Schild’s Ladder

understood them in the same way. Humans had tamed and modified dozens of species of plants and animals before they’d had the slightest idea what DNA was.

Tchicaya started the program running. Without feedback along the lines of “Yes, we understood that, please skip ahead to something ten times harder,” it would take four ship-days to complete. He could choose sections to omit, himself?—?but which ones? What concepts were obvious to a xennobe?

Mariama smiled tentatively. “They haven’t left the room yet.”

“It is an alien artifact. That in itself must merit some level of attention.”

“They chose the primes,” she said. “They picked the language, and it was exactly what we would have picked ourselves.”

Tchicaya scanned the room. “We’re missing something here.” The Colonists had no faces, no eyes, and he had no way of telling what they were attending to, but they were far better positioned to observe the nucleon nugget than the banner.

He said, “They’re showing it the banner. They’re not even trying to make sense of the message themselves. They expect their meteorite to react.”

Mariama was skeptical, but not dismissive. “Why would they think that way? Some kind of category error? They’re intelligent enough to figure out that both these things came from the near side, but they have no concept of inanimacy? Because…everything here is living?” She grimaced. “Are you going to stop me before I start talking complete gibberish? Whether vendeks count as living or not, random collections of them would make very bad translators between xennobe languages.”

Tchicaya said, “So are the Colonists suffering from animist delusions, or is this not a random collection of nucleons?” He addressed the toolkit. “Can you make any sense of its structure? What are the odds that nuclear matter in a star or a planet could be in a state that could come through the border like this?”

“Negligible.”

“So someone wrapped it? Someone prepared it deliberately?”

The toolkit said, “That’s more likely than it happening by chance.”

Mariama said, “Don’t look at me. Maybe someone was running their own secret experiments, but this was not a Preservationist project.”

“Then whose was it? And what has it been doing down here?” Tchicaya asked the toolkit, “Can you model its dynamics? Is there information processing going on in there?”

The toolkit was silent for a moment. “No. But there could have been, once. It looks to me like it started out as a femtomachine.”

Gooseflesh rose on Tchicaya’s arms. Back on the Rindler, comparing their varied experiences of local death, Yann had definitively trumped him with tales of going nuclear.

He said, “It’s the Mimosans. They’re buried in there.”

Mariama’s eyes widened. “They can’t be. The Quietener blew up in their faces, Tchicaya. How much warning would they have had?”

Tchicaya shook his head. “I don’t know how they did it, but we’ve got to look for them.” He asked the toolkit, “Can you map the whole thing? Can you simulate it?” The crushed femtomachine was vastly larger than the Sarumpaet, but having started from merely nuclear densities, it would have made far less efficient use of its graphs.

The toolkit said, “I’ll try. It will take time to get the information out; the probes can only move it at a certain rate.”

They waited. The mathematics lesson played on through the banner; the Colonists floated in place, patient as ever, expecting…what? The femtomachine had talked to them, once. It must have functioned long enough for its inhabitants to learn their language. Had it told them to make the signaling layer? Or had it commenced its own attempts to communicate with a sequence of primes, which they’d gone on to copy?

After almost an hour, the toolkit declared, “I have a complete model of the structure inside the Sarumpaet. Now I’m trying to repair some of the damage.” It juggled connections, looking for gaps in information routes; it searched for redundancies that would allow it to reconstruct the missing pathways.

“There’s a simulation of something resembling a primate body. With standard representation hooks into the model.”

“Show us,” Tchicaya said.

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