Later Doob had figured it out based on background conversations with people at Arjuna and scuttlebutt reaching him through friends working on the planning of the Cloud Ark. It was all about propellant. The Cloud Ark would have to burn a lot of it. Sean didn’t think they had enough.

So he had gone up there and done something about it.

Because Sean wasn’t a talker. He was a doer. And as such he didn’t have to agonize, as Doob was doing now, about what he was going to say. What his public stance was going to be. How he was going to be positioned and perceived.

“That’s a hundred days from now,” Doob said.

He’d been silent for so long that the other occupants of the Oval Office were a bit startled. J.B.F.’s attention had wandered to a tablet on her desk, and Pete Starling was looking out the window.

“I beg your pardon, Dr. Harris?” said the president, turning that gaze back upon him. But he no longer felt intimidated by it. He was going to go somewhere where she could never look at him again.

“This is 260,” Doob said. “You said you wanted me to go up there around 360.”

“Yes,” said Maggie Sloane, relaxing into an entirely new posture. “That’s not the first wave—which is going to be more exploratory, more of a dress rehearsal—but it would be the first real wave of Arkers going into space, and our thought was that we would embed you with them. You could partake of their experiences and show the people of Earth what a day in the life of an Arker consists of. Providing a sense of continuity.”

Holy shit, Doob thought. Seven years a Ph.D. candidate, two postdocs at major European research institutions, a tenured position at Caltech, shortlisted for a Nobel Prize, and here he was, with the fate of the human race at stake, being positioned as an observer to provide a sense of continuity.

“I can do that,” he said. And some other things as well, as long as I’m up there.

What were they going to do, yank him back down to the planet?

The worst they could do was to stop broadcasting his stuff, and that would be fine with him. There had to be something he could do up there that would be more useful than talking into a camera. Sean Probst had identified one problem with the Cloud Ark and taken action to remedy it; in a hundred days, what could Doob learn that might be useful? What actions could he take, once he got up there, to give the whole thing a better chance of success?

“A hundred days,” he said. “Three months for me to spend with my wife and my kids and my embryo.”

“Embryo?” Pete Starling repeated, not getting it.

Margaret Sloane, mother of three, picked it up instantly. “Amelia’s pregnant?” she asked, with the warm smile that, until Zero, had been the normal response to such blessed events. Nowadays, people’s reactions were a bit more complicated, of course; but it was hard to shed old habits.

“Not anymore,” Doob said. “We froze the embryo. My only condition is that it travel up into space with me.”

“Consider it done,” said the president, in a tone, and with a look, that told them the meeting was over.

DAY 287

“Got any tater-related humorous items for me?” Ivy asked. “’Cause oh, man, could I ever use some comic relief.”

Dinah wasn’t sure how she felt about Ivy looking to her doomed family as a source of casual amusement, but as they were only some 433 days away from the end of the world, she didn’t really think there was much point in getting shirty about it.

The situation did breed a kind of coarseness toward those stuck on the ground. It was humanly impossible to extend to seven billion people the full sympathy that each of them deserved. Dinah had begun to hear instances of dark humor over the radio, and had noticed herself being at least a little bit amused by it.

Nor was that dark humor restricted to Arkers, as Dinah’s family demonstrated. They were intelligent people—you had to be, to do what they did—but they went in for a certain brand of mining-camp humor, heavy on the practical jokes and novelty items that you’d never see in a boardroom or a faculty lounge. And once they’d latched on to something that they thought was funny, they’d never let go of it. A half-serious Morse code message about planting a flat of potatoes, transmitted by Rufus shortly after the Crater Lake announcement, had sprouted into a whole subgenre of running jokes about the preparations that the MacQuarie clan was making for the Hard Rain. In her occasional care packages from the ground, Dinah was now accustomed to finding fingerling potatoes, still with real dirt on them, or plastic parts for Mr. and Mrs. Potatohead toys. She even had a rusty old Idaho license plate duct-taped to the wall of her shop now, emblazoned with the slogan FAMOUS POTATOES, courtesy of Rufus, who’d gotten it from a mining industry pal in that state’s silver-rich panhandle.

“Is that a no?” Ivy asked.

“Oh, I have potato shit all over the place now,” Dinah said. “I’m just no longer sure that they’re joking.”

“What do you mean?”

“At first I thought it was their way of saying, ‘We know we are screwed, no point in being babies about it, let’s laugh it up until the end.’ But now I’m starting to ask myself what it is they’re doing. I mean, they’re up there in the Brooks Range with all of this equipment. They could drive down to Fairbanks any time they feel like it, and from there go anywhere in the world. Check out the pyramids. See the Mona Lisa. Visit old friends and family. Instead they’re up in the most godforsaken place I’ve ever seen, doing what?”

“Prepping?” Ivy said.

“That’s the only thing I can think,” Dinah said. “Prepping for a five- to ten-thousand-year stay.”

“They’re not the only ones,” Ivy said.

It took Dinah a few moments to catch her friend’s meaning. Then it was clear, just from the look on Ivy’s face. “Are you shitting me? Cal?”

Ivy made just a suggestion of a nod with her eyes. “Mixed in with the stuff you’d expect from a fiancé—which is none of your business—he asks me questions about things like the comparative merits of lithium versus sodium hydroxide scrubbers. He requests copies of Luisa’s PDFs about the sociology of persons confined in small places for long periods.”

“He can’t think you’re not going to notice that.”

“Sure. I’m going to read between the lines.”

“What do you suppose he’s thinking?”

“Well,” Ivy said, “he does have sole authority over a huge submarine designed to ride out global thermonuclear warfare. And when the United States ceases to exist, I guess there’ll be no one above him, chain-of-command-wise. What’s a commander to do?”

“But how would it work?”

“I think a lot depends,” Ivy said, “on whether the oceans boil dry. If I were him, I’d make for the Marianas Trench and keep my fingers crossed.”

“I would think it would be even harder than staying alive in space.”

Ivy looked at her friend with dry amusement.

“What?!” Dinah said.

“Staying alive in space is going to be a piece of cake, remember?”

“Oh yeah, sorry. I forgot . . .” To put on my makeup. “It would present some fascinating challenges,” she corrected herself, switching to her best NASA PR voice.

“I think it’s like what we are doing,” Ivy said. “You have to break it down into a lot of little things and solve them one at a time, or you get overwhelmed.”

“Is that what we’re doing?”

“Yeah.” Ivy rolled her eyes.

“What’s on your mind? Other than the need for comic relief?”

“You. How you’re doing. Your health,” Ivy said.

“Oh my god, is this an actual meeting? Are we on official business here?”

Ivy ignored her. “You haven’t been logging much T2 time.”

T2—the second torus, which Rhys had been responsible for building—had started to spin on Day 140. Its simulated gravity was one-eighth of Earth normal, only a little greater than that on the first torus. It was bigger and spun more slowly, which Rhys hoped would make it a little more comfortable. Simply being in it helped counteract some of the negative effects of living in space for extended periods of time. People who lived without gravity suffered a gradual loss of bone density and muscle mass. Eyes went out of shape and vision deteriorated. Space station crews tried to fight this by using exercise machines that placed stress on the bones, but these were stopgap measures meant for people who were only going to be in space for a few months. Dinah, Ivy, and the other ten members of the original Izzy crew had now been up here for close to a year. During the first few months after Zero, no one had paid much attention to long-term health issues. Everyone was going to die. Scouts were showing up dead on arrival. It had been all emergency, all the time. But during the months of hamster tube building and structural consolidation, the life scientists had been quietly having their say. This wasn’t the first time Dinah had been nudged in recent weeks about her failure to spend more time in the simulated gravity field of T2.