Schild’s Ladder

A person appeared on the deck in front of them, standing motionless, arms raised as if in defense against a blow, or an impact. The body did not resemble anything Tchicaya had inhabited himself, but it was a piece of software that made no sense unless the femtomachine had contained a sentient inhabitant.

"Can you trace back the sensory and motor hooks?"

"I’m trying. Okay. I’ve found it."

"You’ve found the mind?"

"Yes."

"What kind of state is it in?"

"Wait. I’m computing integrity signatures." Sentient software was always packed with check sums that would allow it to detect whether it had been corrupted. "Not scrambled, just frozen. Most of the physics that leaked in seems to have slowed down the strong force interactions, rather than damaging the quarks and gluons."

Tchicaya said, "Can you run it? Can you wake it?" He was shaking. He didn’t know if he was digging a tenacious survivor out from beneath a rock slide, or breathing unwelcome life back into a mutilated castaway who’d escaped into a merciful local death. Too much was at stake, though, to let the Mimosan rest in peace until he learned the answer for himself.

The simulation twitched, looked around the scape, then dropped to its knees, sobbing wretchedly. "I’m going mad! I’m going mad!" The body being simulated had been designed to function in vacuum; it was even pretending to speak in infrared.

Tchicaya understood the words as they were spoken; his Mediator had turned the data into sounds in his head, and granted him the survivor’s language immediately.

He knelt beside her and wrapped his arms around her shoulders. "You’re not going mad, Cass. We’re real. You’re not home yet, but you’re very close now. And you’re among friends."

Chapter 18

Time was everything, and Tchicaya felt a streak of brutal pragmatism demanding that he press their only hope of a translator into service as rapidly as possible. It would be a false compassion that ended with all of them dead. But though Cass was undoubtedly sane, and increasingly lucid, she was still in shock. Before she could help them, she needed to make sense of her own situation.

Tchicaya told her about the signaling layer, and how the Sarumpaet had been led to this place. He said nothing about the Planck worms; he and Mariama were explorers from the near side, that was all that mattered for now. He invited Cass to complete the account, to bridge the gap between the events at Mimosa and this extraordinary meeting. Seated on a couch they’d conjured up for her, she told them some of the history of her voyage.

For the last of their experiments on the novo-vacuum, the Mimosans had sent clones into a femtomachine, in order to be closer to the event in real time. They had seen the nascent border expanding, and struggled to understand their mistake. In one branch of the femtomachine’s uncontrolled superposition, they had reached Sophus’s insight: the physics of the ordinary vacuum represented just one eigenstate for a quantum graph’s dynamic laws.

Working from that starting point, they had devised a plan to spare the inhabited worlds from destruction. By modifying the border so as to make the emission of light sufficiently asymmetrical, the difference in radiation pressure could be used to accelerate the whole system. While the far side remained small, its mass as an object in the near side would be tiny (in fact, tiny and negative, since it had started at zero and lost energy as radiation). If it was left to others to tackle the problem decades later, the far side would have swallowed entire star systems — at the very least, Mimosa itself. If they acted now, they could send it flying out of inhabited space even faster than it was expanding.

When the border hit the femtomachine, they would have a chance to interact with it, but no fleeting, localized encounter would be sufficient to sculpt the borderlight into a propulsion system. They needed to buy themselves more time. Matching the border’s velocity would have been ideal, but there was no prospect of achieving that. Their only hope was to find a way to keep working on the problem after the far side had swallowed them.

The Mimosans had choreographed a bravura quantum maneuver that would allow the femtomachine to inject a partial clone of itself through the border, and rotate all of its amplitude into the successful branch at the same time. But the passengers couldn’t all pass through. The bulk of the femtomachine would have to become a device whose sole purpose was to implement the move, and only the acorporeals were structured in a way that gave them the power to rewrite their minds right out of existence, converting themselves into pieces of the quantum catapult. All seven had been needed, to make it work. Cass had been left to go in alone.