Ruz said, “Are you badly hurt?”
“No. Give me one shift and I’ll have my strength back.”
“You want to go back there?” Ruz’s tone was neutral; he wasn’t going to pressure her to take Zak’s place, but nor would he try to dissuade her.
“I’ve walked beneath the void once, I can do it again. And I’m sure there’s something out there that we can track, something we can measure.” Roi pictured the strange ribbon of colors stretched across the darkness; she had no idea what it was, but she had seen lights moving within it.
“There must be something simple,” she said. “We have to keep searching for it.”
Zak’s body had been seared beyond recognition. Roi had seen many corpses in her life, most of them half-eaten by murche, but she had never faced a choice before about the fate of a friend’s remains. Though everyone expected to be consumed by scavengers, as it was normally as inevitable as death itself, was it her duty to Zak to ensure that end? It seemed more fitting to leave him here, where the Incandescence had claimed him.
The tracker, made of metal and susk cuticle, was pitted and tarnished but appeared to have survived intact. Roi went to it and adjusted the aim, sighting a bright point of light at the edge of the colored arc. She took the clock Ruz had made for her from her right cavity, and held the moving wheels against her claw so she could time the occultation of the light by the tracker’s wires.
As the light moved, its color changed smoothly. It didn’t take long for it to cross the whole width of the band and vanish completely. Roi had no idea how to explain this peculiar behavior. Was the light now being hidden by something in the void—something opaque, like metal—or had it been destroyed?
She recorded the time it had taken for the light to cross a small portion of the view, but she didn’t trust that number to tell her much about the Splinter’s motion. The lights weren’t merely changing color, they were moving apart as they flowed across the band. To expect the time it took for them to cross one thirty-sixth of a circle to be directly proportional to the whole journey seemed absurdly optimistic.
Ruz called to her anxiously, and she returned to the interior with plenty of time to spare. When she was safe in the shelter of the side tunnel she explained what she had seen.
“I have to go out again,” she said. “Maybe we’ll think of an explanation for all of this, and find some way to calculate the Splinter’s orbital period from this data, but since we don’t really know what we’re measuring, the more observations I can make, the better.”
Back on the outside, Roi confirmed a hunch that she’d had before: if she confined her measurements to one part of the band, all the lights took the same time to move through the same angle; when she reoriented the tracker and looked elsewhere, though, the time was different.
Halfway through her second stint, Roi thought she recognized some familiar patterns among the points of light, appearing again in the same part of the band. She wasn’t sure, though; she hadn’t made an effort to commit the patterns to memory.
The third time she returned, she was certain that some patterns were recurring. By the fifth time, she was convinced that everything she could see in the void was following the same periodic motion. Her first impression of the lights drifting across the band had been that they were like motes of dust, never the same twice. That wasn’t true, though. Notwithstanding the strange distortions of color, angle and speed that accompanied their passage, and the fact that they regularly disappeared from view, she was seeing the lights arranged in exactly the same patterns, again and again. The view as a whole was as cyclic as clockwork.
The period was certainly longer than the window of time she was able to spend making observations during each junub dark phase; it was not, however, equal to the shomal-junub cycle itself, as the lights were not the same each time she returned. Her first guess was that three cycles of the moving lights was close to two shomal-junub cycles, and once she knew what she was looking for her observations bore this out. The two-thirds ratio was not exact, though; it was closer to thirteen parts in twenty.
So much for the simple geometry.
“If we understand anything about orbital motion,” Ruz ventured, “then this period has to be coming from the Splinter. There’s no way that the orbits of all these other objects could conspire together to give the same result.”
Roi would have been happier about attributing everything to the Splinter’s motion if the pattern of lights had moved rigidly across the sky, like the view when she leaped from one side of the Null Chamber to the other, tumbling as she went.
“If these things really are motionless,” she said, “then why does their appearance change all the time?”
Ruz pondered this. “If they’re very distant from us,” he said, “then the natural paths of the light that’s reaching us from them might be affected by the geometry. This isn’t like seeing something that’s right in front of us, when we can reach out and confirm by touch that what we’re seeing is what’s really there. If the geometry can bend the Splinter’s natural path to wrap it around the Hub, why shouldn’t it bend light as well?”
“Ah.” Roi couldn’t see how this could explain the whole strange vision that the void presented, but it did make some sense. They’d been used to thinking of light as traveling in straight lines, like a rapidly flung stone crossing the Null Chamber before anything could divert it. It seemed the void was too big, and even light was too slow, for the comparison to be sustained.
“We’re going to need to do a lot more calculating,” she said. Ruz’s suggestion was both daunting and encouraging; daunting because it complicated the way they needed to interpret the observations, but encouraging because it meant that the same data provided a far richer means of checking new theories about the geometry than the single number—the Splinter’s orbital period—that they’d anticipated gathering.
The eighth time she climbed out into the void, Roi felt her body beginning to falter. Though she’d given herself time to recover from the battering she’d received after fleeing the Incandescence, she hadn’t rested again since she’d started making observations.
Her work here was almost complete. Although the motion of the lights wasn’t rigid, and varied in a complex way across the band of color, there were only so many measurements required to characterize it; she believed she was getting close to the point where further data was merely confirming what she had already recorded.
She chose a bright light that would be easy to follow, and aimed the tracker toward it. It was only halfway through the measurement, when the times for the successive occultations were beginning to diverge from those she’d seen before for this part of the band, that it struck her that she should have noticed this bright object before. She recognized the pattern of lights around it, and she was sure that in the past they had not included this luminous interloper.
Which meant what?
Perhaps this object was not as distant as the others. It could be orbiting the Hub closely enough for its own independent motion to show up against the synchronized rotation of the background.
Could this be their lost half, the other Splinter?
It was an appealing notion, but why should another Splinter moving through the void be bright enough to see at all, when their own was in darkness? Roi fought her tiredness and tracked the object carefully, until Ruz shouted a timely reminder.
When Ruz heard the news he was excited. “I have to see this for myself,” he insisted. Roi was too tired to argue; it was still possible that the void was causing her harm that would only show up in the long run, but it seemed overly cautious to deny Ruz one quick trip when she had survived so many herself.