Schild’s Ladder

He looked around. There were a dozen people nearby, but they were all intent on the view. Then he spotted a lanky figure approaching, an arm stretched up in greeting. Tchicaya didn’t recognize the face, but his Mediator picked up a familiar signature.

"Yann?" Tchicaya had known for centuries that Yann was also weaving his way toward the Rindler, but the last place he’d expected to run into him was the observation deck. In all the time they’d been in contact, exchanging messengers across decades and light-years, Yann had been strictly acorporeal.

The half-stranger stood before him. "How are you?"

Tchicaya smiled. "I’m fine. You seem to have put on weight."

Yann shrugged apologetically. "Conforming to local fashions. I still think it’s an absurdity: boosting millions of tonnes of furniture into a trajectory like this, when a few hundred kilograms of instrumentation and Qusps could have achieved as much. But given that they’ve gone ahead and done it anyway, and given that most of the people here are wearing flesh, I have to take account of that. I need to be in the thick of things, or there’s no point being here at all."

"That makes sense," Tchicaya conceded. He hated the idea of anyone being forced out of their preferred mode, but the political realities were undeniable.

If the optimists were right, and the border’s current velocity was the highest it would ever be, the simplest way to avoid the threat would be to flee from it. If your whole world already consisted of compact, robust hardware that was designed to function in interstellar space, the prospect of engineering in the necessary shielding against relativistic collisions with gas and dust, accelerating to a suitable velocity — half c plus a chosen safety margin — then simply coasting away from the danger, was not unthinkable at all. A dozen acorporeal communities, and countless scattered individuals, had already done that.

For people accustomed to dwelling on a planetary surface, though, the notion of entering a permanent state of flight was more likely to be horrifying. So far, the Mimosan vacuum had swallowed more than two thousand inhabited systems, and while most of the planet-hopping refugees were willing to transmit themselves at lightspeed from point to point, in less than two millennia all the old, established colony worlds that had taken them in would themselves be gone. In principle, the process could be prolonged indefinitely: new, habitable planets could be prepared in advance by high-velocity spore packages, with people following close behind. Each temporary home would last a little longer than the one before, as the border was outpaced. People might even grow accustomed to the fact that every world they set foot upon would be obliterated, not in billions of years, but in a few thousand. It would take six times as long as recorded history before the entire Milky Way was lost, and by then, the gulf between neighboring galaxies might seem less daunting.

Even assuming a watertight proof, though, that the border would not speed up without warning and turn that whole scenario into a rosy-hued fantasy, exile was not a fate to be accepted lightly. If it was physically possible to turn back the novovacuum — to seed its destruction, the way the Mimosans had seeded its creation — Tchicaya’s fellow embodied had by far the greatest stake in making that happen. It was not going to be easy to persuade them that they shouldn’t try.

Yann said, "You’ve just come from Pachner?"

Tchicaya nodded. He was pleased to have met up with Yann, but he was having trouble maintaining eye contact; the spinning sky kept drawing his gaze. "When did you get here?" He’d lost track of Yann’s recent movements; communication between interstellar travelers had always been difficult, with line-of-sight time lags and transit insentience, but having to route signals around a constantly growing obstacle had added a further level of delays and fragmentation.

"Almost nine years ago."

"Ha! And there I was thinking you were the one out of your element."

Yann took a moment to interpret this. "You’ve never been in space before?"

"No."

"Not even planetary orbit?" He sounded incredulous.

Tchicaya was annoyed; it was a bit rich for a former acorporeal to put such stock in where he had or hadn’t been, in the flesh. "Why would I have been in space? Vacuum never used to be much of an attraction."

Yann smiled. "Do you want to take the grand tour, while I fill you in?"

"Definitely." Everything Tchicaya had heard about the state of play on the Rindler was out of date — though not by the full sixty years that his thirty-year journey would normally have implied. He did a quick calculation before confirming the result with the ship: fifty-two years had elapsed here, since the last bulletin that he’d received on Pachner had been sent.