Schild’s Ladder

"No, of course not," Yann agreed. "He’s much too careful to use overheated language like that. The universe is a Deutsch-Bennett-Turing machine’s is not a statement that goes down well with most physicists, since it has no empirically falsifiable content." He smiled mischievously. "It does remind me of something, though. If you ever want a good laugh, you should try some of the pre-Qusp anti-AI propaganda. I once read a glorious tract which asserted that as soon as there was intelligence without bodies, its 'unstoppable lust for processing power would drive it to convert the whole Earth, and then the whole universe, into a perfectly efficient Planck-scale computer. Self-restraint? Nah, we’d never show that. Morality? What, without livers and gonads? Needing some actual reason to want to do this? Well…who could ever have too much processing power?

"To which I can only reply: why haven’t you indolent fleshers transformed the whole galaxy into chocolate?"

Mariama said, "Give us time."

"The equipment seems to have passed inspection." Tarek pocketed the detector package and began lowering the stylus.

Branco folded his arms and pondered this announcement. "Seems? I’ll take that as a general statement of Cartesian skepticism, shall I?"

Tarek replied curtly, "You’re free to instruct it again."

Branco began repeating the sequence. Tchicaya was expecting him to rush through it this time, but instead he took pains to reproduce the same pacing and intonation as he’d employed originally.

Tchicaya caught Tarek’s eye and said, "You know, you have as much to gain from this experiment as anyone."

Tarek frowned, as if the implication was not merely unjust but completely surreal. "You’re right. That’s why I’m taking it seriously." He hesitated, then added defensively, "Don’t you think I’d prefer to believe that everyone was acting in good faith? I’d like to assume that. But I can’t; there’s too much at stake. If that makes me look petty to you, so be it. I’ll answer to my descendants."

Branco completed his second recitation. Yann said, "Approved."

Tarek said, "Yes, go ahead."

Branco addressed the Scribe. "Execute that."

The Scribe remained silent, but a heartbeat later there was a sharp hissing sound from under the floor. Tchicaya had no idea what this could be, until he saw the realization dawning on Branco’s face.

A fine crack appeared in one window, then another. Tchicaya turned to Mariama. "You’re backed up?"

She nodded. "While I slept. You?"

"The same." He smiled uncertainly, trying to reassure her that he was prepared for whatever happened, without discouraging her from expressing her own feelings. They’d been through a lot together, but neither of them had ever witnessed the other’s local death.

"Yann?"

"I’m covered, don’t worry."

Branco and Tarek were in the same position: no one risked losing more than a day’s memory. After his fourth local death, Tchicaya had ceased to feel genuine, gut-churning dread at his own fate — and he had some memories that led up to the moment itself — but in the company of others it was always more stressful. Wondering how much fear they felt, and how careful they’d been.

The hissing beneath them intensified, and the room began to creak. The windows had healed themselves, and the whole structure would be capable of a certain amount of self-repair, but if the border was lapping up against the Scribe, the wound it made would be reopened with every advance. The microjets were designed to compensate for the effects of bombardment with interstellar gas; shifts measured in microns were the crudest adjustments imaginable. The Scribe was not going to whisk them away to safety.

Tarek looked around nervously. "Shouldn’t we head for the shuttle?"

Branco said, "Yes."

The wall behind Tchicaya emitted a tortured groan. As he turned, it concertinaed visibly, the angle between two windows becoming impossibly acute. Tchicaya marveled at the sight. Air leaking from the Scribe couldn’t be producing shear forces of that magnitude; the border had to be tugging on the structure beneath them. Nothing of the kind had ever been witnessed before. Beams constructed from a variety of substances, poked through the border, had always behaved as if the far-side portion had simply ceased to exist; there were no forces exerted on the remainder. Whatever Branco had triggered, he’d done more than displace the border by a few centimeters.