Incandescence

18

“Seventy-two more shifts and we’ll be done!” Bard said proudly.

Roi stared down the length of the giant tunnel. It vanished into the distance, the far end lost in the glow from the walls. She could hear the din of workers chipping away at the rock face, but she couldn’t see them, and it probably would have taken her half a shift to reach them. There might have been other tunnels in the Splinter as long as this, but there were none as wide, or as straight. In a way, she found the sight of it stranger than anything she’d seen in the void; you expected to be shocked when you climbed outside the world, but in this ordinary place the simple rearrangement of rock and empty space had created something unprecedented: a structure with the power to move the Splinter itself.

“Just seventy-two? Are you sure?” They were standing in the middle of the tunnel’s longest segment, but there were a dozen others still growing out from their starting points, reaching toward each other but yet to join up.

Bard retreated slightly. “Something close to that. I can’t say exactly. The team’s been growing steadily ever since the Jolt, but if the numbers level off we might take longer to complete it. We have as many workers as we can fit at the rock face, but we can always do with more shifting rubble.”

Word of Bard’s project had spread throughout the Splinter. In ordinary times that would have counted for nothing, but it seemed that everyone who had been shaken free of their loyalties had come to take a look at the tunnel, and to hear the arguments its builders had to offer. Roi had encountered more than a dozen such travelers on her journey into the sardside, and they had all been willing to listen carefully to the case she’d made on Bard’s behalf. People who, she was sure, would once have turned away in boredom and incomprehension at such useless metaphysical talk had striven patiently to come to terms with the subtleties of weight and motion, the nature of the Jolt, and the way the wind’s free passage through this sardside tunnel might unbalance the Splinter and allow the garmside wind to carry them to safety.

Bard wasn’t even sure of the number of workers he had at any moment; he’d appointed supervisors to take charge of the various stretches of the tunnel, all the way from the rarb edge to the sharq, and they recruited new arrivals for themselves. When a segment was completed earlier than expected, as sometimes happened because the rock turned out to be softer than usual, the workers moved along until they found another place where they were needed.

Roi had come to break the news to Bard that the tunnel was going to require some modifications. With the Wanderer orbiting further out from the Hub, they couldn’t simply open the tunnel to the wind and then trust in their luck to carry the Splinter to safety. They would need to be able to block and reopen the tunnel at will, providing some control over the Splinter’s outward spiral.

Bard listened carefully as Roi explained what she and Ruz had observed. She knew he had lost interest in the fine points of space-time geometry, and he had nothing to say about the strange appearance of the void, but the prospect of a more complex role for his cherished creation seemed to delight him.

“We can build cross-tunnels with plugs we can roll across into the main shaft,” he suggested. “There are plenty of lodes of dense rock that we had to move whole, because they were too hard to break. In fact, if we build a whole system of movable plugs with different kinds of rock, we ought to be able to set the flow to any level you like.”

“That’s a good start,” Roi said. “I was wondering, though, what would happen if we needed to block or unblock the tunnel while we were in the Incandescence?”

Bard was startled. “You think we might need such fine control that we can’t wait for the next dark phase? Isn’t it going to take a shift or two just to get word here that the tunnel should be blocked?”

“I don’t know what we’re going to need,” Roi admitted. “We still don’t know how we’re going to do this: what path we’ll require the Splinter to take, and how we can ensure that we follow it precisely. But even if we don’t need to alter the tunnel at short notice, there’s a chance that as we move out from the Hub we might lose the oscillation the Jolt gave us; we might sink back into the Incandescence permanently. So we need to be able to open and close the tunnel, whether we’re in the Incandescence or the void.”

Bard pondered this new challenge. “We could build some kind of system of ropes. Mount the plugs on wheeled carts, and have people in the side-tunnels—sheltered behind fixed, dense lodes themselves—who can operate the ropes and slide the plugs into place.”

“That sounds perfect.”

Bard pressed himself against the rock, a posture jokingly suggesting that she was putting him under stress. “I hope you theorists know what you’re doing.”

“I can assure you that we don’t. The geometry is still beyond us. All I learned in the void was that our best guess so far is certainly wrong.”

“That’s comforting.” Bard looked down the tunnel and rasped frustration. “So when this magnificent work is finished, you’ll want us to keep it plugged up for another thirty-six shifts while you do your calculations?”

“At least,” Roi agreed. “Maybe longer.”

“So what are we honest workers supposed to do while we’re waiting for you to judge the shape of space-time?”

Roi said, “You had plans for a second tunnel, didn’t you?”

Bard replied wryly, “On skin, a second tunnel costs nothing. It was on the drawing I made, when I first had the idea. But I spent so long failing to get the first one started that I gave up thinking about anything so ambitious.”

“You should build the second one if you can,” Roi said. “Then a third, then a fourth. There’s every chance we’re going to need them. When we go ducking and weaving around the Wanderer, the faster we can move, the better.”

Roi’s second task on the sardside was to visit Neth, and see if she could persuade her to return to the Null Chamber. The theorists would need all the help they could get, and the battle Neth had come here to fight, to win people over to the cause of the tunnel, had been resoundingly won.

Bard had given her directions to the place where she could find Neth, but nobody could keep track of all the obstructions and detours surrounding the Great Project. The signage teams had probably all gone mad, or disbanded. As Roi passed among a group of workers shifting rubble from the tunnel’s construction, she recognized one of them as Jos, the light-maker she’d met when she was traveling with Ruz and Zak.

Jos was happy to see her, but didn’t want to stop working, so Roi walked beside her, helping her to carry a heavy piece of stone. Ideally, everyone doing this job would have had wheeled carts for their loads, but there probably weren’t that many carts in the whole of the Splinter.

“This must be hard work,” Roi said. “Shift after shift.” She was struggling beneath the weight of the stone, even with two of them sharing the burden.

“It’s not so bad,” Jos said. “We’re always taking the rubble downhill, sard of the tunnel. Bard told us that every rock we move shifts the Calm a small way sardwards, strengthening the garmside winds.”

The darkness descended, but Jos insisted that they keep moving. “I’ve traveled this route so many times that I know it by touch.”

Roi had little choice but to trust her. “What happened to your light machine?”

“It’s at one of the rock faces. It’s more useful there, where they can leave it in one place for a while. If I tried to carry it with me everywhere, I’d have no room on my back, and no strength for any rock.”

“Fair enough.” Roi hadn’t brought the one that Cot had given her, even though she had little else to carry; this deep into the sardside the weight would have been too much.

“I still think about light all the time,” Jos said. “What it is, how we can make it and use it.” She added, almost apologetically, “There’s nothing else to think about when you’re carrying rocks.”

Roi was no longer surprised by statements like this. Once, it had gone without saying that work and companionship, loyalty and cooperation, were more than enough to fill anyone’s mind. Now the strange urges that had made people like her and Zak such aberrations were infesting half the Splinter. The strangest thing of all was that it had not brought anarchy and chaos, famine and death. People still carried out their work, still made sure that every necessary thing was done. There was a restlessness, though, a fluidity, reshaping the organization of the Splinter, faster than any tunnel builders could reshape its rock.

“What kind of ways could we use light?” Roi asked her. “Apart from the obvious.”

“Imagine a flat sheet of metal at one end of a tunnel,” Jos said. “An ordinary tunnel, not the one we’re building. You could see it clearly from a very long distance: until the bend in the tunnel took it out of sight. Now if someone turned it edgeways to you, you’d notice straight away. In the dark phase you’d need a light machine beside it, but with care you could keep it visible all the time.”

“I don’t doubt that, but what use would it be?”

“Suppose you needed to get a message to someone on the other side of the Splinter. If we had a team of people positioned in the right locations, watching for changes in each other’s sheets of metal, they could pass the message faster than anyone could run. Like couriers for words.”

Roi was bemused. “Words need drumming or writing. Where are the words?”

“We agree on a list of simple words,” Jos said. “Then we divide the list in half, in half again, and so on, until the last half is a single word. Tilting the metal once can tell us which half of the list the word is in, twice which half of that half-list, and so on.”

The light was returning. Roi said, “You’ve thought about this for a while?”

“It passes the time.”

If they needed to change the plugs in Bard’s tunnel quickly, a system such as this might help. Roi had been struggling to imagine how they were going to navigate their way safely out to the Wanderer’s orbit and beyond, when the one place where they could see into the void and the one place from which they could change the Splinter’s motion were so far apart. She’d thought of trying to construct a platform for observations closer to the tunnel, but the directions of the weight made that a daunting prospect. Having to cling upside-down to the Splinter’s exterior—when there was nowhere to land if you should fall—was not a situation likely to be conducive to accurate measurements.

Roi explained all of this to Jos.

“So you think it could actually be useful?”

“Absolutely! You need to start work on this immediately,” Roi said. “See if you can persuade some of your team-mates to join you. Work out the details, smooth out the problems. Then come and meet me at the Null Line and let me know how things are going.” Roi gave her directions to the Null Chamber.

Jos seemed overwhelmed by the sudden turn of events. “I believe you when you say this is important,” she said. “But my job here, with the rocks. I came here, I listened to Bard. “ She trailed off, confused. The Jolt had changed her enough to bring her here, and enough to make her restless with ideas, but she hadn’t entirely lost the sense that the best thing to do was to stick with your team as long as you could.

“When will it end?” she implored Roi. “I want the old way back.”

“You’ll get it back,” Roi said. “But first you have to do this.”

Jos signaled to her to halt, and they came to a stop together. With a rasp of reluctant acquiescence she eased the rock down between them.

Roi said, “You’re just going to leave that here?”

“It’s not my job any more,” she replied.

Roi found Neth alone in a chamber, surrounded by template frames. Neth greeted her warmly, and listened to all the news.

“I’m sad to hear of Zak’s death,” Neth said, “but I expected it long ago.”

Roi didn’t want to dwell on that. “So how are you spending your time here?”

“I’m trying to understand the wind,” Neth said. “Even before we’ve cut open the mouth of the tunnel, moving all this rock has changed the flow. This whole thing is not as simple as Bard suggests.”

“What do you mean?”

“If the Splinter simply wasn’t here, the wind would blow straight from rarb to sharq; we can all agree on that. I’m not convinced, though, that cutting a long tunnel through the Splinter will necessarily have the same effect. The surrounding rock will still be diverting and complicating the flow of the rest of the wind. It will all mix together in the tunnel. The result isn’t easy to predict.”

Roi was dismayed. She had thought the hard part would be persuading people to help build the tunnel; now Neth was suggesting that it might not even work.

“What can we do if the flow isn’t strong enough to make a difference? Build more tunnels?”

“That could help,” Neth said. “But the important thing will be learning how to shape and control the flow through however many tunnels we have. What you say Bard has planned, with the varying plugs, will make a good start, but we’ll need to study the effects of that arrangement, experiment with it, fine-tune it.”

“And make calculations?”

“Of course.”

Roi struggled to reconcile herself to this new setback. She couldn’t be sure that Neth was right, but she appeared to have thought about the problems of the flow more deeply than anyone else. Bard would certainly get the rock shifted and the machinery in place, but without Neth’s aid, there was a chance it would all be in vain.

She could not ask Neth to leave and join her in the Null Chamber.

“Tell me,” Roi said, “given what I saw in the void, how do you think we should approach the calculations now?”

For a few long heartbeats Roi was afraid that Neth was going to modestly demur that it was not her place to offer advice on the matter, now that she’d left the theorists’ group. Not my job any more.

If that was her inclination, she managed to overcome it. “Try to hold on to as much symmetry as you can,” she suggested. “You’ve shown that there isn’t perfect symmetry around the Hub in all directions. But for all the time we sat in the plane of the Incandescence, nothing in the weights changed while the Splinter completed each orbit. In fact, the period of the orbit was impossible to discern without looking outside the Splinter. That tells us that the geometry as we moved around the Hub was completely unvarying.”

“We were moving through just one plane, though,” Roi said.

“Yes,” Neth replied, “but the simplest way such a symmetry could arise would be if it held true for all planes parallel to the Incandescence. So if you rotate the whole geometry around an axis passing through the Hub, perpendicular to the plane of the Incandescence, it should be left unchanged. Instead of the symmetry of a sphere, look for the symmetry of an ellipsoid.”

As Roi departed, she thought irritably: That’s obvious. I didn’t need Neth to tell me that.

Everything simple was obvious in retrospect, though. What remained to be seen was whether the void itself had any interest in the kind of simplicity that might let their minds reach out and grasp the truth about the world, or whether Zak’s principle was just a beautiful, but misguided, statement of hope.

When Roi returned to the Null Chamber, she found to her delight that it was crawling with hatchlings. Gul was among them, orchestrating their exuberant play.

She climbed out along a wire to reach him.

“I heard the news about Zak,” he said. “I thought you’d probably be too busy to come back to us for a while. Then I thought, why not let them experience weightlessness and see some experiments, instead of just hearing about everything second-hand?”

Roi didn’t recognize any of the pupils; this was a new class. Her and Gul’s children would almost certainly be among them, but if they were she had no way of identifying them. She watched the scampering hatchlings with an uneasy, almost guilty, thrill. Just as Jos had found it hard to defect for a second time, even Roi had her limits, and it was difficult to view the secret obsession she’d developed with her own offspring’s fate as anything but shameful and perverse.

Since the Jolt the Null Chamber was no longer perfectly weightless, but though the changes were enough to ruin long-term measurements it was still possible to demonstrate the basic cycles here, not to mention indulging in the pleasures of simply floating around and throwing things to see how they moved. The place brought back memories of Zak, but Roi could feel no sadness at that when two dozen hatchlings were being steeped in his ideas before her eyes.

Gul said, “If you have a moment, later. I’m in pain.”

Roi had seen the seed packets inside him, but he’d hid the discomfort so well that she’d assumed they weren’t yet ripe. She felt no inclination to berate him, this time, for failing to find someone else to deal with his burden. The simple truth was, she wanted the two of them to have children together. As many as possible.

She turned the baffling notion over in her mind. Why? He was a good teacher, but he didn’t have to be the father of a hatchling, she didn’t have to be the mother, in order for him to teach it. Did she imagine, absurdly, that their individual skills had somehow seeped into their seed and eggs, and would collide within their children to imbue them with a preternatural ability to endure the struggles ahead? None of the hatchlings here were dishing out lessons in space-time geometry and template manipulation. If her children were special in any way, why couldn’t she even pick them from the crowd?

It was a mystery, but she didn’t feel like fighting it; she didn’t even have the energy to ponder it for long. If the next generation turned out to be so brilliant, they could work out the reasons themselves; she’d be content just to see them survive.

She said to Gul, “There’s a machine someone gave me that turns darkness into light. When the children are asleep, come and see me, and I’ll show you how it works.”

Roi met Tan, and they began preparing the way for the calculations that they hoped would lead to the true geometry.

Zak’s principle remained their most trusted guide, but it was a curious thing. Once you knew certain aspects of the space-time geometry it allowed you to deduce the rest, but if you started with a blank skin it could not tell you anything definite. It was less a prescription for a single, self-contained world than a kind of style or constraint that left room for a multitude of possibilities. Before you could apply it, you needed to weed out all but one small, manageable portion of that overwhelming bounty.

As Neth had suggested, their best hope of success was to retain as much symmetry as possible. At the same time, if they pruned away too much of the geometry’s freedom just to make the calculations simpler, they would risk failing, once again, to capture the true richness of the space-time around the Hub.

“I believe in rotational symmetry,” Tan said firmly. “We have evidence for that, and not just in the plane of the Incandescence. Since the Jolt, we’ve been moving periodically out of that plane, and your observations show that each time we’ve entered a shomal or junub dark phase, we’ve actually been at a different place along our orbit. Yet apart from the different view of the lights you saw, nothing else is different from phase to phase. The weights change slightly as we ascend and descend relative to the plane, but at a given point in each cycle, everything feels the same.”

“We’re not going very far out of the plane,” Roi cautioned. “It’s hard to quantify, but I doubt that we’re rising by more than a tiny fraction of our distance from the Hub.”

“No, but the lack of spherical symmetry you discovered manifests itself in the length of the shomal-junub cycle, which we first measured in the Null Chamber with stones that never went further than one span from the plane of the orbit! It was only the fact that the Incandescence and the Splinter were blocking our view of the lights in the void that stopped us from comparing the shomal-junub cycle to the orbital period.”

“That’s true,” Roi conceded. “In any case, even if we can only pin down the geometry close to the plane and use it to explain the Splinter’s motion, that will be a start.” The Wanderer’s orbit appeared to be inclined, taking it high above the Incandescence, but with the strange distortions of the light to account for, making sense of those observations remained a distant ambition.

“We’re agreed then,” Tan said. “We look for a geometry unchanged by rotation around a fixed axis.”

The other symmetry they were committed to retaining was the assumption that the geometry around the Hub was unchanging over time. Though the Splinter and other objects might be nudged into different orbits, it was the fact that they had shifted in space that altered the geometry they experienced; the geometry itself was not melting beneath them.

“The question then,” Tan said, “is how are the two symmetries related? In our last calculation we assumed that the symmetries of space always acted in a direction perpendicular to the time symmetry. But do we have any evidence for that?”

Roi hoped Gul was filling their children’s minds with ideas that would prepare them for questions like this. She had been raised with an understanding of three perpendicular directions in space—garm/sard, rarb/sharq, shomal/junub—and if you added time as a fourth, it seemed obvious that it ought to be measured perpendicular to all three. Certainly, any clock you carried with you would measure time that way, and even in the abstract world of Tan’s geometry, at any given time and place you could simply pick four perpendicular directions.

However, the directions of symmetry weren’t a matter of choice or convenience; they were properties of the geometry itself. And while the framework for the calculations would become more complicated if the two symmetries were allowed the freedom to slant against each other, it would be even worse if they could not rely on a measure of time in which the geometry was unchanging.

Roi said, “What would count as evidence?”

Tan couldn’t answer that immediately. He took a sheet of skin and started doodling. “Throw out one dimension of space, the one that takes us out of the plane of the Incandescence, and use that instead to picture time.” He drew a point for the Hub, then sketched a circle around it for their old, un-Jolted orbit. “The symmetry in time takes this circle into another one in the future, tracing out a cylinder.” He sketched in the cylinder, drawing lines rising straight up from the circle to indicate the direction in which it could be pushed without its geometry changing.

Roi said, “And if the time symmetry isn’t perpendicular to the rotational symmetry?” She scratched a second diagram beside the first, in which the lines that carried the circle forward in time wound around the cylinder in helices. “But wouldn’t we always be able to straighten out these lines?” she said. “The geometry doesn’t change, whether you move around the cylinder as you travel along its length, or just slide straight up and down. It’s all the same.”

Tan thought for a moment. “With one cylinder you could always do that, but don’t forget the rest of the geometry.” He drew in a second, larger orbit on Roi’s diagram, then sketched in helices with a different, steeper pitch. “Suppose the time symmetry makes a different angle with the rotational symmetry at different distances from the Hub. We’re free to combine this whole motion with any fixed amount of rotation around the Hub, but we’re not free to rotate around the Hub by different angles at different distances, and that’s what we’d need in order to straighten everything out.”

Roi said, “So there’d be a kind of unavoidable twist in the geometry?” She pondered this. “Then wouldn’t motion around the Hub in the direction of the twist be different from motion in other directions?”

“That sounds plausible,” Tan said.

“When we throw a stone out of the plane of the Incandescence,” Roi said, “it completes the orbit in much less time than it takes to fall down and rise up again. It’s almost as if it’s being swept around the axis of symmetry, forcing it to go around faster than the other cycle it’s completing, the shomal-junub cycle.”

Tan said, “I think you’ve just answered the question. There might turn out to be some other explanation, but for now we definitely can’t assume that the symmetries are perpendicular.”

That would make the calculations harder, but at least they were doing it for a reason. Roi felt buoyed; the idea that they could anticipate a feature of the geometry that might allow it to conform to the new observations was encouraging. Most of what she’d seen in the void remained utterly mysterious to her, but they were moving in the right direction.

“There’s one more thing we need to decide before we call in the calculating team,” Tan said. “How are we going to measure distances from the Hub now?”

In the previous calculation, they’d described each point’s relationship to the Hub by the size of the sphere on which it lay. You didn’t need to worry about the actual, messy curved geometry all the way from the point to the Hub itself; instead you imagined rotating the point around the Hub in all possible directions, sweeping out a sphere whose surface area would increase the further the point was from the Hub.

With the spherical symmetry gone, they could no longer do this. They could replace the spheres with circles—rotating each point around the axis of symmetry and then considering the circumference of the circle it swept out—but away from the plane of the Incandescence it wasn’t clear how those circles would be related to each other.

Ruz appeared at the entrance to the Chamber. He greeted them politely and apologized for interrupting, but Roi could tell from the way he hunched against the wall that he had something he urgently needed to say.

“We’re seeing more flares from the Wanderer,” he announced. “Nine, in the last report I’ve received.” While Roi had been visiting Bard and Neth, Ruz had arranged a group of new recruits to stay at the junub edge, with pairs climbing up through the crack in the wall each time it was safe, to make observations.

“We’ve felt no new Jolt,” Tan said.

“No,” Ruz replied, “we’ve been lucky. But if this continues, it’s only a matter of time before another one strikes us. We’re also seeing the Wanderer’s orbit changing: it’s losing its inclination, coming closer to the plane of the Incandescence.”

Roi felt a crushing sense of hopelessness descend, but she struggled to fight it off. One tunnel was almost complete, and Neth would help Bard sort out any problems with the flow. They were tracking the Wanderer heartbeat by heartbeat. Now it was up to the theorists to find the way forward, to draw the map that showed the way to safety.

She addressed Tan. “We should assemble the calculating team, next shift.”

“All right,” he said. “But what about the question of distance from the Hub?”

Roi thought for a while. “There’s one symmetry that’s always present, that we forgot to mention: the geometry really doesn’t care how we describe it.” You could wrap space-time in numbers in countless different ways, but the underlying shape was oblivious to the packaging. “We don’t know the best way to express distance from the Hub, and even if we make a certain guess now it might turn out to make things harder. So we should give ourselves room to manoeuvre: we should set up the templates so we can choose the easiest scheme at any point in the calculations.”

Tan concurred. He said, “I’ll go and tell the calculating team.”

When he’d left, Ruz said, “I’d better go and send the messengers back to get the next report.”

Roi said, “Remember Jos?”

“Jos?”

“One of the people we met with the light machine?”

Ruz looked tired. “Vaguely. Why?”

“She’s had an idea for something much faster than any messenger. I think you need to talk to her.”