Schild's Ladder (18 page)

Branco looked up and announced with mock astonishment, “Am I finished already? Is that all I have to do?”

Tarek said, “For now. But I'm invoking my right to a functional audit.”

“Hooray,” said Branco. He pushed himself away from the control panel and floated by the window with his hands on his head.

Tarek took his place, and instructed the stylus to rise from the border. Tchicaya had heard about functional audits, but he'd never witnessed one before. A package of detectors, verified by the faction invoking the audit, was placed under the tip of the stylus, and the particles emitted were scrutinized directly, to be sure that they conformed to the agreed sequence.

Tchicaya was tempted to say something derisive, but he held his tongue. Whatever made Tarek believe that this was necessary, complaining about the procedure would do nothing to lessen his suspicions.

He used the handholds beneath the windows to drag himself closer to Mariama. “Where have you been hiding? I haven't seen you for weeks.”

“I have a lot of meetings.”

“I go to meetings, too.”

“Not these ones,” she said.

She didn't need to spell it out. She'd come to the
Rindler
hoping to work with Tarek on Planck worm design, and apparently the notion still wasn't dead.

The novo-vacuum was already the largest object in the galaxy, and it was growing so rapidly that its surface area would increase almost forty-fold while it was encircled at the speed of light. Even if the Preservationists discovered a potential method for dealing with it, there was no prospect whatsoever of surrounding the entire thing with conventional machinery to administer the cure. The only practical tool would be a self-replicating pattern embedded at the level of quantum graphs, able to “eat” novo-vacuum and excrete something more benign.

To supporters of the idea, these hypothetical Planck worms would do no more than reverse the disaster of Mimosa. To Tchicaya, the symmetry was false. The places lost to Mimosa—ordinary planets, unique as they were—had already been thoroughly understood. Learning just enough about the novo-vacuum to infect it with a kind of fungal rot struck him as a corruption of every impulse that made intelligence worthwhile. He had enough trouble forgiving that kind of cowardice in a child.

“So what do you think the prospects are?” He meant those for Branco's experiment succeeding, though if she cared to disclose her thoughts on anything further down the line, so much the better.

Mariama thought carefully before replying. “I'm almost persuaded that Sophus is right, but I'm not certain that Branco's ideas follow. When we have no access to any particular far-side dynamics, even plucking out a random correlated state seems like too much to ask.”

Yann had been floating a polite distance away, but the room was too small for any real privacy, and now he gave up pretending that he couldn't hear them. “You shouldn't be so pessimistic,” he said, approaching. “No Rules doesn't mean no rules; there's still some raw topology and quantum theory that has to hold. I've reanalyzed Branco's work using qubit network theory, and it makes sense to me. It's a lot like running an entanglement-creation experiment on a completely abstract quantum computer. That's very nearly what Sophus is claiming lies behind the border: an enormous quantum computer that could perform any operation that falls under the general description of quantum physics—and in fact is in a superposition of states in which it's doing all of them.”

Mariama's eyes widened, but then she protested, “Sophus never puts it like that.”

“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.

The wall flexed again, and the pair of windows that had been squashed together separated. Instead of reversing their original motion, though, they parted at the seam, like doors swinging open.

Tchicaya bellowed with fright, and reached out for something to stop himself. He succeeded only in clutching Yann's shoulder, and the two of them tumbled through the opening together.

For several seconds, Tchicaya remained rigid, preparing himself on some instinctive level for intense pain and a swift extinction. When neither arrived, his whole body began shaking with relief. He'd known that his suit would protect him, but the understanding hadn't penetrated far. He'd skydived from altitudes where oxygen was needed, and swum at depths where the next free breath was hours away, but black and starry space had remained the quintessence of beautiful danger: pristine, indifferent to his needs, predating every form of life.
Vacuum
was not a word that offered hope. He should have been snuffed out in an eye blink.

He looked around. The push of the escaping air had been firm but brief, so it was unlikely that they were moving very rapidly, but he was facing the wrong way to catch sight of the Scribe, the only meaningful signpost. The border itself offered no cues as to their velocity in any direction.

He'd been holding his breath deliberately, as if he'd plunged into water, but he realized now that the urge to inhale had vanished as soon as the suit's membrane had sealed off his mouth and nose. His body had shut down its lungs; the
Rindler
's model could operate for days on anaerobic metabolic pathways. His skin felt slightly chilly, but he could see the exposed film of the suit on the back of his hand, silvered to retain heat. He extended his arm shakily so he could examine Yann, whose face had turned entirely metallic except for two holes for his pupils.

“You should have known it was futile, Tin Man, trying to walk among us. Robot nature always shows through.” Tchicaya's teeth were chattering, but that made no difference; his Mediator grabbed his speech intentions and routed them away from his useless vocal cords, shunting them into a radio channel.

Yann said, “Believe me, the effect looks much stranger on you.”

They were rotating slowly together, around an axis roughly perpendicular to the border. As they turned, the Scribe came into view over Yann's shoulder. The lower half of the structure was buckled and twisted, but the control room was still safely clear of the border. As far as he could judge, he and Yann were still four or five meters from the border themselves, and their trajectory was virtually parallel to it. This freakish alignment was sure to prove inexact, though, one way or the other.

He spotted a shiny Mariama standing at the ruptured wall, watching him.

“We're all right,” he said. “Get in the shuttle.”

She nodded and waved, as if he'd be unable to hear a reply.

Then she said, “Okay. We'll come and pick you up.” She vanished from sight.

Tchicaya instructed his Mediator to make his next words private. “Are we all right? I don't have the skills to determine our velocity that accurately.”

“We're moving toward the border, but it would take hours before we'd hit it.”

“Oh, good.” Tchicaya shuddered. His right hand was still locked on to Yann's shoulder, the fingers digging in as if his life depended on it. He knew that wasn't true, but he couldn't relax his grip.

“Am I hurting you?” he asked.

“No.”

Yann's metallic face brightened strangely, and Tchicaya glanced down. A patch of borderlight more intense than its surroundings drifted slowly by.

“What do you make of that?” Tchicaya asked. He was suddenly light-headed, from more than the shock of ejection. The Doppler-shift tints aside, he'd known the border as a featureless wall for centuries. The tiniest blemish was revolutionary; he felt like a child who'd just watched someone reach up and scratch a mark into the blue summer sky.

“I'd say Branco has succeeded in pinning something to the near side.”

“We have physics? We have rules now?”

“Apparently.”

Mariama said, “We're in the shuttle. Everyone's safe here.”

“Good. No rush; the view is wonderful.”

“I won't hold you to that. We'll be there in a few minutes.”

The strange patch of brightness had moved out of sight, but after a few seconds another came into view. They were fuzzy-edged ellipses, traveling from the direction of the Scribe.

“They're like the shadows of reef fish,” Tchicaya suggested. “Swimming above us in the sunlight.”

Yann said, “Do you think you might be coming slightly unhinged?”

As Tchicaya swung around him in their involuntary dance, he caught sight of the shuttle rising from the ruined Scribe. He smiled at the memory of Mariama's voice, promising to rescue him. On Turaev, if they'd given in to their feelings, it would have ended badly, burning out in a year or two. When this was over, though—

Yann said, “That's a bit ominous.”

“What?”

“Can you turn your head back toward the Scribe? That might be quicker than me trying to put it into words.”

Tchicaya twisted his neck. The border had formed a bellshaped hillock, forty or fifty meters high, that had completely swallowed the Scribe. As his rotation forced him to stretch even more, he stopped fighting it and twisted his neck the other way, hastening the sight's return instead of trying to delay its departure.

The hillock was collapsing now, but as it did, a ring around it was rising up. Suddenly, Tchicaya noticed a whole series of lesser rings surrounding the first, like concentric ripples in water. They were undulating out from the center at great speed: the leading edge, the fastest component, in some kind of surface wave. The bulk of the wave was spreading more slowly. But it was still traveling faster than they were.

He searched for the shuttle, and found it, its exhaust a pale blue streamer against the stars. The thrust generated by the ion engine was very low; over time it could accumulate into a significant velocity, but the craft was about as maneuverable as a bathtub on ice. It might just reach them before the wave, and even accelerate away from the border again in time, but there'd be no margin left for any more surprises that might manifest themselves in the wake of Branco's intervention.