"I"ve already designed the vehicle you"re looking for," Yann insisted. "I just need some help to describe it in more palatable terms, so I can sell it to the others."

Rasmah said, "It"s not a vehicle. It"s software. And it"s software for a nonexistent computer."

Yann shook his head. "That"s just the mathematical formalism I"ve used. It"s the best way to describe it - the most elegant, the most transparent. All we have to do now is disguise it." He added, deadpan, "You can obfuscate, can"t you? Physicists have been taking simple mathematical ideas and obfuscating them for centuries. It must have been part of your training, surely?"

Rasmah took a swipe at him, and he flinched away from her. No doubt this was a habit he"d acquired during embodiment, when he"d managed to elicit a similar response from people on a regular basis.

With the queue for bodies growing ever longer as new arrivals flooded in, Yann had decided to remain acorporeal. Tarek had responded to this news at the weekly interfactional meeting with a long, paranoid dissertation on Yann"s self-evident intention to use his new position to "corrupt" the Rindler's processor network, infiltrating the Preservationists' communications and data storage systems, spying on them and undermining all their efforts. Fortunately, Sophus had spoken next, gently guiding Tarek back into contact with reality. Many things in the universe remained difficult and mysterious, but the casual structure of computer networks was not one of them. It would have required an act of cartoonish incompetence on the part of the Rindler's designers to create a network in which any of the abuses Tarek feared were physically possible.

Tchicaya said, "So you shift dynamics, once you"re through the border? You navigate between them?" He had arranged for the three of them to meet in his cabin so that Yann could try out the idea on Rasmah and refine his pitch, before taking it to a meeting of all the Yielders. "The dynamic laws are like stepping-stones that only need to last for as long as you use them?"

Yann grimaced. "That sounds ugly enough, but it"s not even close to the truth. The algorithm never obeys a sharply defined dynamic law; if it tried to do that, it would be doomed from the start." He thought for a while. "You know how a Gaussian wave packet can keep its shape in a harmonic oscillator potential?"

"Yes." Tchicaya felt a burst of confidence; that was just elementary quantum mechanics. In empty space, a particle"s wave packet would always disperse, spreading out without limits. But if the particle experienced an attractive force analogous to the tug of a spring in classical physics, there was a certain shape - a certain Gaussian, like the bell curve of statistics - which was stable. Any tighter, sharper wave packet would necessarily have a range of values for momentum that made it spread out; that was just the uncertainty principle. The right Gaussian, though, in the right environment, was the perfect compromise between uncertainty in position and momentum, allowing the shape of the wave to remain unchanged as it moved.

"This isn"t really the same," Yann admitted. "But it might sound persuasive if I put it that way."

Rasmah glanced at Tchicaya, exasperated. He made puppydog eyes back at her, pleading on Yann"s behalf.

She laughed, and relented. "Why don"t you just give me the description of the graph you want to scribe, and I"ll grind through the calculations using my own picture of Sophus"s model. If I can demonstrate that we"d get some inforamtion back through the border - something more than we put in - that might be enough to persuade people. I"ll make sure I phrase my results in the ugliest possible way."

Yann said, "That"s wonderful. Thank you!"

He passed something to Rasmah - Tchicaya"s Mediator saw the fact of the exchange, but not the content - and then vanished.

Rasmah sighed. "You really think he"s on to something? A quantum computer can simulate any quantum process; that"s old news. It doesn"t mean that there is a quantum computer underlying anything."

"No," Tchicaya agreed. "But qubit network theory doesn"t claim that. It just says that when you get to a low enough level, you have nothing left to lose by treating the system as if it were software. It"s like all the proofs in applied algorithmic theory that are based on imagining Turing machines. No one complains that the real universe is conspicuously devoid of paper tape."

"Old habits die hard," she confessed. "I"m still in mourning for the Sarumpaet rules, and they were disproved before I was born. They"re what I was brought up on, they"re what I"ve thought of all my life as the template for a physical theory. It"s not easy adapting, even to Sophus"s model."

"Yeah. I really am grateful to you for trying this," Tchicaya said. Since the factional rift had widened, it was more important than ever to keep all the Yielders open to each other"s new ideas, and where he wasn"t competent to contribute directly himself, he could at least act as a kind of broker, prodding the appropriate experts into action.

Rasmah seemed on the verge of pointing out that he might have expressed his gratitude to her more palpably, but then she smiled and accepted his words at face value.

"Okay. Here I go."

She turned her attention to something invisible to Tchicaya. For several minutes, she sat in complete silence.

Suddenly, she exclaimed, "Oh, I see! This is actually quite nice."

Tchicaya was excited, and slightly jealous. "Can you explain?"

Rasmah held up her hand for patience, retreating back into her private scape.

After a while, she spoke again. "Think of all the different dynamic laws that might make topological sense, in terms of the propagation of various kinds of particles that are defined as patterns embedded in a graph. I know that"s horribly vague, but I don"t think you"d want the version with added jargon."

Tchicaya said, "Okay. I"m thinking of them." He"d seen enough examples that they"d pinned to the border over the last few months to have some feel for what this meant.

"Now imagine each one is a quantum state vector in a big fat Hilbert space. All of them orthogonal to each other."

"Yes." Tchicaya had never had his mind restructured to enable clear images of more than three dimensions, but since Rasmah"s Hilbert space was infinite-dimensional anyway, three was as good as any other number. "I"m doing that. Go on."

"Now imagine a new set of vectors that consist of equal amounts of all these dynamic-law vectors, and that are all orthogonal to each other. These vectors represent definite values of a variable that"s complementary to the law vectors. Branco calls them law-momenta - which is a bit sloppy, because they"re not true Lagrangian conjugates, but never mind."

"I"ll try not to fret." Tchicaya thought of the directions on a map. If the dynamic-law vectors were north and east, then the new, unbiased, law-momenta vectors would be north-west and north-east. Both had equal portions of the old directions - if you counted west as being the negative of east, and only cared about the size of things, not their sign - and they were at right angles to each other. In three dimensions or more you needed to introduce complex numbers to pull off the same balancing act, but from there you could keep on going to any number of dimensions. The amounts of the original vectors you combined were just a series of complex numbers that moved around a circle in the complex plane; to get different vectors, all orthogonal to each other, you just moved around the circle at different rates.

"Now picture a state vector which has equal components when written as superpositions of the old set, or the new."

In two dimensions, that was easy: north-north-east lay at the same angle to north as it did to north-east, and the same angle to east as it did to north-west. In terms of the quantum mechanics Rasmah was describing, it had equal uncertainty in the two complementary variables: it did not obey a precise dynamic law, but nor did it have any precise law-momentum. It split the difference and compromised, in the most symmetrical way.

Rasmah continued. "These are the states Yann wants to scribe, because if you create one on the border, and then arrange to measure the same kind of state coming back, they yield the highest attainable probability of returning with information about the interior."

" The highest attainable probability? That"s a resounding declaration of confidence." Tchicaya had been hoping for something more reliable. He knew what quantum mechanics was like, but if his own Qusp could pluck certainty from the haze, granting him the ability to make unique decisions, surely Yann could work some similar trick with the vastly more powerful abstract machine behind the border?

Rasmah emerged from her visualization. "I know how that sounds, but it really is the best we can hope for. We"re not arranged in the same way as the far side; we"re stuck in a dynamic-law eigenstate, and that"s always going to make things difficult."

"Yeah." Tchicaya was grateful for anything that took them beyond the current, artificial view of definite laws spread across the border, but it was sobering to realize how much stranger things became as the price of that advance. "I shouldn"t be disappointed, but I keep underplaying the problems in my head: sweeping all the hard parts off to one side, where I don"t have to look at them. If I faced the difficulties squarely, I"d probably just turn around and run."

Rasmah regarded him with a mixture of curiosity and affection. "You really do want to go through the border, don"t you?"

"I think so. What about you?"

"Absolutely. That"s what I came here to do." She hesitated, then added, "For a while, I thought I must have said something too extreme along those lines, and it put you off. But I don"t think that"s it. So what is it about me that you hate so much?"

Tchicaya shook his head vehemently. "Nothing."

"But we got halfway," she said, "and then you changed your mind." This wasn"t a question. Their bodies had ceased the silent exchange of pheromones, and that in itself would have dampened her feelings toward him, but it must have been clear to her that he was the one who"d halted the process.

"You"re very good company," Tchicaya said. "But you remind me too much of someone else, and I don"t feel right about that. I don"t want to confuse you with her; that wouldn"t be fair on either of us." He frowned apologetically. "Am I making any sense?"

Rasmah nodded uncertainly. "The other thing I thought was, maybe you and Yann were still, somehow - "

"No!" Tchicaya was taken aback. "Where did you hear about that?"

She waved a hand dismissively. "Everyone knows."

"Actually, I think Yann might have forgotten."

"But there is no one else, in the present? Just this nameless competitor from the past?"

Not exactly a competitor. And not wholly in the past. But Tchicaya didn"t want to explain any further. "That"s right."

"Okay." Rasmah stood, and Tchicaya rose beside her. In part, he was glad that she"d cleared the air, though at the same time he felt a surge of resentment, now that he"d been forced to put his reasons into words. He and Mariama would never be together. Why was he letting her shape his decisions at all?

"You"ll support Yann with this?" he asked.

Rasmah smiled. "Definitely. This is our best hope, and I"m sure I can sell it to the others. Suitably uglified."

The Blue Room was packed from wall to wall; it hadn"t been so crowded since the Left Hand"s first trial run. The room was near the bottom of its module, and it had already been expanded as far as possible in all horizontal directions; several unobliging neighbors above prevented it from growing upward. As relations had deteriorated, some Yielders and Preservationists had swapped cabins in order to be surrounded by fellow partisans, but the Rindler hadn"t yet reached a state where every module was "owned" by one faction or another.

Yann paced the ceiling, ducking away from the tallest heads and shoulders - making his presence visible, but wisely desisting from trying to claim space that he could not defend with solid elbows. Other acorporeals came and went beside him, and no doubt he was conversing with some who weren"t bothering to display icons. Almost everyone who"d been born acorporeal had now donated their bodies to new arrivals, effectively splitting the Yielders into two distinct communities, more so in some ways than the factions themselves. Tchicaya had mixed feelings about this; their generosity had given many more people a chance to participate in events on the ship, in the only manner that would not have been alien to them. But the acorporeals had been willing to change modes in the first place, so why couldn"t the newcomers make do with software bodies? Maybe he had no right to think that way, having accepted the first such sacrifice himself, but the segregation by birth still depressed him, however well acclimatized to their condition the acorporeals were.

The Left Hand had scribed Yann"s state almost an hour before, and they were still waiting hopefully for an echo. Rasmah had ended up translating Yann"s purely algorithmic account into a kind of sophisticated scattering experiment: they were probing the far side by sending in an elaborately structured pulse that was capable of propagating relatively large distances. At least part of this pulse stood a good chance of bouncing off any structure that lay in its path, and coming back to them bearing an imprint of whatever it encountered.

This made it sound cozily familiar: a cross between radar, particle physics, and tomography. But the "distance" the pulse would travel and the "structures" it might or might not interact with were the raw topological details of an unknown superposition of quantum graphs, not properties of such elaborate near-side constructions as vacuum obeying Euclidean geometry, or the kind of matter that would reflect light or microwaves. Even the pulse itself had no real analogies in the ordinary world: it was not a particle, or a gravitational wave, or any kind of electromagnetic signal. It was a new form of dislocation in the pattern of threads from which all those mundane things were woven.

Rasmah cried out, "We"ve got something!"

People started jostling for a better view of the screen, though the image was being made available directly to everyone in the room. Tchicaya stubbornly stood his ground behind Rasmah for several seconds, then he gave up and let the crowd percolate around him, forcing him back.

He closed his eyes and saw, unobstructed, the first raw image of the returning pulse. It was a speckled, monochrome, pockmarked pattern, like a fuzzy shot of a cratered landscape, taken in such low light levels that you could count the individual photons. As he watched, the speckling of the image shimmered; it reminded Tchicaya of some kind of weird laser effect.

"Interference!" Yann crowed happily from the ceiling. "Wait, wait, let me - " An inset blossomed in the image, a huge, tangled, branching polymer, studded with loops and knots, built from nodes of every valence. Different parts of the pulse would have been modified in different ways by the same topology; Yann had used the interference between these altered components to reconstruct a typical portion of the kind of graph the signal must have passed through.

Rasmah said, "That"s far from an unbiased superposition. It"s not the sum of all random haystacks in there. There"s no vacuum, but there"s still order."

Tchicaya stared at the polymer. From childhood, he"d studied the Sarumpaet patterns, the quantum graphs that could maintain stability under the old rules. And for months, he"d seen the alternatives: all the different possible families of particles, deduced from the physics they"d trapped on the border.

This was like an amalgam that some magpie of a sculptor had created to sum up that experience, combining features from all of them - grabbing fragments of every kind of ordinary, vacuumbased physics and welding them together, without regard to such niceties as having to build a uniform, homogeneous geometry, or having to respect a simple set of rules that stayed constant over time.

Hayashi called out from behind Tchicaya, "Is that fractal? Can you give it a dimension?"

Rasmah invoked some further processing. "No. No dimension, integer or otherwise. The branching"s not at all self-similar; there"s no redundant information."

"Modify the probe pulse and send it again. Here are the details." Branco"s voice rang out from midair, as if he were among the acorporeals; he"d declined to leave his cabin and join the crush. Some Yielders had been reluctant to grant access to the results to anyone who refused to declare their allegiance, but sanity had finally prevailed.

Rasmah said, "Thanks for the suggestion, but it will have to wait." The meeting that had approved Yann"s experiment had set aside a week for the interpretation of the results, before any further action was to be taken.

Branco sighed. "Do it, don"t do it. I couldn"t care less."

Rasmah displayed Branco"s proposal for everyone to see. It was a straightforward alteration to Yann"s original state, accompanied by some calculations suggesting that components would bounce back to them in a staggered sequence that would make changes in the graphs over time easier to deduce. If this worked, it would give them a movie of the far side, in place of a single, still image.

Suljan yelled out, "We should try that, immediately!" Bhandari, in a far corner of the room, disagreed. People started voicing approval and shouting alternative suggestions from all directions. Tchicaya would have covered his ears, but his hands were trapped. This was bedlam, but it was intoxicating. It reminded him of the time he and a group of friends on Peldan had landed a remotecontrolled vehicle on a passing asteroid: everyone wanted to grab the joystick.

Rasmah screamed, "Shut up!"

Something approximating silence descended.

"Read Branco"s proposal," she pleaded. "Think about it. We"ll have a vote in fifteen minutes. And if anyone feels like going out to stretch their legs in the meantime...don"t rush back. You can vote from anywhere."

The noise rose up again, but there was no real note of discord. Rasmah slumped against the control panel.

Yann poked his head down in front of Tchicaya. "You"re all completely mad. Someone"s going to get crushed."

"Some of us have no choice about taking up space."

"There"s plenty of room up here," Yann suggested helpfully.

"Yeah, right, just give me a hand up." The ship could probably have molded a tier of hanging chairs, but the ceiling was so low that this would have meant a constant risk of being kicked in the head.

"Some people are so inflexible. When Cass came to Mimosa, she insisted on a body. We obliged, but we made it small enough to fit."

Tchicaya had never heard this detail before.

"How small?" he asked.

Yann held out his hand, thumb and forefinger a couple of millimeters apart.

"You evil, sadistic bastards."

Tchicaya squeezed his way through the crowd back to the control panel. Rasmah looked frazzled but happy.

"What do you make of this?" he asked, gesturing at the polymer.

"It"s too early for interpretations," she said.

"But it"s structured, isn"t it?" he suggested. "You said as much yourself."

Rasmah had grown more cautions. "It"s not an equal superposition of all the things it could be. It"s not a maximum-entropy quantum blancmange. That still leaves a lot of room for it to be disordered, in lesser ways."

Tchicaya didn"t pursue the point, but the very fact that Yann"s pulse had come back to them bearing information proved that there was some potential for setting up causal processes on the far side. Lawless as it was in the conventional sense, it could still support a kind of machinery. They could try to build more sophisticated exploratory vehicles. Perhaps, eventually, even bodies and Qusps.

More importantly, if they ever succeeded in doing that, the place they"d be entering was looking less and less like a featureless desert. When Tchicaya had arrived on the Rindler, it had still been conceivable that the world behind the border would be nothing but a different form of empty space, with no particular reason to contain even the equivalent of the tiny smudge of matter that enlivened the near side. They"d barely glimpsed the structure of the far side, but his first impression was that the hundred million cubic light-years of vacuum claimed by Mimosa had been rewoven into something orders of magnitude more complex.

"Do you think we should show this to the opposition?" Tchicaya asked. "It might give them pause, if they can finally see that they"re not just dealing with a corrosive void."

Rasmah laughed. "You honestly believe they"d care?"

"Some would. And I don"t see what we have to lose."

"Nor do I, but only because I"m sure they"ll end up with exactly the same details, whether we inform them officially or not."

Tchicaya was startled. "You think someone"s spying for them?"

"Of course."

"What makes you so sure? Do we have spies with them?"

"Not that I know of," Rasmah admitted. "But that"s not a fair comparison. The most relaxed Preservationist is an order of magnitude more security-conscious than our most diligent supporter."

The vote was taken, returning ninety-two percent support for Branco"s suggestion. Rasmah scribed the modified pulse, and they waited again.

Tchicaya sat on the console as people talked around them. "I never really thought we"d get this far," he admitted. "Even once I"d made up my mind to come here, it seemed like a mad, quixotic notion." He described the legend of the falling Sappers.

"I like that story," she said, "but it"s not a good metaphor. Bombs hit the ground, and that"s that. We"re not facing a single, decisive deadline. Thousands of planets have fallen, but there is no moment when everything will be won or lost. So long as the border doesn"t accelerate, we could hang on here for another thousand years, learning whatever we need to learn."

"Unless we lose everything to the Preservationists first."

Rasmah shrugged, as if that went without saying. Tchicaya hadn"t told her about Mariama"s ultimatum; the actual words had been so ambiguous that to most people they"d convey little more than the obvious fact that Planck worms were on the Preservationists' agenda. He hadn"t given up hope of finding a way to freeze the border, but there was no clear path leading toward that outcome; randomly pinning dynamics was never going to do it. They had to look deeper, they had to learn more.

He said, "So you never doubted that this moment would come?"

"Never. Not for a second." She laughed. "You should see your face, Tchicaya. I grew up with the border, remember? My parents used to take me outside at night and show me this tiny little disk of light, where the brightest star in the sky used to be. Sixty years later, it was on top of us. I"d never felt as angry as the day we had to evacuate. Not just because I was losing all the places I"d known on Maeder. I hated running from this thing."

"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."

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."

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?"

"Just thinking about home." Birago nodded vaguely in the direction of the blue shift, but Tchicaya knew which star he meant. It had been chosen by the people on Viro before they were scattered, and Tchicaya had had it pointed out to him by the evacuees he"d encountered on half a dozen worlds. The spore packages had already been launched from Gupta, and the evacuees - who"d spread out to many different intermediate destinations, to avoid overtaxing the hospitality of the locals - would follow within a couple of centuries. "We"re not losing this one," he said. "Not until the sun burns out."

Tchicaya had heard the slogan many times before. Whether it was a matter of being the oldest community of evacuees, or some other factor in the original culture, people from Viro always appeared more focused on their new home than on the loss of the old. Birago himself had no clear memories of Viro - he"d left as an infant, and moved from world to world a dozen times - but if his family had wrapped him in any vision of permanence, any sense of belonging, it was anchored to their future, not their past.

Tchicaya said, "There"s good reason to be hopeful now." That wasn"t giving anything away: the Preservationists would know, at the very least, that his side had had a series of breakthroughs. Their understanding was snowballing; a concrete plan for some form of stable compromise could only be a matter of time now.

Birago laughed. "Hope is for when you have nothing else. When I was a child, no one around me would ever look up at the border and say, It"s too big. We"re too late. It"s unstoppable. We had no plans, we had no remedies; the only strength we had came from refusing to give up. Which was all very laudable...but you can"t go on like that forever. There has to come a time when hope turns into something more tangible."

"Honey or ashes."

"Ah, know-it-all travelers." Birago smiled, but there was an edge to his voice. Picking up a few idiomatic phrases in passing didn"t mean you understood anything.

"We"ll both have certainty soon," Tchicaya insisted. "I can"t believe it will be much longer now."

"We? What counts as certainty for you?"

"Safeguarding the far side."

Birago was amused. "And you think that could ever be part of certainty for us?"

Tchicaya felt a chill of disappointment, but he persisted. "I don"t see why not. Once we understand this thoroughly, we"ll know what is and isn"t safe. No one runs around extinguishing stars out of fear that they might go supernova."

Birago gestured with his right hand, "There are tens of billions of stars to learn from" - then with his left, toward the border - "but there"s only one Mimosa."

"That doesn"t mean it will remain a mystery forever."

"No. But no one"s patience lasts forever. And I know where the benefit of the doubt belongs."

Tchicaya arrived late in the Blue Room, missing the start of Suljan"s experiment. Many more people had chosen to avoid the crush and watch from their cabins, so the place was far less crowded than before, to the point where there was space for furniture.

As Tchicaya joined Rasmah, Yann, and Umrao at a table not far from the console, Rasmah was saying, "I"m not optimistic about seeing anything new, such a short distance in. If the outermost mixture of vendeks is converting our vacuum at the fastest possible rate, there could be light-years of them behind the border."

"Light-years?" Yann regarded her with amusement, as if she"d made some kind of category error: a liter of energy, a kilogram of space. The normal geometrical meaning of a quantum graph was intimately bound up with the presence of particles, and they were yet to unravel any simple notion of distance for the far side.

"You know what I mean," Rasmah retorted. "Ten-to-the-fiftieth nodes' worth."

Umrao said, "The hardest thing for me to wrap my mind around is the complete lack of Lorentz invariance. If you picture the graph"s history as a foam - the edges all extending into surfaces, the nodes all extending into lines - you"d actually see different vendek populations if you re-sliced that foam in a different way."

Tchicaya grimaced. "Doesn"t that imply that there"s a preferred reference frame? Couldn"t you assign yourself an absolute velocity, just by seeing what kind of vendeks you were made from?"

Umrao gestured with his hands in a fashion that Tchicaya"s Mediator translated as negation. "Without any external cues to guide you, you"d always slice your own world foam the same way, and see yourself as being made from the same vendeks. Other people moving past you might see your constituents change, depending on their velocity relative to you, but you"d see them change in the same way. And both of you would be entitled to claim that you were the best judge of your own composition."

Tchicaya pondered this. "So everything ends up on the same footing as rest mass? It"s as if speeding past an electron fast enough could make it look like any other particle at all - but in its own reference frame, it"s still an electron?"

"That"s right."

Suljan shouted triumphantly, "We have an echo!"

Tchicaya turned to face the screen. It showed a simple blip, the plot of a returning pulse. Suljan"s method had coarser resolving power than Yann and Branco"s, but that was what allowed it to penetrate further: his signal wouldn"t reflect back from the middle of a vast sea of vendeks repeating the same population mix, so any return at all meant that it had encountered a larger-scale change.

Hayashi was beside Suljan at the console. "There must be a layer population, like Umrao predicted," she said. "Some ten-to-the-forty nodes from the border."

Rasmah leaned toward Tchicaya and whispered, "A hundred kilometers, in good old reactionary language."

Umrao was pleased. He said, "I wish we could tell exactly what the border mix changed into, though." He looked around the table. "Come on, there"s a challenge for you. Range and resolution. How?"

Rasmah joked, "I"m sure using the Right Hand as well would do wonders."

Tchicaya said, "They"ll be getting echoes, too, right now, won"t they?" The two Hands themselves were about a hundred kilometers apart, so it was plausible that the scatter could reach them.

"Only if they know precisely what to look for." Rasmah raised her hands defensively. "Don"t say it: I"m the one who believes in spies."

A sense of anticlimax had descended on the room; the result was important, but it didn"t compare to their first glimpse of the Planck-scale structure of the far side. That there was macroscopic structure, too, was encouraging, but extracting further detail would be difficult. A hundred kilometers of solid rock would be no barrier to investigation, but a shift of vendeks was not like a change from crust to mantle, refracting and scattering seismic waves in a simple, predictable fashion. It was more like the boundary between two distinct ecosystems, and the fact that remnants of their expedition had straggled back intact after crossing a wide savanna didn"t mean the adjoining jungle would be so easily probed.

Suljan said, "I think it"s moving." Successive pulses were coming back with slightly different delays. The reflective layer was more or less keeping pace with the expanding border, but the signal showed it drifting back and forth. "Vibrating, maybe?"

Rasmah replied, "It"s probably something changing in the border region, messing with the propagation speed." That explanation made more sense to Tchicaya; the signal was crossing a vast tract with potentially variable conditions, so it was more economical to attribute any delay to the vendeks it encountered along the way.

Suljan gave her a withering look. "More expert commentary from the peanut gallery. The returns are too clean, and too sharp; that much variation in propagation speed would broaden them detectably."

"Hmm." Rasmah didn"t argue, but her eyes glazed over; she was checking something. When she emerged, she said, "Okay, you"re right. And the changes are too fast and too regular; the source of the variation would have to be fairly localized, so it must be the reflector, not the medium."

Tchicaya turned to Umrao. "Any ideas?"

"I didn"t see anything like this in the simulations," he said. "But then, I just remixed the vendeks from the border region. This layer might hold completely different ones."

The vibrations stopped.

Yann stared at the plot on the screen. "Just like that? No decay curve?"

The vibrations resumed.

Tchicaya looked around the room. Several people had left; apparently, the ringing of the far side"s equivalent of a planetary ionosphere was of no interest to them. Anything that influenced signal propagation was of crucial importance, though, and if this layer could move, it might even break up and reveal something deeper.

The vibrations halted again, only to restart a few seconds later. "One hundred and thirty-one oscillations," Yann noted.

Rasmah said, "What"s that going to tell us?"

Yann tapped his fingers against the table, one hand in time with the returning pulses, the other beating out the rhythm of the reflecting layer itself. Tchicaya resisted an urge to tell his Mediator to stop rendering Yann"s icon; the constant drumming was annoying, but he"d never edited anyone from his sensory map before, and he wasn"t about to start.

"One hundred and thirty-seven," Yann announced.

Tchicaya said, "You think there"s some longer-period cyclic process, modulating the faster one?"

Yann smiled enigmatically. "I have no idea."

Suddently, Rasmah groaned. "I know what you"re thinking!"

"What?" Tchicaya turned to her, but she wasn"t giving anything away.

She said, "I"ll bet you anything that you"re wrong."

Yann shook his head firmly. "I never gamble."

"Coward."

"We have no mutually beneficial assets."

"Only because you threw yours away," she retorted.

Umrao said, "I"m completely lost. What are you people talking about?"

"One hundred and thirty-seven," Yann counted. "One hundred and thirty-eight. One hundred and thirty-nine."

He fell silent. The vibrations had stopped.

Tchicaya said, "The slower cycle is varying, a little. Maybe lengthening. What does that tell us?"

Rasmah had turned pale. At the console, Suljan, who"d been paying no attention to the conversation at their table, suddenly leaned into a huddle with Hayashi. Tchicaya couldn"t hear what they were whispering about, but then Suljan let out a long, loud string of obscenities. He turned to face them, looking shocked but jubilant.

"You know what we"ve got here?" he asked.

Umrao smiled. "I just worked it out. But we shouldn"t jump to conclusions."

Tchicaya pleaded, "What conclusions?"

"Three consecutive primes," Suljan explained.

The vibrations had resumed, and Yann was calmly tapping them out again. Tchicaya calculated the next number in the sequence, and thought about trying to quantify the odds of the first three occurring by chance, but it would be simpler just to wait for the pattern to be broken or confirmed.

"One hundred and forty-seven. One hundred and forty-eight. One hundred and forty-nine."

On cue, the vibrations halted.

Yann said, "I wouldn"t rule out nonsentient processes. We don"t know enough about the kinds of order that can arise in this system."

Umrao agreed. "There"s no reason evolution couldn"t have stumbled on something useful about primes in the far-side environment. For all we know, this could be nothing more than an exotic equivalent of cicada calls."

"We can"t rule out anything," Suljan conceded. "But that has to cut both both ways. It has to include the possibility that someone is trying to get our attention."

"It looks as if the Colosseum is about to welcome us in," Rasmah said. "You first."

"I don"t think so." Tchicaya held up his hand; it was shaking. They"d spent almost two hours sitting in the corridor outside the impromptu amphitheater where the Preservationists were meeting, and now the blank, soundproof wall in front of them was beginning to form a door.

"Turn down your adrenaline," she advised him.

"I don"t want to do that," he said. "This is the right way to be. The right way to feel."

Rasmah snorted. "I"ve heard of traditional, but that"s ridiculous."

Tchicaya bit back an irritated reply. If he was going to harness his body"s natural agitation, he could still keep his behavior civilized. "I don"t want to be calm," he said. "This is too important."

"So I get to be the rational one, and you get to be impassioned?" Rasmah smiled. "I suppose that"s as good a strategy as any."

It had taken Tchicaya six days of arguing to push a motion through the Yielders' convoluted decision-making process, authorizing disclosure of the recent discoveries to the opposition, and he had hoped that it would be enough. The Preservationists would repeat the experiments, see the same results, reach the same conclusions. He"d set the chain of events in motion, and it would have an unstoppable life of its own.

Then the Preservationists had announced that two Yielders would be permitted to address them before they made their decision on a moratorium, and he"d found himself volunteering. Having worked so hard to create a situation where they were apprised of the facts and prepared to listen, it would have been hypocritical to back out and leave this last stage to someone else.

The door opened, and Tarek emerged, looking worse than Tchicaya felt. Whatever the body did in times of stress could be ameliorated at will, but Tarek had the eyes of someone whose conscience was robbing him of more than sleep.

"We"re ready for you," he said. "Who"s first?"

Rasmah said, "Tchicaya hasn"t smeared himself in goat fat yet, so it"ll have to be me."

Tchicaya followed her in, then hung back as she approached the podium. He looked up at the tiers of seats that almost filled the module; he could see stars through the transparent wall behind the top row. There were people here that he knew well, but there were hundreds of complete strangers, too; the ranks of the Preservationists had been swelled by new arrivals.

The audience was completely silent. There was an expression of stony resentment on some faces, an unambiguously hostile gaze, but most people just looked tired and frayed, as if the thing they hated most was not the presence of Yielders bearing unpalatable revelations, but the sheer burden of having to make an invidious choice. Tchicaya could relate to that; part of him longed for nothing more than a turn of events that would render all further effort irrelevant, one way or another, so he could curl up and sleep for a week.

Rasmah began. "You"ve seen the results of our recent experiments, and I"m going to assume that you"ve replicated them successfully. Perhaps someone will correct me if that"s wrong, and the raw data is in dispute."

She paused. Sophus called out, "That"s not in dispute." Tchicaya felt a small weight lifting; if there"d been a technical hitch, or some elaborate bluff in which the Preservationists claimed that they"d seen nothing, the whole discussion would have bogged down in recriminations immediately.

Rasmah said, "Good. You"ve also seen Umrao"s simulations, and I hope you"ve performed some of your own. We could sit here for a week debating whether or not the structures we"ve called vendeks deserve to be described as living creatures, but it"s plain that a community of them - or a mixture, if you prefer a more neutral term - forms a completely different backdrop than the vacuum we"re familiar with, or anything else most of us imagined we"d find behind the border when we made our way here.

"We"ve all pinned states with exotic dynamic laws to the border. We"ve seen tens of thousands of samples from the whole vast catalog of vacuum-based physics. But the far side"s natural state, the closest it can come to emptiness and homogeneity, has access to all of those possibilities at once.

"I came here expecting to see physics written in a different alphabet, obeying a different grammar, but conforming to the same kind of simple rules as our own. It was Sophus who first realized how myopic that expectation was. Our vacuum isn"t just devoid of matter; our universe isn"t simply sparse, in a material sense. What lies behind the border is neither physics in a different language, nor an amorphous, random Babel of every possibility jumbled together. It"s a synthesis: a world painted in hues so rich that everything we"ve previously imagined as a possible universe begins to seem like a canvas filled from edge to edge with a single primary color.

"We"ve seen hints, now, that there might be organisms far more sophisticated than the vendeks, just behind the border. There"s probably nothing I can say that will influence your interpretation of the evidence. I"m not certain what it means, myself. It could be anything: sentient creatures longing for contact; a mating song between animals; an inanimate system constrained by far-side physics to lie in a state more ordered than our instincts deem likely. I don"t know the answer, nor do any of you.

"Maybe there is no far-side life worth speaking of. Maybe there are just different pools of vendeks, all the way down. We can"t tell yet. But imagine for a moment that the signal we"re seeing comes from a creature even as complex as an insect. If life of that sophistication can arise in just six hundred years, then the far side must be so amenable to structure, and order, and complexity that it"s almost inconceivable that we"d be unable either to adapt to it, or to render parts of it hospitable.

"Suppose we were handed a galaxy"s worth of planets, all so near to Earthlike that we could either terraform them easily, or tweak a few genes of our own in order to flourish on them. What"s more, suppose they came clustered together, so close that the time it took to travel between them was negligible: days or weeks, instead of decades or centuries. If we migrated to these worlds, it would mean an end to our fragmentation, an end to the rule that says: yes, you can see how other cultures live, but the price you pay will be alienation from your own.

"On top of this, imagine that interspersed among these Earthlike worlds was another galaxy"s worth of planets, all dense with a riotous variety of alien life. On top of that, imagine that these worlds were immersed in a new kind of physics, so rich and strange that it would trigger a renaissance in science that would last ten thousand years, transform technology, reinvigorate art.

"Is that what the far side really is offering us? I don"t know, and neither do you. Maybe there are some of you for whom it makes no difference: whatever lies behind the border, it can"t be worth the price of even one more planet lost, one more people scattered. But I hope that many of you are willing to pause and say: Mimosa has brought tragedy and turmoil, and that has to be stopped, but not at any cost. If there is a world behind the border that could bring new mysteries, new knowledge, and ultimately a new sense of belonging to billions of people - a place that could mean as much to our descendants as our home worlds mean to us - then it can"t be unimaginable that the balance could ever tip in its favor.

"People left families and nations behind them on Earth. They"d swum in rivers and walked on mountains that they would never see again. Were they all traitors, and fools? They didn"t destroy the Earth in their wake, they didn"t force the same sacrifice on anyone else, but they did put an end to the world as it had been, when humanity had been connected - when the speed of light was a phrase that meant instant contact, instant collisions of cultures and values, not a measure of your loss if you tried to achieve those things.

"I don"t know what lies behind the border, but possibilities that seemed like castles in the air a year ago are now a thousand times less fanciful. Everything I"ve talked about might yet turn out to be a mirage, but if so, it"s a mirage that we"ve all seen with our own two eyes now, hovering uncertainly in the heat haze. A few more steps toward it will tell us, once and for all, whether or not it"s real.

"That"s why I"m asking for this moratorium. Whether you recoil from the vision I"ve painted, or merely doubt its solidity, don"t make a decision in ignorance. Give us one more year, work beside us, help us find the answers - and then make your choice. Thank you."

Rasmah took half a step back from the podium. Someone in the audience coughed. There was no polite applause, but no jeering either. Tchicaya didn"t know how to read the indifferent silence, but Rasmah had been fishing for converts rather than searching for a compromise, and if anyone had been swayed by her message that would probably not be a response they"d wish to broadcast.

Tarek said, "We"ll take questions when Tchicaya has spoken."

Rasmah nodded and walked away from the podium. As she passed Tchicaya, she smiled encouragingly and touched his arm. He was beginning to wish he"d gone first, and not just because she was a hard act to follow. Before a gathering of Yielders, a speech like the one she"d just delivered would have fired him up, filling him with confidence. Watching it received with no visible effect by the people who counted was a sobering experience.

Tchicaya reached the podium and looked up at the crowd, without fixing his eyes on any one face. Mariama would be here, somewhere, but he counted himself lucky that he hadn"t spotted her, that her certain presence remained an abstraction.

"There is a chance," he said, "that there is sentient life behind the border. We have no proof of this. We lack the depth of understanding we"d need even to begin to quantify the odds. But we do know that complex processes that would have been inconceivable in a vacuum - or in the kind of hot plasma present in our own universe, six hundred years after its birth - are taking place right now on the far side. Whether or not you count the vendeks as living creatures, they reveal that the basic structure of this region is nothing at all like empty space.

"None of us arrived here armed with that knowledge. For centuries, we"d all pictured the novo-vacuum as the fireball from some terrible explosion. I came here myself in the hope that we might gain something from the challenge of learning to survive inside that fireball, but I never dreamed that the far side could harbor life of its own.

"Life does not arise easily in a universe of vacuum. Apart from the Earth, there are just four quarantined planets strewn with single-celled organisms, out of almost a million that have been explored. For twenty thousand years, we"ve clung to a faint hope that the Earth would not be unique as the cradle of sentience, and I don"t believe that we should abandon that hope. But we"re now standing at the border, not between a desert with rare oases on one side, and a lake of molten lava on the other, but between that familiar desert and a very strange ocean.

"This ocean might be a desert, itself. It might be turbulent, it might be poisonous. All we know for certain is that it"s not like the universe we know. But now we"ve seen something fluttering beneath the surface. To me, it looks like a beacon, a declaration of intelligence. I concede that this interpretation might be completely wrong. But if we"d ever spotted something a tenth as promising on a planet, wouldn"t we be shouting with joy, and rushing to investigate?

"The homes and communities of billions of people are at stake here. One full year"s delay would mean the certain loss of one more world." Tchicaya had agonized over the best way to phrase this; apart from starkly requesting an entire planet as a sacrifice, he had to tiptoe around the issue of exactly how close the Preservationists were to producing Planck worms. "But whole worlds have been evacuated before, to leave the rare life we"ve found with a chance to develop undisturbed. We can create far more sophisticated organisms in vitro, but we"ve still recognized in the simplest alien microbes both a chance to understand better the science of our origins, and a distant kinship with whatever these creatures might become. I"m willing to write off the vendeks as little more than Planck-scale chemistry, but even a slim possibility of sentient life on the far side, just beyond our grasp, has to count for at least as much as the possibility that the microbes we"ve left to their own devices will flourish into anything as rich as life on Earth.

"I"m not asking anyone in this room to abandon the values that brought them here. But no one came here with the goal, or even the thought, of wiping out another civilization. If you believe there can be no sentient life on the far side, take the opportunity to prove yourself right. If you harbor even the slightest doubt, take the opportunity to gather more information.

"We"re not asking you to wait for certainty. The far side is too large; however advanced our techniques became, there"d always be a chance that a part of it remained hidden. But after six centuries in which the border has been completely opaque, and a few weeks in which we"ve managed to see through it a very short distance, we"re asking for one more year of exploration. We might never find out what"s at stake here, but now that we have our first real chance to do more than guess, I don"t believe we have the right to shut our eyes and refuse to look any closer.

"Thank you."

Tchicaya backed away from the podium. He hadn"t felt too bad while he was speaking, but the discouraging silence that followed turned his stomach to water. Maybe the Yielders had merely decided to present the enemy with their best poker face, but the effect was still one of indifference verging on hostility. He instructed his Exoself to calm his body; whatever sense of urgency he"d managed to convey by allowing his stress hormones free reign, the effect had either succeeded or failed by now.

Tarek said, "Questions and comments."

Birago rose to his feet and addressed his former colleague. "The vendeks appear genuine to me, and I doubt that you could have engineered them into existence without us noticing. I"m much less confident about this so-called signaling layer. How do we know you didn"t create it?"

Rasmah replied, "I"m not sure what you expect me to say. I suppose you could move the Right Hand away across the border and look for an edge to the layer, then see if the whole thing lies centered around the Left Hand. But if you seriously believe that we were skilled enough to create the layer at all, maybe you believe we could have disguised its point of origin." She spread her arms. "Look more closely, gather more evidence. That"s exactly what we"re asking for, and if you have doubts, that"s the only cure for them."

Birago laughed curtly, unimpressed, but he resumed his seat.

Tchicaya had come prepared for accusations of fake data, but the idea that anything indisputably present behind the border could be taken as counterfeit had never crossed his mind. If the Preservationists did have spies, surely they"d know how ludicrous this was? But then, spies would probably only share that knowledge with people who would not be swayed by it.

Sophus stood. "I"ve studied this question, and I don"t believe the layer could have been built from the Left Hand without us noticing, any more than the vendeks could. This thing is genuine, and it needs to be investigated. I came here to preserve civilizations, not to destroy them. The chance that we"re seeing intelligence here is extremely slim, but this is a matter of the utmost seriousness.