The strange creaking and rasping from the rock did not abate, though.
"Half a shomal-junub cycle," Roi said. "Almost exactly half."
Some of the hatchlings began to stir. Gul made soothing noises and drew them close to his body. "Why would a void in the Incandescence be half the size of our orbit?" he said. "That seems like too much of a coincidence."
Roi took advantage of the normal light to survey the chamber. All the hatchlings were accounted for, and the basic structures around her were intact — the entrances to the chamber were clear, the ceiling hadn't fallen — but there were some cracks in the walls that she was sure she'd never seen before. The rock continued its maddening groan. If she could feel no change in weight, what was tormenting it?
She could hear people in the distance, calling to each other, fearful and confused. "Where should we go for safety?" she asked.
Gul said, "We're as safe here as anywhere. There's nowhere to go."
The light and the wind began to fade again. Why were some things repeating themselves, while the flash and the jolt had happened only once?
Roi said, "We were pushed." The pattern was unmistakable; she'd tossed enough stones in the Null Chamber to know how to set things cycling back and forth. "That's what threw us off the ground. It wasn't the fact that we entered the void that did it: the push came first, the disturbance came first. Whatever struck us changed our orbit slightly, enough to knock us into the void."
"Why is the void half as big as our orbit, though?" Gul protested.
The darkness thickened, the wind fell away. Roi pictured the orbit of the Splinter, and the motion of the stones in the Null Chamber. What happened twice in every shomal-junub cycle? The "falling" stone passed by the "fixed" one. First it passed it on its way shomal, then it did so again on its way junub. Twice in each cycle, the stones were close together. And twice, they were far apart.
"The void's not half as big as our orbit," she said. "It's far bigger than that. And it hasn't wandered up to us by chance; it hasn't moved at all. It's been right beside us all along."
Gul was silent for a while, contemplating her cryptic remarks. Then he said, "If the Incandescence isn't everywhere, but we never left it before, then maybe it's confined to a thin layer around the plane of our old orbit. Now something's disturbed the Splinter, and we're moving shomal and junub — above and below that plane — for the first time."
"Exactly!" Roi said. "Out of the Incandescence, then back. Twice every shomal-junub cycle. The whole Splinter has become the falling stone."
She waited, picturing the stones in her mind's eye. As one imaginary stone ascended from its low point and approached the other, the walls began to brighten.
Gul said soberly, "We're lucky we survived this. And lucky we can understand it." Then he let out an ecstatic chirp that woke half the hatchlings. "We're not going to die!" He scooped up two bewildered children and tossed them on to his back, then started running around in a circle. "Darkness, light, it doesn't matter! We're safe, we're fine. Everything is perfect!"
Roi watched him, dizzy with relief herself, if not so exuberant. This was not the end of the Splinter, not the plunge into the Hub that Neth had foretold. The crops would suffer, though. There would be food shortages, and everyone would struggle to complete their work as the darkness came and went.
The strange event had shown them something new about the Incandescence, even as it had confirmed Zak's picture of the Splinter orbiting the Hub. It might even persuade some people to accept his ideas and agree to the tunnel. The loss of crops was a hard price to pay, but in the end it might change things for the better.
The one thing that worried Roi most was that she still had no idea what dazzling thing had flown past and knocked them out of their orbit. Where had it gone? To the Hub? Into the void? Could it cross their path again?
And if it did return, which way would it push them next?
Zak stretched his legs out across the wall of his chamber, trying to ease the pain in the joints. "I have a plan," he said. "But I'm going to need your help."
"Whatever you want from me, just ask." Roi had left the hatchlings in Gul's care to travel to the Null Line and check on Zak's condition. He had survived the Splinter's Jolt and the aftermath, with members of the theorists' team still bringing him food regularly, in spite of their own problems and distractions. His health had been fading for a long time before the event, though, and Roi suspected that his death was close now.
Zak said, "When I was working in the library, I heard about a crack in the wall at the junub edge. Some people had climbed right through it and reached the Incandescence."
Roi was skeptical. "Are you sure that's not just a story?"
"I have a map."
"You always have a map. Did anyone come back?"
"Of course not. The Incandescence killed them; nobody has ever walked into it and survived. It's not just the strength of the unfiltered wind: even at the Calm, there's something fatal, something that the rock protects us from."
Roi could see where this was heading. "You think it might be possible to survive there, now? In the times when our orbit takes us right out of the Incandescence?"
"It's worth trying," Zak said. "We don't know how long the new orbit will last. This might be our only chance to look into the void."
There had already been measurable changes in the orbit. Although the period of the complete light/dark cycle remained the same, with Ruz's clock it had been possible to detect a small reduction in the time the Splinter spent in darkness. This suggested that the total distance they were traveling away from the old orbital plane had diminished slightly.
Other experiments in the Null Chamber had shown that the Null Line had, strictly speaking, vanished; although the weight throughout the chamber remained very small, there was no longer a line of perfect weightlessness running through the Splinter. The small weights that were present now were difficult to measure, but they seemed to undergo cyclic changes. Tan had suggested two possible explanations for this: either the Splinter's rate and axis of spin had been disturbed in such a way that the spin weight no longer canceled the rarb-sharq weight, or the rarb-sharq weight itself was no longer constant throughout each orbit, and hence could no longer be canceled by any constant spin.
In either case, the ceaseless groaning of the rock was probably due to the fact that the weights throughout the Splinter were no longer fixed; the precise forces were always shifting, repeatedly tightening and relaxing their grip on the rock. Tan believed that the price to be paid for this restlessness would be a gradual return to a state of alignment, whether that meant a change in the Splinter's spin, its orbit, or both.
Roi said, "This journey will be hard for you. Someone younger and healthier should go instead."
"Someone younger and healthier might climb out through the crack in the wall and never come back. It makes far more sense for me to risk the last few shifts of my own life than to allow someone else to throw away the best part of theirs."
"You can barely walk," Roi protested. "How are you going to reach the junub edge?"
"I've arranged for some couriers to bring me a cart."
"Are they going to deliver you to your destination as well?"
Zak said, "I want you to pull the cart. You and Ruz. Ruz has already made some instruments for me, to allow me to take measurements of whatever's there to see."
"So you want Ruz along to fix them if they break?"
"Yes."
Roi didn't ask what her own purpose would be, apart from sharing the load. She said, "You should have peace and ease at the end of your life, not a dangerous journey like this."
Zak rasped irritably. "If I knew that the Splinter was safe, I'd have peace. But I'm sure that it's not, so the best I can do is keep struggling to make that happen."
Roi made a sound of acquiescence. "What do you think it will tell us? Looking into the void?" The thing that had lit up the rock when it touched them seemed to have vanished, but then
, from inside the Splinter the whole Incandescence seemed to vanish when they were no longer immersed in it.
Zak said, "We've been half right about a lot of things, but there's something missing from our theories, something whose nature we haven't even guessed yet. If we don't learn to understand it, it will kill us."
When Roi returned to the hatchlings' chamber to explain her plans, she found Gul in pain, full of ripe seed packets. She had helped him dispose of them many times before, but she was surprised that he hadn't found someone else while she was gone.
"I've been busy with the hatchlings," he said. "What was I supposed to do? Walk the tunnels begging for a mate, with the children lined up behind me copying every move?"
The hatchlings were asleep, so there was no danger of that now, but Roi had no contraceptive leaves. She was too tired to go hunting for the stupid weed, but she couldn't bear to see Gul in so much pain.
"Open your carapace," she said. "I'll take them."
"Are you sure?"
"Quickly, before it gets dark. If I can't see what I'm doing you'll be sorry."
As she snipped the seed packets free and loaded them into her egg cavities, the pleasure that spread through her body felt muted. Without the contraceptive to compete with them, the packets were producing far weaker secretions than she was accustomed to. She had never been entirely sure why it had always seemed right to keep her eggs from being fertilized; she had understood that the Splinter could only feed so many mouths, but other people made hatchlings all the time. Now, with the crops diminished, that should have been a stronger reason than ever, but even as the rush of contentment faded she felt no regret for what she'd done.
She had planned to stay for less than a shift before returning to the Calm to meet up with Zak and Ruz, but she found herself lingering, waiting for her eggs to be ready to lay. Six had been fertilized, and when their cases finally hardened she found a snug crevice close to the chamber where Gul worked, and she packed the eggs carefully into the gap in the rock.
She was aware of how strange it was that she was arranging for these hatchlings to be educated by their father, rather than leaving it to chance. The job itself was the thing, and every member of every work team, not to mention every hatchling, was supposed to be interchangeable. Still, in these dangerous times everyone's children needed to learn what Gul could teach them. She would have counselled any stranger to do the same.
Although Roi was late returning to the Calm, when she arrived she found that the cart Zak had hoped to receive several shifts before had only just been delivered. That the metalworkers, couriers and depot operators had managed to fulfill Zak's strange request at all — while the food around them became ever more sparse, and the world of constant brightness they had known all their lives flickered in and out of existence — was testimony to the robustness of the work teams. Some people, Roi suspected, would not miss a shift even if the Splinter itself was torn apart.
The cart was big enough to hold Zak, the instruments Ruz had built for him, and a reasonable amount of provisions. Roi had already collected some food on her way back from visiting Gul, but she spent another shift foraging until she had as much as they could carry. Although the Calm supposedly became less barren as you moved away from the Null Line, and so in theory they'd be traveling into a more bountiful region, Roi had spent so long around the Null Chamber that she knew a dozen places where the seeds that drifted in tended to settle and grow. She would not have the same local knowledge once the journey was under way.
There were two harnesses for the cart, strung together one behind the other, so she and Ruz could share the load if they wished, but the cart would not be unbalanced if they chose to take turns pulling it instead.
The whole team of theorists came to bid them farewell; Tan addressed Zak on behalf of everyone. "We wish you a safe journey, and clear observations," he declared. "Our frames are ready for your numbers and templates. You built this team from nothing; perhaps you will return to us with the knowledge that will make our work complete." Zak replied simply with a murmur of thanks, but the send-off seemed to lift his spirits.
Roi took the harness first, leaving Ruz free to walk ahead of her, checking for hazards and clearing obstacles. The Jolt had left debris almost everywhere, and the less-traveled the tunnel the more chance there was that nobody had yet moved it aside.
Their journey would take them rarb and junub, uphill all the way, but it would be a while before their weight made much difference. Even in near weightlessness the cart was unwieldy, but by far the greatest irritation was the darkness. In her earlier trips between the hatchlings and the Null Chamber, traveling alone with no burden, Roi had found it impossible to make progress once the light fell away and her vision failed. The path ahead could be clear for dozens of spans and she could declare to herself that nothing terrible would befall her if she simply advanced at a leisurely pace through the darkness, but her body would still refuse to obey her after the first few halting steps. Attempting the same thing with Zak swaying on the cart behind her was inconceivable, even if Ruz had been in the harness to remove him as an unknown. The periods of enforced rest might have been welcome if not for the fact that they came so much more frequently than they were needed, making them more frustrating than recuperative.
"What is light?" Roi wondered, waiting for the darkness to end.
"A very fine part of the wind, perhaps," Zak suggested. "That would explain why it can penetrate more deeply through the rock than any other component. It seems it can penetrate anything but metal."
"It must be easily scattered, though," Ruz said, "or there'd be no light at all here in the Calm. The rock can't block it completely, but still manages to change its direction."
"Yes." Zak seemed intrigued by this observation, but unsure how to pursue it further.
Roi said, "If light is part of the wind, how can we hope to see anything at all once we're out of the Incandescence?"
"Some light might be scattered up to us from the Incandescence," Zak replied. "But the void itself might contain a faint wind."
"Including light?"
"Let's hope so," Zak said. "All we know for sure about the void is that it's a thinning of the Incandescence, to the point where nothing can reach us through the rock. That need not mean that there's absolutely nothing there."
The tunnel began to brighten again. It always took a while for the walls to begin glowing with their full intensity, though how much of that was due to the time it took for the light to penetrate the rock, and how much might be the product of a gradual transition between the void and the Incandescence, was hard to say. From outside the rock it might be possible to judge how sharp the border between the two regions was, though it would be risky to stay outside beyond the periods of full darkness.
It was only after they'd been traveling for nearly a shift and a half, according to Ruz's clock, that they decided to stop and sleep. Before the Jolt, most people had more or less agreed on the length of a shift, growing tired after a similar period of wakefulness. The stretches of darkness had led to an increase in that time, but not always an equal one for each person.
When they woke, Ruz was first in the harness. After a dozen light/dark cycles Roi took his place, and this time she finally felt the burden of pulling the cart uphill. The junub weight grew less than half as rapidly with distance as the garm and sard weights — and they were also traveling rarb, which contributed nothing — but beyond those excuses it was a measure of how slow their progress had been that it had taken so long to reach the point where they really cared which way was up.
The Calm appeared more sparsely populated than ever; apart from occasional couriers that Roi glimpsed in the distance, their role made obvious by carts of their own, the tunnels seemed deserted. The expeditioners passed the time with light-hearted speculation, eschewing any grim predictions about the fate of the Splinter. By the end of the journey's second shift, Roi and Ruz were dragging the cart together, with the lead harnessee also
keeping a lookout for obstacles. It was hard work now, and Roi was beginning to feel that their enforced breaks didn't come a moment too soon.
Halfway through the third shift, as they slowed for the onset of darkness, Roi noticed a flicker of light ahead. At first she thought it was merely a lode in the rock that was dimming more slowly than its surroundings, but as the darkness deepened the contrast only grew stronger. A reddish patch of light stood out against the blackness; it was an unsteady glow, but it never failed entirely. It was moving slightly, with a rhythm that reminded her of a person's gait, as if someone was carrying the source of the light toward them.
Ruz said, "Can you hear footsteps?"
Roi listened carefully. "Yes."
"There are five people," Ruz declared. "And some kind of machine."
"I'll take your word for it." A dozen heartbeats later, she could make out two people in the front of a small group. The light was coming from an object strapped to one of their backs.
Zak said quietly, "That I lived to see such wonders."
Roi called out a greeting, unsure if the three of them would be visible by this strange illumination. A reply came back, cautious but friendly.
When the group drew closer, Roi could see that Ruz was correct: there were five people. They made introductions; the light-bearer was called Lud, and the others were Jos, Rud, Cot and Sad.
The light that emerged from the machine on Lud's back was weak, rendering the group sketchily. Their bodies were merely hinted at by a glimmer of surfaces, as if their carapaces had turned to metal. Seeing your companions' beating hearts was not the point, though; this modest light would still be enough to allow you to spot obstacles and walk through the darkness with confidence.
"Where are you headed?" Ruz asked politely. Roi was sure that he was twice as eager as she was to hear how the light machine worked, but it would be discourteous to raise the matter immediately.