Schild’s Ladder

As he dressed, Tchicaya examined himself in the wall mirror. From the whorl of dark bristles on his scalp to the glistening scar running down his right leg, every visible feature had been reproduced faithfully from a micrometer-level description of his body on the day he’d left his home world. For all he could tell, this might as well have been the original. The internal sense of familiarity was convincing, too; he’d lost the slight tension in his shoulder muscles that had been building up over the last few weeks before his departure, but having just rid himself of all the far more uncomfortable kinks he’d acquired in the crib, that was hardly surprising. And if this scar was not the scar from his childhood, not the same collagen laid down by the healing skin in his twelve-year-old body, nor would it have been the same in his adult body by now, if he’d never left home. All an organism could do from day to day was shore itself up in some rough semblance of its previous condition. The same was true, from moment to moment, for the state of the whole universe. By one means or another, everyone was an imperfect imitation of whatever they’d been the day before.

Still, it was only when you traveled that you needed to dispose of your own past, or leave behind an ever-growing residue. Tchicaya told the crib, "Recycle number ten." He’d forgotten exactly where the tenth-last body he’d inhabited was stored, but when his authorization reached it, the memories sitting passively in its Qusp would be erased, and its flesh would be recycled into the same kind of waxen template as the one he’d just claimed as his own.

The crib said, "There is no number ten, by my count. Do you want to recycle number nine?"

Tchicaya opened his mouth to protest, then realized that he’d spoken out of habit. When he’d left Pachner, thirty years before — a few subjective hours ago — he’d known full well that his body trail would be growing shorter by one while he was still in transit, and he wouldn’t have to lift a finger or say a word to make it happen.

He said, "Keep number nine."

As he stepped out of the recovery room, Tchicaya was grateful for his freshly retuned sense of balance. The deck beneath his feet was opaque, but it sat inside a transparent bubble a hundred meters wide, swinging for the sake of gravity at the end of a kilometer-long tether. To his left, the ship’s spin was clearly visible against the backdrop of stars, all the more so because the axis of rotation coincided with the direction of travel. The stars turning slowly in the smallest circles were tinted icy blue, while away from the artificial celestial pole they took on more normal hues, ultimately reddening slightly. The right half of the sky was starless, filled instead with a uniform glow that was untouched by the Doppler shift, and so featureless that there was nothing to be seen moving within it: not one speck of greater or lesser brightness rising over the deck in time with the stars.

From the surface of Pachner, the border of the Mimosa vacuum had appeared very different, a shimmering sphere of light blazing a fierce steely blue at the center, but cooled toward the edges by its own varied Doppler shift. The graded color had made it look distinctly rounded and three-dimensional, and the fact that you could apparently see it curving away from you had added to an already deceptive impression of distance. Because it was expanding at half the speed of light, the amount of sky the border blotted out was not a reliable measure of its proximity. Looking away from its nearest point meant looking back to a time when it had been considerably smaller, and starlight that had grazed the sphere centuries before — skirting the danger, and appearing to delineate it — actually told you nothing about its present size. When Tchicaya had left, Pachner had been little more than two years away from being engulfed, but the border had barely changed its appearance in the decade he’d spent there, and it would still have occupied a mere one hundred and twenty degrees of the view at the instant the planet was swallowed.

Tchicaya had been on Pachner to talk to people on the verge of making their escape. He’d had to flee long before the hard cases, who’d boasted that they’d be leaving with just seconds to spare, but as far as he knew he’d been the only evacuee who was planning to end up closer to the border than when he left. Doomed planets were useless as observation posts; no sooner did the object of interest come near than you had to retreat from it at the speed of light. The Rindler was constantly retreating, but no faster than was absolutely necessary. Matching velocities with the border transformed its appearance; from the observation deck, the celestial image that had become an emblem of danger for ten thousand civilizations was nowhere to be seen. The border finally looked like the thing it was: a vast, structureless, immaterial wall between two incomparably different worlds.

"Tchicaya!"