The sound had been turned down, so Doob couldn’t hear what J.B.F. was saying, but he could guess it well enough, and a few seconds later the highlights began to show up in the crawl at the bottom of the screen. The so-called People’s Justice Blockade was no grass-roots movement but an operation planned and carried out by the Venezuelan government. It was a reprehensible political stunt that was actively interfering with the all-important building of the Cloud Ark. It was not true, as some had been whispering and the Venezuelan president was now openly saying, that the White Sky was a hoax. The blockade was not, as its sympathizers would have you believe, a peaceful civil disobedience protest; armed intruders had begun landing on the beaches of French Guiana a few hours ago, and were now being held at bay by the French Foreign Legion, bolstered by a multinational force including United States and Russian marines. Doob, doing his best to tune it out, couldn’t defeat the irrational feeling that J.B.F. was staring directly at him: a feeling he had come up here partly to get away from.

One of the PR flacks down in Houston reached him over a video chat link that Doob had not had the presence of mind to disable. He talked Doob into spending the next hour writing a little homily about how everyone down on Earth needed to unite behind the all-important mission of the Cloud Ark, and detailing how the Kourou blockade was affecting that. Doob wanted in the worst way to tell this guy to get lost, but he had a soft spot for people who had only three weeks to live.

Doob called Ivy—for Izzy had its own cell-phone system now—and got her to supply a few hard quotable numbers, which he rounded off and typed into his script. He then devoted a minute to psyching himself up to adopt the Doc Dubois persona. Formerly the ruin of his first marriage, the basis of his livelihood, and his ticket to the Cloud Ark, Doc Dubois was a person he rarely had to be anymore. That guy seemed as dated as a character from a 1970s television serial. Getting into the persona was nearly as cumbersome as donning a space suit. It required an extra cup of coffee with sugar. When he felt he was ready, he turned on his tablet’s video camera, identified himself as Doc Dubois, greeted the people of Earth, and read his little script.

When he was finished, he emailed the file down to Houston. Then he tried to go back to his memo, but he became distracted when the Situational Awareness Monitor flashed up a red BREAKING NEWS banner and began to show footage of indistinct flashes against a dark background. Some sort of hostilities had broken out on the ground in French Guiana, between the perimeter of the spaceport and the beach. The French Foreign Legion was participating in what might be the last battle ever fought. But the television news cameras couldn’t get anywhere near the action, so the coverage mostly consisted of journalists interviewing each other about how little they knew.

In the middle of all that, the flack in Houston got back to him and asked if he could please relocate to a part of Izzy where zero gravity prevailed, and rerecord the little pep talk. Conspiracy theorists were saying that the Cloud Ark didn’t really exist and that it was actually just a bunch of movie sets in the Nevada desert. Whenever they saw video from parts of the space station with simulated gravity, they cited it as evidence, and added millions of friends and followers to their social media profiles.

Doob said he’d see what he could do, and departed from the Farm. Nothing was going on here anyway; Markus wasn’t around at the moment. He ascended a spoke to H2 and thus entered zero gravity.

H2 had been the aft-most piece of the Stack—the train of modules that ran up Izzy’s central axis—until several weeks ago when the Caboose had been launched up from Kourou and mated to its aft end. The main purpose of the Caboose was to house a large rocket engine, burning hydrogen and oxygen, which would do most of the work of boosting Izzy’s orbit. It wasn’t possible to extend Izzy any farther back because, beyond that point, anything tacked onto it would no longer reside safely within Amalthea’s protective envelope. And indeed there had been long discussions of contingency plans for the case where the Caboose took a hit and its engine was destroyed.

Putting his back to the Caboose, Doob began to drift forward up the Stack. H2 led to H1, which led in turn to the old Zvezda module. This had formerly sported small photovoltaic panels to its port and starboard sides, but these—like most of Izzy’s solar panels—had been folded up and removed to make space for other construction. During an intermediate stage of the Arkitects’ labors, power had come not from photovoltaics but from little nukes, the same as those on the ark-lets. These still protruded from attachment points all over the space station, aglow with red LEDs meant as a warning to spacewalkers and pilots. And they still produced a significant amount of power and served as a valuable backup. But most of the station’s power now came from a full-fledged nuclear reactor, adapted from those used on submarines, which was mounted on a long stick that projected to nadir from the Caboose. There were a number of reasons why a big power plant might be needed, but the most important of these was to produce rocket propellant by splitting water into hydrogen and oxygen. And this explained why the reactor was where it was. The Caboose housed the big boost engine that was Izzy’s largest consumer of propellant. And it was also the central nexus of the Shipyard complex, where smaller vehicles could be assembled from a kit of parts. Once assembled, they too would need propellant.

Zvezda’s forward terminus was a docking station with ports to the zenith and nadir sides, where scientific laboratories had been connected back before Zero. This tradition had been preserved, in a way, by turning that docking site into Grand Central station for work related to the Cloud Ark’s primary function of preserving the Earth’s heritage. If Doob went “up” in the zenith direction, he entered a long module whose main purpose was to support multiple docking ports where other vessels could be, and had been, attached. In general these were crammed with priceless cultural relics, but some of them also supported server farms where digital recordings were stored. Certain relics were easier than others to send into space; the Magna Carta had made it up here, but Michelangelo’s David was still on the ground. Considerable effort had gone into sealing up heavy relics in “everything-proof vaults” and leaving them on the bottom of the oceans, or in deep mine shafts, but Doob had long since lost track of the progress of that undertaking.

If instead Doob went “down” in the nadir direction, he entered a similar three-dimensional maze of modules. Most of these were devoted to storage of genetic material: seeds, sperm samples, eggs, and embryos. All of these needed to be kept cold, which in space wasn’t too difficult; it was primarily a matter of shielding the storage containers from sunlight, which could be done with a featherweight piece of metallized Mylar film, and secondarily a matter of just preventing the warmth of surrounding objects from seeping into the samples. Doob always paused when passing by that hatch. He was not a spiritual man, but he could not humanly ignore the fact that his potential fourth child, the embryo he and Amelia had created, was in there somewhere. Along with tens of thousands of other fertilized embryos waiting to be thawed out and implanted in human wombs.

He passed into Zarya, which was the next module forward in the Stack. Having been mildly spooked by thinking about embryos, he now had a vague intention of going into the Woo-Woo Pod to rerecord his video. This was a spherical inflated structure, ten meters in diameter, with several large domed windows. It was accessed from Zarya via a hamster tube on the nadir side, so it was aimed at the Earth. Ulrika Ek had drawn the ire of every religious group on the planet by refusing to provide separate places of worship for every single one of them in the Cloud Ark. Instead of sending up a church pod, a synagogue pod, a mosque pod, etc., she had provided this one structure, which was something like the interfaith chapel at an airport in that all the different religions had to share it. Internal projectors would display crosses, Stars of David, or what have you on its interior surfaces, depending on what sort of service was happening there at the moment. It had a long, cumbersome, politically correct name, but someone had dubbed it the Woo-Woo Pod and the name had stuck.