Schild’s Ladder

"I suppose so," Umrao said cautiously. "But remember, these things are much, much simpler than single-celled organisms. They don’t have anything remotely akin to genomes. In most multicellular creatures, all the cells in all the tissues share their full genome, with different parts of it switched on and off. It’s hard to see how vendeks could be regulated with the necessary precision."

Rasmah frowned. "Maybe multicellularity’s not the right analogy. What’s it actually like, on a larger length scale, to be immersed in these different vendek populations?"

Umrao shrugged. "For what to be immersed? I don’t know what kind of organized patterns of information can persist, apart from the vendeks themselves. If we’re going to model the behavior of some object, we need to know what it’s made from."

Tchicaya took a stab at this. "Different vendek populations, with stable layers between them? A kind of honeycomb of different heterogeneous communities?"

Suljan said, "Hey, maybe they’re the cells! Vendeks themselves are too small to play tissue types, but certain communities of them can be maintained within intact membranes, so maybe our xennobes could regulate the population mixtures as a surrogate for cell differentiation." He turned back to Umrao. "What do you think? Could you look for a form of motility in these walled communities?"

"Motility?" Umrao thought for a moment. "I think I could build something like that." He began tinkering with the simulation, and within minutes he’d produced an amoebalike blob moving through a sea of free vendeks. "There’s one population mix for the interior, and a layer around it that varies as you go from the leading surface to the trailing one. The leading surface acts like an invasion front, but it decays into the interior mix as it travels. The trailing surface does the reverse; it actually invades its own interior, but it lets the external population take over in its wake. Perpetual motion only, though: this cell could never stand still. And it’s a contrived setup. But I suppose there are all kinds of opportunities to modulate something like this."

Tchicaya looked away from the simulation to the mundane surroundings of the cafeteria. He was beginning to feel more optimistic than he had since he’d arrived, but this was all still speculation. To build a machine, a body, from anything like these "cells" was going to be a dauntingly complex endeavor.

He said, "We have to win time from the Preservationists. There has to be a truce, a moratorium, or this could all be wiped out before we learn anything."

Rasmah said, "You think they could make effective Planck worms, without knowing what they’re dealing with?"

"You’re the one who’s convinced that they have spies."

"If they have spies, why should telling them anything buy us more time?"

"When did spies ever share their intelligence with the masses?" Tchicaya countered. "Suppose Tarek was looking over our shoulder right now, but everyone else remained in the dark?" He turned to Umrao. "I don’t suppose you’ve investigated the possibility of Planck worms? A plague that kills the vendeks, and leaves a sterile vacuum in its wake?"

Umrao glanced around the table warily. "If any of what you just said was serious, I don’t think I should answer that question."

Suljan groaned. "Forget about politics. We need more data!" He slumped down across the table, drumming his fists on the surface. "I was playing around with something last night, before I stepped out for a snack and ended up mired in this discussion. I think I might have found a way to extend Yann and Branco’s technique, pushing the range about ten thousand times further." He looked up at Yann, smiling slyly. "The only way I could make any progress with your work, though, was to translate it all into my own formalism. Everything becomes clearer, once you express it in the proper language. It only took me a few hours to see how to scale it up, once I’d dealt with the mess you left us."

Rasmah asked sweetly, "So what was the great conceptual breakthrough, Suljan? How did you sweep our Augean stables clean?"

Suljan straightened up in his seat and beamed proudly at them all. "Qubit network theory. I rewrote everything as an algorithm for an abstract quantum computer. After that, improving it was simplicity itself."

On his way to the Blue Room, crossing the observation deck, Tchicaya spotted Birago standing by the starside wall. His first thought was to walk on by; minimizing friction by minimizing contact had become an unwritten rule of shipboard life. But the two of them had got on well enough before the separation, and Tchicaya was sick of only talking to Preservationists at the interfactional meetings, when the entire discussion was guaranteed to revolve around a mixture of procedural issues and mutual paranoia.

As Tchicaya approached, Birago saw him and smiled. He looked slightly preoccupied, but not annoyed at the interruption.

Tchicaya said, "What are you up to?"