Schild's Ladder (23 page)

“You wanted to stay and fight?”

“I wanted to stay and understand it. I would have been on the
Rindler
from the start if I'd heard about it early enough. Instead, I went chasing rumors of another project. That fell through, and it took me centuries to make my way here. But I always knew we'd find a way through the border. The night before I left Maeder, I stood on the roof of my house and promised myself: next time, it won't just look as if I could reach up and push my hand into the far side. It will be possible. It will be true.”

Tchicaya could easily picture her in this scene. “You're making me feel very old and indecisive,” he complained.

She smiled. “I'm sorry, but that's because you are.”

The console said, “Move your backside, please.” Tchicaya slid off; data was coming through.

This time, he fought harder to stay beside Rasmah, peering over her shoulder at the console as the pulse appeared, and its interference pattern was analyzed.

Branco's refinement had been on target: the new set of images showed a graph changing smoothly. Again, this was just an average for the whole path that had been traversed, not any particular piece of the far side, but it was still as informative as, say, a sample of images of terrain from a million different Earth-sized planets of different ages. You didn't need to have the entire history of one specific world to get a qualitative sense of how things changed.

Rasmah set the image looping, and the Blue Room crowd fell silent. The intricate waves of knotted edges flowing through the graph were mesmerizing. Animations of standard particle physics could be austerely beautiful; watching something like pair-production, with the mirror-image patterns of electrons and positrons forming out of their parent photons and moving through the vacuum, you couldn't help but admire the elegant symmetry of the process. This was a thousand times more complex, without being random or chaotic. The still image had reminded Tchicaya of a clumsy sculptural collage, but that was only because he'd imagined all the separate parts still playing their old, vacuum-based roles. Seeing the integrated whole in action destroyed that impression completely. Rather, the old Sarumpaetstyle patterns and interactions were beginning to look like repetitive attempts to imitate parts of
this
—like the work of some awful, sample-driven artist who took a tiny piece of someone else's intricately composed, wall-sized image and treated it as a decorative tile to be stamped out a thousand times in a rectangular grid.

Near-side physics did achieve the same kind of complex beauty, but not at this scale, twenty orders of magnitude smaller than a proton. You had to move up to the size of atoms, at least, and even the richness of chemistry appeared crude and stodgy in comparison. When atoms changed their bonds, it was generally a haphazard, rough-and-tumble process, driven at random by thermal collisions, or at best chaperoned by enzymes or nanomachines. These polymers of indivisible nodes and edges were reweaving themselves with a speed and precision that made the most sophisticated molecular factories look like children tossing snowballs.

Tchicaya heard someone clear their throat, nervous and tentative, reluctant to break the spell. He turned away from the console, curious and slightly annoyed, wondering what anyone thought they could add to this extraordinary sight with words. But the crowd moved respectfully away from the speaker, making space as if in encouragement.

It was Umrao, a recent arrival from Nambu who Tchicaya had only met once. He looked around shyly, even more nervous now that he had everyone's attention.

He said, “That's not particle propagation, but it's something I've seen before, in simulations. It's persistence, and replication, and interdependence. It's not a superposition of a billion different vacua—or if it is, that's only one way to describe it, and I don't believe it's the best.

“It's a biosphere. It's an ecology. Right down at the Planck scale, the far side is crawling with life.”

Chapter 11

Tchicaya said, “We should tell them, now! Take them all the evidence. No, no—better, teach them Yann and Branco's method, and let them probe the far side for themselves. Then they'll know they're not being cheated with some kind of elaborate simulation.”

Hayashi groaned. “And then what? They convince themselves that they're now facing the Virus That Ate Space-Time. While we've surrendered our sole advantage.”

Pacing the ship, unable to sleep, Tchicaya had run into Suljan and Hayashi. When a casual exchange of views in the corridor had come perilously close to disclosing all the latest discoveries, he'd accompanied them to the Yielders' cafeteria, which was supposedly secured against listening devices. Other people passing through had become entangled in the debate.

Rasmah said, “I agree. This isn't going to sway anyone. Even if they're willing to interpret this as evidence for Planck-scale biota, and even if that destroys all their preconceptions about the ‘Mimosan vacuum’...if you didn't care that much about far-side physics, why should you care about far-side microbiology?”

Yann's icon appeared, seated beside her. “Microbiology? These organisms are a few hundred Planck lengths wide: about ten-to-the-minus-thirty-three meters. This is
vendekobiology
.”

Suljan picked up a mug and raised it threateningly. “What are you doing here? This is where the real people come, to metabolize in peace.”

Yann said, “My mistake. I thought you might be sitting around singing the praise of everyone who helped win you a glimpse of the far side. But I can see you're more interested in getting in some valuable belching and farting time.”

Hayashi reached over and slapped Suljan on the back of the head. “You're an oaf. Apologize.”

“Ow. It was a joke!” He turned to Yann. “I apologize. I'm in awe of your accomplishments. I'm already working on an ode to your sacred memory.”

Umrao looked embarrassed by all the bickering going on around him. He said, “I suppose we need more evidence if we're going to convince the skeptics, but for what it's worth, I've been doing some simulations.” He summoned graphics, floating above the table. “The mix of replicators is probably not the same throughout the far side. There are other possible equilibria, other population mixtures that look more or less stable—and that's just changing the relative numbers of the species we've seen, not accounting for entirely different ones.” The images showed both a graph-level view of these teeming communities of organisms, and a higher-level map of a possible set of neighboring regions.

“The transition zones tend to be quite sharp, and sometimes they just advance relentlessly in one direction at a constant velocity, like the border itself. But there are other situations where an intermediate mix of species forms in a narrow layer, and it stops either side from invading the other.”

Tchicaya seized on this. “A kind of internal freezing of the border?”

Umrao nodded. “I suppose you could think of it like that. Except that our side of the border is completely sterile, so it's not really subject to the same effects.”

“You don't think we could create a layer population like these, that worked with one side unpopulated?”

Umrao thought for a while. “I couldn't say. For a start, these are simulations, so I'm not even sure that any of this happens in reality. And we'd need to understand many things much more thoroughly before we set out to engineer a layer population with particular properties.”

Suljan said, “Screw it up, and the border might just move faster.”

Tchicaya gazed into the simulation.
Our side of the border is completely sterile
. All these millennia looking for life, scratching around on rare balls of dirt for even rarer examples of biochemistry, only to find that the entire substrate of the visible universe was a kind of impoverished badlands. Life had still arisen here, thirty orders of magnitude up the length scale, as heroic and miraculous as some hardy plant on a frozen mountain peak, but all the while, infinitely richer possibilities had been buzzing through the superposition that the dead vacuum concealed.

He said, “Keeping this quiet is insane. People have evacuated whole planets for fewer microbes than there are in one atom-sized speck of the far side.”

“Not always enthusiastically,” Rasmah replied dryly.

For a moment, Tchicaya was certain that she knew what he'd done. Mariama had revealed their secret, whispered it in a few well-chosen ears, to punish him for his hypocrisy.

That was absurd, though. It was common knowledge that compliance with the ideal of protective isolation had often been begrudging, and everyone suspected that there'd been cases where the evidence had been ignored, or destroyed.

“This could win us the Wishful Xenophiles,” he persisted. “One glimpse of this, and they'd desert
en masse
.” Not all Preservationists shared the view that cultural upheavel was the worst consequence of Mimosa; a sizable minority were more afraid that it might obliterate some undiscovered richness of near-side alien life. Four known planets dotted with microbes—whatever potential they offered for evolutionary wonders in a few hundred million years' time—might not be worth fighting for, and most people had abandoned hope that the galaxy contained other sentient beings, but unexplored regions could still be home to alien ecologies to rival Earth's. Now, that uncertain possibility had to be weighed against life-forms by the quadrillion, right in front of their noses.

“These aren't sophisticated creatures,” Hayashi pointed out. “We can quibble about the definition of life in different substrates, but even if that's conceded, these things really aren't much more complex than the kind of RNA fragments you find in simulations of early terrestrial chemistry.”

“That's true,” replied Suljan, “but who says we've seen all the life there is to see?” He turned to Umrao. “Do you think these could just be the bottom of the food chain?”

Umrao spread his hands helplessly. “This is very flattering, but I think some of you are beginning to ascribe oracular powers to me. I can recognize life when I see it. I can extrapolate a little, with simulations. But I have no way of knowing if we're looking at the equivalent of Earth in the days of RNA, or if this is plankton on the verge of disappearing into a whale.”

Yann said, “Now we're talking xennobiology!” Tchicaya shot him a disgusted look, though on reflection the hideous pun seemed inescapable. A complex organism based on similar processes to the primitive ones they'd seen probably would be about a xennometer in size.

Suljan wasn't satisfied with Umrao's modest disclaimer. “You can still help us take an educated guess. Start at the bottom, with what we've seen. I don't think we should try to imagine evolutionary processes; we don't know that these things are
primeval
, we just know that they seem to be ubiquitous. So we should ask, what else can fit in the same picture? The vendeks don't really prey on each other, do they?”

“No,” Umrao agreed. “Where they coexist in a stable fashion, it's more like exosymbiosis. In totality, they create an environment in the graph where they can all persist, taking up a fixed share of the nodes. A given vendek in a given place in the graph will either persist or not, depending on the surrounding environment. At least in the sample we've seen, most do better when surrounded by certain other species—they don't flourish in a crowd of their own kind, but they can't make do with just any sort of neighbor. In microbiology, you get similar effects when one species can use the waste of another as food, but there's nothing like that going on here—there is no food, no waste, no energy.”

“Mmm.” Suljan pondered this. “No vacuum, no timetranslation symmetry, no concept of energy. So even if there's another level of organisms, there's no particular reason why they should
eat
the vendeks.”

“They might have subsumed them, though,” Hayashi suggested. “Imagine the equivalent of multicellularity. A larger organism might have different vendeks playing specialized roles. Different ‘tissues’ of a xennobe might consist of—or be derived from—some of the species we've seen.”

“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.”