The Math

Rachel had run numbers under pressure before — six years of budget hearings had taught her how to hold a figure steady in her voice even when her hands wanted to shake — but she had never, in her whole career, sat down at an instrument panel already knowing, on some deep, unwelcome level, that the number she was about to find was going to be the worst one of her life.

She started with the stars.

It was the only clean data she had. The suit — the skull, the brittle, wrong-jointed suit she was doing her level best not to think about while she worked — gave her nothing but a feeling, and feelings weren't data. Feelings didn't hold up in front of a subcommittee, and they didn't hold up here either, not when three other people were waiting on her to turn a feeling into a fact they could act on.

Stars held up. Stars were honest, in the long run, even when everything else about tonight had lied to them.

She pulled the external camera feed and began cross-referencing it against Hope 's full stellar catalogue — every star bright enough to register, matched by position and magnitude against the reference charts they'd launched with, the same charts that had, ninety-three days ago, matched the sky perfectly. If the ship had simply drifted off course, gotten knocked somewhere unexpected by whatever had hit them, the stars would still be the stars. Constellations might look strange from a new angle, distances might read differently, but the stars themselves — their positions relative to each other, their proper motion — didn't rearrange over the timescale of a bad flight.

Except they had.

Not wildly. Not into some alien configuration a science fiction film would have dreamed up. Subtly — degrees of drift here and there, individual stars sitting fractionally off from where six years of careful preparation told her they belonged, in a pattern that made no sense for a positional error and made perfect, horrifying sense for something else entirely.

Proper motion. Every star in the sky crept, infinitesimally, across the depths of time — a drift measured in arcseconds per century, so slow that human civilization's entire recorded history barely registered it. She'd built her career around numbers other people found abstractly large. This was the first time one had ever made her hands go cold.

She ran it three times. She would have run it a fourth if Darrell hadn't come to find her.

"Rachel."

"Give me a minute."

"You've had forty."

She looked up. He was standing in the hatchway with the particular stillness of a man bracing for something, and behind him she could see William and Xavier waiting in the corridor, close together, not saying anything, the way people wait outside a hospital room.

"Come in," she said. "All of you. You should all hear this at once."

They gathered around her station in the cramped half-circle the module allowed, and Rachel looked at the three of them — Darrell steady and grim, William's jaw tight in a way that told her he already suspected something close to the truth, Xavier pale and young and clearly hoping, against everything, that she was about to tell them something survivable — and understood that there was no way to make this smaller than it was. No way to break it into a gentler shape. She'd tried, in her head, three different times, and every version came out the same size.

"I want to start by telling you I checked this every way I know how to check it," she said. "I didn't want this number. I ran it assuming I was wrong, more than once, and I kept getting the same answer, and I don't have a way to get a different one out here without lab equipment I don't have."

"Rachel," Darrell said, gently. "Just say it."

She nodded. "The stars have moved. Not us relative to them — I checked that first, that was the easy explanation, that we'd been knocked off course and everything just looked different from a new angle. That's not what this is. The stars themselves have drifted from where they should be, relative to each other, in a pattern that only makes sense over a timescale of proper motion. Which means — " her voice wanted to catch here, and she made it not catch, because they needed her steady more than they needed her honest about how frightened she was — "which means time has passed. A great deal of time. Not for us. We didn't experience it, our bodies didn't age through it, our supplies haven't run down for it. But somewhere between the moment the star ignited and the moment the lights came back on, something happened that moved us forward — displaced us — by an amount of time I can only get from the drift itself."

"How much," William said. His voice was very quiet.

"Best estimate — and I want to be clear, this has margin of error, I'm working from proper motion drift with instruments that weren't designed for this kind of measurement — is somewhere in the range of four million years. Plus or minus a few hundred thousand." She made herself keep going before anyone could speak. "I cross-referenced it against something else, too. The Sister Star's collapse — the event we were there to observe — has a known recurrence interval, based on the stellar remnant's mass and the binary system's orbital mechanics. Another comparable event, in that same system, isn't expected for another 4.2 million years. That's not a coincidence I can explain away. That number matches my drift estimate almost exactly."

The module went very quiet.

"Four point two million years," Xavier said, like the number itself might rearrange into something smaller if he said it slowly enough. "You're telling me it's — Rachel, you're telling me we're four point two million years in the future."

"I'm telling you that's what the data says. I know how it sounds."

"It sounds insane." William's voice had an edge to it now, not at her, she understood, but at the situation, at the universe, at anything solid enough to be angry at. "It sounds like something out of a — Rachel, that's not a delay, that's not getting knocked off course, that's not anything I have a category for. Four million years. The suit—" He stopped himself, but she saw the understanding land in his face anyway, saw him make the same connection she'd been carefully not saying out loud. "The suit. That's not from another mission. That's — whatever that was, it's from now. Whatever now is."

"I think so, yes."

"Everyone we know is dead," Xavier said. It came out flat, stunned, a fact being stated rather than absorbed. "Everyone. Not — not old. Not gone the normal way. Dead the way — Rachel, dead the way dinosaurs are dead. Dead the way everything from our whole world is dead, all of it, all at once, while we were sitting here for what felt like—"

"A blackout," Darrell said. "It felt like a blackout. A few minutes."

"It felt like nothing," Rachel said. "That's the part I can't explain yet. However this happened — whatever the mechanism was — it didn't move us through four million years of experience. It moved us past it. However it works, that's the only mercy in any of this, that none of us had to live through it."

Nobody found that especially comforting. She hadn't expected them to.

Darrell was the first to move, which didn't surprise her — she'd watched him, over ninety-three days, absorb bad news the same way every time, a brief total stillness followed by motion, like his body had decided grief was a problem to be scheduled around rather than felt in real time.

"Okay," he said. "Okay. I need — give me something I can use. Priya. Mara. Casey. Are you telling me there's no chance—"

"Darrell." Rachel kept her voice as gentle as she could make it. "There's no version of this where anyone we knew is alive. I'm sorry. I wish I had a number that let me tell you something different."

He nodded, once, sharp, and didn't say anything else about it, and she understood that he was going to keep not saying anything else about it for as long as he possibly could, because the alternative was falling apart in front of the rest of the crew, and Darrell Grant did not fall apart in front of the rest of the crew.

William had gone very still, staring at nothing, and when he finally spoke his voice had a rawness to it she'd never heard from him before. "My sister," he said, to no one in particular. "I hadn't talked to her in years. I always figured there was time." He laughed, short and terrible. "Guess I was wrong about that."

Xavier didn't say anything at all. He'd curled forward slightly, elbows on his knees, staring at the floor, and Rachel recognized the specific silence of someone doing math he didn't want to be doing — the same math she'd watched him do out loud in the observation module, ninety-three days that felt like a lifetime ago now, about appointments and faint test lines and a sentence that had cut off mid-thought. She didn't say anything to him. There wasn't anything to say that wouldn't make it worse.

"Marcus," she said, quietly, mostly to herself, and found that the grief hadn't arrived yet — that it was sitting somewhere just outside her, held off by the sheer scale of the number she'd just delivered, too big to feel all at once. She understood, distantly, that it would arrive eventually, probably badly, probably at some moment she wouldn't get to choose. For now there was only the number, and the number needed to be useful, or none of them were going to survive whatever came next.

"We need to see it," Darrell said, after a long moment, and his voice had found its steadiness again, the particular flat calm she recognized as him choosing to function. "Whatever's down there. Earth, or whatever Earth is now. We need eyes on it before we decide anything."

"Descent's a risk," William said, but it was reflexive, procedural, the shape of an objection rather than the substance of one. "We don't know atmospheric composition. We don't know what's changed. We don't know if there's anything down there to land near. "

"We don't know anything," Darrell said. "That's the whole problem. We can sit up here not knowing forever, or we can go find out." He looked around at the three of them — Rachel, William, Xavier, each of them carrying a version of the same enormous, unabsorbed grief — and something in his face settled, the captain surfacing through the man. "I'm not asking anyone to be alright. I don't think any of us are going to be alright for a long while. But we can't fix anything up here. Whatever's left down there — whatever this world turned into — we're not going to understand it from orbit."

Rachel looked at the dead, sealed hatch of the airlock, at the memory of a skull tipped at its small permanent angle inside a suit built for something that had started out, a very long time ago, as human.

"Agreed," she said. "We go down."

Xavier didn't lift his head, but he nodded, slow, and William exhaled something that wasn't quite a laugh and wasn't quite a sob and said, "Well. Let's go meet the neighbors, then," in a voice that was trying, badly, to sound like it was joking.

Nobody laughed. But nobody argued, either.

Darrell moved to the console, and Rachel moved with him, and behind them Xavier finally lifted his head and William squared his shoulders, and the four of them began, in the flat, procedural language of people who had no other way left to hold themselves together, the work of bringing Hope down toward whatever the Earth had become.