under the great display, which showed four things on a nine-minute cycle and had for two hundred and sixteen years.

There was no choir. There had not been a choir in the Long Gallery since year eighty, and there was a standing motion, renewed every eleven years by voice and never once opposed, that there would not be one.

Nine thousand people came anyway, which at a twentieth of a gravity meant nine thousand people arriving early and holding onto things.

Yara Amse had not wanted to do it and had been told, by a Bureau chief of seventy who had the good grace to look embarrassed, that third shift had been asked and third shift had put her name forward unanimously and that she could of course refuse, and that if she refused they would ask the second name, who was eleven years younger and would be sick with fright.

So she stood on the boards in her working coverall, because she had refused twice to be given anything else, and she put a slate down on a stand where the display could mirror it, and she said:

"My name is Yara Amse. Third shift, hull and thermal. I'm not going to make a speech, because there's a thing I have to type and I'd rather you all watched me type it than listened to me."

She opened the open maintenance archive, in front of them, on the wall, four storeys high: revision 44-C, filed year eighty, thermal timing-chain revision, by C. Anselm, staff number 8104-Anselm-C, third shift, hull and thermal. Six lines. Documented. In plain language.

Beside them, scanned, a single sheet in a very old man's very steady hand, and eleven thousand people had read it in school and read it again now.

"Everything I'm about to do is in front of you," Yara said. "It's been in front of you since year eighty. Nobody had to find this. She published it the same day she used it, under her own name and number, with the location of every nest, and she wrote in her note that she'd promised a machine with an off switch and wasn't going to be the second person to break that promise." She looked up. "I'd like somebody to read the six lines out loud while I type them, so that anybody who can't see the wall can still check me. Not from the Bureau. Somebody in year nine."

There was a pause of about eleven seconds, and then a boy of fifteen came down out of the second mezzanine with a slate and his ears scarlet, and read the six lines out in a voice that broke twice, and Yara typed them, and the second line had a semicolon in it that he read out as "semicolon," which got a laugh that the Gallery badly needed.

She stopped before the last line.

"There's one more thing," she said, "and it isn't in the procedure, and I checked with nobody, so if it's wrong it's mine. The tenth nest is in the water-quality telemetry for Bay 4. He hid it there because Bay 4 is where she was born, and he didn't know that, and it's a coincidence, and I've read four papers arguing that it isn't and they're all rubbish." She put her hand flat on the stand. "Bay 4 goes last. It's twelve seconds. That's all."

She entered the last line.

The great display did not change, because the great display read the datastore and the datastore read the world. What changed was a small grey box in the technical margin that nine thousand people had learned to read over four days of published explanation, and in it a count went from ten to nine, and then to six, and then, over about ninety seconds — because a machine that migrates does not die in order — to one.

Then, for twelve seconds, to one.

Then to nothing.

Nobody applauded. Yara had been afraid of applause and had said so, and the Bureau had published a note asking people not to, and — she thought about this for the rest of her life — nine thousand people did not.

What they did instead was that somebody at the back began counting, and the count was picked up along the mezzanines and down into the floor, and Yara Amse stood on the boards under a live picture of a world nineteen minutes stale and listened to nine thousand people count to forty-one out loud, once, together, and stop.

For two hundred and forty-four years something had woken up every forty-one seconds. It didn't, now.

The residual came off zero in the eleventh week.

Not visibly. Yara did the fit herself on a Fourthday at 0230, wedged into the crawl with the coolant run warm against her shoulder, and got a slope of one part in a very great many, with an uncertainty larger than the slope, and sat with it for a while and then wrote in her log: nothing.

Fourteen weeks: still nothing, and a slope one and a half times the noise, which is nothing.

Nineteen weeks: two and a bit times the noise, which is nothing that any honest person calls anything, and which the year-nine class that autumn was made to look at as an exercise in not fooling yourself, and which four of nineteen of them declared to be a detection and were, gently, taken through why they were wrong.

At twenty-six weeks it was outside the noise.

Yara had a full shift of work that night. She did the shift. That was the last discipline of a very long tradition and she never regretted it: forty-one items, four faults, one of them real, a shim at Frame 31 that had been holding for six months and had begun to sing again at eleven hertz. She logged it and put it up for second shift.

Then she went up the spine ladder.

There was no chair at the bottom of it any more; the chairs had come down in the second year of the burn, all forty-one of them, and gone back to Ag and Recyclers and the machine shop that had made three hundred and eighteen of them four centuries ago and still had the jig. There was nobody in the corridor. There was nobody on the ladder. It was 0217 on a Fourthday and the ship was two hundred and forty-nine days into a hundred and nineteen years.

She wedged herself in. Feet against the stringer, not the pipe.

Hot dust. Old solder. Behind her in the dark, an uncatalogued holding of pencil going away along the curve of the hull further than anyone had ever followed it, and somewhere in it, four hundred and eleven years deep, nineteen pages in a woman's handwriting that had gone on quietly not being needed for three hundred and thirty-three years.

Yara Amse pulled the array feed.

TEV-9 flickered in its little grey waveform box, long, long, short, short, long, the stutter, the gap. She counted it under her breath and it came round at forty-one, because at this distance and this speed the change was still four parts in ten million and no eye would ever see it and no ear would ever hear it and the song was the song.

Then she pulled the residual, three hundred and thirty-four years of it, and looked at the end of the shelf.

It was not flat.

It was flat for three hundred and thirty-three years and eight months, dead flat, a shelf with a hair of sensor noise on it and one small step in year eighty where a thermal engineer had put a translation layer underneath an architecture built by a man who had wanted, on the whole, for somebody else to have made the decision.

And then, at the very end, in the last two hundred and forty-nine days, it lifted. A hair. Less than a hair. A slope you could put a straightedge against and argue about, except that you could not argue about it any more, because it was four and a half times the noise now and it would be nine times the noise by midwinter and by the time the fifteen-year-olds currently in the year-nine lab had children of their own it would be a line so obvious that nobody would ever again be able to teach the phase argument by pointing at a shelf.

The shelf had stopped existing.

Yara Amse sat in the crawl above Frame 44 with her knees up and her shoulder against a warm pipe, and put her palm flat against the inner skin of a ship that was going somewhere, and felt the hum, which was the same hum it had been for four hundred and eleven years, and under it the wrongness that was not wrong any more because everyone aboard had been born into it, a direction, a slow patient hand on the long axis.

Eleven thousand nine hundred people below her, asleep, or awake and arguing about legumes, or standing at one of the nineteen windows looking at a world that was falling behind them at eleven kilometres a second and would be a bright dot in four years and nothing in a hundred.

She thought about writing it up properly. There would have to be a note; the Bureau published the residual quarterly and the autumn plot would carry it whatever she did, and four hundred people would fit it themselves within a week because four hundred people always did.

Instead she reached back along the hull, behind the coolant run, into the dark, and found the paper.

She had brought a pencil. Everybody who came up here brought a pencil; nobody could tell you when that had started either.

She wrote, on the back of a fault sheet, in the amber dark, badly, because you cannot write well wedged into a crawlspace:

Yr 313 d249, 0230. TEV-9 phase residual departs zero. Slope 4.5σ and rising. First measurable motion of this vessel in 245 years.

I checked it twice and got it wrong the first time and was happy for about nine minutes. Then I checked it again.

Anyone can check this. The array logs are open. They have always been open.

Y. Amse, third shift, hull & thermal

She taped it up with the rest, four generations deep, where a hand would find it and where nobody would ever index it, and then she took the slate and logged the visit, inspection, no fault found, which was true in every word.

She went down the ladder and out along the amber corridor toward Ag-3, where the false dawn would be coming up in the grow-lamps and the night crop crew would be arguing about something, and where there was a filter on her list.

On the way she hummed it. Long, long, short, short, long, a stutter, then a gap of forty-one seconds, then the whole phrase again with the stutter one beat earlier — a star, keeping its own time, eleven light-years behind her now and beginning, at last, very slowly, to turn its face.

The shelf was gone, and the line took some getting used to.

For three hundred and thirty-three years the phase argument had been taught by pointing at a flat thing, and every child on the Ambit had learned the same lesson in the same shape: a clock that reads the same time is not a clock. Now the residual sloped. It sloped gently up and to the right and it never stopped, and by year three hundred and forty the slope was thirty-one times the sensor noise and by year three hundred and sixty it was so gross that it had to be plotted on a compressed axis or it ran off the wall.

Which created, as the Bureau of Verification noted drily in its year-341 report, an entirely new pedagogical problem. You could no longer teach a child to be suspicious of a flat line, because no living instructor had ever seen one. You had to teach them, instead, to be suspicious of a line that was too good — of a slope so beautifully straight that nobody bothered to fit it any more, of a plot everyone glanced at and nobody checked. The autumn exercise was rewritten in year three hundred and forty-four and has not been rewritten since. It gives the year-nine class the true residual and, in one year out of every four chosen at random by a process published in advance, a residual with a fabricated correction quietly folded into it, and asks them to say which they have been given and how they know.

Roughly a third of them, every year, get it wrong. This figure is published.

The array was hearing older news, too, which delighted people out of all proportion to its usefulness. TEV-9 was eleven light-years off the beam and falling behind at four and a quarter percent of light, and so the light-travel time from it lengthened by about a fortnight every year. The song they counted at 0217 in year three hundred and forty had left the star eleven years and nine months earlier. The song they counted in year three hundred and eighty had left it thirteen years earlier. There was a whole small literature about this, most of it written by fifteen-year-olds — we are receding into the star's past at the rate of a fortnight a year — and one genuinely good paper by a laundry technician in year three hundred and fifty-two which pointed out that TEV-9 had, in all probability, changed its behaviour at some point in the last thirteen years, since subdwarfs of that class do, and that nobody aboard would find out for over a decade, and that this was the ordinary condition of every fact about the universe and always had been, and that people ought to be more relaxed about it than they were.

The tank fraction went down.

That was the other thing, and it was harder. It had gone up by one part in a thousand a year for the best part of a century, and children had written a rising number on the Long Gallery wall in the fourth position where the eye rested, and their parents had cried about it. Now the tugs were four light-years astern and the boil-off had nothing to fight it and the number fell by a quarter of a percent a year, exactly as physics required, and it fell in a ship where nobody under a hundred could remember it falling.

The Bureau published the distinction in plain language nine times in the first twenty years, and Ag-3 taught it in the beans rota, and it is still the first thing said in the autumn session before the stylus is handed over:

A number that falls because nobody looked is a different object from a number that falls because we chose. The first is weather. The second is a decision, and decisions have authors, and the authors of this one are named in the ballot record of year one hundred and forty-one and in the ballot record of year three hundred and eight, and you may read what they said.

In year three hundred and forty-one the sensor above Frame 44 failed.

It had been mounted in year sixty-nine by a woman with a pencil and had been the throat of the largest lie in human history for eleven years and the reference of its correction for two hundred and sixty-one, and it went in the ordinary way that such things go: a slow rise in dark current, a bias drift, four months of degrading data, and then a Fourthday in autumn on which it reported the sky as uniformly grey.

Yara Amse was sixty-seven and had been off the ladder for six years, and she went up anyway, wedged in for eleven minutes with two hull techs holding the harness rig from below, and when she came down she said what everybody had known she would say, which was: like for like, from the original drawings, and put the old one in the archive.

The argument took nine weeks and got surprisingly hot. There was a good case for repointing sensor nine at TEV-4 — the array was no longer load-bearing for navigation, the ship had four interferometric baselines built during the burn years that could out-resolve the whole Tertiary catalogue before breakfast, and a heritage sensor staring at a receding subdwarf for the sake of ritual was, said a Fabrication delegate of twenty-four, exactly the sort of thing this ship claimed to be against.

She was answered by a woman from Recyclers who had never spoken in session before.

"Nothing on a ship is junk," she said. "Only unwatched. That's in the year-nine text on page four and everyone quotes it and nobody thinks about what it means. It doesn't mean keep everything. It means the thing you stop looking at is the thing that gets used against you. You want to point our oldest eye at the place we're going, because that's where the interesting news is. And in ninety years' time, when there's news at TEV-4 that somebody would rather manage, the one instrument on this ship that nobody thought to check will be the one aimed at the last place we were."

They fabricated the replacement to the original drawings, including four tolerances that no longer made any sense, and Yara Amse mounted it herself over two shifts at sixty-seven years of age in defiance of three separate medical recommendations, all of which she signed.

The old sensor went into the Kesh archive under an index line, class open, petitionable, described as: silicon photodetector assembly, TEV array, position 9, mounted yr 69, replaced yr 341. Retained for no operational reason.

It is the fourth such entry. The second is an apple core.

Iyabo Roque-Amse was thirty-one in year three hundred and seventy-seven and worked survey, which by then meant sitting in a room on Deck 3 with eleven other people and reducing four hundred hours a week of interferometric data from an instrument with a baseline of nine hundred metres, most of which had been built by her grandmother's generation out of hull stock and stubbornness during the long dull middle of the crossing.

TEV-4 had resolved into a system in year three hundred and sixty-two. It had two candidates in the band and the ship, out of a rule it had made about itself after Kesh, had refused to name either of them: you did not name what you had not measured. They were four-c and four-d, and four-d was a cold volatile-rich rock with no air worth the word, and four-c was blue and white and had a moon and had, since year three hundred and seventy-one, a published atmospheric composition with oxygen and methane in a disequilibrium that no geology could hold up.

A living world. Everybody had known for six years. There had been no announcement, because there was no longer any machinery capable of making one; the spectra had gone up on the open archive in the ordinary weekly reduction with a covering note four lines long, and the Long Gallery had put four-c into the fifth position on the display where the eye rested after the tank, and the ship had spent six years looking at a dot and arguing about names it had forbidden itself to use.

In the ninth month of year three hundred and seventy-seven Iyabo Roque-Amse ran the surface reflectance reduction on eleven months of stacked frames, and got the band.

She did not understand what she was looking at for about four minutes. It was a narrow absorption feature at nine hundred and forty-one nanometres, weak, three-sigma at best, sitting in a part of the spectrum that nobody in survey cared about because nothing interesting happens there. She had seen it before. She had seen it in the year-nine text, on page nineteen, in a figure she had copied out with a pencil at fifteen because copying figures out was what you did.

The Kesh Programme had spent two hundred and thirty-five years characterising the agent that closed Kesh-3, and in year two hundred and eighty-eight, nine years before the departure vote, a working group of forty had published the mineral-organic precursor chemistry: a class of layered catalytic complexes, not alive, not replicating in any sense a biologist would accept, which formed slowly in wet silicate crust over hundreds of millions of years in the presence of an old biosphere, and which taught certain protein folds a new shape, and which had a surface reflectance signature at nine hundred and forty-one nanometres.

The figure in the year-nine text was Kesh-3's.

Iyabo Roque-Amse sat in a room on Deck 3 with the two plots on the wall and did not call anybody for nineteen minutes. Then she called her section lead, who came and looked, and then went and was sick, and then came back and said, "Check it again. Bring me your working."

That is what a section lead says. Nobody now knows who first said it.

They checked it for nine days. That was the standing interval, published, argued over for a century: nine days of internal checking on a finding of this class before publication, on the grounds that four days was too few for arithmetic and fourteen was long enough for a secret. Forty-one people worked on it. They pulled the calibration frames, they pulled the reference cell logs, they had the whole reduction repeated independently by a group in Ag-3 under a beans rota using duplicate instruments, because Turi Achebe's nine pages had been law since year eighty-four and applied to survey exactly as they applied to the Bureau.

On the ninth day they published four things.

The first was the band: three point one sigma, rising, consistent with the Kesh precursor complex at a surface concentration between one and eleven percent of Kesh-3's, and consistent also — the note said this in the same sentence, at Iyabo's insistence — with eleven other mineralogies, four of which were common and harmless.

The second was the temperature. Four-c orbited an orange dwarf at the cold edge of its band and had a mean surface temperature, from four independent methods, of four point one degrees. Kesh-3's was nineteen.

The third was the gate. Idris Achebe-Roque had proved in year one hundred and thirty-one, off a query he had sent an archivist at sixteen, that the fold propagation rate fell by three orders of magnitude below four degrees. Two of Iyabo Sarr's nine had declined more slowly than the rest and both had run the cold-store inventory, and she had written it down on day sixty-six of her quarantine in a hand that was already beginning to change, and it had sat unread for thirteen years because a fact had been retired.

The fourth was the plainest sentence the Programme ever produced, and it is on the plate in the Long Gallery now:

The world we are going to may be closed in the same way Kesh-3 is closed, and it may be cold enough that the closure is survivable, and we cannot distinguish between these at this distance. We will know at forty years out. We recommend no decision be taken before then.

Hana Merrick asked for the floor eleven days later.

She was fifty-eight and had been Chief of the Bureau of Morale for nine years, an office with no classification authority, no power to withhold, and a standing statutory obligation to publish its own reserve curves quarterly whether they were flattering or not. There had been thirty-one chiefs since Mattias Anselm and four of them had resigned rather than publish, and all four resignations were in the archive with their reasons attached, class open.

She stood at the front of the Long Gallery under a live picture of a blue and white dot, in ordinary clothes, because the whites had been abolished in the third quarter of year eighty-one and there was a standing motion about that too.

"I am here to make a recommendation that I know will be defeated," she said, "and I would like the record to show that I understood that before I opened my mouth, so that nobody afterwards has to be charitable about my intelligence."

Nine thousand people had come. They had come because the Bureau of Morale had filed the subject line four days in advance, in plain language, as required: Recommendation concerning the presentation of the four-c uncertainty.

"The reserve is at sixty-one," said Hana Merrick. "It has been at sixty-one for two quarters. It was at sixty-four before the ninth month and it has fallen three points in eleven weeks, which is the largest quarterly fall since year two hundred and thirty-one, when Frame 12 went. I published that curve on Fourthday and you have all seen it and none of you needed me to interpret it.

"Here is my recommendation. I am not asking this hall to retire a fact. I want to be precise about that because precision is the only currency I have left and I would like to spend it carefully. Every measurement in the survey publication should stand, unaltered, in the archive, in perpetuity, indexed, petitionable, and taught in year nine. I am not asking you to conceal the band. I am asking you to change what goes in the fifth position on this wall, where the eye rests, and what is said in the four-line summary that eleven thousand people read on a Fourthday instead of reading the paper. "I want the temperature first," she said. "Four point one degrees. Then the gate — three orders of magnitude, Achebe-Roque, year one thirty-one, checkable by anybody with the assay data and an afternoon. Then the band, third, with its three point one sigma and its eleven alternative mineralogies, and then the Programme's sentence entire, unedited, which I would read out at every autumn session for the next fifty-five years if you asked me to.

"Every fact. All of them. In a different order.

"That is the whole of my recommendation and I am aware of exactly what it is." She put her hands at her sides. "It is Verrat. It is the Managed Disclosure Framework with the classification stripped out and the stagecraft left in, and it is what I was trained to do, and I have been doing it in small ways all my working life every time I chose which of two true things to put at the top of a bulletin, and so has every chief before me, and so has every one of you who has ever told a frightened person the reassuring true thing first. I am asking to do it in the open, on the record, with my name on it, subject to review, for one specific quantity, for fifty-five years, because the reserve is at sixty-one and falling three points a quarter and I have read the year-seventy trace and I know what the bottom of that curve looks like from the inside."

Somebody near the front said something. Merrick did not ask them to repeat it.

"The objection is that ordering is management and management is the thing that killed four hundred and six people," she said. "I know. I have made that objection myself in this hall, twice. I will say the strongest version of it for you, because if I don't, somebody will do it worse and we will lose an hour. The objection is: whoever chooses the order is choosing what nine thousand people think about at breakfast, and there is no reading of that which is not power, and this ship spent eighty years being steered by people who were absolutely certain they were only choosing an order.

"My answer is that the order gets chosen whether we admit it or not. Something goes in the fifth position. Something goes at the top of the summary. Today it is the band, because the band is the news, and the band is the news is itself an editorial decision made by four exhausted people in survey at three in the morning on the ninth day, and nobody voted on it, and nobody has audited it, and I would like it audited." She let that sit longer than was comfortable. "That's it. That's the case. I'd rather lose it in front of you than win it quietly, and I have three hundred years of institutional evidence that I would be able to win it quietly."

The hall took nine hours over it, and then four more sessions across eleven days, and the transcript runs to two thousand pages and is on the syllabus.

The answer that beat her came on the third day from an orchardist of forty-four named Delphine Achebe, of no particular office, who had come because the Ag-1 rota had a gap and because she was Sefi's great-granddaughter and had been raised on the story of an apple cut into eight pieces on a seedling flat.

"I want to say first that the Chief is right about everything except one thing," she said, "and I want that in the minute, because in about ten years somebody is going to quote me as having called her a liar and I would like the record to be able to hit them with a chair.

"She's right that the order gets chosen. She's right that survey chose it at three in the morning and nobody audited them. She's right that the reserve is falling and she's right that she knows more about what that means than anyone in this hall. And she is right that what she is asking for is smaller than what Verrat did, by an enormous margin, and that pretending otherwise is childish.

"Here is the one thing. She said the difference between her and Verrat is that she'd do it in the open with her name on it. That is a real difference and it is not the load-bearing one." Delphine Achebe put her hand flat on the rail. "The load-bearing difference is who does the arithmetic. Verrat's ship had four people who could check and eleven thousand who couldn't, and every single thing that went wrong went through that gap. Ours has nine hundred children a year doing the boil-off inversion with a pencil and a third of them getting the autumn plot wrong and being told so.

"And what the Chief is asking us to do — kindly, honestly, with her name on it — is to decide that those nine thousand people can be trusted to check the band but cannot be trusted to look at it first. That's the sentence. Say it out loud and hear it. We trust you with the data and not with the order.

"I've thought about it for three days and I can't get it to come out any other way, and I want to be clear that I understand it may cost lives, because that's what falling reserve is, it isn't a mood, and I have read the same trace she has." She stopped, and then said, not to the hall: "Chief, when it costs them, will you publish the number?"

Hana Merrick, from the floor, said: "Yes."

"Under your own name?"

"Under my own name and with the recommendation you're about to defeat attached to it, so that anybody who wants to say she told us can have the ammunition without having to dig for it."

"Then that's the ship working," said Delphine Achebe, "and I vote no."

The recommendation was defeated by seventy-one point three percent to twenty-eight point seven, on a turnout of ninety-two percent.

The band stayed in the fifth position. The reserve went to fifty-eight in the following quarter, and to fifty-four, and bottomed at fifty-one in the third year, and Hana Merrick did not resign and did not soften a single curve, and in the fourth year she published, under her own name, a plain file: eleven names, dates, no cause, no commentary, and the defeated recommendation of year three hundred and seventy-seven attached in full as an appendix.

She took it to the wall on Deck 5 herself and held the light while other people wrote.

There is an entry in the Register of Consequential Omissions, number one thousand four hundred and nine, filed in year three hundred and eighty-two by H. Merrick, Bureau of Morale, which reads in its entirety:

I have spent five years unable to decide whether I was right, and I have concluded that this is the correct condition for a person in my office and that any successor who feels certain should be watched. The eleven are named in the file. I knew four of them. Nothing in this entry is offered as a defence.

The reserve came back to sixty-one over nineteen years, at four points a decade, by nothing anybody could identify except apples and chairs.

Iyabo Roque-Amse was forty-six in year three hundred and ninety-two, which was forty years out, and she was in the room when the interferometer resolved four-c to nine hundred and eleven pixels.

She had waited fifteen years for it and had spent nine of them building the instrument that did it, a phased extension of the old baseline out to four kilometres along the truss, fabricated in eleven segments over a decade, of which two had failed and been remade and one had killed a woman named Prisca Ouma in year three hundred and eighty-eight, and whose name was on the wall on Deck 5 and on the segment.

The band was still there.

That was the first thing, and it went up in the weekly reduction with a four-line note on the same Fourthday it was measured, because the ship had had fifteen years to decide what it would do and had decided this: no nine days. Not for this. Nine days had been a rule for findings that might be wrong, and the whole point of forty years out was that it would no longer be possible to be wrong, and a rule kept past its reason is the oldest way there is of becoming weather.

Nine hundred and eleven pixels. Surface reflectance in eleven bands. The nine-forty-one feature at nineteen sigma, mapped, continent by continent, correlated with the wet silicate crust exactly as the year-two-eighty-eight precursor chemistry required and inconsistent with all eleven of the harmless mineralogies at better than four sigma each.

Four-c was closed. It was closed in the same way Kesh-3 was closed, by the same chemistry, and there was no longer any question about it at all.

The second thing took another eleven months, and Iyabo presented it herself in the Long Gallery on a Fourthday in the autumn of year three hundred and ninety-three, to nine thousand people, in her working clothes, with a slate on a stand where the display could mirror it.

"Mean surface temperature four point one one degrees," she said. "Four independent methods, agreeing to within four hundredths. Diurnal range at the equator, one point nine. Polar minimum, minus thirty-one. Equatorial maximum — and this is the number, this is the whole number, everything else I say today is decoration around this number — equatorial maximum in the warmest month, at the warmest hour, at the surface, at sea level: nine point one degrees."

She let the hall have it.

"The gate is at four. Below four, three orders of magnitude. Between four and nineteen it climbs. Kesh-3 was nineteen and it killed four hundred and six of us in eleven weeks.

"Four-c spends most of itself under the gate. Some of it, some of the time, is over it — by five degrees, in a band around the equator, in summer. Nobody in this ship's history has ever measured a propagation rate at nine degrees, because Kesh-3 never offered us one and we could not build one in vitro that anybody trusted."

She put her hands on the stand.

"So here is the honest statement, and it is the same honest statement the Programme published in year three seventy-seven, and I would ask you to notice that fifteen years and four kilometres of interferometer have changed the numbers and not the shape.

"We are going to a living world with an ocean and air we could breathe, and it is closed by the same thing that closed Kesh, and it is cold enough that the closure might be survivable in most places for most of the year, and we will not know whether might means anything until somebody goes down.

"That's it. That's forty years out. There isn't any more, and there isn't going to be any more from four light-years, and the next real measurement anybody makes is made by a person standing on it."

Somebody in the second mezzanine — it is in the transcript, unattributed, and the Bureau has never been able to identify her, which delights everybody — called out: "Then what do we do?"

"That's not mine," said Iyabo Roque-Amse. "I measure. You decide. I've been telling year-nine classes that for eleven years and I'm not going to start being interesting now."

The decision was the deceleration.

It had to be taken at forty years out and not later, and everybody had known that for a hundred and nineteen years, because it was arithmetic and the arithmetic was on page nine of the year-nine text.

The Ambit was moving at four and a quarter percent of light. To arrive — to fall into orbit around a dim orange star and stay there — required a deceleration burn of thirty-nine years, beginning within eleven months, and consuming sixty-eight percent of the tank. Afterward the ship would be at TEV-4 with three percent of a fuel load, which bought nothing at all: no return, no departure, no second chance, nothing but the slow sensible use of a tank as ballast, exactly as it had been at Kesh for two hundred and forty-five years.

Or you flew past.

That was the other half, and it was the half nobody had properly thought about until year three hundred and seventy-seven, because for a century and a half four-c had been a hope and hopes do not require alternatives. You flew past at four and a quarter percent, spent nothing, kept the tank, looked at a blue and white world for nineteen months at close range with the best instruments any human beings had ever built, and went on — into a great deal of dark, with a hundred and eighty years of consumables and a working ecology and eleven thousand nine hundred people and, at the far end of it, four more candidates in the old junk catalogue that nobody had ever measured, the nearest nine light-years further on, two hundred and eleven years away.

Two hundred and eleven years, spent, by people who had already spent a hundred and nineteen. On the promise of a catalogue.

The argument ran four years and two months, which by then everybody knew was how long an argument ran, and there was a paper about that, and it was mostly wrong.

The case for flying past was made best by a Fuels engineer of twenty-nine called Ines Amse, who had the family habit of being right early and unbearably.

"They gave us a rule and we have kept it for three hundred and thirteen years," she said. "The generation which becomes able to depart is not bound by this vote and may resolve to remain. Read it the other way round. It cuts both ways or it doesn't cut. We are not bound by year one forty-one and we are not bound by year three-oh-eight, and I want somebody in this hall to say out loud that we are allowed to not want this.

"Four-c is closed. It is closed by the thing that killed four hundred and six of us. And what is being proposed is that we spend everything — everything, the whole tank, the entire remaining capacity of this vessel to ever change its state — to park beside it and find out whether nine degrees for three months of the year is survivable. Find out how? The way we found out at Kesh. Nine people. Sixty days. Helmets off, and everyone cheers.

"I've read Sarr's notebooks. Everybody has, they're in the annex in facsimile and the last four pages are in the year-nine text. I have read the page where her handwriting changes and I would like to know what this ship thinks it is doing walking a second cohort of nine into the same eleven weeks with a slightly better thermometer."

She was answered, on the eleventh day, by a Bureau instructor of seventy-one named Bakri Roque, who had taught the phase argument for forty years and had been named for a man who left his coat folded on a deck plate in year eighty.

"She's right that we're allowed to not want this," he said. "I want that first. Nobody in this hall gets to call her a coward and I'll say so to their face in the corridor afterwards.

"Here's what I think she's wrong about. She said: find out how? Nine people, sixty days, helmets off. That was year sixty-nine. In year sixty-nine there were four biologists who could check and eleven thousand people who couldn't, and the reason nine people took their helmets off on day sixty is that the fact that would have stopped them was in a filing system and the man who could have read it was on the sterilisation crew.

"We are not that ship. We have not been that ship since a maintenance engineer wedged herself into a crawlspace and would not put a thing down. We have three hundred and thirteen years of assay data, we have a propagation model with published error bars, we have four laboratories forbidden to share instruments, we have an eighty-year-old rule that nobody goes down until the year-nine class can derive the risk with a pencil, and we have a ship that has spent four centuries being catastrophically, boringly, magnificently unable to keep a secret.

"So the question isn't whether nine people go down and take their helmets off. Nine people don't. Nobody takes a helmet off at four-c in my lifetime or my grandchildren's. What goes down is instruments, for forty years, and then cultures, and then a sealed station at forty degrees south where it never once goes above four, and then, in about a hundred and fifty years, if the numbers hold, somebody's descendant makes a decision I do not get a vote on and should not.

"That's not landfall. I want to be very careful, because this is the sentence where a man of my age starts singing. It is not landfall. It is proximity. It is being close enough to a living world to do real science on it for a hundred and fifty years instead of looking at nine hundred and eleven pixels.

"And against that, flying past buys us two hundred and eleven years of dark and four names in a junk catalogue that nobody has measured, chosen by a sensor in year sixty-nine because it needed something to look at."

He sat down, and then stood back up, which is in the transcript with the note (delegate rose again).

"One more. She said we're spending everything. We are. And I've heard people in the corridor say that means we'd be a ship that can never go anywhere again, and I want to name that, because it's the actual fear and it isn't about four-c at all. It's about becoming Kesh again. Parked. Fifty-seven point four and falling. The window shut.

"We were parked for two hundred and forty-five years and we were not nothing. We built four kilometres of interferometer and eleven tugs and a curriculum, and we found the gate, and we caught our own Bureau lying twice, and we planted four hundred and six trees and then nine thousand. The window was shut the whole time. What was open was the arithmetic."

The ballot ran eleven days. Turnout was ninety-seven percent, the highest ever recorded aboard.

The vote to decelerate passed with fifty-four point one percent.

Not sixty-one. Nobody expected sixty-one any more; the superstition had died in year one hundred and forty-two along with the woman who had been wrong about it, and the year-nine text used it as its worked example of an anchor destroyed by publication.

Fifty-four point one. Four and a half thousand people had voted to fly past, and their reasons were in the record under their own names, and the drafting committee — over eleven objections, all published — put the minority statement on the same plate as the majority one, in the same size letters, in the Long Gallery, where it is now.

Yara Amse died in year three hundred and ninety-six at eighty-two, four months before the deceleration burn lit, and did not see it, and had said in the annex to anyone who would sit that she did not mind, on the grounds that she had already seen the good one.

"Everybody thinks the burn is the thing," she said. "The burn is four hours of being sick. The thing was twenty-six weeks later, on a Fourthday, at half past two, when the shelf stopped existing." She had a bad hand by then and could not hold a cup. "Nobody was there. That's the part I'd want written down. There was no chair at the bottom of the ladder and there was nobody in the corridor and it was on my list anyway."

They wrote her name on the wall on Deck 5, in the ordinary way, in whatever hand was holding the stylus, which turned out to be a hull tech of nineteen who got the Y slightly wrong and was sick with fright.

The deceleration lit at 0217 on a Fourthday in year three hundred and ninety-seven, because Astro had a sense of occasion that five hundred years of institutional humility had entirely failed to kill, and eleven thousand nine hundred people fell over slowly in the other direction and were sick, and the corridors filled with the ugly frightened laughter, and there was a queue at the crawl above Frame 44 that ran to three hundred and forty-one people, and a chair at the bottom of the ladder with a kettle on the folding table, and a woman from Ag-3 in it.

Delphine Roque-Amse drew the last slot, 0409, because she had traded her fourth away to a man of ninety-one from Recyclers who had wanted the first hour and had nothing to give her for it.

She was thirty-nine. She worked hull and thermal on third shift, which meant she was awake at 0217 anyway.

She had four faults on her list that night and one of them was real: a stringer clip at Frame 31 that had been shimmed in year three hundred and thirteen by a woman whose name was on the log and on the wall on Deck 5, and which was singing again at eleven hertz because a twentieth of a gravity in the other direction is not the same question, and she shimmed it and logged it and put it up for second shift.

Then she went up the ladder.

The queue was gone. The woman from Ag-3 poured her a cup of the tea that nobody liked and said, "You're the last one," and Delphine said, "I'm third shift, I'm not the last one, I'm just the one who has to be here anyway," and neither of them knew they were quoting anybody.

The crawl was the same.

Hot dust. Old solder. The coolant run warm against her shoulder, ticking as it warmed. Feet against the stringer — not the pipe, that — and nobody could tell you who had taught it first.

She pulled the array feed out of habit, because it was the first thing on her home screen the way it was on the home screen of everyone on the ship who had ever been fifteen.

TEV-9 flickered in its little grey waveform box, long, long, short, short, long, the stutter, the gap. Eighty-four years astern and falling behind at four and a quarter percent of light, its light nineteen years old and getting older by a fortnight a year, a small dim junk star that had once been a metronome and a deadline and was now simply the oldest thing anybody looked at.

She counted it under her breath and it came round at forty-one.

Then she pulled the residual: four hundred and seventeen years of it, flat as a shelf for three hundred and thirty-three, and then the long slow beautiful line that no living person had ever seen bend.

At the very end of it, in the last one hundred and eleven minutes, there was nothing. There would be nothing for eleven weeks. The ship was doing four and a quarter percent of light and shedding it by about eleven metres a second per night, and the change in light-travel time from a star it was running away from was four parts in ten million, and the year-nine text said so on page nine, in four lines, with the arithmetic worked out, and at the bottom of the passage a sentence that had been there for over three centuries and that nobody could attribute:

You will see nothing. Go up anyway.

Delphine Roque-Amse sat in the crawl above Frame 44 with her knees up and put her palm flat against the inner skin of a ship that had spent four hundred and seventeen years being a lie and then a correction and then a house and then, briefly and at enormous cost, a ship again, and felt the hum, which was the same hum, and under it the slow patient hand on the long axis, pulling the other way now.

Eleven thousand nine hundred people below her. Asleep, or awake and arguing about legumes, or standing at one of the nineteen windows looking at a dim orange star that would be a sun in thirty-nine years, or sitting on a deck plate somewhere being quietly and privately terrified of a chemistry that a woman named Sarr had first written down in a hand that was already beginning to change.

She reached back along the hull, behind the coolant run, into the dark, and found the paper.

Sheaves of it. Taped and re-taped, layered, some of it soft as cloth, running away along the curve of the hull further than anyone had ever followed. Six hundred years of other people's arithmetic. A boy's parallax homework with his mother's corrections on it. Forty-one drawings of a chair. Nine pages written by somebody who had worked the chairs in the first year and never told anyone what she heard. Nineteen pages in pencil, four hundred and seventeen years deep, that had gone on quietly not being needed since before anyone's grandmother.

Everybody brought a pencil. Nobody could tell you when that had started.

She wrote, on the back of a fault sheet, badly, because you cannot write well wedged into a crawlspace:

Yr 397 d1, 0409. Decel burn lit 0217. TEV-9 residual: no measurable change, as expected, four parts in ten million, see yr-9 text p9.

Nothing to report. Came up anyway.

Frame 31 clip singing at 11 Hz again under the new load. Shimmed. Somebody check it in a hundred years.

Anyone can check any of this. The array logs are open. They have always been open.

D. Roque-Amse, third shift, hull & thermal

She taped it up with the rest, where a hand would find it and where nobody would ever index it, and took the slate and logged the visit — inspection, no fault found — which was true in every word.

Then she went down the ladder, past the chair and the kettle, and out along the amber corridor toward Ag-3, where the false dawn would be coming up in the grow-lamps and the night crop crew would be arguing about something, and where there was a filter on her list.

On the way she hummed it, because everybody did, because it was in a children's book from year eighty and in the year-nine text on page four and in the bones of the place: long, long, short, short, long, a stutter, then a gap of forty-one seconds, then the whole phrase again with the stutter one beat earlier.

A star, keeping its own time, a long way behind her now — indifferent, unhurried, having been made a clock and then a metronome and then a deadline and then, at last and for as long as anybody kept looking at it, simply something anyone could see.

The deceleration took thirty-nine years and it was, by universal agreement afterwards, the dullest thing that ever happened to the Ambit.

That was the point. Two hundred pages of preparation had gone into making it dull, and the preparation held: a twentieth of a gravity along the long axis, unchanged for four decades, so that every fastener in the hull was asked the same question every day for thirty-nine years and answered it, and the only real work was the shimming of clips that had never been loaded in this direction and the slow rebuild of forty-one drainage runs that had been designed in year twelve for a spin-only ship and had spent four centuries not mattering.

The Frame 31 clip was checked in year four hundred and eleven, as requested on a fault sheet taped inside the crawl above Frame 44, by a hull tech who had gone up to read the paper and had come down with a job. It was singing at eleven hertz. She replaced it.

Consumables held. The reserve sat between fifty-eight and sixty-four for the whole burn and nobody could account for it, which the Bureau of Morale published as a failure of its own discipline. Fabrication spent nine years of its output on the interferometer and eleven on the drainage and four on a laboratory quarter that had been argued about for two decades and that was, on the day it opened, the largest single volume aboard not devoted to growing something.

Four-c resolved. That was the news of the era, and it arrived a pixel at a time over four decades, and the Ambit watched a dot become a disc become a world the way you watch a face come up out of water. Continents. Then coastlines. Then, in year four hundred and twenty-nine, weather: the first cyclone anybody aboard had ever seen that was not two hundred and forty-five years astern of them, walking east across an ocean at four kilometres a second of angular sweep, and eleven thousand nine hundred people stood in the Long Gallery in a twentieth of a gravity and held onto things and watched it for nine days.

The nine-forty-one band held too. Nineteen sigma, then forty, then a number so large that the survey reductions stopped quoting it and simply mapped it, continent by continent, wet silicate crust by wet silicate crust, and the maps went up in the fifth position on the wall where the eye rested, and a generation grew up reading them the way their ancestors had read a fuel fraction: this is the number that decides us, and it goes on being the same.

They did not name it.

There was a ballot in year four hundred and thirty-one, eleven days, turnout ninety-one percent, four options on the paper, and the option that won with sixty-eight percent was the fourth one, which had been added late by amendment and which read: no name until somebody stands on it. The minority statement was printed on the same plate in the same size letters, as had been required since year three hundred and eight, and it said that a world you refuse to name is a world you have already decided to be afraid of.

Orbital insertion was completed on a Fourthday in year four hundred and thirty-six at 0217, because Astro had a sense of occasion that six hundred years of institutional humility had entirely failed to kill.

The tank read three point one percent.

That figure went onto the Long Gallery wall in the fourth position, in the ordinary way, in autumn, written by a girl of fifteen with a stylus while eighteen others watched her hand, and it is the frame everybody knows, and her hand is not steady. The window was shut. It had been shut on purpose, in the open, by a majority of fifty-four point one percent in a ballot whose entire minority argument was preserved in letters of the same size four decks below her, and the Ambit was now, for the second time in its history and for the last time, a house.

The instruments went down in year four hundred and thirty-seven.

There were forty-one of them in the first decade and none of them came back. That had been settled sixty years earlier and never seriously reopened: no material returns from the surface, ever, by any route, for any reason, under any authority. Not a sample. Not a probe. Not a filter. The landers were built to go down and stay down, and they reported by radio, and when they died they were left where they lay, and there is a map in the archive with forty-one dots on it and the dots have dates.

You could not touch it. You could only look at it from a hundred and ninety kilometres up and drop machines into it and read what they said before the cold and the salt took them.

What they said, over twenty-three years, was this.

The band was the precursor complex, and it was everywhere the crust was wet, and it was in the air as dust and in the water as suspension and in the rock as the rock. The mean surface temperature was four point one one degrees, as measured from four light-years out by four independent methods, which the survey people found more satisfying than anything else that happened in their lifetimes. The diurnal range at the equator was one point nine. The polar minimum was minus thirty-one. And the equatorial maximum, in the warmest month, at the warmest hour, at sea level, was nine point one degrees, and the gate was at four, and nobody had ever measured a propagation rate at nine because Kesh-3 had never offered one and no in vitro model had ever been trusted by more than a third of the people qualified to distrust it.

And there was a biosphere. That was the thing the year-four-hundreds argued about at dinner: not the closure, which was old news and had been old news for a hundred and fifty years, but the fact that four-c had a photosynthetic mat in its shallow seas that was purple and eleven centimetres thick and had, by the isotopic evidence, been doing the same thing for nine hundred million years without ever once inventing anything more ambitious than itself.

"It's Ag-3," said a survey technician of twenty-six, in a session, and it went into the language. It's Ag-3. A whole world of night crop crew, arguing about nothing, forever.

The rule about descent was eighty years old by then, and it was one sentence, and it had been written in year three hundred and ninety-three by a hall of nine thousand people over eleven days:

No person shall descend to the surface of four-c until the year-nine class can derive the risk of descent from published data with a pencil.

It was, everyone conceded, an absurd rule. It was also unamendable in practice, because four generations of fifteen-year-olds had been set the derivation as their autumn exercise and four generations had failed it, not out of stupidity but because the derivation could not be done: the propagation rate at nine degrees was not published, because it was not known, because knowing it required a person.

In year four hundred and sixty-one a girl of fifteen named Hana Achebe-Roque submitted a derivation which concluded, in four lines, that the risk of descent could be bounded above by the Kesh figure and below by zero, and that the interval was therefore eleven weeks to never, and that this was a correct answer and not a failure, and that the rule had been written by people who had not wanted to admit that they were asking for a human being.

Her section lead read it and said, "Check it again. Bring me your working."

She brought her working. It was published. It was argued about for four years and two months.

The station went down in year four hundred and sixty-six.

It was at forty degrees south on the western coast of the second continent, in a place where the surface temperature had not been recorded above three point four degrees in twenty-nine years of instrumental record, and it was built out of two decommissioned tugs and eleven years of Fabrication's output, and it was designed on one principle, which was that nothing that entered it would ever leave.

Eleven people went down in the first rotation. They signed a covenant that had been drafted in open session and revised nine times, and the load-bearing clause was four words long — I will not return — and beneath it, on the same page, the thing the drafting committee had insisted on over eleven objections:

The vessel makes no promise that this is worth it. You are not being sent. You are going.

They lived at four degrees. They worked in suits at four degrees. The station ran a cold-store regime that would have been recognisable to Iyabo Sarr, who had written on day sixty-six of her quarantine in year sixty-nine, in a hand that was already beginning to change, that two of the nine were declining more slowly than the rest and that both of them had been running the cold-store inventory, and whose notebooks had been sealed and read for the first time by a working scientist thirteen years later, and which were now in the annex in facsimile and on page nineteen of the year-nine text.

Nothing happened for thirteen years. Rotations came down every four years and did not go up. The station grew to forty-one people. They mapped the mat. They dated the crust. They ran the assay eleven times a day on everything, including themselves, and published the results by radio in the weekly reduction, and the Ambit read them at breakfast.

The reserve sat at sixty-four. It was the longest quiet stretch in the ship's recorded history and the Bureau of Morale published, in year four hundred and seventy-eight, a report whose first line was: we do not know why this is working and we would like to state that clearly before anybody credits us.

Iyabo Ouma was forty-one and had been a hull tech before she was a biologist.

That was in her file and it was the thing people mentioned about her, because it was unusual to come up out of third shift into the laboratory quarter and it meant she had spent nine years wedged into crawlspaces with a slate and a pencil before she had ever run an assay. She had grown up on the ladder to Frame 44. She had read the paper behind the coolant run, all of it, or as much of it as any one person had ever followed along the curve of the hull, over eleven years of night visits, and she had left four sheets of her own in it, three of them wrong.

There were nine Iyabos in her year-nine class. It was that kind of name.

She had gone down in the fourth rotation in year four hundred and seventy-four, at thirty-six, with a covenant signed in her own hand and one personal item, because the mass budget allowed one, and hers was an apple.

She ate it on day four and wrote about it in the station log, which was published in the weekly reduction like everything else, and it is the most-read page in the whole twenty-nine years of that log:

It was slightly bruised on one shoulder. There were nine thousand in the bin and I did not pick. I have eaten it in a room at four degrees on a world with an ocean, and it tasted like a place with weather, which is a joke I am not going to explain because everybody aboard already knows it.

I have buried the core outside the west lock in a place where it will never come to anything. That is the most human thing I have done all week.

The breach was on day one thousand six hundred and eleven of her rotation, in the eleventh month of year four hundred and seventy-nine, during a storm.

There was nothing interesting about it. That was in her own later account and in the four independent reviews and in the finding: nothing interesting. A shoulder seal on a suit that had done nine hundred and forty cycles and was rated for eleven hundred, a fold in the inner membrane that the pre-check protocol had been checking for since year four hundred and sixty-six and that the pre-check protocol had checked for on that morning and had passed, and a pressure differential of four kilopascals in a wind that stood the west coast of the second continent on its end for nineteen hours.

She was outside for four hours and eleven minutes, recovering a mat corer that had walked off its anchor. She came in, cycled, showered, ate, slept, and worked the following day, and the assay found it on the routine at 0217 on the second morning: nine-forty-one complex on the interior surface of the suit's left shoulder, on the liner, on her skin, in the swab from her sinus, at a concentration four orders of magnitude above the station's action threshold.

She was, by the standing definition that had been written in a hall four light-years away eighty-six years before she was born, exposed and contaminated and irrecoverable.

Iyabo Ouma read the assay herself, because she was the one on the night rota, and she sat with it for eleven minutes, and then she woke the station lead, and then she did the thing that made the rest of it possible.

She went and got a pencil.

The first notebook page went up on the Ambit in the ordinary weekly reduction, because there was no other channel and had not been one for four hundred years. It went up eleven hours after the assay, in facsimile, in her own hand, unedited, under a four-line covering note from the station lead, and it said:

Day 1. I am exposed. Four hours eleven minutes, shoulder seal, storm, my own suit, my own pre-check, no fault attributable to any other person and I would like that in the record before the reviews start.

Ambient temperature at the working face for the whole exposure: two point nine to three point four degrees. Body core throughout: thirty-six point nine.

Which is the entire problem, and everybody reading this already knows it, so I will say it plainly and then stop. The gate is at four degrees ambient. I am not ambient. I am thirty-seven degrees inside and I have been for forty-one years, and the propagation rate at thirty-seven has been measured exactly once, in year sixty-nine, in nine people, and the answer was eleven weeks.

So: eleven weeks. That is the honest expectation and I have written it down on day one so that nobody has to be brave about it later.

I am going to keep this by hand and I would like it published every night, entire, without editing, including the days when I am wrong and the days when I am frightened, and I have asked the station lead to send it whether or not I ask him to on the day.

The reason is not courage. The reason is that in year sixty-nine there were nine people in a quarantine writing down exactly what I am about to write down, and one of them was called Iyabo, and her notebooks were sealed for thirteen years, and by the time anybody read the page where she got it right, three of the four people who could have used it were dead and the fourth was an administrator.

I am not going to be that. Publish it nightly. That's all I want.

I. Ouma

The Chief of the Bureau of Morale asked for the floor on the fourth day.

Her name was Ines Merrick-Ouma and she was fifty-two and no relation, which she had to say aloud twice in the first minute because nine thousand people in the Long Gallery had arrived at the same wrong conclusion.

"I am going to make a recommendation that I know will be defeated," she said, "and I want the record to show I understood that before I opened my mouth, because a hundred and two years ago a woman in this office said that sentence and lost, and she was right to say it and right to lose, and I have read her Register entry perhaps four hundred times."

She had filed the subject line four days in advance in plain language, as required. Recommendation concerning the publication interval of the Ouma notebooks.

"The reserve is at sixty-four. It has been at sixty-four for eleven quarters and it is the longest quiet stretch in the ship's recorded history and I did not cause it and I have published that.

"Here is my recommendation. Every page stands. Nothing is retired, nothing is edited, nothing is withheld, no word of hers is ever touched by any hand in my Bureau or any other. I am asking for a delay of nine days.

"Nine days. The same nine days survey has used for four centuries on findings of consequence: long enough for arithmetic, short enough that it cannot become a secret. Her page of day one goes up on day ten. Her page of day two goes up on day eleven. The ship reads every word she writes, in her own hand, in order, complete, nine days behind her.

"The case for it is one sentence. If she declines in the way the year-sixty-nine cohort declined, then somewhere between day sixty and day eighty this ship is going to read, at breakfast, on a Fourthday, in facsimile, a page on which the handwriting begins to change. And it will read it at the same hour that it is happening, live, with the woman still on the radio, and eleven thousand nine hundred people will be inside that with her in real time for however many weeks it takes.

"I have the year-seventy trace. I have the year-eighty-one trace. I have the eleven names of year three hundred and eighty-two with my predecessor's own name on the file. Nine days is not concealment. Nine days is a hand on the back of somebody's neck while they read."

Somebody near the front said something. She did not ask them to repeat it.

"The objection is that she asked," said Ines Merrick-Ouma. "I know. She asked in writing on day one and she gave her reason and her reason is the best reason anybody has ever given for anything on this ship, and I am asking you to overrule a dying woman about the timing of her own notebooks, and I would like everybody to be completely clear that that is what I am asking. I would rather lose it in front of you than win it quietly, and I have six hundred years of institutional evidence that I could win it quietly."

The hall took nine hours over it and then four more sessions across eleven days, and the transcript is on the syllabus, and the answer that beat her came on the second day from a machinist of thirty-four who had never spoken in session before and never did again.

"Nine days is the right length for a finding," he said. "It's the wrong length for a person. Survey uses nine days because a finding can be wrong and can be checked and doesn't mind waiting. She minds. She's writing it to us — she says so, that's the whole of day one, she's writing it to the people who are going to have to use it, and if we take the nine days then for nine days she is writing into a room she has been told is empty.

"And there's the other thing, and I'll say it badly because I'm not a speaker. In year sixty-nine the ship found out about a quarantine thirteen years late and it made four hundred and six people into a lie. In year eighty a maintenance engineer wouldn't put down a thing she found and it cost this ship nineteen dead in the first year and the Chief's predecessor published every one of them. We have never once, in six hundred years, been made stronger by a delay. Not once. It's not in the record. I've looked, and so has everybody, and if it were there the Chief would have cited it, and she didn't, because she's honest.

"So. She asked. It's her handwriting. Send it nightly."

Someone from the fourth row of the public gallery, unattributed in the transcript, said: "It's year sixty-nine again with better manners."

The machinist said: "Different in direction."

The recommendation was defeated by seventy-nine point one percent to twenty point nine, on a turnout of ninety-four percent.

Ines Merrick-Ouma did not resign, and published her quarterlies unsoftened, and filed Register entry one thousand five hundred and eleven, which reads in its entirety:

I was overruled and I believe the hall was right and I would make the same recommendation again, and any successor of mine who cannot hold both of those should be watched. The pages are hers. Nothing in this entry is offered as a defence.

The pages came up nightly for eleven weeks.

Nobody who was aboard for it ever managed to describe it properly afterwards, and there are two hundred and eleven recorded attempts. What they agree on is the shape of the day: the reduction went out at 0400 ship-time, which was third shift, which meant that for seventy-seven consecutive nights the first people on the Ambit to read Iyabo Ouma's handwriting were hull techs and recyclers and night crop crew, standing in amber corridors with a slate in one hand, and that by the wake-shift bell it had gone everywhere, and that the Long Gallery had four hundred people in it every morning at 0600 for eleven weeks, reading a wall.

She wrote about the assay. She wrote about the mat. She ran, in the first fortnight, the entire cold-store protocol on herself, ambient four degrees, eleven hours a day, on the reasoning that if the gate was a rate and not a wall then a human being who spent two-thirds of her life at four degrees ambient was a different measurement from a human being who did not, and she published the protocol and the four objections to it that came up from the ship, and adopted three of them.

She wrote about being frightened. That was in the covenant of the thing she had set herself and she kept it. Day 19. Bad. Nothing in the assay, nothing in the neuro, no change in anything measurable, and I sat in the west lock for two hours this morning because it is the only place in this station with a window at eye height and I could not make myself go and work. I am writing that down because I said I would write down the days when I was frightened and I have noticed that I have been about to not.

She wrote, on day forty-one, four lines that went into the year-nine text within the decade:

Everybody keeps asking me on the radio what it's like to know. It isn't like knowing. It's like third shift. You get up, and there's a list, and one item on the list is enormous and forty are filters, and you do the filters.

Day sixty came and went, which was the day the year-sixty-nine cohort had taken off their helmets and everyone had cheered.

She did not mention it. She wrote about a corer.

Day seventy-seven came, which was eleven weeks, and the assay was unchanged and the neuro was unchanged and the four independent panels on the Ambit, forbidden to share instruments, said the same thing in four different vocabularies, which was: nothing.

The Long Gallery had eleven hundred people in it at 0400 that night and there is no recording of any noise at all.

Her page said:

Day 77. Eleven weeks. Nothing.

I want to be extremely careful here and I want everybody reading this to be careful with me, because this is the exact hour in which a ship gets itself killed.

Nothing at eleven weeks does not mean I am clear. It does not mean the world is open. It does not mean the gate holds at thirty-seven degrees core. It means that the year-sixty-nine figure of eleven weeks, obtained from nine people who had been ambient at nineteen degrees for sixty days with their helmets off, does not describe me, and I could have told you that on day one, and I did.

What it means is that the rate is lower. Not zero. Lower. And a rate that is lower than eleven weeks has a number, and I am the only instrument in the universe that can read it, and I am going to be reading it for a long time.

Do not cheer. I have read what happened the last time anybody cheered.

I. Ouma

The first sign came on day one hundred and thirty-three.

It was in the neuro, not the assay: a fine tremor in the left hand, four hertz, present on sustained load and absent at rest, which she found herself and logged herself at 0217 on a Fourthday because she was on the night rota and had been since the breach at her own insistence.

She wrote the page in her right hand and noted that she had.

Over the following nineteen weeks it became what everybody had been waiting nineteen weeks for, and it became it very, very slowly. The four panels fitted the curve eleven times over four years and their published figure — with error bars, revised quarterly, argued about in every autumn session for the rest of the century — was that the fold propagation in a human being maintained at four degrees ambient with a thirty-seven degree core ran at between eight hundred and four thousand times slower than the year-sixty-nine cohort.

Three orders of magnitude. Idris Achebe-Roque had put that number on the wall in year one hundred and thirty-one off a query he had sent an archivist at sixteen, and had been dead for three hundred and forty-eight years, and his name is on page nineteen next to Sarr's.

What it meant in the only currency anybody cared about was this: eleven weeks became something on the order of thirty years.

Iyabo Ouma was forty-two when the tremor started. The panels' median estimate for the onset of significant cognitive involvement was her early seventies, and their published interval ran from fifty-eight to never, and the word never was in it because the fit permitted it and the Ambit had a four-hundred-year-old habit of putting things in the interval that the fit permitted.

She published her statement in the weekly reduction on the fourth anniversary of the breach, in her own hand, four pages, and the load-bearing part is the second page:

So here is what I am, and I would rather say it than have four panels say it about me.

I am not proof that four-c is open. I am one exposure, one seal, one storm, one body, four hours eleven minutes, at three degrees ambient, in a woman who was forty-one and healthy and had spent nine years in crawlspaces and had good lungs. I am n equals one. And n equals one is not nothing. It is the difference between an interval that runs eleven weeks to never and an interval that runs thirty years to never, and I have spent four years being the instrument that narrowed it, and I would like the year-nine class to notice that the narrowing came from an accident and a pencil and not from anything anybody planned.

What I would ask of the ship — and I have no standing to ask anything and I know it — is that nobody uses me as a permission. I am a rate, not a door. If anybody stands up in the Long Gallery and says Ouma proves it can be done, I would like somebody in Ag-3 to stand up and say Ouma says she is n equals one, because I will not be there to say it myself, and in about thirty years I may not be able to.

The other thing I would ask is smaller and it is the only thing I want for me. When I stop being able to write this by hand, publish the pages anyway. Publish them getting worse. I have read the four pages at the end of Sarr's notebooks that are in the year-nine text and I have read them since I was fifteen and they are the reason I am a biologist and not a hull tech, and the reason they work is that nobody tidied them.

Do not tidy me.

I. Ouma, forty-degrees-south station, day 1,464*

They did not tidy her.

She wrote by hand for nineteen more years and by dictation for six after that, and the pages came up in the weekly reduction every night of it, and there was never again a proposal to delay them. In the twenty-fourth year she began repeating herself, and the ship read the repetitions. In the twenty-sixth she wrote a page about a corer she had recovered in a storm eleven times in fourteen nights, each time as though for the first time, and the station lead published all eleven, unedited, and Ag-3 read them at four in the morning and did not say anything about it in session, ever, which was a decision nine thousand people took separately and simultaneously without a single word being minuted.

She died in year five hundred and six at sixty-eight, at forty degrees south, in a room at four degrees with a window at eye height, and she did not come up, because nothing that entered the station ever left it.

They wrote her name on the wall on Deck 5 in the ordinary way, four light-years from where her body was, in whatever hand was holding the stylus, which turned out to be a survey technician of twenty-two who got the second O slightly wrong and was sick with fright.

Somebody put an apple on the deck plate underneath. Somebody else cut it into eight pieces and gave one to each of the seven people standing nearest and kept the last and put it in her pocket, and nobody asked why, because everyone in the corridor understood that some things are kept.

The rule was satisfied in year five hundred and nineteen.

That is the flat institutional way of saying it and it is how the archive says it, and the archive is right, because what happened was not a discovery or a decision but a piece of homework.

The autumn exercise that year gave the year-nine class the whole holding: two hundred and forty-one years of Kesh assay data, four hundred and fifty years of precursor chemistry, Sarr's nine weeks, Achebe-Roque's gate, the forty-one dead landers with their dates, twenty-nine years of station log, and the four panels' fit to a woman who had been n equals one, with its error bars and its eleven revisions and the word never still sitting honestly at the far end of the interval.

And it asked, as it had asked every autumn for a hundred and twenty-six years: derive the risk of descent.

Nineteen of them derived it. All nineteen, independently, with pencils, over four weeks, and their answers agreed to within a factor of two, and the reason they agreed was not that any of them was clever but that there was finally a number to converge on: a per-person, per-decade probability of fold onset under a four-degree ambient regime, bounded above and below, checkable in an afternoon by anybody who could read a plot.

Their section lead read the first one, and said, "Check it again. Bring me your working."

She brought her working. Eighteen others brought theirs. It was published in the ordinary weekly reduction with a four-line covering note, and the note said only that the year-nine class of five hundred and nineteen had, on the standing definition of year three hundred and ninety-three, satisfied the rule, and that the Bureau of Verification offered no opinion on what should follow, that not being its function.

The argument took four years and two months.

Nobody was surprised. There was a paper about it by then, eleven papers, most of them wrong, and one good one from a laundry technician who pointed out that four years and two months was simply how long it took nine thousand people to say everything they had to say twice.

What came out of it was not a landing. It was a rota.

Four hundred people, in the first cohort, descending over nineteen years to four stations at four different latitudes, all of them at ambient four, all of them under covenant, none of them ever returning; and above them the Ambit, in a two-hundred-year orbit, with three point one percent in her tanks and eleven thousand nine hundred people and a working ecology and a hundred and eighty years of consumables, being a house.

The covenant clause stayed at four words. The line beneath it stayed too, over eleven objections, all published:

The vessel makes no promise that this is worth it. You are not being sent. You are going.

They named it in the same ballot. Turnout ninety-six percent. The rule of year four hundred and thirty-one had said no name until somebody stands on it, and somebody had stood on it for twenty-nine years and written it down by hand and then by dictation and had asked not to be tidied.

There were four hundred and eleven names on the paper and the one that won took sixty-one point four percent, and Bakri Roque, who was ninety-one and had taught the phase argument for sixty years, laughed for a very long time in the Bureau room and had to be sat down and could not explain it to anybody except the archive.

They called it Ouma.

There was a proposal for a plate. Ag-3 had opinions about plaques. The plate went on anyway, at the west lock of the forty-degrees-south station, four kilometres from a place where an apple core had been buried in ground that would never come to anything, and it has four lines on it, and the fourth is hers:

Do not use me as a permission. I am a rate, not a door.

The first descent of the rota went down at 0217 on a Fourthday in year five hundred and twenty-four, because Astro had a sense of occasion that seven hundred years of institutional humility had entirely failed to kill.

Nobody aboard felt anything. There was no burn, no tilt, no fastener in the hull asked any question it had not been asked for eighty-eight years. A lander separated, and went down, and reported, and a woman of thirty-nine put her boot on the western coast of the second continent of a world with a name, and the Long Gallery had nine thousand people in it, and there was no choir, because there had not been a choir in the Long Gallery since year eighty and there was a standing motion about it, renewed every eleven years by voice, never once opposed.

Ines Achebe-Ouma had a full shift that night. Forty-one items, four faults, one of them real: a stringer clip at Frame 31, which had been shimmed in year three hundred and thirteen and replaced in year four hundred and eleven and had begun to sing again at eleven hertz for reasons nobody would ever satisfactorily explain, because there was no load on it any more at all and there had not been for eighty-eight years.

She shimmed it and logged it and put it up for second shift.

Then she went up the spine ladder to Frame 44, at 0409, which was the slot nobody wanted, because everyone who had come up to see history had gone back down to watch the wall.

There was no chair at the bottom of the ladder. The chairs had come down in the second year of the burn, a hundred and twenty-seven years ago, all forty-one of them, and gone back to Ag and Recyclers and a machine shop that still had the jig.

The crawl was the same.

Hot dust. Old solder. The coolant run warm against her shoulder, ticking as it warmed. Feet against the stringer — not the pipe, that — and nobody could tell you who had taught it first, and everybody taught it.

She pulled the array feed, because it was the first thing on her home screen the way it was on the home screen of everyone aboard who had ever been fifteen.

TEV-9 flickered in its little grey waveform box. Long, long, short, short, long. The stutter. Then the gap.

It was two hundred and eleven years astern of her and its light was nineteen years older than the last time anybody had bothered to remark on it, and it had almost certainly changed its behaviour at some point in the last two centuries, because subdwarfs of that class do, and nobody aboard would find out for a long while yet, and a laundry technician had written a good paper in year three hundred and fifty-two about how this was the ordinary condition of every fact about the universe and always had been, and that people ought to be more relaxed about it than they were.

Ines Achebe-Ouma counted the gap under her breath and it came round at forty-one.

Then she pulled the residual, five hundred and twenty-four years of it: flat as a shelf for three hundred and thirty-three, and then the long rising line, and then, from year three hundred and ninety-seven, the long falling one, and then eighty-eight years of a new shelf, flat again, because the ship had arrived and stopped and stayed.

She sat and looked at it for a while. It was a very beautiful plot and everybody said so, and a third of the year-nine class got it wrong every autumn, and that figure was published.

She reached back along the hull, behind the coolant run, into the dark, and found the paper.

Sheaves of it, taped and re-taped, layered, soft as cloth in places, running away along the curve of the hull further than any one person had ever followed. Seven hundred years of other people's arithmetic. A boy's parallax homework with his mother's corrections on it. Forty-one drawings of a chair. Nine pages by somebody who had worked the chairs in the first year and never told anyone what she heard. Four sheets left by a hull tech who had become a biologist and gone down and not come up, three of them wrong. And somewhere in it, five hundred and twenty-four years deep, nineteen pages in pencil that had gone on quietly not being needed since before anybody's great-grandmother.

Everybody brought a pencil. Nobody could tell you when that had started.

She wrote, on the back of a fault sheet, badly, because you cannot write well wedged into a crawlspace:

Yr 524 d1, 0409. First descent of the rota, 0217. Nothing measurable from up here. Came up anyway.

TEV-9 residual flat, 88 yrs. Same song. Forty-one seconds.

Frame 31 clip singing at 11 Hz again. There is no load on it. Shimmed anyway. Somebody check it in a hundred years.

Anyone can check any of this. The array logs are open. They have always been open.

I. Achebe-Ouma, third shift, hull & thermal

She taped it up with the rest, where a hand would find it and where nobody would ever index it, and took the slate and logged the visit — inspection, no fault found — which was true in every word.

Then she went down the ladder and out along the amber corridor toward Ag-3, where the false dawn would be coming up in the grow-lamps and the night crop crew would be arguing about something, and where there was a filter on her list.

On the way she hummed it, because everybody did: long, long, short, short, long, a stutter, then a gap of forty-one seconds, then the whole phrase again with the stutter one beat earlier — a star keeping its own time, unimaginably far behind her, indifferent, unhurried, having been made a clock and then a metronome and then a deadline and then, at last and for as long as anybody kept looking at it, simply something anyone could see.

The rota was four hundred people in nineteen years and it was eleven hundred in forty, and by year five hundred and eighty it was not a rota any more, because a rota is a thing you take turns at and by then nobody was taking turns; they were going.

Four stations became nine and nine became nineteen. The word settlement arrived in the language somewhere around year five hundred and fifty and nobody decided it and nobody minuted it, in the way that the window had arrived four centuries before and third shift had arrived before anybody now living was born. There was a season in which people still said the surface and a season in which they said down there and then a season in which a hull tech on the Ambit said, in an open session, without noticing, up here, and the transcript records a silence of some seconds and then nine thousand people laughing at nothing.

They lived at four degrees. That was the whole architecture of the thing and it never changed and it is why the settlements look the way they look: low, thick-walled, half-sunk, heated to four and not one degree more, with the working faces and the sleeping rooms and the schools all at the temperature of a cold-store, and every person in them dressed for it from birth, and a hundred and eleven years of published argument about whether four point one was cautious enough and whether three point four was cautious enough and whether the whole regime was a superstition built on a woman who had been n equals one.

The Ambit held a high orbit with a four-second lag each way, and the joint sessions were conducted across it, and the four seconds turned out to be the healthiest thing that had ever happened to the Long Gallery. You could not interrupt anybody. You said your piece and then you sat in a hole in the conversation for eight seconds while your words went down and theirs came up, and a generation of speakers learned to be brief because the alternative was to be brief later and embarrassed. There is a paper about it, from a laundry technician in year five hundred and sixty-eight, and it is one of the good ones.

The population of the ship was eleven thousand nine hundred in year five hundred and twenty-four. It was nine thousand four hundred in year five hundred and sixty. It was four thousand one hundred in year six hundred.

The first child born on Ouma was born at forty degrees south in the eleventh month of year five hundred and twenty-nine, and her name was Delphine, and the argument about her ran four years and two months, which by then everybody knew was simply how long it took nine thousand people to say everything they had to say twice.

The covenant was four words long. I will not return. Every adult who had ever gone down had signed it in her own hand, and beneath it, over eleven objections all published, sat the line the drafting committee had insisted on in year five hundred and nineteen: The vessel makes no promise that this is worth it. You are not being sent. You are going.

Delphine had not signed anything. She was four kilograms and she had been born into a covenant, at four degrees, on a world whose crust was full of a chemistry that taught proteins a new shape, and she would live her whole life inside a decision taken by two people who had loved each other in a cold-store and by nine thousand people four seconds of light above her head.

The Ambit took this badly, and took it badly at length, and the strongest version of the objection was made in the second session by a Bureau instructor of thirty-one whose name is in the minute.

"We have spent six hundred years on one sentence," she said. "Anyone may check any load-bearing fact about the vessel. It is on the wall of every year-nine lab and it is the founding line of the Bureau and it was written by a woman who found a flicker in a crawlspace. And I would like somebody to explain to me how a child born at forty degrees south checks the decision that put her there. She can't. It's already happened to her. She can check every number in the holding and every one of them will confirm that she is inside a risk she never took." A pause; and then, because the lag made everybody merciless with themselves: "I am not proposing a rule. I know I'd lose. I'm asking whether we have finally found the thing we can't fix, and I'd like it written down as that and not as a policy problem."

The answer came up four seconds later and eight seconds after that, and it was from a station lead at forty degrees south called Osei Roque-Ouma, who was sixty and had gone down at twenty-nine.

"With respect," he said, "you are four hundred thousand kilometres up telling us what we may do with our bodies, and there is a version of this session that ends with the ship regulating the wombs of people who cannot come up and argue about it, and I want that possibility named early so that everyone can be frightened of it in good time."

Eight seconds.

"I take the point about the child. It's the right point and it is not new. It is the oldest point there is. Nobody on this ship or this world has ever signed the covenant that mattered. I did not consent to be born on a vessel eleven light-years from Sol with a lie in its navigation stack, and you did not consent to be born on one with a Bureau and a wall of names, and Delphine did not consent to four degrees. The question was never whether we hand our children a situation. We always do. The question is what we hand them with it."

Eight seconds.

"So here is what we propose from down here, and it is not a rule either, because we've all had enough of rules that outlive their reasons. At fifteen every child in every settlement gets the entire holding — Sarr, Achebe-Roque, the forty-one landers, Ouma's twenty-nine years, the panels' fit with the word never still in it — and does the autumn derivation with a pencil, exactly as the year-nine class does up there, and is told in plain language: this is where you are, this is what it costs, this is who decided and what they said, and you may read every word of the argument including the part where they were frightened of what you would think of them.

"And then she is fifteen, and she is on a world she cannot leave, holding a number she derived herself." He let the lag do the work. "That is not consent. There isn't any consent available. It's the only thing on offer that isn't a choir."

The Register of Consequential Omissions took its two thousand and forty-first entry that year, filed jointly, which was unusual, by a Bureau instructor on the ship and a station lead on the ground:

We can give a child everything except the choice. We have looked for eleven years for a way to say this that is not a defeat and have not found one, and we are filing it here rather than in a policy document so that it stays a wound and does not become a procedure.

The first surface-born class did the derivation in year five hundred and forty-four. There were nineteen of them. Eleven got it right, and their section lead read the first one and said, "Check it again. Bring me your working," which is what a section lead says, and nobody now knows who first said it.

The curve came in over eighty years, because a curve like that cannot be hurried and everybody had known it since the panels first published a fit to a woman who had asked not to be tidied.

What it said, when the first surface-born cohort passed forty in year five hundred and sixty-nine and again when it passed sixty in year five hundred and eighty-nine and again when the four panels — still forbidden to share instruments, still audited annually by a body that was not any of them — published the ninth revision in year six hundred and four, was this.

Living at four degrees ambient from birth did not protect you. It slowed you. The fold arrived in a human being on Ouma the way arthritis arrives, or the way the small strokes arrive: late, quietly, at a median of about seventy-one years, with a first quartile at sixty-two and a long tail into the nineties, and with something between a fifth and a quarter of people never showing it at all before something else took them.

It was not eleven weeks. It had not been eleven weeks since year four hundred and seventy-nine, when a hull tech turned biologist got a fold in her shoulder seal in a storm and wrote it down with a pencil at 0217 because she was on the night rota.

It was, in the flat phrase that the settlements adopted and never afterwards abandoned, an old age.

There were people who could not bear that and came back up. That was permitted from year five hundred and thirty-one onward, because the four-word clause had been written for a world that killed in eleven weeks and could not survive contact with a world that killed at seventy-one, and the amendment — I will not return became I will not return without quarantine, and the quarantine was nineteen years and had to be spent in a sealed volume on the truss — was carried in a joint ballot with a turnout of ninety-eight percent and a majority so large that the drafting committee published the minority statement in the same size letters and had trouble filling the space.

Four hundred and eleven people took the nineteen years across the following century. Two hundred and six of them completed it. The others died in the volume on the truss, which had windows at eye height, because that argument had been settled in the annex on Deck 2 five hundred years earlier and nobody had ever reopened it.

The Ambit was a house, and houses run down.

The consumables had a hundred and eighty years in them at year four hundred and thirty-six, and the ecology was working and had been working for six hundred years, and neither of those facts survived contact with a population that was falling by a hundred and forty people a year and taking its fabricators with it. You cannot run an ecology at a tenth of scale by running it a tenth as hard. Ag-1 lost four of its eleven rows in year five hundred and seventy-one because there were not enough hands to prune them, and the tank fraction sat at three point one and did nothing, and the drainage runs that had been rebuilt at enormous cost for a burn began to silt because they had been designed for a load that no longer existed.

The decision was taken in year six hundred and eight and it took four years and two months, and the ballot was joint, and the turnout was ninety-seven percent, and the question was two sentences long:

Shall the Ambit be maintained indefinitely in orbit as an instrument and an archive, with a standing complement of not fewer than four hundred, drawn by voluntary rotation from ship and settlement, funded as a first charge on the fabrication of both?

Shall the vessel be brought down, in stages, for material recovery?

You voted separately. The first passed with sixty-one point four percent, and Bakri Adeyemi, who was fifty-eight and had taught the phase argument for nineteen years, laughed for a very long time in the Bureau room and had to sit down and could not explain it to anybody except the archive, where the explanation is filed under an index line, class open, petitionable.

The second failed with eighty-one percent against, and the load-bearing sentence of the debate was said by an orchardist of forty-four in Ag-1 with pruning shavings in her hair.

"You want to cut it up for hull stock," she said. "Fine. It's good hull stock. Here's what it costs. There are seven hundred years of paper in a crawlspace above Frame 44 and nobody has ever counted it, and there is a wall on Deck 5 with every name anybody ever wrote on it, and there is a room where nine thousand people once watched a woman type six lines that turned off the oldest machine we ever built, and none of it is worth a single kilogram of anything.

"And I would like to point out, because somebody has to, that this ship spent eighty years being a lie and the lie worked. It worked because there was no outside. Every fact reached eleven thousand people through a system that belonged to forty of them, and it was easy, and the ease is the horror.

"Down there we have nineteen settlements and one radio net and four fabricators and a chemistry in the ground that gives us an old age at seventy-one. In four hundred years there will be a generation that has never seen this ship, and somebody in a room will have a very good reason to make something simpler than the truth. And when that happens I want there to be a thing in the sky that they can point an instrument at, that is not ours, that we did not build, that runs whether we like it or not — and I want the whole record of what we did to be up there in a place that has to be travelled to, in handwriting, uncatalogued, where a fifteen-year-old has to wedge herself into a crawlspace with a pencil to read it.

"That's not sentiment. That's an audit trail with an orbit."

Which brought them, in the way that everything on the Ambit eventually did, to the paper.

The proposals came in year six hundred and thirteen and there were nine of them and they were all reasonable. Index it. Photograph it. Print a facsimile edition for every settlement school. Laminate the oldest sheets, which were soft as cloth and going. Move it, at least, out of a working crawlspace in a hull that would be four hundred years older still before anybody thought about it again.

The standing rule was eleven words long and had been law since somewhere in the nine-hundreds of the first pages: You may read anything. You may leave anything. You may not take anything down. It had been added to once, in year one hundred and something, with and you may not index it, and the argument had come round every eleven years or so ever since and had always ended the same way, and the way it ended was that somebody stood up and said it was a crawlspace, and nine hundred children a year knew exactly where it was, and if you could find it and read it then it was not hidden, and if you made it a document then somebody would eventually have to be in charge of it.

In year six hundred and thirteen the argument did not end that way, because the ship was emptying and the objection had grown teeth. A conservator of thirty-six put it plainly in the fourth session:

"Uncatalogued is a luxury of a full ship. In a hundred years there will be four hundred people up here and none of them will be from Frame 44's watch, and the difference between uncatalogued and lost is a number of hands, and the number is falling. You are not defending openness. You are defending a ritual, and the ritual is going to eat the thing it was built to protect."

She was right, and she was answered by a hull tech of sixty-one who had been up the ladder perhaps four thousand times, and the answer became the compromise and the compromise is what stands.

"Then we do what she did," he said. "Not what we did to her. What she did.

"She published the off switch the same day she used it, under her own name and number, with the location of every nest, and she wrote that she'd promised a machine with an off switch and wasn't going to be the second person to break that promise. She didn't hide it and she didn't tidy it. She put it where anybody could reach it and made it cost something to reach.

"So: nobody indexes the crawl. Nobody photographs it. Nobody takes a sheet down, ever. And every settlement school and every ship-side lab gets a full facsimile edition of the whole of it — every page, in order of depth, in facsimile, wrong sheets and all, published in the ordinary weekly reduction over however many decades it takes — produced by fifteen-year-olds, wedged in, with a plate camera, one page at a time, as the autumn exercise, forever."

"That's four hundred years of work," said the conservator.

"It's four hundred years of reading," he said. "That's the point. You wanted it preserved. I want it read by somebody with a sore back at three in the morning. Those aren't the same and I'll take mine."

It carried by sixty-eight percent. The first facsimile page went out in the weekly reduction on a Fourthday in year six hundred and fifteen, and the four thousand three hundred and eleventh went out in year seven hundred and six, and the work is not finished, and the estimate is published quarterly and has been revised nine times and has never once been met.

Ag-3 had opinions about plaques. There is no plaque at the bottom of the ladder. There is a hook for a lamp, and a shelf that somebody put up in year six hundred and forty for pencils, and it is never empty, and nobody knows who fills it.

The last child born aboard the Ambit was born in year six hundred and ninety-one, and there was a small unpleasant fuss about it in the settlements, because the standing complement was voluntary and rotational and had been for eighty years and children were understood not to be part of the arrangement, and the mother, who was a thermal engineer of thirty-four on a nine-year rotation, told a joint session that she had read the entire debate and had a four-line statement.

"He'll go down at fifteen or he'll stay, and he'll decide, and either way he'll be the only person in two worlds who did," she said. "I'd ask everybody who has spent six hundred years being unable to give a child a choice to sit quietly for once and let one have one."

Eight seconds.

Nobody replied. It is one of four recorded instances in the transcripts of a joint session in which the lag ran out and nothing came up from the ground, and the chair, after some time, moved to the next item.

He went down at nineteen, in the end, four years late, and his name is on the wall on Deck 5 because he came back up at eighty-one and took the quarantine and did not finish it, and the hand that wrote his name was his own daughter's, and she got the second letter slightly wrong and was sick with fright.

Cleo Sarr-Achebe was fifteen and had never in her life been warm.

That was not a complaint and she had learned early not to say it out loud to anybody over sixty, because there were people in the settlement who had been born on the ship and who would go misty about corridors at twenty-one degrees and the smell of a protein line, and Cleo had heard it all and thought, privately, that a world with weather in it was worth a cold room. She had been to the equatorial coast once, at fourteen, on the survey boat, wrapped and hooded and assayed twice a day, and had stood in a wind at nine point one degrees and had understood in about four seconds why the whole architecture of her life was the way it was, and had not needed anybody to explain it, and had come home and written that down.

Cleo had become a common name in the settlements in a way that nobody had planned and nobody had prevented.

She went up in the autumn of year seven hundred and eleven with eleven others from four settlements, on the ordinary lift, for the ordinary fortnight: the phase exercise, the tank exercise on a tank that had read three point one for two hundred and seventy-five years, four days in the archive, and one shift each in the crawl above Frame 44 with a plate camera, photographing pages nobody had photographed yet, of which there were, at the current rate, another three hundred years' worth.

Spin gravity made her sick for two days. Everybody said it would and it did.

Her instructor was Bakri Adeyemi, who was seventy-four and third shift, hull and thermal, and who had taught the phase argument for thirty-five years and had been up the ladder something over eleven thousand times and had a bad hip and went up anyway. The ladder was ninety-one rungs and he did it in four stages and made no apology for any of them, and at the top he said what everybody said, which was: "Feet against the stringer. Not the pipe — that."

"I know," said Cleo Sarr-Achebe.

"Everybody knows. Everybody's known for seven hundred years and every eleven years or so somebody puts a hand on the coolant run at four hundred kelvin and finds out that knowing and doing are different departments." He wedged himself in with a grunt that he clearly regarded as private and passed her the plate camera. "Right. Depth marker's at nine hundred and forty. You're photographing from there. Don't hurry, don't tidy, don't straighten a sheet that's curled, and if a page is wrong you photograph the wrong page."

"Why?"

"Because we don't tidy people. It's on the plate at forty-degrees-south and it's on page nineteen of your own text and I'd be embarrassed to have to say it to a girl from Ouma."

The crawl was warm.

That was the first thing, and nobody had told her, or rather everybody had told her and none of it had meant anything: she had lived her entire life at four degrees, in rooms built to keep the fold slow, dressed for cold from the hour she was born, and she wedged herself between the inner skin and a pipe on a ship in a high orbit and was, for the first time she could remember, too warm, and had to stop for a moment because her eyes had gone stupid.

Hot dust. Old solder. She had read those two words in a facsimile at eleven and had thought they were a figure of speech.

And behind her, along the curve of the hull, the paper.

She had seen the reductions. Everybody had; four thousand three hundred and eleven pages had come up in the weekly over ninety years and there was a shelf of them in the settlement school and Cleo had read perhaps six hundred, which was more than most and considerably less than she implied. She had known, in the way you know a number, that it went back seven hundred years and that nobody had ever followed it to the end.

Knowing it was a different department.

It went away from her into the dark past the reach of the lamp, taped and re-taped and layered, sheaves gone soft as cloth where the tape had let go and somebody eighty years later had taped them again, and the depth marker at nine hundred and forty was a strip of yellow tape with a date on it and beyond it the paper simply continued, unphotographed, unindexed, uncounted, in the same amber dark it had been in since before anybody's great-great-grandmother.

"How far does it go?"

"Further than my arm." Bakri Adeyemi had his head back against the skin and his eyes shut. "I got to about a thousand and four in year six-eighty-one with a shoulder I no longer own. There's a boy's parallax homework at nine hundred and sixty with his mother's corrections on it and I have thought about that boy more than I have thought about most of my relatives. Past that it's all hands and no names. There's supposed to be nineteen pages at the bottom of it in pencil."

"Anselm's."

"Anselm's, if it's there. Nobody's touched them for six hundred years and there's a strong argument that the tape's gone and they've been lying loose against the skin since the year four hundreds." He opened one eye. "There's a very good paper by a laundry technician in year six-fifty-two arguing that they're not there at all, that they were taken down in the disclosure century and the story grew over the gap. It's a good paper. I hope she's wrong. I'm not going to go and find out and neither are you."

"Why not?"

"Because it's nine hundred and forty on the marker and you're photographing, and because the day somebody goes to the bottom of that to see whether the relic is real, we've stopped being a ship that reads and started being one that venerates." He shut the eye again. "Take your photographs, Sarr-Achebe."

She took them. It was tedious in the way she had been promised and had not believed: eleven pages an hour if you were careful, the plate steadied against the stringer, the lamp moved four times a page, a hull tech's fault sheet from year six hundred and two on the back of which somebody had worked out the drainage silting rate and got it wrong by a factor of nine, then a set of four sheets in a child's hand about the mat at forty degrees south, then a page that was nothing but a list of names with dates, no explanation, which she photographed without comment because that was the rule.

At some point past the fourth hour, with her back gone and her hands cold in a room that was too warm, she pulled the array feed on her slate, because it was the first thing on her home screen the way it was on the home screen of everyone in two worlds who had ever been fifteen.

TEV-9 flickered in its little grey waveform box.

She had done this four hundred times. Every child did it; it was the oldest exercise there was, on page four, the one you did at nine before you understood any of it and again at fifteen when you did. Long, long, short, short, long. The stutter. Then the gap, and you counted the gap under your breath, and it came round at forty-one, and the whole phrase again with the stutter one beat earlier.

She counted the gap and got thirty-nine.

Cleo Sarr-Achebe sat very still with her shoulder against a warm pipe.

She counted it again and got forty. Then forty. Then thirty-nine.

"I've done it wrong," she said.

"Mm."

"I'm counting the gap and I'm getting thirty-nine and forty."

"You're counting in your head at four in the morning in one gravity you're not used to after four hours of holding a camera," said Bakri Adeyemi, without opening his eyes. "Count with the slate."

She counted with the slate. She marked the leading edge of the stutter, four times, and took the intervals, and got 40.61, 40.58, 40.62, 40.60.

"Bakri."

"Mm."

"It's forty point six."

There was a silence of a length she did not have the experience to interpret, and then the old man opened both eyes and said, in a completely ordinary voice: "Check it again. Bring me your working."

She checked it for nine days.

That was the standing interval and had been for six hundred years, published, argued over, defended every eleven years against people who wanted four and people who wanted fourteen: long enough for arithmetic, short enough that it could not become a secret. She spent it in a lab on Deck 3 with four thousand people alive above her and a hundred and forty thousand below, and she was fifteen, and nobody helped her, and eleven people watched her not be helped.

She pulled the raw array logs, which were open, which had always been open. She pulled the sensor's calibration record — the assembly mounted in year three hundred and forty-one to the original drawings including four tolerances that had made no sense for three centuries — and its annual audit by a body that was not the array's. She had the whole reduction repeated independently by a night crop crew in Ag-3 under a beans rota, using duplicate instruments, because Turi Achebe's nine pages had been law since year eighty-four and applied to a fifteen-year-old exactly as they applied to the Bureau.

The period had been 41.00 seconds for seven hundred and eleven years.

It was 40.61 and it had been falling since some point in the previous nineteen months, in a way that nothing in the archive had ever seen it do, and that was a fact about a star and not about a ship, and Cleo did the light-travel arithmetic on the fourth night, on paper, with a pencil, because that was what you did.

Fifteen years and four months.

Whatever had happened to TEV-9 had happened fifteen years ago. It had happened while she was being born at forty degrees south in a room at four degrees, and the news of it had been crossing the dark ever since at the only speed news travels, and it had arrived at 0430 on a Fourthday and gone into a grey box on a slate and been counted by a girl with a sore back who thought she had miscounted.

She wrote that down. It went into her working, in the fourth paragraph, and the four panels left it in when they published, and it is the sentence out of the whole affair that ended up in the year-nine text:

The star changed while I was being born and I found out at fifteen. This is not a special circumstance. It is the ordinary condition of every fact about the universe and always has been, and the only unusual thing here is that we had four hundred years of records to notice it against.

They published on the ninth day, in the ordinary weekly reduction, on a Fourthday, with a four-line covering note. Period of TEV-9 departs 41.00 s, first departure on record, 40.61 s and falling, consistent with the class, no navigational consequence, holding open, checkable by anybody with the array logs and an afternoon. Attributed to C. Sarr-Achebe, year-nine class, Ouma, forty degrees south, and to the Ag-3 night crop crew of the eleventh rota by name, all four of them, because she had insisted and had been told she would have to insist twice and had.

Four hundred people fitted it themselves within a week, because four hundred people always did. Eleven of them got a different answer and nine of those were wrong and two of them found a bias term in the audit chain that had been sitting there since year six hundred and something and that nobody had had a reason to look for, and there is a Register entry about that, number three thousand one hundred and nine, and it is one of the cheerful ones.

There was no ceremony. There was a proposal for one and it was voted down in open session, twice, and on the second occasion somebody read out the minute of a meeting from year one hundred and twenty-nine in which a woman had said that a room with a name on it is a room that has stopped being audited.

On the last night of her fortnight Cleo Sarr-Achebe went up the spine ladder alone at 0409, which was the slot nobody wanted, because everybody who had come up to be part of it had gone back down to be part of it somewhere warmer.

There was no chair at the bottom of the ladder. There had not been for five hundred and eighty years. There was a hook for a lamp and a shelf that somebody had put up in year six hundred and forty for pencils, and it was not empty, and nobody knew who filled it.

She took one.

The crawl was the same. Hot dust, old solder, the coolant run warm against her shoulder and ticking as it warmed, feet against the stringer — not the pipe, that — and nobody could tell you who had taught it first and everybody taught it.

She pulled the feed and watched the little grey box for a while.

Long, long, short, short, long. The stutter. Then the gap, and she counted it under her breath the way eleven thousand people had once counted it together in a hall four storeys under a planet that had killed four hundred and six of them, and it came round at forty point six, and it would keep coming round sooner, a fraction sooner every year, for as long as anybody kept looking at it and probably long after.

She had been humming the old one her whole life. Everybody did. It was in a children's book from year eighty and in the text on page four and in the bones of both places, and it was wrong now, and she thought about the sheer nuisance of that, and about the fact that a hundred and forty thousand people were going to have to learn a new gap or go on humming a dead one, and that there would be an argument about it, and that the argument would take four years and two months.

Then she reached back along the hull, behind the coolant run, into the dark, and found the paper.

Sheaves of it. Taped and re-taped, layered, soft as cloth in places, running away along the curve further than her arm and further than the lamp and further than anybody had ever followed. Seven hundred and eleven years of other people's arithmetic. A boy's parallax homework with his mother's corrections on it. Forty-one drawings of a chair. Nine pages by somebody who had worked the chairs in the first year and never told anyone what she heard. Four sheets left by a hull tech who became a biologist and went down and did not come up, three of them wrong. And somewhere at the bottom of it, if the laundry technician of year six hundred and fifty-two was wrong, nineteen pages in pencil that had gone on quietly not being needed since before anybody.

She did not go looking for them.

She wrote, on the back of a fault sheet, badly, because you cannot write well wedged into a crawlspace:

Yr 711 d19, 0409. TEV-9 period 40.61 s and falling. First change on record in 711 yrs. It happened 15 yrs ago and we found out on a Fourthday.

I counted it in my head and got 39 and thought I was tired. I was tired. I checked it anyway. That is the whole method and there isn't a better one.

Anyone can check this. The array logs are open. They have always been open.

Bring a pencil. There's a shelf.

C. Sarr-Achebe, yr-nine, 40°S, Ouma

She taped it up with the rest, where a hand would find it and where nobody would ever index it, and took the slate and logged the visit — inspection, no fault found — which was true in every word.

Then she went down the ninety-one rungs and out along the amber corridor toward Ag-3, where the false dawn was coming up in the grow-lamps and the night crop crew would be arguing about something, and where there was a filter on her list, because Bakri Adeyemi had put it there on purpose and had not explained why and she had not asked.

On the way she hummed it: long, long, short, short, long, a stutter, then a gap — and she caught herself at forty-one, and stopped, and started again at forty point six, and got it wrong, and laughed out loud alone in a corridor at four in the morning, and started again.

A star, keeping its own time. Unimaginably far behind, indifferent, unhurried, having been made a clock and then a metronome and then a deadline and then, at last and for as long as anybody kept looking at it, simply something anyone could see — and having, in its own good time and for its own reasons, and fifteen years before anybody heard of it, changed its song.

The argument about the gap took four years and two months, which by then nobody even remarked on.

The technical question was trivial and was settled in a fortnight: TEV-9's period was falling, the fall was accelerating in the way the class did, and there would not be a stable number to hum ever again. The real question was what to do about a children's book from year eighty, a line on page four of the year-nine text, and a habit that a hundred and ninety thousand people had in their bones.

Three positions were argued at enormous length. The first was that the text should be corrected to the current value and revised annually, which was defeated on the grounds that it would produce a generation of children solemnly humming a number that was wrong by the time they had learned it. The second was that the whole exercise should be retired and the phase argument taught off the interferometric baselines, which was defeated by seventy-nine percent and which nobody had seriously expected to pass; it had been tabled, its proposer said afterwards, because somebody had to say the sensible thing out loud so that everybody could hear how it sounded.

What carried, in year seven hundred and fifteen, by sixty-one point four percent, was the third position, and it was frankly ridiculous, and it stands.

The Star That Kept Time was reissued in its original text, unaltered, forty pages, illustrated, with a new final page in which the little star, having kept the same time for a very long while, begins quietly to keep a different one, and the girl who wrote the pattern down has to write it down again. Page four of the year-nine text kept 41.00 as a historical figure with a date attached. And the children went on humming forty-one, because you cannot legislate a tune, and the ones who had done the autumn exercise hummed the current gap on purpose in order to be insufferable about it, and there was a period of about eighty years in which the surest way to identify a fifteen-year-old at four in the morning was that she was humming something slightly too fast.

By year eight hundred nobody was doing it any more. By year eight hundred and fifty the old gap had won completely, the way old tunes do, and a hundred and ninety thousand people hummed forty-one seconds at a star that no longer had one, and the year-nine text noted this on page four in a marginal line that had been added by amendment and never removed:

The song is not the measurement. Be careful in your life about the number of things you know only as songs.

There were forty-one settlements on Ouma in year eight hundred and eighty-four, and a hundred and ninety-one thousand people, and the whole architecture of all of it was still four degrees.

That had not changed and could not. The precursor complex was in the crust wherever the crust was wet and it had been for nine hundred million years, and the fold rate through a human being ran as a function of core temperature and ambient exposure, and every published revision of the panels' fit for four centuries had moved the numbers by fractions and never once moved the shape. You lived cold. You worked cold. You built low and thick-walled and half-sunk and you heated your rooms to four and not one degree more, and your children were dressed for it in the hour they were born, and the reward was an old age: a median onset at seventy-one, a first quartile at sixty-two, a long tail into the nineties, and something between a fifth and a quarter of everybody who never showed it at all before something else took them.

That was the bargain and it had been on the plate at forty degrees south since year five hundred and nineteen and every fifteen-year-old in two worlds derived it with a pencil in the autumn.

The trouble was that you cannot feed a hundred and ninety-one thousand people at four degrees.

You can feed forty thousand. The cold-store agriculture of the first two centuries was a marvel and it was also a marvel of a particular kind, which is the kind that does not scale: mat-culture in shallow trays under lamps, a purple photosynthetic sheet nine hundred million years old and profoundly uninterested in being farmed, plus the ship-derived beans and grain in tunnels at four degrees where everything took three times as long to do anything and a third of it did nothing at all. Yield per square metre per year was a number that the settlements had improved by eleven percent over two hundred years of very hard work by very good people, and eleven percent over two hundred years is a curve that does not meet a population.

The warm coast met the population.

There was a band around the equator of the second continent, four thousand kilometres of it, where the mean surface temperature ran between six and nine and where the mat grew in the shallows like something that wanted to, and where a hectare produced in a season what a cold tunnel produced in four years. The first coastal season was year six hundred and forty-one. By year seven hundred the coast fed a third of Ouma and by year eight hundred it fed nine-tenths of it, and every kilogram of that came out of ground and water above the gate, harvested by people who had gone up there on rota out of the cold, in suits, for a fixed and published number of hours.

Hours above gate.

That was the number. That was the fourth position on the wall, in the Long Gallery on the ship and in the assembly hall of every settlement, the direct and undisputed heir of a fuel fraction that had been read off a radiator log with a pencil eight hundred years earlier by a woman on third shift: hours above gate, per capita, per year, the integrated exposure that the population of Ouma bought its dinner with, written every autumn by a fifteen-year-old with a stylus while eighteen others watched her hand.

It had been thirty-one in year seven hundred. It had been thirty-six in year eight hundred. In year eight hundred and eighty-four it was 39.4.

It had been 39.4 for nineteen quarters.

Turi Lund-Amse was thirty-four and worked hull and thermal on third shift aboard the Ambit, which meant she was one of about ninety people in the universe who were awake at 0217 for a living and one of about eleven who were awake at 0217 and bored.

The standing complement was four hundred and eleven that year, drawn by voluntary rotation from ship and settlement and funded as a first charge on the fabrication of both, exactly as the ballot of year six hundred and eight had required, and it was not a hardship posting and had not been for centuries; you came up for nine years, or nineteen, or you never went down at all, and you ran an archive and an instrument and a school, and you were warm, which was the thing nobody from the ground ever stopped remarking on.

Her job that autumn was the coastal thermal survey, which was tedious in a way she had been warned about and had not believed.

The Ambit had, on its forward truss, an interferometric array four kilometres long that had been built in eleven segments over a decade by people whose names were on the wall on Deck 5, and it had, on its underside, a much less glamorous thing: a wide-field long-wave imager that stared at the night side of Ouma and made a map of where the heat was. It had been built in year five hundred and ninety-one for weather. It was still used for weather. It was also used, four times a year, for the occupancy reconciliation, which was a housekeeping exercise that nobody on either world had ever found interesting and which was on Turi's list because the imager's radiators were hers.

The reconciliation was arithmetic of the crudest possible kind. A human being at rest is a hundred watts. A human being working is two hundred and fifty. A coastal camp is a warm patch on cold rock and every fabricator in it is a known load with a published duty cycle, and if you integrate the excess radiance over a camp for a season and subtract the plant you get, to within about eleven percent, the person-hours that were spent in it.

Heat is public. Heat is the one thing that leaves. A man named Paavo Lund had said that to a Council in year sixty-nine, and had told them they could classify every instrument on the ship and could not classify the radiators, and Turi Lund-Amse had a photograph of the relevant page of the inquiry transcript in her quarters because she was that kind of relative.

She ran the reconciliation on the ninth day of the autumn quarter, at 0217, alone in a compartment on Deck 3 with her feet on a crate, and she got a number, and the number was sixty-one.

Sixty-one point four person-hours above gate per capita per year, inferred from waste heat, against a reported ledger figure of thirty-nine point four.

Turi looked at that for a while and then laughed, one bark, alone, because the answer was obviously that she had done it wrong. The reconciliation was crude. It had an eleven percent error bar on a good day. Fifty-six percent was not an error bar, it was a mistake, and the mistake would be hers, and she would find it in an hour and go and clean a filter.

She did not find it in an hour.

She found, instead, the thing that stopped her sleeping, and it was not the discrepancy. It was that she went back and ran the reconciliation for the previous nineteen quarters, which took the cluster four hours and her about nine minutes of actual work, and the inferred figure crept. Fifty-one, fifty-three, fifty-four, fifty-six, fifty-eight, sixty-one — up and up, quarter on quarter, in step with the coastal harvest tonnage, which was published, which had risen by a fifth in the same period, and which anybody would expect, because if you land more food you have spent more hours landing it.

And the ledger figure was flat.

39.4. 39.4. 39.5. 39.4. 39.3. 39.4. Nineteen quarters of a number that had crept steadily for two hundred years, sitting perfectly still while the thing it measured got bigger.

Turi Lund-Amse sat in a compartment on Deck 3 with her feet on a crate, eight hundred and four years after a woman had wedged herself into a crawlspace above Frame 44 and looked at a flat residual, and thought the same thought in almost the same words.

It should have crept.

She checked four things over the next nine days, because that was the interval, and because nobody was going to hold it against her if she took nine days and everybody would hold it against her forever if she took four.

The first was her own instrument. The imager's calibration record was open, its annual audit was performed by a body that was not the imager's, and its reference cell had been replaced in year eight hundred and eighty-one; she pulled all of it, and put a source in front of the detector chain, and bench-tested the plant-load library against four fabricators on the ship whose duty cycles she could measure with her own hands, and the whole apparatus was fine. She spent one shift very happy and one shift proving to herself that the happiness had been unearned, and she wrote that down in her working, because everybody wrote that down, because it was on page nine.

The second was the harvest. Coastal tonnage, landed mass, published weekly for two hundred and forty years, cross-checked against consumption at nineteen settlements and against the mat-culture returns. It was real. They were landing what they said they were landing. Nobody was inventing food.

The third was labour. And here it began to go wrong in a way that made her put her stylus down, because the coastal rota rolls were also published — names, camps, dates, in and out — and when she counted heads in the camps and multiplied by the published shift lengths she got fifty-nine point one person-hours per capita per year, which was not thirty-nine point four either, and which agreed with her heat curve to within the error of both.

Two entirely independent methods agreeing, and neither of them agreeing with the number on the wall.

So the ledger was not measuring what she thought it measured, and the fourth thing she checked was what the ledger measured, and it took her six days and it broke something in her that never quite set again afterwards.

Hours above gate was defined in the technical annex to the coastal exposure standard, and the technical annex was published, indexed, and petitionable, exactly as recommendation forty-two of year three hundred and eighty-two had required for five hundred years, and its revision history was open, and Turi read it at 0400 on a Fourthday.

Revision 44-B, adopted in the first quarter of year eight hundred and seventy-nine by the Coast Board on the recommendation of its own technical committee, published in the ordinary weekly reduction on the ordinary Fourthday, indexed under the ordinary line, unopposed because unremarked.

It changed the definition of an hour above gate from one hour spent by one person at a working face whose ambient temperature exceeds four point zero degrees to one hour spent by one person whose shift-averaged thermal exposure index exceeds four point zero degrees.

Twelve words. And the shift-averaged thermal exposure index was defined further down, in a sub-annex, and it averaged the working face against the transit and the rest periods and the cooled sleeping van, weighted by duration, so that a person who spent six hours at nine degrees and eighteen hours at two degrees had a shift-averaged thermal exposure index of three point seven, and therefore, from the first quarter of year eight hundred and seventy-nine, had spent no hours above gate at all.

Not one. She had been at nine degrees for six hours with the mat in her hands and the wind off the water, and the ledger recorded zero, and the ledger was right, because the ledger recorded what it had been redefined to record, and the redefinition was published, and anybody could have read it.

Turi Lund-Amse read the twelve words about nine times.

The panels' fit — every revision of it for four hundred years, all four of them, forbidden to share instruments, audited annually by a body that was none of them — modelled onset as a function of time at ambient above the gate, because that was what the assay measured and what Iyabo Ouma had spent twenty-nine years being the instrument of. It was not a function of a shift average. A shift average was not a physical quantity. It was an administrative one. You could not average an exposure any more than you could average a fall.

Which meant that the number on the wall in the fourth position, the number a fifteen-year-old wrote with a stylus every autumn while eighteen others watched her hand, the direct heir of a fuel fraction read off a radiator log with a pencil, had for nineteen quarters been an answer to a question that nobody had asked and that no instrument aboard either world could check.

And the real number, the one that went into the fit, the one that told a hundred and ninety-one thousand people what their dinner cost them in years off the far end of their lives, was sixty-one point four and rising, and had not been written on any wall anywhere since the third quarter of year eight hundred and seventy-eight.

She did not have a list of four people.

That was the difference, and she thought about it for a long time afterwards, and said so publicly more than once in a tone that people found irritating. There was no arithmetic to do about who could be trusted. There was a procedure: nine days of internal checking on a finding of consequence, an independent repetition by a body with duplicate instruments that was not yours, and then the ordinary weekly reduction on the ordinary Fourthday with a four-line covering note.

She did it all, and it was still the worst nine days of her life, and she was sick twice.

The independent repetition was done by the Ag-3 night crop crew of the fourth rota, four of them, using the ship's own duplicate long-wave instruments under a beans rota, because Turi Achebe's nine pages had been law since year eighty-four and applied to the imager exactly as they applied to everything, and the crew got sixty point nine and an argument about the plant-load library that took a further two days and improved the estimate.

On the eighth day Turi went to see the Bureau of Verification, which was eleven people and a room and had a window onto the Ag-2 dome that its first director had asked for and got and had never once admitted was sentimental, and she sat down in front of a woman of seventy and said: "I want to know what happens next, because I have never done this and I would like to not do it badly."

"You publish on Fourthday," said the director. "That's what happens next."

"To the ground. It's the Coast Board. It's a hundred and ninety thousand people's food."

"You publish on Fourthday."

"I know that. I'd like to know what it costs."

The old woman looked at her for a while.

"Four hundred and six people," she said. "That's the first thing it costs and it's a debt somebody else already paid. After that: it costs the Coast Board, it costs whoever signed the annex, it costs about nine points of reserve on the ground and four up here, and I would guess between eleven and forty people over the next twenty years, because there'll be a fortnight of confusion during which the coast doesn't run properly and food doesn't move, and somebody always dies in a fortnight like that." She turned her cup a quarter-circle, which was a gesture nobody could account for and everybody made. "Balanced against about eleven hundred people who have accrued exposure in the last nineteen months that they would have declined if the number had been on the wall, and however many thousand accrue it next year if it stays off.

"Nobody is going to thank you and you should not want them to. Publish on Fourthday."

"And if I'd rather somebody on the ground had a day's warning? Not to bury it. To be ready."

"Then you'd be choosing the order," said the director of the Bureau of Verification, "and there's a woman in year three hundred and seventy-seven who asked this hall for nine days for the best reasons anybody ever had, and lost, and published her own dead under her own name afterwards with the losing recommendation attached. Read her file tonight. Then publish on Fourthday."

Turi Lund-Amse published on Fourthday, in the ordinary weekly reduction, with a four-line covering note, at 0400 ship-time, which was third shift, which meant that the first people in two worlds to read it were hull techs and recyclers and night crop crews standing in amber corridors with a slate in one hand.

Nea Achebe-Merrick asked for the floor at 0900 the following morning, which was to say eleven hours later, and did not wait to be invited.

She was fifty-eight and had chaired the Coast Board for nine years and had signed revision 44-B in the first quarter of year eight hundred and seventy-nine, and she came up on the ordinary lift with no delegation, and the joint session convened at four seconds' lag with nine thousand people watching on the ground and four hundred in the Long Gallery, and she stood at the front of a hall she had never been in before, in working clothes, because there had not been anything else to wear on either world since the whites were abolished in the third quarter of year eighty-one.

"I signed it," she said.

She let the lag take it down and bring back nothing, because there was nothing to bring back.

"I want the record to start with the plainest available sentence, because there will be a great deal said in the next four years and I would like the first thing in it to be true. My name is Nea Achebe-Merrick, I chair the Coast Board, I proposed revision 44-B to my own technical committee, I signed it, I published it in the ordinary weekly reduction on the ordinary Fourthday under the ordinary index line, and I did that in the specific and considered knowledge that nobody would read it.

"That is concealment. I want to say it in that word, in my own voice, before anyone else has to work up the courage to use it at me. I did not falsify an assay. I did not touch the panels' fit. Every measurement the Coast Board has ever taken is in the holding, unaltered, indexed, and Engineer Lund-Amse reconstructed the true exposure from our own published rota rolls in an afternoon, which I would ask everybody to notice, because it is the whole of my situation. I hid nothing. I put it where it could be found and I chose the place because it could not be found conveniently, and I have been telling myself for nineteen months that the difference between those two things was a moral one.

"It is not. "It is not. It is the oldest trick in this ship's history and I learned it from a woman who has been dead for eight hundred years, and the fact that I learned it out of the year-nine text does not improve it."

Eight seconds.

"You'll want to know why," said Nea Achebe-Merrick, "and I am not going to make you drag it out of me over four years, so here it is in one piece and then you may do what you like with me.

"Hours above gate was thirty-eight point one in the last quarter of year eight hundred and seventy-eight, and it had risen every year for two hundred years, and it was going to be forty-four the following autumn and fifty by year eight hundred and eighty-four, which is where the engineer's honest curve now has it. And a fifteen-year-old was going to write fifty on the wall in the fourth position while eighteen others watched her hand.

"I have the coast rota. I have four hundred years of it. Every time that number goes up by more than four in a year, volunteering falls in the following season by between nine and nineteen percent, and it recovers, and it always recovers, and it recovered in year seven hundred and forty-one and in eight hundred and three and in eight hundred and sixty. But it recovers over about three seasons, and the coast is a seasonal system. The mat is ready when it is ready. There is a window of eleven weeks in each hemisphere and if you go into it nineteen percent short of hands you land nineteen percent less, and there is no cold store on this world capable of carrying a hundred and ninety-one thousand people through a nineteen percent shortfall, because the cold stores were built for forty thousand.

"So the position I was in, and I want the exact position on the record because I am not going to be hanged for a worse one, was this. If I put the true number on the wall in the autumn of eight hundred and seventy-eight, I forecast a shortfall in the following harvest of between eleven and twenty-two percent, which is starvation for somewhere between four and forty thousand people at the margins, mostly the far settlements, mostly the ones who are already thin.

"And if I changed twelve words in a technical annex, the number went to thirty-nine point four and sat there, and everybody ate."

Eight seconds. Nobody used it.

"Everybody ate," she said. "That is the part you will have to hold, because I am going to hold it for the rest of my life. Nineteen quarters. Nobody was short. The far settlements put on weight for the first time in a century. And the price of it was about eleven hundred people accruing exposure they'd have refused, and every one of them will die about four years earlier than they would have, and I did that arithmetic, on paper, with a pencil, and I did it four times, and it came out in favour every time, and I want somebody in this hall to tell me which term in it was wrong."

Eight seconds, and then a voice from the Long Gallery floor that the transcript attributes to a hull tech of twenty-six.

"The term where you're the one doing it."

Eight seconds.

"Yes," said Nea Achebe-Merrick. "I know. I have known that since the day I signed, and knowing it did not stop me for nineteen months, and that is the actual finding of whatever inquiry you're about to hold, and you may save yourselves four years if you'll take it from me now.

"I am going to say the rest of it quickly because I have been awake for two days.

"There is a document in the archive called the Register of Consequential Omissions. It has three thousand one hundred and forty-one entries. I have read all of them, twice, the second time last night, and I would recommend the exercise to anybody who thinks well of themselves. And the thing about that document that nobody says out loud is that it is a record of things that were not done because a fact was in a filing system — and the ship has spent eight hundred years making sure that no fact is ever in a filing system again, and it worked, it has completely worked, and so I could not put my fact in a filing system.

"So I put it in the light. In the weekly reduction, on a Fourthday, indexed, petitionable, in twelve words, in a sub-annex.

"I have thought since about what I actually relied on, and it was not secrecy. It was fatigue. I relied on the fact that a hundred and ninety-one thousand people cannot read everything, and that the only defence any of us has ever had against a determined administrator is that somebody, somewhere, is bored enough at three in the morning to check a number that has already been checked.

"That is a thinner defence than this ship believes it has. I would like that written down as the whole of my contribution. Everything else I have to say is mitigation and I have decided not to offer any."

The inquiry sat for eleven months and was joint, which had never been done, and the lag made it slow and merciless in equal parts.

It did not find against her personally, which enraged about nine thousand people and was, the record notes, the only survivable outcome; the finding observed that a hundred and ninety-one thousand people had eaten for nineteen quarters on the strength of the thing she had done, and that no punishment available was proportionate to either side of that, and declined to perform one and call it justice. It quoted, because it could not help itself, four lines from year eighty-one, and everybody knew the lines and everybody read them again anyway.

What it did instead was produce forty-one recommendations, and Turi Lund-Amse counted them and laughed until she had to sit down, and had to explain the joke to eleven people on the ground who had never heard it.

Two of them stuck.

The first was that no quantity appearing in any of the four wall positions could have its definition altered except by ballot of both worlds, eleven days, published question, minority statement in the same size letters. That one was obvious and unopposed and is the sort of thing that gets written into a text and read by children for four hundred years without anybody thinking about it.

The second was the one that mattered, and it came out of the sentence Nea Achebe-Merrick had asked to have written down as the whole of her contribution.

It established the reconciliation as a standing obligation: four times a year, forever, every load-bearing reported figure on either world checked against an entirely independent physical proxy by a body with no interest in the answer, with the method published, the residual published whether interesting or not, and the whole thing performed — and this was the clause that was argued about for two of the four years, and that Ag-3 supported and the Coast Board's technical committee opposed and the year-nine classes of both worlds carried by a landslide in the indicative — by fifteen-year-olds as the autumn exercise.

Not because they were good at it. They were not especially good at it; the published figure for the first century was that a third of the reconciliations contained an arithmetic error serious enough to change the sign of the residual, and that figure was itself published every autumn in the fourth position on the wall, underneath the thing it was checking.

They were used because they were bored, and unimportant, and had nothing invested, and because the entire eight-hundred-year history of both worlds could be read as a single unbroken argument for the proposition that the only reliable auditor is a person with a sore back at three in the morning who has been told to check it again and bring their working.

They called it the reconciliation and then, within about forty years, nobody called it anything; it was just the autumn, the way the wall was just the wall.

Nea Achebe-Merrick resigned the chair, which nobody had required, and went back down, and spent the last eleven years of her working life on the coast in the ordinary rota, above gate, in a suit, landing mat.

She published her own hours. That was not required either. Every quarter, in the ordinary weekly reduction, on the ordinary Fourthday, under her own name: hours above gate, this quarter, cumulative, with the panels' current fit applied and the resulting shift in her own median onset stated in years, to one decimal place, with the error bars.

She did it for forty-four quarters. The last one, filed from the eleventh camp in the autumn of year eight hundred and ninety-six, when the cumulative figure had gone past the point where the fit stopped being kind, reads in its entirety:

Q4. 61.9 hrs. Cumulative 2,411. Median onset now 63.1 (58.4–71.9). This is four years and two months earlier than when I signed.

I am not doing this as penance and I would be grateful if nobody wrote it up that way. I am doing it because it is the number and it should be on the wall, and I spent nineteen months arranging for it not to be, and the only correction available to me is to put my own on it every quarter until I stop.

Do not tidy me.

N. Achebe-Merrick, 11th camp, coast

She died in year nine hundred and four at sixty-six, at the eleventh camp, with the fold well advanced and the last four months of her quarterlies filed by dictation and published unedited, including the two that repeat.

They wrote her name on the wall on Deck 5, four hundred thousand kilometres above where her body was, in the ordinary way, in whatever hand was holding the stylus, and there was an argument about it in the corridor beforehand — there is always an argument, it is practically a rite — and the argument was settled in the way it had been settled since year eighty-two, which is that the wall is for everybody, in the order they went, and that whoever they were, they get to be in the same book as somebody's mother.

Somebody put an apple on the deck plate underneath, and somebody else cut it into eight pieces with a knife and gave one to each of the seven people standing nearest and kept the last and put it in her pocket, and nobody asked why, because everyone in the corridor understood that some things are kept.

Turi Lund-Amse was fifty-one in year nine hundred and one and had not left the ship.

She had meant to. She had come up on a nine-year rotation at twenty-six and had signed for nine more at thirty-five and then had stopped signing anything and had simply gone on being awake at 0217, which is how the third shift has always retained people and always will. She ran the imager. She ran the reconciliation four times a year with whatever fifteen-year-olds were up on the autumn lift, and she was, by all accounts, an indifferent teacher who was extremely good at not helping.

On the last night of the autumn of that year she went up the spine ladder at 0409 with a girl from the fourth camp who had spent the fortnight being sick from the spin and photographing pages nobody had photographed yet, of which there were, at the current rate, another two hundred years' worth.

Ninety-one rungs. A hook for a lamp at the bottom, and a shelf that somebody had put up in year six hundred and forty for pencils, which was not empty, and which nobody knew who filled.

"Feet against the stringer," Turi said. "Not the pipe — that."

"I know," said the girl.

"Everybody knows."

The crawl was the same. Hot dust, old solder, the coolant run warm against the shoulder and ticking as it warmed, and behind them along the curve of the hull the paper: taped and re-taped, layered, soft as cloth in the deep places, nine hundred and one years of other people's arithmetic running away past the reach of the lamp further than anybody had ever followed.

The girl pulled the array feed, because it was the first thing on her home screen the way it was on the home screen of everyone in two worlds who had ever been fifteen.

TEV-9 flickered in its little grey box. Long, long, short, short, long. The stutter. Then the gap.

She counted it under her breath, which everybody did, and got thirty-eight, and marked it on the slate four times and got 38.11, 38.09, 38.12, 38.10, and wrote that down without any particular ceremony, because the period had been falling for a hundred and ninety years and a girl of fifteen had first caught it at forty point six with a sore back and had thought she had miscounted.

"Still going," she said.

"Still going." Turi had her head back against the skin. "It'll bottom out in a few thousand years, probably. Somebody'll be up here."

The girl was quiet for a bit, and then said: "Is it true nobody's ever been to the bottom of the paper?"

"It's true nobody admits to it."

"Somebody must have."

"Somebody must have, and whoever it was had the sense not to say so, which I've always thought was the most impressive thing anyone's ever done in this crawlspace." Turi shifted her shoulder off the pipe. "There's a paper by a laundry technician in year six-fifty-two arguing the nineteen pages aren't down there at all — that they came out during the disclosure century and the story grew over the gap. It's a good paper. There's a better one from year eight-eleven that says it doesn't matter, and I think that one's right, and I'd rather you read it than went looking."

"Why doesn't it matter?"

"Because the thing she left wasn't the pages." Turi nodded at the dark. "It was that everybody after her also left something, and none of it's indexed, and you had to come up ninety-one rungs and be warm and uncomfortable and bored to read any of it. That's the artifact. The pencil's the point. She'd have hated a relic; she voted her own name off a door four times."

The girl thought about that, and then reached back along the hull, behind the coolant run, into the dark, and found the paper, and took a pencil off her ear.

She wrote, on the back of a fault sheet, badly, because you cannot write well wedged into a crawlspace:

Yr 901 d19, 0409. TEV-9 gap 38.10 s. Still falling. Everyone still hums 41.

Reconciliation this autumn: coast hours above gate, reported 62.1, inferred from waste heat 61.7, residual within error. I got the plant library wrong the first time and had to do it again.

Anyone can check this. The array logs are open. They have always been open.

Bring a pencil. There's a shelf.

S. Vaan-Ouma, yr-nine, 4th camp, Ouma

She taped it up with the rest, where a hand would find it and where nobody would ever index it, and Turi Lund-Amse took the slate and logged the visit — inspection, no fault found — which was true in every word.

Then they went down the ninety-one rungs and out along the amber corridor toward Ag-3, where the false dawn was coming up in the grow-lamps and the night crop crew would be arguing about something, because there was a filter on the list, because there was always a filter on the list.

On the way the girl hummed it, and got the gap wrong at forty-one, and did not correct herself, because by then nobody did.

By year nine hundred and seventy-seven there were two hundred and forty-one thousand people on Ouma and a hundred and ninety-one aboard the Ambit, and the standing complement had been below three hundred for so long that the ballot of year six hundred and eight — not fewer than four hundred, drawn by voluntary rotation from ship and settlement, funded as a first charge on the fabrication of both — was taught in the autumn exercise as an example of a decision that had gone on being obeyed in its letter for three centuries after it had stopped being obeyed at all.

That was published. The shortfall was in the fourth position on the wall in the Long Gallery under the hours above gate, and it had been published every quarter for a hundred and eleven years, and the ground had voted four separate times to make it good and had four separate times funded something else instead, and every one of those ballots was in the archive with its minority statement in letters of the same size.

The ship was old. That was also published, in a way, and had been for six hundred years: the spine fatigue index, a single number, plotted quarterly against a model, with its residual underneath. The residual was flat. It had been flat since year three hundred and ninety-one. It was the flattest line in either world and it was on page nine of the year-nine text as the worked example of a well-behaved system, and a hundred and forty generations of fifteen-year-olds had glanced at it on their way to the interesting part of the exercise.

Kesia Roque-Anselm was seventy-one and had been awake at 0217 for forty-four years.

She had come up at twenty-seven on a nine-year rotation and had signed for nine more at thirty-six and had then stopped signing anything, which is how the third shift has always retained people and always will. She had been born at forty degrees south. She had been named for a woman who chaired a Council in year sixty-eight and gave an order at 0340 on the eleventh of the ninth of year sixty-nine, and the name had become common in the settlements in a way nobody planned and nobody prevented, and there was a small unpleasant literature about why, and Kesia had read all of it at nineteen and had decided to go on being called Kesia.

She had gone up the ladder to Frame 44 something over eleven thousand times.

What she had that nobody else had was not skill. She was a competent hull tech and had never been anything better, and she said so, at length, to people who tried to make her into something. What she had was that she had heard the same crawlspace come up to temperature four thousand times in the dark.

The coolant run ticked as it warmed. Everybody knew that; it was the first thing anybody wrote about the crawl, it was in the facsimile pages by the hundred — hot dust, old solder, the coolant run ticking as it warms. It ticked because the pipe grew four millimetres along its length between the cold of the shadow pass and the heat of the sun side, and because it grew against four clips that gripped and slipped and gripped, and every slip was a tick, and the ticks came in a run of eleven as the pipe took up its length, spaced out at the end the way a dropped coin settles.

On the ninth night of the autumn quarter of year nine hundred and seventy-seven, wedged in with her shoulder against the pipe and nothing much on her list, Kesia Roque-Anselm counted nine.

She did not think anything at all for about a minute. Then she thought: I've miscounted.

She waited seventy minutes for the next shadow pass and counted it cold and counted it warm and got nine. She went down and came back on the following night and got nine, and on the night after that she brought a contact microphone she had signed out for a different job and got nine, and the intervals were wrong too — the first four came faster and the last one did not come at all, so that the run stopped short, like a phrase with the end bitten off.

She sat in the dark with her hand flat on the inner skin, which was the same skin, and which hummed, and thought about the fact that a pipe slips against a clip when the pipe grows faster than the frame it is clipped to.

It should have ticked eleven times.

That was all, at first. A technician's small objection.

She went to Frame 31 because it was eleven metres aft and because she had shimmed the clip there herself in year nine hundred and fifty-one and had thought nothing of it at the time.

The clip was singing. Eleven hertz, on sustained load, the way it had been singing intermittently for six hundred and sixty-four years.

Kesia pulled the fault history. It was open; it had always been open; nobody had ever needed to petition anything to read a stringer clip's life, and nobody ever had, because a stringer clip's life is the single least interesting document in the possession of two worlds.

It ran to forty-one entries.

Yr 313 d1. Clip singing 11 Hz under new load. Shimmed. Somebody check it in a hundred years. — D. Roque-Amse, third shift.

Yr 411. Singing 11 Hz. Replaced. — Y. Amse.

Yr 524 d1. Singing 11 Hz again. There is no load on it. Shimmed anyway. Somebody check it in a hundred years. — I. Achebe-Ouma.

And on, and on, at intervals of thirty and forty and nineteen and sixty years, forty-one times, in forty-one hands, every one of them a competent person doing a competent job at four in the morning: shimmed, replaced, packed, shimmed, replaced. Four of them had written somebody check it in a hundred years. One, in year seven hundred and two, had written this is the fourth shim in my own service and I do not understand it, and had shimmed it.

Nobody had ever asked it why.

Kesia Roque-Anselm sat on a stringer in the amber dark with a slate in her hand and understood, with a completeness that made her feel physically cold in a compartment at twenty-one degrees, that for six hundred and sixty-four years a piece of this ship had been trying to say something and had been silenced forty-one times by people who were good at their jobs.

That was the finding. Everything that came after was arithmetic.

She took nine days, because nine days was the interval and had been since before anybody, and because she was seventy-one and had been told by two separate directors of the Bureau of Verification over the course of her life that the only thing that ever went wrong with a finding was hurry.

The first thing she checked was the strain gauge archive on the spine, frames 31 to 61, six hundred and eighty-six years of it, quarterly, open, indexed, and beautifully behaved.

The residual against the model was flat. She sat with the plot for an hour and could not make it be anything but flat, and had the brief unearned happiness that everybody who has ever done this gets and that everybody writes down afterwards, and she wrote it down.

Then she went and read the model.

The spine fatigue model was a nine-parameter fit. It had been written in year three hundred and eighty-one for a ship under a twentieth of a gravity, revised in year four hundred and forty for a ship in orbit, and it was refitted — this was the part Kesia read four times and then went and stood in a corridor — refitted annually, automatically, against the incoming gauge data, and the residual published each quarter was the residual of the data against the fit that the data had just produced.

For five hundred and thirty-seven years the Ambit had been checking whether its own measurements agreed with a curve drawn through its own measurements.

There was no dishonesty in it anywhere. Kesia went looking, and looked for four days, and found the whole provenance in the open: a technical committee in year four hundred and forty that had adopted annual refit because the ship's thermal environment was changing under deceleration and a static model would have been useless; a note in the minute observing that the residual would thereafter be a measure of scatter and not of model error, and recommending an independent five-yearly validation against a physical proxy; the validation performed in year four hundred and forty-five, and four hundred and fifty, and four hundred and fifty-five, and four hundred and sixty; and then a line in the year four hundred and sixty-four workplan, four words long, in the same flat administrative register that had once written no operational requirement against a cometary survey: validation to biennial cycle.

And then to five-yearly again, and then to eleven-yearly, and then, in year five hundred and one, in a schedule consolidation that ran to nine hundred items and was published in the ordinary weekly reduction on an ordinary Fourthday and read by nobody, off the list.

Four hundred and seventy-six years. The instrument had never lied. The gauges were good; four independent laboratories confirmed them inside a fortnight. The number had never been falsified and no one had ever concealed anything, and there was not one human being anywhere in it who had made a decision they would have been ashamed to publish, and that was the whole trouble.

What the physical proxy said, when Kesia Roque-Anselm finally built one — a laser interferometric span across the spine's inner skin between frames 39 and 51, cobbled up in two nights out of survey spares, a bench-grade instrument that any competent hull tech could have built in any century — was that the frames in that section had lost eleven percent of their bending stiffness.

That does not sound like much. It is the difference between a coolant pipe that ticks eleven times and one that ticks nine.

She ran the crack-growth arithmetic on paper, with a pencil, three times over two nights, because she had stopped trusting anything with a processor in it, and she got a through-thickness date in the inner skin of frames 41 to 47 of somewhere between year one thousand and forty-one and year one thousand and ninety, with a wide interval and an ugly tail.

Sixty-four years. Not centuries. And the worst of it, the deepest of the growth, was at Frame 44, because Frame 44 had a warm coolant run laid four centimetres off the cold skin, and had had for nine hundred and seventy-seven years, and every shadow pass of every orbit for five hundred and forty of those years had put a thermal gradient across that skin and taken it off again, two point six million times.

The crawl was warm. That was the first thing anybody said about it. It smelled of hot dust and old solder and it was warm, and everyone from the ground remarked on it, and the warmth was the thing that had been eating the hull for as long as there had been anybody to be warmed by it.

Kesia had the whole reduction repeated independently by the Ag-3 night crop crew of the third rota, four of them, using duplicate instruments under a beans rota, because Turi Achebe's nine pages had been law since year eighty-four and applied to a hull tech of seventy-one exactly as they applied to everything, and the crew got twelve percent and an argument about the span calibration that took two more days and improved the estimate.

She published on Fourthday, in the ordinary weekly reduction, at 0400 ship-time, with a four-line covering note.

Then she went and cleaned a filter in Ag-3, because it was on her list, and the filter was a filter, and the false dawn was coming up in the grow-lamps, and two of the night crop crew were arguing about whether the mat counted as a vegetable.

The argument took four years and two months.

Nobody remarked on that either. There is a paper about it, from a laundry technician in year eight hundred and eleven, and it is one of the good ones, and its conclusion is that four years and two months is simply the length of time it takes a quarter of a million people to say everything they have to say twice.

There were three positions and everybody knew all three by the end of the first month.

Sleeve her. Cut and fit a structural sleeve over frames 39 to 51, nineteen segments, in the same way and to the same tolerances as the interferometric truss had been built five centuries earlier by people whose names were on the wall on Deck 5. Cost: eleven years of both worlds' fabrication as a first charge, which meant eleven years of no new cold tunnel at the four far settlements, eleven years of the coastal landing gear running on the old plant, and — this was the number that did the work, and the Coast Board put it on the wall in the fourth position under the hours, because that was the law now — eleven years at an estimated additional four point one hours above gate per capita per year, because a fabrication charge is paid in labour and labour on Ouma is paid in exposure. Buys two hundred years.

Seal her. Pump down frames 39 to 51, weld the bulkheads at 38 and 52, and let that section of spine be vacuum forever. Cheap. Four months of work. Costs the crawl above Frame 44, and everything taped inside it.

Bring her down. Reverse the ballot of year six hundred and eight. Recover eleven thousand tonnes of hull stock over forty years, which was more structural material than Ouma had fabricated in its entire history, and which the far settlements had been quietly and not so quietly wanting for two hundred years.

The case for coming down was made in the fourth session by a woman of thirty-eight from the eleventh camp, and it was not sentimental and it was not cruel, and it is on the syllabus.

"I want to answer the orchardist," she said. "The one from Ag-1, year six hundred and eight, with the shavings in her hair. Everybody quotes her and nobody has answered her and I have had three hundred and sixty-nine years to think about it, which is more than she had.

"She said: in four hundred years there will be a generation that has never seen this ship, and somebody in a room will have a very good reason to make something simpler than the truth, and when that happens I want there to be a thing in the sky they can point an instrument at.

"I am that generation. I have never seen the ship. My mother never saw it and my grandmother never saw it. And I would like the record to show that what has kept us honest for three hundred and sixty-nine years is not the object in the sky."

Eight seconds.

"It's the autumn. It's forty-one settlements doing the reconciliation four times a year with a third of them getting the sign wrong. It's the wall in every assembly hall and the minority statement in the same size letters and a woman at the eleventh camp who published her own median onset every quarter until she couldn't hold a stylus. Those are ours. We built them down here, in the cold, and we would go on doing them if that ship burned up tomorrow, and if we wouldn't then the ship was never what was holding us up. "And here is the part nobody up there will say to your faces, so I will. There are four settlements that have been waiting eleven years for a cold tunnel. Not for comfort. For four degrees. There are children in the far south sleeping at six because the plant they were promised in year nine hundred and sixty-one was deferred, and six is not four, and the panels' fit is not a metaphor. That is exposure, and it is accruing tonight, and it is accruing in children.

"So when you cost me eleven years of fabrication to sleeve a hull, I am going to make you write down what the eleven years buys and what it costs in the same units, because that is the whole discipline and this ship invented it. Two hundred years of an archive in orbit. Against four point one hours above gate per capita per year for eleven years, and four cold tunnels that do not get built.

"I have done that arithmetic on paper with a pencil and I did it four times and I want somebody in this hall to tell me which term in it is wrong."

Eight seconds, and then, from a hall of a hundred and ninety-one people four hundred thousand kilometres up, nothing at all came back, and the chair, after some time, moved to the next speaker.

Sealing was the position of the technical committee and it was the position that made everybody unhappiest, because it was cheap and sound and correct and it took the paper.

There were four thousand three hundred and eleven pages in facsimile by then, or rather there were eleven thousand and six, because the plate-camera work had gone on for three hundred and sixty-two years at the pace of a fortnight's autumn exercise and had reached a depth of one thousand nine hundred and forty on the marker, and the published estimate said another hundred and ninety years to the end at current rates, and that estimate had been revised nine times and never once met.

Everything above depth nineteen-forty existed in facsimile in every settlement school and every ship-side lab. Everything below it existed once, taped to the inner skin of a hull that was going to open in sixty-four years.

The proposal to go in and get it — to strip the crawl, sheet by sheet, before the weld — was tabled in the first month, and it was reasonable, and it was defeated in the ninth by seventy-nine percent, and the sentence that beat it was said by a conservator of forty-one who had spent her working life arguing for exactly the opposite.

"I have wanted that paper indexed for nineteen years," she said. "I have filed four proposals. I have lost all four and I was right all four times about the risk and wrong about everything else.

"Here is what I have finally understood, and it took a stringer clip to teach me. That crawlspace has been read continuously for nine hundred and seventy-seven years by people who had to be uncomfortable to do it. Forty-one hands shimmed a clip and none of them asked why, and the reason we caught it is that a woman of seventy-one had heard the pipe tick four thousand times.

"You cannot get that out of a facsimile. You cannot get it out of an index. It is not information. It is a person having been in a place enough times to notice that it had changed, and there is no archive in the universe that stores that, and the only way to keep it is to keep sending people up ninety-one rungs with a pencil.

"So: if we seal, we do not strip it first. We do not go in and save the relic. We photograph what the autumn reaches in the time it has, at the ordinary pace, by fifteen-year-olds, and whatever we do not reach we do not reach, and the weld goes over it.

"I hate that. I want it minuted that I hate it. But the alternative is that we spend four months teaching two hundred and forty thousand people that when a thing is finally about to be lost, we stop doing it the slow way and send in professionals — and that lesson would outlive the paper by a thousand years and it would be the worst thing we ever taught them."

The ballot ran eleven days in the autumn of year nine hundred and eighty-one. Turnout was ninety-six percent, joint, and the question was three sentences long because the drafting committee had lost an argument about brevity.

Sleeve carried with fifty-four point one percent.

Not sixty-one. Nobody had expected sixty-one for eight hundred years; the superstition had died in year one hundred and forty-two along with the woman who had been wrong about it, and it was on page nine of the text as the worked example of an anchor destroyed by publication, and there was always somebody in the Long Gallery on ballot night who said it's always sixty-one as a joke, and it never was.

Fifty-four point one. Four percent of a quarter of a million people had voted to bring the ship down and their reasons were in the record under their own names, and the minority statement went onto the plate in the same size letters, and the load-bearing part of it was the woman from the eleventh camp's four point one hours, printed exactly as she had said it, in the units she had demanded.

The four cold tunnels were funded in the same ballot, as a separate question, by ninety-one percent, out of the settlements' own charge and eleven years late.

They cut the first sleeve segment in year nine hundred and eighty-four and fitted the nineteenth in year nine hundred and ninety-five, and four people died doing it, and their names are on the wall on Deck 5 in the order they went, in whatever hand was holding the stylus.

The crawl above Frame 44 was open the whole time. That had been a condition, argued for two years, carried by a majority so large that the drafting committee had trouble filling the space beneath the minority statement: the sleeve went on the outside, the working faces were rerouted, and at no point in eleven years was the ladder closed to the autumn exercise.

They moved the coolant run. That was the actual engineering answer and it took nine months and it was the single most consequential thing anybody did to the Ambit in its second millennium: the warm pipe came off the inner skin at frames 39 to 51 and went up onto the stringers, eleven centimetres out, with a radiation shield between, and the thermal gradient across the skin at Frame 44 fell by a factor of nine, and the crack-growth date went from year one thousand and forty-one to something in the four thousands with an interval so wide that the panels declined to quote a median.

The crawl was cold after that.

Nobody had thought about it. It was in nobody's assessment and nobody's minority statement, and the first autumn class to go up after the reroute — nineteen of them, in year nine hundred and ninety-six, from four settlements — came down at the end of the fortnight and reported it as a fault.

Kesia Roque-Anselm was ninety and did not go up any more and heard about it in the Bureau room, where somebody read her the girl's log entry out loud: Crawl above Frame 44 is at four degrees. Feels like home. Recommend investigation.

She laughed until she had to sit down and could not explain it to anybody in the room, all of whom had been born on the ground.

"You don't understand," she said, when she had got it back. "The whole of it. Nine hundred and ninety-six years of children coming up ninety-one rungs to be warm and uncomfortable, and every single one of them wrote it down, hot dust and old solder and the pipe ticking — and we fixed the hull and now it's four degrees up there and a girl from the fourth camp says it feels like home."

"Is that good?"

"It's not good or bad. It's just the last thing that was still the same." She wiped her face with the back of her wrist, like a woman clearing a work surface. "Somebody write it down."

Somebody wrote it down. Everybody wrote it down; that was the point and had been for nine hundred and ninety-six years.

The pipe stopped ticking. That went into the fault log as a closure — coolant run 39–51 relocated, thermal cycling on inner skin reduced by 9x, tick signature no longer present, this entry closes the anomaly first reported yr 977 by K. Roque-Anselm, third shift, hull & thermal — and the anomaly's whole life ran to four lines and forty-one prior shims, and a hull tech in year one thousand and eleven, reading the file for an unrelated reason, wrote in the margin of her own working: forty-one people fixed this and none of them asked. Do not be the forty-second.

That sentence went into the year-nine text in year one thousand and forty, on page nine, in the margin, where it is now.

Frame 31's clip sang for another two hundred years and was shimmed nineteen more times, by people who all knew the story and all wrote investigated, no underlying cause found, shimmed, because there genuinely was no underlying cause; it was a clip with a resonance, and it had been singing since a woman shimmed it on the first night of a deceleration burn six hundred and eighty-three years earlier, and it is singing now.

Kesia Roque-Anselm died in year one thousand and two at ninety-five, aboard, in a chair by a window at eye height, which had been the arrangement for the old and the dying since before there was anything else to arrange.

There were nineteen windows in the Deck 2 annex and there had been since year eighty-six. She was at the fourth one, which looked out along the spine at nothing in particular: a great deal of dark, and stars, and off to one side, if you had the geometry and a good decade, a dim thing that nobody bothered to point out any more because there was no vector for it to be nineteen degrees off.

She had asked, in the last month, for the sports and got them, and for the array feed and got that too, and in the last fortnight, when she could not hold a slate, a hull tech of nineteen sat with her at 0217 and counted the gap out loud.

Thirty-six point nine.

"It's still going," Kesia said.

"It's still going."

"Everybody still hums forty-one."

"Everybody still hums forty-one." The girl had the ship's own habit of not filling silences and was good at it. "There's a paper this year saying we should stop and teach the current value and revise it annually."

"There's a paper like that every eighty years."

"It got sixty-one percent in the indicative."

Kesia Roque-Anselm laughed, which cost her something, and said: "Then it'll fail in the real one," and it did, four years and two months later, and the little star went on being hummed at wrong by a quarter of a million people, and page four kept 41.00 with a date attached, and the marginal line beneath it kept saying the song is not the measurement.

They wrote her name on the wall on Deck 5 in the ordinary way, in whatever hand was holding the stylus, which turned out to be a survey technician of twenty-four who got the K slightly wrong and was sick with fright. Nine hundred people came, which was five times the standing complement, most of them up from the ground on the autumn lift, which had been rescheduled by four days for the purpose and which was the only concession anybody made.

Somebody put an apple on the deck plate underneath, and somebody else cut it into eight pieces with a knife and gave one to each of the seven people standing nearest and kept the last and put it in her pocket, and nobody asked why.

The last thing to say about Frame 44 is that nothing happened there.

That is the whole of it and it is the reason the place survived a thousand years: it was a crawlspace on a spine with a bracket in it, and the bracket had been reseated in year eighty by a woman of thirty-nine who had come up to do a job and had brought her slate out of habit, and the bracket was fine, and had been fine for nine hundred and twenty years, and was checked every autumn by somebody who put a hand on it and wrote no fault found.

In year one thousand and eleven the autumn exercise reached depth two thousand and forty on the marker.

The girl who took the photographs was seventeen, which was two years late, because she had failed the derivation twice at fifteen and had come back for it, which was permitted and unremarkable and happened to about one in nine.

She was from the far south, from one of the four settlements that had waited eleven years for a cold tunnel and had got it in year nine hundred and ninety-two, and she had been born in the year it opened, and she had never in her life slept above four degrees.

The crawl was cold. She wedged herself in — feet against the stringer, not the pipe, that, although the pipe was eleven centimetres away now and cold and nobody could tell you why the instruction had survived — and she photographed pages at eleven an hour with the lamp moved four times a page, and it was tedious in the way she had been promised and had not believed.

At depth two thousand and thirty-eight she found four sheets in a hand she recognised, because everybody recognised it, because two of the four were on page nineteen of the text: a hull tech turned biologist who had gone down at thirty-six and had not come up, three of them wrong.

She photographed them, including the wrong ones, because you do not tidy people.

At depth two thousand and forty she stopped, because the fortnight was over, and she reached back into the dark past the marker with her arm to the shoulder, and felt paper going away from her further than she could follow, and did not follow it.

She had brought a pencil. There was a shelf at the bottom of the ladder that somebody had put up in year six hundred and forty and it was never empty and nobody knew who filled it, and it is one of the four genuinely unsolved questions in the archive of two worlds, and there are papers.

She wrote, on the back of a fault sheet, badly, because you cannot write well wedged into a crawlspace:

Yr 1011 d19, 0409. Autumn plates to depth 2040. Reached I. Ouma's four sheets, photographed all four incl. the wrong ones.

Bracket at Frame 44: no fault found. It's been fine for 931 years, which everyone knows, which is why I put my hand on it.

Pipe is cold. Crawl is at four degrees. I'm told that's new. It feels like home and I'm told that's funny.

TEV-9 gap 36.4 s. Everyone still hums 41. I hum 41.

Anyone can check this. The array logs are open. They have always been open.

Bring a pencil. There's a shelf.

A. Achebe-Lund, yr-nine (repeat), far south, Ouma

She taped it up with the rest, where a hand would find it and where nobody would ever index it, and took the slate and logged the visit — inspection, no fault found — which was true in every word.

Then she went down the ninety-one rungs, past the hook and the lamp and the shelf with its pencils, and out along the amber corridor toward Ag-3, where the false dawn was coming up in the grow-lamps and the night crop crew would be arguing about something, and where there was a filter on her list, because there was always a filter on the list.

On the way she hummed it.

Long, long, short, short, long. A stutter. Then a gap of forty-one seconds — which was wrong, and had been wrong for three hundred years, and which she knew was wrong because she had counted it herself four hours earlier and got thirty-six point four, and which she hummed at forty-one anyway because that was the song, and because a woman on third shift had memorised it in nine hours in a crawlspace in year seventy-six the way you memorise a song you hear during a bad week, and had hummed it, and had written in her personal log 41s, call it 41 exactly, cute.

A star, keeping its own time, a thousand years and eleven light-years behind, indifferent, unhurried, changing at its own pace for its own reasons and telling nobody, having been made a clock and then a metronome and then a deadline and then a song — and remaining, through all of it and for as long as anybody kept climbing ninety-one rungs at four in the morning to look, simply something that anyone could see.

By year one thousand and thirty-nine there were three hundred and eleven thousand people on Ouma and a hundred and forty aboard the Ambit, and the four wall positions had not changed in two hundred years: the world, live, with its weather; the phase box, with a star whose gap was now thirty-five point one seconds and falling and which everybody still hummed at forty-one; the four air chemistries from four laboratories forbidden to share instruments; and, last, where the eye rested, hours above gate.

It was 64.9 that autumn, and rising, and it had been written by a girl of fifteen with a stylus while eighteen others watched her hand, and the reconciliation underneath it — inferred from waste heat by the autumn class of the ninth rota, four of whom had got the sign wrong and said so in the note — read 64.6, residual within error.

The ship was sound. The sleeve had held for forty-four years and the model that watched it was validated five-yearly against a physical proxy by a body that had no interest in the answer, which was recommendation eleven of the inquiry of year nine hundred and eighty-one and was the least glamorous thing that inquiry ever did and the only one anybody would have missed.

The crawl above Frame 44 was at four degrees and had been since the reroute, and every autumn class that came up wrote that it felt like home, and by then nobody found it funny except historians.

Bakri Ouma-Vaan was sixty-one and had been awake at 0217 for thirty-four years.

He was radio and thermal, which meant the ground link, which meant the two dishes on the dorsal truss that carried nine hundred channels of session traffic and school and weather and the weekly reduction down to a world four hundred thousand kilometres below with a lag of four seconds each way, and it meant the radiators that took the heat off the transmitter chain, and it meant, four times a year, a housekeeping document that nobody had ever read for pleasure.

The system noise temperature log.

Every receiver in the universe has a noise floor and it is measured in kelvin, because noise is heat and heat is the one thing that always arrives. The Ambit's ground-link receivers logged theirs every eleven seconds and had done for nine hundred and forty years, and the log existed because a warm receiver is a sick receiver and because a hull tech in year one hundred and something had wanted to know when to clean a feed horn. It was open. It had always been open. Nobody had ever petitioned anything to read it because nobody had ever wanted to.

On the ninth night of the autumn quarter, with the transmitter down for a feed swap and nothing much on his list, Bakri Ouma-Vaan pulled a year of it to see whether the west dish was ageing, and it was, by about a millikelvin a decade, tediously, as expected.

There was also a bump.

It was four millikelvin high and it lasted about nineteen minutes and it happened once per orbit, and it had happened once per orbit for as long as the log went back, and it was so small and so regular that every automated cleaner in nine hundred and forty years had classified it as a spacecraft artefact, which is what you call a thing that recurs with your own period.

Bakri looked at it for a while.

Then he thought: it should have moved.

That was all, at first. A technician's small objection, and the whole of what followed came out of it. The Ambit's orbit was not fixed in the sky. It precessed. Slowly, four degrees a year, the way any orbit does around an oblate world, so that the plane of it turned like a slow hand — and a thing that happened once per orbit because of the spacecraft would keep happening at the same place in the orbit forever, and a thing that happened once per orbit because the sky was in a particular direction would creep.

He pulled forty years and fitted it.

It crept. It crept at four degrees a year, exactly against the precession, which meant it was not in the ship. It was outside, and it was fixed in the sky, and it had been sitting in the same place in the sky for nine hundred and forty years while a receiver's fourth sidelobe swept across it once every ninety-one minutes and warmed by four millikelvin and nobody in two worlds had ever asked why.

Bakri Ouma-Vaan sat in a compartment on Deck 3 with his feet on a crate and worked out the direction with a pencil, because he had stopped trusting anything with a processor in it about an hour earlier, and the direction was fifteen light-years away and had a name that every child in two worlds learned at nine and no adult in either had said out loud in earnest for eight hundred years.

He took nine days, because nine days was the interval and had been since before anybody.

The first thing he checked was his own instrument, and he spent one shift very happy, because the west feed had been swapped four hundred times in nine centuries and a periodic thermal artefact in a receiver is the most ordinary thing in the world. He put a source in front of the chain. He ran the east dish, which had different feeds and a different amplifier and had been built two hundred years later, and the east dish saw it too, at the same place in the sky, four millikelvin high.

He wrote the happiness down and wrote down that it had been unearned, because everybody did, because it was on page nine.

The second thing was the direction, properly, with the interferometric baseline, which took two nights of somebody else's telescope time and an apology. The source was point-like to the resolution of a four-kilometre array. It was not the star. It was within nineteen arcseconds of the star and it was not the star, and the star at that distance was a fourth-magnitude nothing that the survey people had been using as a photometric standard for six hundred years without ever once mentioning what it was, because it was on the standards list under a catalogue number.

The third thing was the spectrum, and this was where he stopped being a man with a tedious log and became a man who could not eat.

It was narrow. It was a carrier about one and a half gigahertz and it was narrower than any natural thing has ever been or ever will be, narrower than the receiver could measure, and the entire four millikelvin was sitting inside a band that a hydrogen cloud could not have produced in the lifetime of the universe.

The fourth thing was the drift, and the drift was the proof, and Bakri Ouma-Vaan understood while he was doing it that he was performing the oldest exercise in the culture that had raised him.

A signal in your instrument does not move. A signal fifteen light-years away moves in frequency exactly as much as your own motion makes it move: the ship around Ouma, ninety-one minutes; Ouma around its dim orange sun, four hundred and eleven days. Two periods, two amplitudes, both computable from published ephemerides by anybody with a pencil, neither of them adjustable by any wish of his.

He measured the ninety-one-minute term first and it was right to four parts in a thousand.

Then he pulled nine hundred and forty years of noise floor and folded it on four hundred and eleven days, because the bump's height changed as the sidelobe pattern swung, and there in the fold was the annual term, in the amplitude rather than the frequency, riding along on an orbit the Ambit had been making around a star it had chosen out of a junk catalogue.

The source was outside. It was narrowband. It had been there for nine hundred and forty years at least, which was as far back as the log went, and it was in the direction of Sol.

He had the whole reduction repeated independently by the Ag-3 night crop crew of the eleventh rota, four of them, using the duplicate radiometer that had been kept under a beans rota since year eighty-four because a woman named Turi Achebe had written nine pages and lost an argument publicly and won it in the end, and the crew got four point one millikelvin and an argument about the sidelobe model that took two more days and improved the estimate.

He published on Fourthday, in the ordinary weekly reduction, at 0400 ship-time, with a four-line covering note, and because it was 0400 the first people in two worlds to read it were hull techs and recyclers and night crop crews standing in amber corridors with a slate in one hand.

Then he went and cleaned a filter in Ag-3, because it was on his list, and the filter was a filter, and the false dawn was coming up in the grow-lamps, and two of the night crop crew were arguing about whether the mat counted as a vegetable, and one of them said, without looking up, "Is it them?"

"It's narrowband and it's fifteen light-years away in the right direction," said Bakri Ouma-Vaan. "That's all four measurements say and I'm not going to say a fifth."

"But is it them."

"Check it again," he said. "Bring me your working," and threw her a tomato, and she laughed at him, and he went to bed and did not sleep.

Register of Consequential Omissions, entry four thousand one hundred and eleven, filed by B. Ouma-Vaan, third shift, radio and thermal, in the fourth month of year one thousand and thirty-nine:

No receiver on this vessel or this world has ever been pointed at Sol.

Not once, in one thousand and thirty-nine years. Not for an hour. There is no line in any workplan declining to do it, because there is no line in any workplan proposing it. I have looked for four days with an archivist and we cannot find the decision, and the reason we cannot find it is that there wasn't one.

This is the largest entry in this Register and it is nobody's. I want that stated plainly before anybody goes looking for a villain, because there isn't one, and the ease of it is the horror and not the malice, which is a sentence a woman said in a hall in year sixty-eight and which we have been quoting for a thousand years without noticing that it applies to omissions as well as to acts.

Here is the best reconstruction the archive supports. For eighty years the vessel believed it was in transit and there was nothing to hear from and no one who could have proposed listening without being told why. In year sixty-nine we lost the ability to return and in year eighty-two we published that we had lost it, and somewhere between those two dates Sol stopped being a place and became a direction. Nobody wrote the second date down. After that there was the disclosure century, and the tugs, and the departure, and the burn, and Kesh, and four hundred years of a world that killed at seventy-one, and at every point a proposal to build a receiver and point it back the way we came would have been answered — correctly, by good people, in the open — with the observation that we could not go there, that any news would be fifteen years stale, and that the fabrication charge would be paid in hours above gate by people who had not asked to pay it.

No operational requirement. That is the phrase. It is item four hundred and eleven of this Register, filed by I. Vaan in year eighty-three about a cometary survey that turned out to be the difference between a house and a ship, and I have read that entry perhaps four hundred times in my life as a piece of school and I did not recognise it when I was standing inside it.

I have no recommendation. I measured a noise floor.

B. Ouma-Vaan

The receiver took eleven years.

The ballot ran eleven days in the autumn of year one thousand and forty, joint, turnout ninety-eight percent, the highest ever recorded in two worlds, and the question was one sentence long because for once the drafting committee won its argument about brevity.

It carried with eighty-eight point one percent, and the minority statement went onto the plate in the same size letters, and it was not stupid and nobody pretended it was. It said that a fabrication charge of nine years was four point four hours above gate per capita per year for nine years and that this was three hundred and eleven thousand people paying in the far end of their lives for the privilege of overhearing something they could not answer, verify, or use; that the last time this ship had built a great instrument out of longing it had been the interferometer and it had been worth it, and that this was not an argument, it was a precedent, and a precedent is what you have instead of an argument.

It was signed by four thousand and six people, which the archive notes was a coincidence and which nobody has ever entirely believed.

They built a phased array nine hundred metres across on the dorsal truss out of eleven segments over nine years, and two of the segments failed and were remade, and nobody died, which was remarked upon at the time as the first great fabrication in the history of either world to be completed without a name going onto the wall on Deck 5.

What they got, over the following two decades, was this.

The carrier was there and it was steady to eleven parts in a billion, which is a stability no natural object achieves and no drifting wreck maintains, and which meant somebody was keeping a clock.

It was modulated, extremely slowly. The bit rate, when they finally established it in year one thousand and fifty-one, was four bits a second, which is the rate you choose when you have decided that reaching a very long way matters more than saying very much, and it meant that the thing took nine days to transmit what a settlement school sent to the ship in a heartbeat.

It repeated on a cycle of four hundred and forty-one days.

And inside the cycle, when the array had been running for a decade and the error correction had been worked out by three separate groups who were not allowed to share instruments, it was a catalogue.

That is the flat word and it is the right one. It was a list. It was a very long list of vessels, with dates, with mass and drive class and declared destination, and with a field at the end of each entry that took the survey people four years to interpret and which turned out to be, when they were sure, the date on which Sol had last had any information about the vessel at all.

The Ambit was on it.

She was the ninth entry in the fourth block, launched year zero by the reckoning of a calendar that had a different zero, mass and drive class correct to within the tolerance of the published specification, declared destination Kesh, and her last-information field held a date that corresponded to about eleven months after departure, which was when the Ambit had passed out of usable range of the deep net and had begun, as every vessel of her generation had begun, to be a rumour.

There were nine hundred and forty-one entries.

There were nine hundred and forty-one, and Ouma read the list for a year, and the thing that took the ground apart was not that the Ambit was on it. It was the last-information dates. Four hundred and eleven of the entries had a date within a decade of launch, like theirs. Sixty-one had a date centuries later, which meant those ships had been heard from, which meant they had arrived somewhere or had at least been able to say something. And four had a date and then a second field which the working groups argued about for six years and finally agreed, on a majority of three panels to one, meant ended.

Nobody had ever told Sol that the Ambit had arrived. Nobody had ever told Sol that four hundred and six people died in year sixty-nine, that a world was closed, that the ship had gone on to a junk star out of the tertiary catalogue and stopped there, that there were three hundred and eleven thousand people living at four degrees on a world called Ouma with a chemistry in the ground that gave them an old age at seventy-one.

Sol had gone on listing them for a thousand years, four bits a second, in a cycle of four hundred and forty-one days, into a sky that had not once answered.

The beacon was not addressed to them. That was established early and repeated often, in sessions and in the year-nine text, because it was the load-bearing fact and it was the one people kept mislaying. It was omnidirectional. It was addressed to nobody, which meant it was addressed to everybody, which meant it was the largest and longest and most patient act of unrewarded bookkeeping in the recorded history of the species, and it had been running for at least a thousand years and had been carried out by people none of whom could have expected to see it answered.

There was a phrase for that, on Ouma. It was on a plate at the west lock of the forty-degrees-south station and it was on page nineteen of the text, and it had been said first by a woman who kept a list she could not give to anyone: shame is not a plan. But there was another one, older and less quoted, and it turned up now in every second session for a decade, because it fitted and nothing else did.

The argument about whether to answer took four years and two months.

It began before the catalogue was decoded and it did not wait for it, and it was, by universal agreement afterwards, the argument that the whole thousand years had been rehearsing for.

The technical part was nothing. A reply cost power, and power was reactor time, and reactor time on a ship with three point one percent in her tanks was a matter of thermal budget and radiator margin, which meant it was Bakri Ouma-Vaan's department. A hundred kilowatts into a nine-hundred-metre array would reach Sol at a signal-to-noise anybody there could work with, provided anybody there had an instrument as good as the one Ouma had spent nine years and four point four hours per capita per year building, which was an assumption the panels published with a wide interval and a note.

Thirty years to a reply, if there ever was one. Fifteen out and fifteen back and nothing at all in between, and everybody who voted would be reading the outcome at seventy or not at all.

The real question was what to say, and it took four years because it turned out to be a question about who they were, and nobody had had to ask that out loud for eight hundred years. The technical part was nothing and the four years were spent on the rest of it, and the first thing the four years produced was a piece of arithmetic that a fifteen-year-old did in an afternoon and that nobody afterwards was able to get out from under.

Four bits a second is what reaches. You can put more power into the array, and they modelled that to death, and the honest conclusion of three panels forbidden to share instruments was that a hundred kilowatts into nine hundred metres at fifteen light-years bought you four bits a second and no argument was going to buy you forty.

Four bits a second is a hundred and twenty-six million bits a year.

The year-nine text, entire, in plain language, with its figures: nine months.

The Register of Consequential Omissions, four thousand one hundred and eleven entries: four years.

The ledger — every name in the book from Bay 2 forward, four hundred and six and then a thousand years of everybody else, with dates and no cause: eleven years.

Iyabo Ouma's twenty-nine years of handwriting, in facsimile, unedited, including the pages that repeat: sixty-one years.

The transcripts of the argument they were currently having: a hundred and sixty years, and rising by about eleven months per year of argument, which somebody put on the wall in the Long Gallery as a joke in the second year and which stopped being funny in the third.

The whole holding of two worlds, everything either of them had ever measured or written down: something on the order of a hundred and forty thousand years.

So you could not send everything. That was established in the first month and it never went away, and it meant that the Ambit and Ouma, having spent a thousand years constructing an entire civilisation around the proposition that a fact's purpose is not to be chosen for you, were now obliged to choose an order.

"It's Verrat," said a Bureau instructor of thirty-four in the ninth session, and she was not being provocative; she was reading. "Not all true things are load-bearing. The purpose of a fact aboard a closed vessel is not to be known but to be useful. That is the sentence that killed four hundred and six people and it is also, word for word, the design brief for a four-bit-a-second link, and I would like everybody in both halls to sit with that for a minute before we start being clever."

Eight seconds. Nobody used them.

"The difference," she said, "the only one, and I have looked for a bigger one for two years — is that the framework was applied to us by forty people in a room, and this will be applied by us to strangers, in the open, with the ordering itself published and votable and revisable forever. That is a real difference. It is not as large as I would like it to be."

They quoted Hana Merrick constantly that year. She had been dead for six hundred and sixty years and her Register entry — number one thousand four hundred and nine, five lines, filed by a woman who had been overruled and had published her own dead afterwards with the losing recommendation attached — was read out in session eleven times in four years, and the settlements' schools taught it that autumn to children who had previously known her only as an exam question.

I have spent five years unable to decide whether I was right, and I have concluded that this is the correct condition for a person in my office and that any successor who feels certain should be watched.

The positions sorted themselves into four, as positions did.

Send the warning. Kesh-3's coordinates, the precursor chemistry, the reflectance signature at nine hundred and forty-one nanometres, the gate at four degrees, the panels' fit with its error bars and the word never still honestly at the far end. Nothing else. It was the only part of the holding that could keep anybody alive, it fitted inside four hundred days of transmission, and it was addressed to the only audience that mattered, which was the next nine people who would otherwise take their helmets off on day sixty and cheer.

Send the method. The warning, and then everything required to check the warning: the assay archive, the forty-one dead landers with their dates, Sarr's nine weeks, Achebe-Roque's gate, Ouma's twenty-nine years. Because a conclusion you cannot audit is a rumour, and a rumour is what a fact becomes when it has travelled fifteen light-years and lost its working.

Send nothing. Nine hundred and forty-one entries, four of them ended. We do not know what ends a ship. We have been silent for a thousand years by pure administrative accident and we are alive and there are three hundred and eleven thousand of us, and the proposal on the table is to spend nine years of fabrication to become audible.

Send the whole thing, in an order, forever. Start with the warning, because the warning is the part that saves lives; then the method, because a warning that cannot be checked is a rumour; then the Register, then the ledger, then the transcripts; and go on transmitting for as long as there is a reactor and somebody willing to run the radiators, in the certain knowledge that nobody alive will see the end of the transmission and that the ledger alone will still be going out when every person who voted is on the wall on Deck 5.

The case for sending nothing was made best in the second year by a man of fifty-one from the far south named Osei Vaan-Ouma, who ran a cold tunnel and had never spoken in a joint session before.

"I'm not frightened of the four," he said. "I want that first, because everybody expects the far south to be frightened and I'd rather disappoint them early. Four out of nine hundred and forty-one is a rate and I can read a rate. Ships end. Ours nearly ended nine times and four of those were us.

"Here's mine. That beacon has been shouting for a thousand years without an answer and we are about to be the answer. Not an answer. The first one, so far as we know. And the moment we are, we are a fact in somebody else's holding — a line in a catalogue in a room fifteen light-years away, with a mass and a drive class and a last-information date, and a place. And they will do with that line whatever people do, and none of it will be checkable by us, ever, and I would like this hall to notice that we are proposing to hand our position and our chemistry to an institution about which we know precisely one thing, which is that it keeps very good lists.

"So does the Morale Directorate."

Eight seconds.

"I know what happens next. Somebody will tell me that they cannot come here in less than centuries and cannot do anything to us that we could not do to ourselves, and that is true and it is not what I am afraid of. I am afraid that in four hundred years there will be a generation on Ouma that has been listening to Sol for four hundred years and has begun to hold its own arguments with one eye on what Sol will think of them. That's it. That's the whole of my objection. Not invasion. Deference. We are the only people in the universe who have ever had to be honest with nobody watching, and it made us, and I would like somebody to argue that we won't lose it."

Nobody managed to, in four years, to his satisfaction or anyone else's. His statement went onto the plate in the same size letters when it was over.

What decided it was said in the third year by an orchardist of forty-four in Ag-1 on the ship, up on a nine-year rotation, with pruning shavings in her hair, and it was not an argument anybody had prepared for because it was not about Sol at all.

Her name was Delphine Sarr-Achebe and she had asked for four minutes.

"I've listened to two years of people saying what will they do with it," she said, "and I want to turn it round, because I think we've been holding the wrong end.

"For a thousand years every single thing this ship and this world has said out loud has been said to an audience that could check it. That is not a virtue of ours. It's a condition. We built the condition on purpose after it nearly killed us, and then we spent nine hundred years congratulating ourselves on a discipline that we have never once had to keep without a hundred and ninety thousand fifteen-year-olds standing behind us with pencils.

"Now, for the first time since year eighty, we are going to speak to somebody who cannot audit us.

"Fifteen years out. They will have the assay data and they will not have the world it came from. They will have our numbers and no way on this side of a century to catch us in a single one of them. We could send the warning and leave out Bay 2. We could send Kesh and leave out the twelve years. We could send a thousand years of a well-run civilisation and simply not mention that it began with forty exhausted people in a room deciding that eleven thousand others could not survive the truth, and nobody out there would ever know, and — this is the part I would like said slowly — nobody in here would ever be able to prove that we hadn't done it for good reasons.

"So the message isn't about them. It's the only exam we have ever been able to set ourselves. We are going to find out, in public, at four bits a second, what this ship says when nobody is checking.

"And I think we know the answer. I think we've known it since a maintenance engineer walked onto a stage with nineteen pages of pencil and put them on the floor unread and told eleven thousand people the first thing out of her mouth was that they shouldn't believe her.

"Send the lie first. Not the warning. The lie. Put Bay 2 and the twelve years at the top, in the header, in the part that repeats every cycle forever, before the chemistry, before the coordinates, before anything useful — so that the first four hundred bits anybody out there ever receives from us is the worst thing we ever did, and everything after it arrives from a source that has already told them it once decided that four hundred and six deaths were not load-bearing.

"That costs us nothing. That's what I'd like the far south to hear. It costs us four hundred bits and a fortnight of transmission a year. And it makes every number that follows it worth having, which the numbers otherwise are not, because a warning from a stranger with a clean record is worth about as much as a fuel margin in a year-nine textbook."

Eight seconds, and then, from the ground, eleven separate people trying to speak at once, which the lag rendered as a noise the transcript records only as (overlap).

The ballot ran eleven days in the autumn of year one thousand and forty-four. Turnout was ninety-eight point two percent, joint, which broke the record set four years earlier by the ballot that had built the array.

There were two questions.

The first — shall the vessel transmit — carried with seventy-nine point one percent.

The second was the order, and it was four options and a write-in, and what carried, with sixty-one point four percent, was the header-first proposal, whole, exactly as the orchardist had said it and as the drafting committee had subsequently spent nine months failing to improve.

Bakri Ouma-Vaan was sixty-six and read the figure in the Bureau room at 0400 on the twelfth day and laughed until he had to sit down, and could not explain the joke to any of the eleven people present, all of whom had been born on the ground, and had to send them to the archive, where the explanation is filed under an index line, class open, petitionable, and has been consulted nine thousand times.

There was a third thing on the paper, added late by amendment on the floor of a settlement hall in the far south and carried on the indicative before anybody on the ship had had time to think about it, and it was the shortest item and the one that took the longest to draft.

A question.

A girl of sixteen from the ninth camp had asked for it and had been told she would have to ask twice and had asked four times. "Everyone keeps saying we're not asking them for anything," she said, "and everyone says it in the voice people use when they're being dignified. I'd like to know why. We have a chemistry in the ground that gives us an old age at seventy-one and four candidate approaches that are all wrong and eleven hundred people working on it, and there might be a laboratory fifteen light-years away that solved it four hundred years ago and doesn't know we exist. Thirty years for an answer. I'll be forty-six. My mother will be dead and I'll be forty-six and I would like to have asked."

They put four questions in, at the end of each cycle, after the warning and before the ledger, and the drafting committee wrote them in the plainest register two worlds could manage, and the fourth one is the one that ended up on the plate:

Do you know how to stop a fold?

The transmission began at 0217 on a Fourthday in year one thousand and forty-five, because Astro had a sense of occasion that a thousand years of institutional humility had entirely failed to kill.

Nobody felt anything. There was no burn and no tilt and no fastener in the hull was asked any question it had not been asked for a hundred and forty years, and the Long Gallery had a hundred and thirty-one people in it, which was almost the entire standing complement, and eleven thousand more on the ground in forty-one assembly halls at four seconds' lag, watching a number.

The number was radiator margin. That was what there was to watch: a hundred kilowatts going into an array is a hundred kilowatts of heat coming out of a ship, and the only visible fact of the greatest act of speech in the history of either world was a thermal load curve on the fourth position of a wall, climbing through its transient and settling, and Bakri Ouma-Vaan sat at a bench on Deck 3 with his feet on a crate and watched it settle and said, to nobody, "That's it, then."

Heat is public. Heat is the one thing that leaves.

Eleven weeks later a girl of fifteen at the fourth camp on Ouma, doing the autumn reconciliation with a duplicate radiometer under a beans rota, folded four hundred days of her own instrument's noise floor and found the ship in it: a bump, four millikelvin high, at the Ambit's orbital period, creeping against the precession, narrowband, unmistakable. She published it on Fourthday in the ordinary weekly reduction with a four-line covering note and the observation that her method was Ouma-Vaan's, that she had got the sidelobe model wrong the first time, and that anybody could check it.

It is the most-taught page of that century. Not because it was hard. Because they had answered a beacon and then, without anybody planning it, had immediately gone and measured their own answer from outside, with the same instrument and the same arithmetic, and had published the residual.

The header ran to four hundred and eleven bits and took a hundred and three seconds to send, and it went out at the top of every four-hundred-and-forty-one-day cycle, and it goes out now.

The drafting took nine months and four hundred amendments and the final text was carried by voice in both halls, which had happened four times in a thousand years.

This is the vessel Ambit, ninth of your fourth block, launched from Sol, declared for Kesh.

We arrived at Kesh forty years early, in our year sixty-eight, and we did not tell you and we could not.

In our year sixty-nine we put nine people onto Kesh-3 and four hundred and six of us died in eleven weeks, and our Council sealed two hundred and forty living people into a bay from the outside and vented it, and then decided that the rest of us could not survive knowing, and manufactured a voyage, and sang about it to our children for twelve years. It was not a feat. It took forty people and eight months and it was easy, and the ease of it is the horror and not the malice.

One of us found it with four measurements and a pencil and would not put it down.

Everything that follows this is checkable. We will send you the way to check it before we send you what to think. If any of it turns out to be false, it is because we were wrong and not because we chose, and you will be able to demonstrate which.

We cannot come to you. We are not asking you for anything except the answer to four questions at the end of each cycle.

Check us.

Osei Vaan-Ouma, who had spent four years arguing that they should stay silent, voted for the header and said so in session, and his reason is in the transcript and in the year-nine text.

"I still think we'll learn to speak with one eye on them," he said. "I think it'll take about four hundred years and I think it'll be nobody's fault and there'll be no decision anybody can point to, and somebody in year fourteen hundred will find it in a noise floor at three in the morning. I'd like that written down now so they don't have to work out that we didn't see it coming.

"But I'll tell you what changed my vote and it isn't the argument, it's the order. If we'd sent the warning first I'd have gone on fighting it in the corridor for the rest of my life. We're sending the worst thing we ever did first, forever, to people who can't check it and can't punish us and can't do anything with it at all.

"That isn't diplomacy and it isn't penance. There's no audience it's aimed at. It's just what we say now."

Bakri Ouma-Vaan died in year one thousand and fifty-one at seventy-three, aboard, in a chair by a window at eye height, which had been the arrangement for the old and the dying since year eighty-six and had never been reopened.

He had run the radiators for the first six years of the transmission and had handed them over in his last autumn to a hull tech of twenty-six from the eleventh camp, and the handover document is four pages of duty cycles and one line at the end which reads: It is a hundred kilowatts and a filter. Do not let anybody tell you it is anything else, and do not let them stop you cleaning the filter.

They wrote his name on the wall on Deck 5 in the ordinary way, in whatever hand was holding the stylus, which turned out to be an archivist of thirty-one who got the B slightly wrong and was sick with fright, and there was an argument in the corridor beforehand, because there is always an argument, and it was settled the way it had been settled since year eighty-two.

Somebody put an apple on the deck plate underneath. Somebody else cut it into eight pieces with a knife and gave one to each of the seven people standing nearest and kept the last and put it in her pocket, and nobody asked why, because everyone in the corridor understood that some things are kept.

His Register entry — four thousand one hundred and eleven, the largest in the document, the one that was nobody's — was never closed. Entries were invited from any resident and eleven hundred residents added to it over the following two centuries, and the Register itself went out at four bits a second in the fourth year of the cycle, all four thousand and then eleven thousand entries of it, a confession with no addressee, transmitted into a sky by people who would not live to finish sending it.

The reply window opened in year one thousand and seventy-five.

That was the arithmetic and everybody had it: fifteen years out, fifteen back, and a fortnight either side for the fact that Sol would have to notice, and nobody pretended that thirty years was a schedule rather than a floor. The panels published an interval and the interval ran from year one thousand and seventy-five to never, and the word never was in it because the fit permitted it and because two worlds had a nine-hundred-year habit of putting into the interval everything the fit permitted.

The array listened. It had been listening the whole time; that was the arrangement, one array, transmit and receive on alternate halves of the orbit, which cost them half their duty cycle and which the technical committee had proposed and the ballot had confirmed by ninety-one percent on the grounds that a civilisation that spends nine years building an ear and then spends all of it talking has learned nothing at all.

In the autumn of year one thousand and seventy-five the year-nine classes of forty-one settlements were set, as the reconciliation exercise, the folding of nine hundred days of the array's noise floor against the ephemerides of two worlds, looking for a narrowband source at fifteen light-years with a Doppler signature that no wish of theirs could adjust.

A third of them got the sign wrong. That figure was published.

None of them found anything, and they published that too, on Fourthday, in the ordinary weekly reduction, with a four-line covering note: no source detected above threshold; threshold stated; method stated; residual attached; anybody can check this.

They set the same exercise the following autumn, and the one after that.

Nine hundred and thirty-one kilometres above a cold world, on the ninth night of the autumn quarter of year one thousand and seventy-five, a hull tech of twenty-two went up ninety-one rungs at 0409 with a plate camera and a sore back, because the fortnight was ending and there were pages at depth two thousand three hundred and nineteen that nobody had photographed yet, of which there were, at the current rate, another hundred and forty years' worth.

There was a hook for a lamp at the bottom of the ladder and a shelf that somebody had put up in year six hundred and forty for pencils. It was never empty. Nobody knew who filled it, and there are four papers about it, and it is one of the four genuinely unsolved questions in the archive of two worlds.

She took one.

The crawl was cold, four degrees, the way it had been since the reroute a hundred and eighty years earlier, and she wedged herself in — feet against the stringer, not the pipe, that, although the pipe was eleven centimetres away now and cold and nobody could tell you why the instruction had survived and everybody taught it.

It smelled of dust and old solder.

Behind her along the curve of the hull the paper went away past the reach of the lamp: taped and re-taped, layered, soft as cloth in the deep places, one thousand and seventy-five years of other people's arithmetic. A boy's parallax homework with his mother's corrections on it. Forty-one drawings of a chair. Nine pages by somebody who had worked the chairs in the first year and never told anyone what she heard. Four sheets by a hull tech who became a biologist and went down and did not come up, three of them wrong. A page from year one thousand and thirty-nine, in a radio engineer's hand, which read in its entirety: Bump in the noise floor. Four millikelvin. It should have moved. It didn't. Check it again.

She photographed eleven pages an hour with the lamp moved four times a page, including the wrong ones, because you do not tidy people.

At 0430 she pulled the array feed, because it was the first thing on her home screen the way it was on the home screen of everyone in two worlds who had ever been fifteen.

TEV-9 flickered in its little grey waveform box. Long, long, short, short, long. The stutter. Then the gap.

She counted it under her breath, which everybody did, and marked it four times on the slate and got 34.81, 34.79, 34.82, 34.80, and wrote it down without any ceremony at all, because the period had been falling for three hundred and sixty-four years and a girl of fifteen with a sore back had first caught it at forty point six and had thought she had miscounted.

Then she reached back into the dark and found the paper and took the pencil off her ear, and wrote on the back of a fault sheet, badly, because you cannot write well wedged into a crawlspace:

Yr 1075 d19, 0409. Autumn plates to depth 2319.

Reply window opened this quarter. Nothing. Threshold and residual published Fourthday. I folded 900 days myself and got the sign wrong and had to do it again.

Bracket at Frame 44: no fault found. 995 years. I put my hand on it.

TEV-9 gap 34.80 s. Everyone still hums 41. I hum 41.

Anyone can check this. The array logs are open. They have always been open.

Bring a pencil. There's a shelf.

N. Sarr-Ouma, third shift, hull & thermal

She taped it up with the rest, where a hand would find it and where nobody would ever index it, and took the slate and logged the visit — inspection, no fault found — which was true in every word.

Then she went down the ninety-one rungs, past the hook and the lamp and the shelf, and out along the amber corridor toward Ag-3, where the false dawn was coming up in the grow-lamps and the night crop crew would be arguing about something, and where there was a filter on her list, because there was always a filter on the list.

Above her, in a compartment on Deck 3 with nobody in it, a hundred kilowatts went on going out into the dark at four bits a second, in the fourth year of its cycle, transmitting a list of names with dates and no cause to an audience that had not answered and might not exist, and had another seven years of the ledger to send before it reached the transcripts, and after that a hundred and sixty years of an argument about whether to speak at all.

On the way she hummed it.

Long, long, short, short, long. A stutter. Then a gap of forty-one seconds — which was wrong, and had been wrong for three hundred and sixty-four years, and which she knew was wrong because she had counted it herself twenty minutes earlier and got thirty-four point eight, and which she hummed at forty-one anyway because that was the song.

A star, keeping its own time, unimaginably far behind, indifferent and unhurried, changing at its own pace for its own reasons and telling nobody — having been made a clock, and a metronome, and a deadline, and a song — and remaining, through all of it and for exactly as long as anybody kept climbing ninety-one rungs at four in the morning to look at it, simply something that anyone could see.

The filter in Ag-3 was a mesh panel the size of a door, and it was the fourth of its line, and the three before it were in the archive with their service dates because somebody in year four hundred had decided that a thing which had been cleaned eleven thousand times was a document. The night crop crew were arguing about beans. They were always arguing about beans; the rota was nine hundred and ninety years old and had been amended four hundred times and was still wrong in the fourth quarter, and the argument had the quality of weather. She got the panel out, and knocked it against the frame the way you were not supposed to, and brushed it, and put it back, and logged it, and drank something warm standing up, and went to bed at 0710 with the grow-lamps coming up behind her like a sunrise that had been running on a timer for a thousand and seventy-five years and had never once been late.

She cleaned that filter, or the two that came after it, for nineteen more years.

In the autumn of year one thousand and ninety-four a hull tech of sixty-nine from the eleventh camp, who had run the radiators for forty-three years and had been twenty-six when a dying man handed her four pages in a chair by a window, handed the same four pages to N. Sarr-Ouma, who was forty-one. There was a duty-cycle table, and a note about the third pump, and a note about the note about the third pump. The line at the end had been recopied by hand at every handover because somebody in year one thousand and sixty had ruled that a printed copy would let it become furniture.

It is a hundred kilowatts and a filter. Do not let anybody tell you it is anything else, and do not let them stop you cleaning the filter.

The change was found on a Thirdday in the autumn of year one thousand one hundred and six, thirty-one years after the reply window opened, by a boy of fifteen at the ninth camp doing the reconciliation exercise with a duplicate receiver under the beans rota, and he got the sign wrong, which he said afterwards he was glad of, because it meant he did it twice.

What he found was not a message. It was a field.

The beacon's catalogue ran nine hundred and forty-one entries and had run them, unaltered, for as long as two worlds had been able to read it. The ninth entry of the fourth block held a mass and a drive class and a declared destination and a last-information date corresponding to eleven months after launch. In the cycle the boy folded, the last-information field of the ninth entry of the fourth block held a different number.

That was all. Four bits a second, nine days to say a shipload of nothing, and somewhere fifteen light-years back along the line of the launch a clerk or a committee or a machine had gone into a list a thousand years old and corrected one line in it, because new information had arrived.

He published it on Fourthday in the ordinary weekly reduction with a four-line covering note stating his threshold, his method, his first error and its sign, and the observation that anybody could check this. Three groups forbidden to share instruments confirmed it in eleven days. The Bureau of Verification then did the thing it had been built in year eighty-one to do, and constituted a panel of nine whose whole task, funded, with instruments, was to demonstrate that the change was an artefact of the ship's own array, a processing ghost, a forgery, or a wish. The panel worked for four years. Its final report is nineteen pages and is taught at year nine in both worlds, and its conclusion is one line long and has the tone of a woman putting a tool down: We could not do it, and we would like to record that we tried hard enough to be disappointed.

The addressed block came in the following cycle, after the catalogue, where nothing had ever been. It took nineteen days to send and it repeated, and they had it whole by the winter of year one thousand one hundred and eight, and the drafting of the translation took a year and four public disputes and the disputes are in the archive with the losing readings attached.

Received. Your first four hundred and eleven bits are held.

This beacon is maintained by an office of about ninety people. We are not a government and we do not speak for one. We were established a long time ago and our function is to keep the list. We have been overruled twice in our history and defunded once for forty years, and the gap in the catalogue between your block and the next is that gap and not a silence of ships.

It took us twenty-one years to answer you. Eleven of those were argument. We are not going to describe the argument at this rate. We record only that it existed and that it was not unanimous, so that you do not imagine us as one thing. We are not one thing. Nobody is.

We have never before had cause to write a sentence in this position and there is no established form, so we are using yours. We will send you the way to check what follows before we send you what to think, insofar as four bits a second permits, and where it does not permit it we will say so.

Your four questions.

One. Yes. The reflectance signature at nine hundred and forty-one nanometres is in our assay literature under another name and has been since before your launch. It was not in your library because it was published after your library closed and because it was, at that time, of interest to nine people.

Two. Yes. Nine vessels of your generation carried the same landing protocol and we have last-information dates for four of them consistent with the interval you describe. We cannot tell you that they died of it. We can tell you that we stopped recommending the protocol, on other grounds, in the second century, and that this is the first evidence anyone has offered that the grounds were the wrong ones.

Three. No. Nothing has come back from Kesh. You are the only thing that has ever come back from anywhere.

Four. We do not know how to stop a fold.

We are appending what we have, which is four hundred years of chemistry, eleven long-lived cohorts, and the assay of a body of similar composition in our own system that nobody has stood on. Our people who read your description believe that one of your four candidate approaches — the second, as you have numbered them — is excluded by work done here in our year six hundred and forty, and they have asked us to send the exclusion before the rest of it, and to say plainly that they may be wrong and that the work has not been repeated in two centuries. Send us your objection. We will be dead. Somebody here will read it.

Four vessels of your block are still outbound with declared destinations in the same catalogue class as Kesh. Two are beyond argument. Two are not. We have moved your warning — coordinates, chemistry, signature, gate, error bars, and the word never — to the top of the cycle, before the catalogue, in the part that repeats. It is now the first thing this beacon says. We did not put your header above it and we discussed doing so for a year. We decided that a warning is for the living and a confession is for the record, and that the living go first. You may consider that a reply to your header. It is the only one we are competent to make.

They read the last question in eleven halls and forty-one camps at four seconds' lag and there were eight seconds and then no overlap at all, which the transcript records, unusually, as (silence), because the operator that night thought it was worth distinguishing.

A thousand years of shouting into a sky, and the office that shouted had wanted to know the same thing they had wanted to know, and had been keeping the list for the same reason, which was that keeping it is how you go on being a person who could use it.

The reply is not a document that made anybody happy, and the year-nine text is careful about this, because the first generation to grow up with it kept expecting it to be. It was ninety people with a budget. It had been defunded for forty years. It could not stop a fold. It had ruled out one approach out of four on work two centuries old and had said so with its hands open, and the exclusion turned out, after nineteen years of assay under a beans rota with duplicate instruments and three groups who were not allowed to speak to each other, to be correct, and eleven hundred people who had spent their working lives on the second approach were told this in the ordinary weekly reduction on a Fourthday, and four of them published objections, and the objections went out at four bits a second in the following cycle, and one of the four was right about a detail, and the detail is in the literature of two systems under her name.

The gate at four degrees was seventy-one in year one thousand and forty-four. It was seventy-four in year one thousand two hundred and six and seventy-nine in year one thousand four hundred, and it moved by nobody's genius, by assay and rota and duplicate instruments and by four hundred years of people being wrong in public in a way that could be counted, and the word never stayed in the interval at the far end, honestly, where it belongs.

The girl of sixteen from the ninth camp, who had asked four times, whose name is in the transcript and is not on the plate because she asked for it not to be, died in year one thousand and ninety-nine at seventy-one, seven years before a boy from her own camp got the sign wrong twice and found a corrected field. That is in the text too. It is in the text on the same page as the answer, deliberately, by a drafting decision that was contested and carried by voice, and the sentence the committee finally used is four words long and nobody has ever improved it.

She did not know.

They answered the four questions in the next cycle. Population and age structure took nine days. The fourth reactor took an hour and was mostly the ledger. The third question took a hundred and forty days, because the honest answer to what is the arrangement by which a person of twenty-two is permitted to stop a decision of your Council is not an arrangement, it is a history, and they sent the history: the four measurements, the pulsar, the forty-one-second load spike, the boil-off inversion, nineteen pages of pencil put on the floor unread, and the six-line off switch published under its author's own name so that no institution could hold it.

The fourth they answered in eleven bits, which was the shortest reply ever composed on either world and took four months to agree.

Not to us. Keep the list.

N. Sarr-Ouma ran the radiators for thirty-eight years. She saw the catalogue field change when she was fifty-three and she was in the Long Gallery for the reading of the addressed block, standing, at the back, and what she said about it afterwards, which is in Register entry four thousand one hundred and eleven under her name along with eleven hundred others, was this:

They are ninety people with a bad budget who kept a list for a thousand years with no reason to think anybody would ever read it. I had believed, without noticing that I believed it, that we would be answered by something larger than us. We were answered by something the same size. I find I have no idea what to do with how much better that is.

She handed the four pages on in year one thousand one hundred and thirty-two, at fifty-nine, to a hull tech of twenty-four, and recopied the last line by hand, and got the word filter slightly wrong the first time and started again on a fresh sheet, and kept the spoiled one, because some things are kept. She died aboard in year one thousand one hundred and forty-four at seventy, in a chair by a window at eye height, an arrangement then a thousand and fifty-eight years old and never once reopened, and they wrote her name on the wall on Deck 5 in whatever hand was holding the stylus, and there was an argument in the corridor beforehand, because there is always an argument. Somebody put an apple on the deck plate underneath. Somebody cut it into eight and gave one to each of the seven standing nearest and put the last in her pocket.

Osei Vaan-Ouma's page was pulled from the archive on the ninth of the autumn quarter, year one thousand four hundred and forty-one, at 0300, by a woman of thirty-one at the fourth camp who was not looking for it.

She was doing an audit nobody had commissioned, on her own time, of the reconciliation exercise itself, because she had a suspicion so small she was embarrassed to write it down: that the year-nine folding was getting easier. Not better. Easier. She pulled four hundred years of it, all forty-one settlements, every autumn, the marked residuals and the constants each class had used, and she folded the folding, and at three in the morning it came out of the noise.

Nine settlements out of forty-one had stopped using their own duplicated constants. They were using the values that came down the cycle from fifteen light-years away, because those values were better — they were genuinely better, measured with instruments nobody on either world could build, published with intervals two orders tighter — and using them made the exercise converge faster and made the classes look competent and made the marking simpler, and it had happened over about ninety years with no decision anybody could point to, and nobody had done anything wrong, and the beans rota had quietly become a ceremony in nine places out of forty-one.

She published it on Fourthday in the ordinary weekly reduction with a four-line covering note. Then she went and found the transcript, because she had been taught it at year nine like everybody and had not recognised it when she was standing inside it, and she read a man of fifty-one from the far south saying, four hundred and one years earlier, I'd like that written down now so they don't have to work out that we didn't see it coming.

It is filed under an index line, class open, petitionable. It had been consulted eleven times in four centuries. It has been consulted nine hundred thousand times since.

The Register entry is number eleven thousand four hundred and nine and it is short. The remedy took nine years and was mostly furniture: the duplicate instruments were made mandatory again under a rota with teeth, the Sol constants were kept — nobody was mad enough to throw away good numbers — but they were placed in a separate column, on the right, marked, and no class was permitted to open the column until it had published its own value and its own error, and the two were compared afterwards in front of everybody, and the disagreements were published with the disagreements' signs.

A third of them still get the sign wrong. That figure is still published.

And in the ninth camp, on the plate at the west lock beside shame is not a plan and do you know how to stop a fold, they added a third line that autumn, cut in the same size letters, and it is a sentence from a session four hundred years old spoken by a man who lost the argument and voted for the winner:

We are the only people who ever had to be honest with nobody watching.

Which was no longer true, and had not been true since year one thousand one hundred and six, and that is why they cut it.

The transmission did not stop.

It reached the end of the ledger in year one thousand and eighty-three and the end of the Register in year one thousand one hundred and nine and it entered the transcripts in year one thousand one hundred and twelve with a hundred and sixty years of argument to send and it never got out of them, because the argument kept being had. In year one thousand five hundred the queue stood at four hundred and eleven years and was growing at about eleven months per year, and somebody put that on the wall in the Long Gallery as a joke, and it stopped being funny in the third year, and then, after about a century, it became funny again in a different way, which is what happens to institutions that survive.

They never sent everything. That was established in the first month of year one thousand and forty-one and it never went away. What they sent, in the fourth year of every cycle, forever, was a list of names with dates and no cause, and at the top of every cycle, for a hundred and three seconds, the worst thing they ever did.

Sol went on correcting the ninth entry of its fourth block. It became, over centuries, the longest entry in the catalogue and then longer than the rest of the catalogue, and at some point in the fifteenth century of the Ambit's reckoning the office of about ninety people — which had by then been defunded twice more and restored three times, which had changed its name and its charter and, four times, its species of authority — stopped calling it an entry and started calling it the second block, and told them so, four bits a second, in a note of nine hundred bits that took two years to argue about on Ouma and was finally judged to have been meant kindly.

Nobody else ever answered. Nine hundred and forty-one, and four of them ended, and one of them wrote back, and the rest were rumour, and the beacon went on saying so, patiently, into a sky, with a warning about a cold blue world at the top of it in somebody else's words.

There is a fortnight in the autumn quarter, still, when somebody goes up ninety-one rungs with a plate camera.

The paper does not stop. It has been growing for sixteen hundred years and it is soft as cloth in the deep places and it goes away along the curve of the hull past the reach of any lamp anybody has ever carried up there, and the photographing project, which began in year six hundred and eighty and was to take a hundred and forty years, has never once caught up, because the crawl fills faster than eleven pages an hour.

In year one thousand two hundred and eighty-four a hull tech of twenty-three photographed, at depth two thousand three hundred and nineteen, a fault sheet with writing on the back of it, badly done, the way you write wedged against a stringer, and the plate is in the archive and is not remarkable and is one of eleven million. It reads:

Yr 1075 d19, 0409. Autumn plates to depth 2319.

Reply window opened this quarter. Nothing.

Bracket at Frame 44: no fault found. 995 years. I put my hand on it.

TEV-9 gap 34.80 s. Everyone still hums 41. I hum 41.

Anyone can check this. The array logs are open. They have always been open.

Bring a pencil. There's a shelf.

The shelf is still there. It was put up in year six hundred and forty for pencils and it has never been empty. There are now nine papers about it and one dissertation, and the surveys have ruled out four hypotheses and have twice detected a person putting pencils on it and both times that person turned out to have been putting pencils on it because she had found it empty once, at twenty, and had been frightened by it, and had assumed she was the only one, which every one of them assumes. It remains one of the four genuinely unsolved questions in the archive of two worlds, on the grounds that the surveys cannot exclude the possibility that somebody is doing it for a reason nobody has thought of. Nobody has ever proposed watching it continuously. There was a petition, in year nine hundred and two, and it was refused, and the refusal is four lines and is taught: We may find out. We are not going to find out by lying in wait for a person carrying pencils toward a crawlspace at four in the morning. Some things you are allowed to leave.

The gap went on falling.

It was forty point six seconds when a girl of fifteen with a sore back first counted it and thought she had miscounted. It was thirty-four point eight when a hull tech of twenty-two marked it four times on a slate and did not think it worth any ceremony at all. In year one thousand six hundred and eleven it was twenty-nine point one, and the fit — published with an interval, with never still honestly at the far end, because the far end is where it belongs — said that in about eleven hundred years the stutter and the gap would run together and TEV-9 would stop doing the thing it had been doing since before anybody aboard had a word for it, and would do something else, or nothing, and that when it happened it would have happened four thousand years earlier and nobody would be able to do anything about it except look.

They still hummed it at forty-one.

That is the fact the year-nine text ends on, and it has ended on it for eight hundred years, and there have been four attempts to change it. Every generation is told the true number and every generation counts it themselves on a slate at four in the morning at least once, because a thing you have not measured is a thing somebody is holding for you; and every generation hums the wrong one, in corridors, over filters, up ladders, at the chairs, at the wall on Deck 5 with an apple cut into eight pieces on the deck plate, because the song is nine hundred years older than the correction and because a people who cannot tell the difference between a measurement and a song will eventually seal a bay from the outside, and a people who have no song will not last the two centuries to find that out.

So: long, long, short, short, long. A stutter. Then a gap of forty-one seconds, which is wrong, and which everybody knows is wrong, and which is written down as thirty-four point eight and falling in the ordinary weekly reduction on Fourthday with the method stated and the residual attached and the note at the bottom that has been on every page either world has published since year eighty.

Anybody can check this.

And nine hundred and thirty-one kilometres below, on a cold world with a chemistry in its ground, three hundred and eleven thousand people and then four hundred thousand and then more went out in the winter dark and looked up at a star that was slightly wrong in the sky, and were told what it was, and told what it wasn't, and told what nobody knew, and went in.

Above them a hundred kilowatts went out into the dark at four bits a second, in the fourth year of its cycle, sending a list of names with dates and no cause, with another two hundred years of it to send.

And the star kept its own time, unimaginably far behind, indifferent and unhurried, changing at its own pace for its own reasons and telling nobody — having been made a clock, and a metronome, and a deadline, and a lie, and a song, and finally only itself again — and remaining, through all of it and for exactly as long as anybody kept climbing ninety-one rungs at four in the morning to look at it, simply something that anyone could see.