The quantum comm window opened at 03:47 on a Tuesday in March, which was not unusual. What arrived through it was.

Tomás Ferreira-Voss had been the Ouroboros's chief mathematician for nine years, which meant he was the fourth chief mathematician the ship had carried in its sixty-one-year journey. The first three were dead. He was thirty-four and expected to be the last, though there were seventeen children aboard under the age of twelve and at least two of them showed the necessary aptitude, which meant the ship would have a fifth if it ever needed one. The ship's trajectory suggested it would not arrive at Kepler-442 for another three hundred and twelve years. The children would be dead by then too, along with their children and their children's children, and the fifth mathematician would be someone none of them had met yet, someone whose great-grandmother was currently six years old and sleeping in Berth Seven with her arm wrapped around a stuffed animal that had lost both its eyes somewhere between Neptune and here.

Tomás found this a useful thing to think about when the distance became oppressive, which it did sometimes, at night, when the ship's hull creaked in the specific register that suggested the cold outside was absolute and very close.

The quantum comm burst arrived compressed and flagged at priority level zero, which was reserved for stellar cartography updates and emergency medical transmissions. He was alone in the comm bay. He opened it.

Inside was the entire body of human mathematical knowledge.

Not a summary. Not an index. The actual work: every theorem, every proof, every conjecture with its accumulated attempts, every notation system, every translation between notation systems, every correction and revision and refutation going back to the earliest recorded numerical marks on bone. Approximately seven hundred years of organized mathematics, presented in a unified notation he did not recognize but could read, the way you can sometimes read a foreign language in a dream that uses letters you know.

It was annotated.

The annotations were in the same unified notation and they were, he understood within minutes, corrections. Not corrections of minor errors — corrections at the foundational level, in the axioms, in the logical primitives, in the places where human mathematics had made choices it did not know it was making because the alternatives were not yet visible.

He sat with this for a long time.

He was a careful man. He had grown up in a closed system — the ship was a closed system in almost every sense — and he had learned that careful was the only viable mode for people living inside something finite. You measured twice. You checked assumptions. You did not follow an extraordinary finding to its conclusion without first confirming that you had read it right.

He confirmed that he had read it right. He worked through the foundational corrections first, the cleanest ones, the ones he could verify against his own training. They held. They were better than what he had been taught. They were better in the way that a flat road is better than a road that is slowly, invisibly tilted — you do not know the tilt is there until you are running on the flat and realize how much effort you had always been spending compensating for it.

He followed the corrected mathematics forward.

It took him eleven hours. He did not eat. He drank two cups of water without tasting them and ignored the three internal comm calls from his colleague Sujata who wanted to know if he was coming to the morning systems review. He worked in the way he only worked when something was true and pulling at him from ahead, and the work had the quality of being led rather than driving, and he did not stop until he had reached the conclusion.

The conclusion was this:

The universe was older than humanity believed by approximately seven billion years. Humanity itself was younger than it believed by approximately the same amount. The discrepancy was not a measurement error. It was an artifact of a correction event — a reset, in the specific mathematical sense of a function returning to a prior state. The universe had been here before, in a prior iteration, running the same initial conditions forward to the same conclusion. And before that. And before that.

The corrected mathematics implied eleven prior iterations. This was the eleventh time the function had run. The previous ten times, at approximately this point in the cycle, something happened that the mathematics described in terms Tomás could parse technically but could not — would not — translate into plain language in the privacy of his own mind, because once you translated it you could not un-know what it said.

He knew what it said.

He sat for a long time looking at the comm terminal and listening to the ship breathe.

The data burst had arrived from a direction that, according to every stellar map the Ouroboros carried, contained nothing. No star. No body. No source. A direction that the ship's instruments had always cataloged as void, as the absence of anything worth pointing at.

He checked where the data had been sent from.

It had been sent from the Ouroboros itself. Timestamp: eleven hours from now.

He understood the choice.

It was not, he thought, really a choice in the sense of a decision between alternatives, because one of the alternatives was not to act and the other was to act, and both of them led to the same place — the mathematics made this clear, had made it clear since the first iteration, would always make it clear. The choice was in the doing. In whether to do it fully, with understanding, or to have it happen to you in the way that things had always happened to the people who came before him and believed themselves the first.

He wanted to do it fully. He thought that was true. He checked whether it was true and found that it was, in the surprised way you find things you had not known you believed.

He opened the broadcast array.

The Ouroboros's quantum comm system was designed for tight-beam transmission to Earth: low power, high precision, narrow angle. What he needed was not tight-beam. He needed omnidirectional broadcast at maximum power, the corrected mathematics encoded in the signal, repeated, redundant, every register they had, loud enough to saturate the quantum comm channels at the receiving end with something that could not be flagged as instrument artifact, could not be redacted, could not be filed away under Possible Instrument Artifact by someone who understood and chose silence.

He wrote the broadcast protocol. He checked it. He began reallocating power from non-essential systems.

The lighting in the comm bay dimmed. He could feel the ventilation slow. He could feel the ship's thermal management shift, the quiet hum of redundant systems going offline, the particular silence of something large drawing breath before speaking.

Sujata appeared in the doorway. She took in the terminal, the power readings, his face.

"Tomás."

"I know," he said.

"The drive is going to—"

"I know."

She came in and looked at the terminal. She read it the way he had read it, starting with the corrections, following them forward. He watched her face move through the stages. She was faster than him — she had always been faster, which was why he had never beaten her at anything that required speed and had always beaten her at anything that required patience.

She reached the conclusion. She stood with it.

"How long do we have?" she asked.

"Until the power draw hits life support? About four hours."

"And after?"

He looked at the terminal. "The mathematics says something comes after. The mathematics is not specific about what."

Sujata sat down. Not in the chair — on the floor, with her back against the wall, which was something she only did when she was thinking very hard or very slowly.

"Eleven times," she said.

"Eleven."

"And they all—"

"Every time."

She was quiet for a while. Down the corridor, someone knocked on a door. A child's voice. A parent answering. The ordinary sounds of people who did not yet know, living inside the last closed system humanity had managed to build, sixty-four light-years from a planet they would never reach, three hundred and twelve years from an arrival that was not going to happen in the way anyone had planned.

"Wake them up," Sujata said.

He looked at her.

"All of them," she said. "Wake everyone up. If this is the eleventh time, I want to be awake for it. I want all of us to be awake."

He thought about the child in Berth Seven. Six years old, one arm around something soft and eyeless. He thought about what she would see, if they woke her — the comm bay full of people, the screens full of mathematics, the careful face of a man who had decided to be fully present for something enormous.

He thought she would probably not understand it.

He thought she would probably remember it anyway.

He opened the ship-wide channel and said, quietly, in the voice he used for important announcements: "This is Ferreira-Voss. All hands to the main deck, please. Bring the children."

Then he turned back to the terminal and pressed send.

---

The light from Ouroboros reaches Earth in sixty-four years.

By then, Earth no longer needs it. Earth received the same transmission at 03:47 on a Tuesday in March, in the year 2401, from a direction that the instruments catalogued as void. Eleven hours to process the corrected mathematics. Eleven hours to follow it forward.

Earth had eleven hours to prepare.

That was enough.

It has always been enough.

In every iteration, at the moment of the correction, there are people who are awake for it — who chose to be awake, who woke others, who sat together in the same room and held the weight of it collectively, spread across enough minds to be survivable and then some. In every iteration they are afraid. In every iteration they are also something else, something for which there is no good word in any human language, something adjacent to awe and adjacent to recognition, the feeling of remembering a place you have never been.

In every iteration, one of them says: we've been here before.

And this is true. And it is also, in every way that matters, the first time.

The mathematics is clear on both points. The mathematics, corrected, is very clear.

The Ouroboros goes dark at 14:52, its broadcast still transmitting, its hull warm for a while longer than the cold outside would suggest is possible, and then not warm, and then something else entirely — something the instruments, if there were instruments, would not have the right names for yet.

The light from the broadcast spreads outward in all directions at the speed of light.

In sixty-four years it reaches Earth.

In eighty it reaches the relay stations at the edge of the inner system.

In four hundred it reaches the distance that the Ouroboros was meant to reach. In four hundred years, in the place where Kepler-442b turns in its long orbit around a quiet orange star, the signal passes through and continues outward, still carrying its message, still repeating it in every register, growing thinner with distance but not silent. Signals like this do not go silent. They just become part of the background.

They become part of what the oldest light carries.

They become, eventually, something a person at a very large telescope, in a station whose ventilation system breathes in a way that feels almost deliberate, might find one Wednesday afternoon when looking for something else entirely.

The universe is very patient with its remainders.

It has always known they would come back around.