Incandescence

by Greg Egan

  When he found what he'd been looking for, it was like an elephant stepping out of the wallpaper. There was a vast network of linked genes and proteins that could influence neural structures both in the embryo and in adulthood, and it bore the clear fingerprints of an engineered design. The Arkmakers had had their hands all over this part of their children's genome.

  If there was a vital spark missing from the generic Arkdweller, these genes were designed to light the fire. Without imaging Zey's brain, Rakesh couldn't say just how far from the average the random biochemical detour she'd experienced in the egg had taken her, but a one-in-ten-thousand surge would have triggered a cascade of events that guaranteed a thirst for knowledge comparable to all of her other basic drives. The frequency of such individuals in the population would obviously be low, but Rakesh did not believe for a moment that Zey was an accident. The Arkmakers had wanted people like her, but not too many.

  He was sure she had been born, or hatched, this way, because if the other trigger he'd found had been the cause then there was no explaining her team-mates' apathy. Extreme stress could bring on the development of the same neural structures in an adult's brain. Mild hardship wouldn't start the cascade, though; it would require a sustained, dramatic change in the environment. Depending on the circumstances, and the exact range of individual susceptibilities, it looked as if anything from thirty to sixty per cent of the population could be transformed by that route, but only if the Ark itself was subjected to a massive upheaval.

  From there, the process would snowball, with an ever greater proportion of each subsequent generation driven by an urge to understand the crisis they were facing. If the threat subsided then the status quo would eventually return; the simulations suggested that a few dozen generations of tranquility would be enough to put out the fire. Then, as before, only a handful of individuals would exhibit the trait, until the next emergency.

  Rakesh had performed the whole analysis in a couple of Zey's heartbeats, but she already had an air of impatience.

  "What's your answer?" she said. "What's the nature of my sickness?"

  Rakesh explained everything he'd found, as clearly as he could. He'd already told her all he knew about the Arkmakers, so the idea that her distant ancestors had shaped her people's nature did not come as a shock in itself.

  "Why am I here now, though?" she said. "If the world was falling apart, of course it would be good to have people who tried to repair it, instead of just tending their herds and waiting to die. But why did they arrange for people like me to be hatched when there is no need for us?"

  "I don't know," Rakesh confessed. "I can't read their minds, I can't know what they were thinking. Perhaps they wanted a kind of sentinel, a small group who would be vigilant enough to notice the first signs of danger and prepare the way, while the evidence was still below the threshold for the rest of the population. Or perhaps they wanted a route for the cultural transmission of some crucial ideas that everyone else would consider too impractical to retain."

  "As long as the world is safe, though," Zey replied despairingly, "I'm useless, aren't I?"

  Rakesh said, "Knowledge is good in itself. Understanding is good in itself."

  Zey chirped amusement. "I can't argue with that sentiment, can I? I've been built to think like you. But you come from a world where the ones who disagree with you are the sad, strange few. You haven't spent a lifetime as the only one with that point of view."

  Rakesh didn't know how to reply to her. The chasm between her and the other Arkdwellers was not something that any of them were capable of bridging. She could never be his ambassador, and he couldn't hope to enter into any kind of dialogue with them himself, slowly coaxing them out of their shells, opening them up to new possibilities, turning their faces to the stars. Without a calamity to throw the switch, they were physically incapable of caring about such things.

  Zey's mind was working faster than his now. She said, "I would never ask you to bring trouble to my brothers and sisters, to damage the world, to sow fear and death. But is that the only way to bring change?"

  Rakesh asked nervously, "What do you mean?"

  "These genes, these molecules, these signals in our bodies. my ancestors built them to work one way, but I believe you are more powerful than my ancestors. These are all just made from atoms, aren't they? Your little machines can move them around the way I move cargo from one side of the depot to another. If you wanted to, you could ask them to make these signals appear in all of our bodies, without any reason, without any danger.

  "If you wanted to, you could wake us from our sleep."

  24

  "Any progress?" Haf asked, as he wound the light machine.

  Roi looked up from her template frame. "Not really," she admitted. "Be patient, though. We haven't followed this to the end yet."

  She had come to the sardside for the opening of the third tunnel, and to confer with Neth and Bard. Haf had tagged along as her helper, gathering food, providing light, and checking her interminable calculations. Even as they waited in this small chamber for their hosts to call them to the big event, Roi could not put her frames aside.

  Since Cho and Nis had measured the Wanderer's curvature from the tiny angle by which it bent the incoming light, she had been spending most of her time trying to discover a template for a geometry that could encompass both the Wanderer and the Hub. Without any of the old symmetries to rely on, though, the templates became vastly more complicated.

  The curvature that wrapped the Wanderer was about six to the eighth times weaker than that around the Hub, so it might have been simpler to take the idealized geometry of the Hub alone as a guide to their calculations, and then rely on the observations of the void-watchers to tell them when their true position was deviating from their predictions. Like someone sliding down a steep tunnel that had been crudely mapped but never actually traversed, they could try to avoid the smaller hazards by sight, rather than aspiring to a mathematically perfect foreknowledge of every bump that lay ahead. The only problem with that eminently practical approach was that the dark phases were shrinking, so the observations of the void-watchers were already being curtailed. If it ever came to the point where the dark phases vanished, they would be skidding down the tunnel blind, entirely at the mercy of their calculations.

  As the natural light dimmed, Roi handed Haf her last frame and started on a fresh one.

  "Your templates are like weeds," Haf remarked helpfully. "No shape at all, they just grow where they like."

  "Thanks for the encouragement. How about checking whether they're true or not, and then you can weed out all the false ones to your heart's content."

  As Haf set to work, Roi stared pensively at the stones of the blank frame. Sometimes the problem really did appear to be impossible to solve, but the geometry that twisted around the Hub had once seemed almost as intractable, and now the Splinter was spiraling out along a path that was confirming that solution, shift after shift. The weights, the cycles, the view of the void, all fitted together exactly as the templates decreed. Ruz had been up to the surface a few times, and he'd told her that the strange quarter-circle was expanding: the angle of the arc, its radius and its thickness had all grown visibly larger. Part of this change was due to the Splinter traveling more slowly around its larger orbit, and part to the gentler space-time curvature as they moved away from the Hub bending the incoming light less severely.

  "I have a friend called Tio," Haf said, without looking up from his frame. "He told me that the best way to think about curved geometry is to imagine it as lots of little flat pieces stuck together. I mean, a cube is just six flat pieces, but it's not that far from the shape of a sphere. And if you use more pieces, you can get closer."

  "That's true," Roi said. "You can shift all the curvature into the corners between the pieces. But I'm not sure where that gets you. Who did Tio study with? Kem? Nis?"

  "I don't think it was either of them. He spoke to a lot of different people. Picked things u
p here and there."

  Roi kept staring at the frame, but her mind was blank. Having exhausted all the elegant tricks she knew, she had finally attacked the problem directly, with no subtlety but all the diligence she could muster, hoping that somewhere along the way an opportunity to simplify the mess would appear before her eyes. It hadn't happened yet. There must be something simple, Zak had declared. But he'd found that once already, in the principle of the weights. In a void full of Jolts and Wanderers, and countless distant lights that for all Roi knew could be wrapped in curvature of their own, how much more simplicity could they expect?

  Sen, one of Neth's students, appeared at the entrance to the chamber. "We're opening the tunnel now," she said.

  Roi put down her frame. Haf made ready to heft the light machine on to his back, but Roi said, "I don't think we'll need that." The dark phase was almost over, and Sen knew the area so well that she'd come to them without any light of her own. Roi was getting better at following people by the sound of their footsteps, even when she was in an unfamiliar place, a skill that seemed to come naturally to Haf and the others hatched since the Jolt.

  They followed Sen down a narrow, sloping tunnel toward the rarb-sard edge.

  By the time they reached their destination, there was enough light to see Neth, Bard, and a few dozen others gathered in the plug chamber adjoining the new tunnel. The outer wall where the tunnel approached the surface had been thinned and weakened to the point where it had almost certainly broken apart during the last light phase. From this chamber, the first of the sets of stone plugs that were keeping the tunnel sealed would be pulled aside, at the same time as eleven others further downwind were withdrawn. If everything went as planned, the wind would flow freely across the width of the Splinter and strike the sharq end of the tunnel with enough force to break through the thin crust that had been left by the workers there, opening up a third unimpeded channel from Incandescence to Incandescence.

  Roi approached Neth. "Surely your work's done here now," she joked. "We'll be waiting for you to join us at the Null Chamber." In fact the Null Chamber was empty of theorists and Roi had no reason to visit it any more, but no other place had the same ring to its name.

  "When the tunnels have steered us past the Wanderer, I might take you up on that," Neth replied, in all seriousness. "I want to work with someone who's interested in a deep understanding of the changes we've seen in the density of the Incandescence as we've moved away from the Hub. There are many mysteries there. We understand weight and motion pretty well for rocks like the Splinter, I think, but when it comes to anything else we're still just gathering data, and guessing."

  Bard consulted a clock, and called out to the plug operators. There was no need to send a light-message to the operators in the other chambers; they'd be following prearranged instructions and clocks of their own.

  The plug operators, lined up in rows, began hauling on their ropes, which ran through a system of pulleys to the huge stone sitting at the far end of the chamber. Although this single stone was probably close to the limit of what could be moved with a wheeled cart and metal tracks, it was only about a sixth of the size of the tunnel's aperture; six separate plugs inserted from their own separate chambers came together to block the tunnel at this point alone.

  As the stone moved Roi could see a halo of light shimmering around it; though she wasn't gazing directly into the Incandescence through the small gap between the stone and the chamber's walls, even the reflection from the tunnel wall was dazzling. There was scarcely any wind leaking out through the gap, though; the path straight ahead through the great tunnel was so much easier for it to take.

  The halo shrank and dimmed as the plug came closer, though the light remained visibly brighter than that flowing through the stone itself. It occurred to Roi that they could have put void-watchers here after all, in spite of the inconvenient direction of the weight; with one of Cho's contraptions poking out into the void, the observer would not have needed to cling to the surface. It was only the historical accident of the order in which various things had been invented that had kept the void-watchers at the junub edge. With the present system working smoothly, though, and all the teams accustomed to it, she couldn't bring herself to suggest rearranging everything for the sake of efficiency. Light-messages reached their destinations quickly enough.

  It would be a few shifts yet before the void-watchers could tell them precisely what the new tunnel had achieved. The further they moved from the Hub, the less powerful the wind became, but they were also ascending a gentler slope as they struggled toward the fateful distance of the Wanderer's orbit.

  As they headed toward the exit together, Haf said, "We should find a way to capture the wind and then push it out ourselves, with a strength that suits us. Why should we be hostage to the speed it travels naturally?"

  Neth assumed a posture containing a mixture of respect and amusement. "That's a nice idea, but where does the 'strength that suits us' come from?"

  "Give me time," Haf replied. "There must be a way."

  Roi heard a deep groaning sound coming through the rock. She had no idea what its cause was, but she had never heard anything like it when she had visited the other tunnels. Perhaps they were experimenting with a new configuration of flow-control baffles, but if that was the case then this ominous noise suggested that the wind was making short work of them. She looked to Neth for an explanation, but it was Bard who shouted for all of them to run.

  The noise grew louder as they reached the exit tunnel, and as they clambered up the slope an intense light rose up behind them. It could not be the baffles; Roi hoped it might just be a single plug coming loose, but she didn't waste time looking back and trying to weigh up various scenarios. She saw that Haf was far ahead of her, his youthful vigor carrying him to the front of the pack. Amid the chaos and fear, and her own determination to outrace the danger if she possibly could, a small part of her relaxed, resigned to anything so long as he survived.

  As they passed the chamber where she'd waited with Haf, the ground rasped and screamed like a susk in agony. The tunnel flattened, making progress easier, and the light from behind dimmed even as the sound became unbearable. Roi finally paused to look back and saw a fissure opening in the rock behind her, separating the tunnel they'd ascended a few heartbeats ago from the one they were now following. It was the kind of terrible spectacle that she had once imagined a division of the Splinter might bring, but the weights had done nothing but ease as they'd moved away from the Hub. If rock was parting from rock, the curvature of space-time was not to blame. As she bolted on down the tunnel, she understood that the most likely cause was not a fresh Jolt from the Wanderer, either; the timing would have been too much of a coincidence. This was a disaster they had brought upon themselves.

  They ran until the rock fell silent and the glare of the Incandescence was left behind. When they finally paused to take stock of the situation, Neth was nowhere to be found. Roi couldn't remember seeing her at all during their panicked flight, but it was possible that she'd split up from them at some point, taking a different turn once they'd had a choice. More than a dozen other people from the chamber were missing.

  Bard led them to a point where a terrified light-messenger was still standing at her post, though the next station to her rarb was now deserted. It was still possible to send queries skirting around the tunnel in the other direction, and Bard was slowly able to build up a picture of what had been lost and what remained.

  It seemed that a large piece of rock had sheared off the side of the Splinter. What was gone included the original mouth of the new tunnel, and all six of the first set of plug chambers. The next set, downwind from that, remained intact. Many dozens of people had certainly been killed, some of them carried off into the Incandescence inside the fragment that had broken away, others seared by exposure. The ordinary system of tunnels was now open to the Incandescence, but that in itself wouldn't cause any more harm if people kept away from the damaged reg
ion.

  Roi had sent Haf to search for Neth, but he returned with no news of her. She tried to set aside her fears for her friend, and think through the other ramifications of the disaster. The tunnel was still open, and could still be controlled by the remaining plugs and baffles. If the cracks caused by the construction ran deeper, if more of the Splinter's rock was threatened, it was hard to imagine any easy solution to that now. Leaving this tunnel open, and closing down the other two instead if they needed to adjust the balance of forces, was about the only strategy Roi could think of to minimize the risk; shutting off the flow was just as likely to trigger another failure in the rock.

  Haf said, "Why is the wind blowing from rarb-junub?"

  "What?" Roi had become disoriented. She looked to the nearest wall sign; Haf was right. She found Neth's student, Sen, huddled against the rock and asked her if she could explain the anomaly in terms of the damage, the local density of the rock, the possibility of a redirection of the flow.

  Sen had trouble concentrating; she was still in shock from their brush with death, and Neth's disappearance. She did her best to analyze the problem, but she couldn't rule anything in or out.

  Roi asked Bard to send a message to the void-watchers, asking them if they'd noticed any changes in their latest observations. When the reply came back from Ruz, it was exactly as she'd feared:

  "The Splinter has gained a spin around the garm-sard axis. Direction is junub to rarb. Period about seventeen times shomal-junub cycle."

  The slow spin would be rotating the tunnels in and out of alignment with the wind, slashing their effect to a fraction of what it had been. If it could not be corrected, they would be left with far less speed and manoeuvrability than when the first tunnel had been opened.