by Greg Egan
"Acceleration. Get used to it."
"I don't understand."
"Be patient," Rakesh implored her. "Just enjoy the view."
Even with the limited range of frequencies that the combination of the hull's filters and their vision afforded them, the neutron star made a majestic sight. Parts of the disk and the central jet shone brightly, and the narrow band brought out complex structures woven into the jet that would have been much harder to discern in the glare of a full-spectrum image.
As the spinning ring of Lahl's Promise came into view, Rakesh's anxiety began to rival Zey's. With the sight of his last fragile link to the Amalgam looming in front of him, the prospect of renouncing it, of cutting his ties, was beginning to seem a thousand times more daunting than leaving the node had been. He had not felt the same vulnerability since the day he'd left Shab-e-Noor. In the bulge, nothing would be certain. He did not understand the Aloof and their whims. There was no guarantee that he'd ever see Parantham, or any other citizen of the Amalgam, again.
So be it. That was what backups were for.
He brought the ferry to a halt a hundred meters from the ship.
"This is the cart I traveled in," Rakesh told Zey. "Though not all the way from the place where I was born."
"I don't understand," Zey complained. "How you traveled, where you've been."
"Don't worry," Rakesh said. "Forget about those things. Think about this place, and your own journeys."
He spoke to Parantham as she sat in the cabin, through a radio link bridging the vacuum between them.
"I've found Tassef's star on the map," she said. "If I ask the ship to go there, I suppose the Aloof will try to inject me back into the Amalgam's network."
Tassef was on the far side of the bulge from Massa, where they'd entered. Parantham would be re-enacting Leila and Jasim's first journey in reverse. Assuming the Amalgam let her back in.
"Safar bekheyr, my friend," Rakesh replied. May your journey be blessed. They had said their goodbyes, and he had made it clear to her that he was resolved in his decision; he didn't know what else to add.
"I'll see you again, Rakesh," she promised. Whether or not that was possible, he knew she meant it honestly; she would try to return.
For a few long heartbeats nothing happened to Lahl's Promise, and Rakesh wondered if that was the way: the Aloof simply rescanned the ship's contents each time, and left the latest incarnation behind, intact, as a kind of fossil.
Then the spinning ring began to smear out before his eyes, each speck of material cut loose from its neighbors and set free to follow a separate trajectory. Before long it was a faint, diffuse cloud of dust.
Zey was running in rings around the cabin now. "The people who did that? Where do they live?"
"I don't know," Rakesh replied. "Don't worry, though; they're not going to do that to us."
"How do you know?"
Rakesh chirped amusement. "I don't know anything about them, for certain. But I'll tell you what I'm thinking right now."
Zey managed to calm herself, and she stood beside him, waiting for him to compose his reply.
"I think they might be sleepwalking," he said. "Like your team-mates. I think they've done many things, learned many things, seen many things, but now they've had to find a way to live without needing what the world can no longer provide for them." He could understand the attraction of a strategy like that, for the Arkdwellers, for anyone. It was better than going mad with boredom. "Maybe there are one or two among them who are a bit like you, but a lot less restless. Sentinels, not quite awake, who can watch the world go by, and even intervene in it a little, but who can't, or won't, reengage with the universe until it has something new to offer them."
Zey absorbed this. "But they brought you here, just to wake us?"
"That's what I believe," Rakesh said. "But I'm not certain about any of this."
He waited until the last traces of Lahl's Promise had drifted out of sight, then he started the ferry's drive.
"Forget the Aloof," he said. "Let's go and find out if any of your team-mates are ready to engage with the universe."
28
The message from Ruz began, "Cho has found the Wanderer."
Roi read on, amazed.
While most of the void-watchers had given up their old job and come to join the geometry-calculators, Cho had refused to accept that the act of observation had become impossible. The junub edge had become useless; not only had the Incandescence hidden all the ordinary, distant lights that might have been used as guides to the Splinter's motion, once the Wanderer was orbiting in the same plane as the Splinter, the rock of the Splinter itself blocked any chance of a view of it from the junub edge.
So Cho had gone first to the sard edge, hunting for another crack in the rock through which he could extend his light-gatherer. He'd had no luck, though, in finding such an opening, or even a promising site where one could be made.
Once the Splinter crossed the Wanderer's orbit, the garm edge, facing in toward the Hub, became the only feasible observation post. Cho had journeyed back across the length of the Splinter, carrying all his metal plates, to search for a new vantage point.
He had found a suitable crack in the rock, and lowered his light-gatherer through to the surface. By blocking the aperture with punctured metal sheets to limit the amount of light transmitted, and then projecting what remained on to a smooth stone surface backed with roughened metal, he had been able to form an image which could be viewed safely.
The image was not sharp, but even through the Incandescence a dazzling smear of elevated radiance could be seen. It was the Wanderer orbiting the Hub, its intensity cycling dramatically. The emission of a flare or some other misadventure had apparently knocked it into an elliptical orbit, and on its closest approaches to the Hub it was now shining with an unprecedented brightness, which fell away again as it moved further out.
Roi conferred with Kem and Nis. "What does this mean?" she wondered. "How strong can this new light become?"
"I have no idea," Nis confessed. "I don't understand what's happening. The weight is squeezing the Wanderer, agitating its material somehow, but this effect is out of all proportion to that. It's as if. a child had teased a susk a dozen times, always getting a response as mild as their teasing, but then they found they'd crossed some kind of threshold and driven it into a fury."
Roi did not like the sound of that. What could the Wanderer do to them, in a fury?
Kem said, "We have two choices, I think. We could simply keep moving out, trying to put as much distance as we can between us and the Wanderer."
"That's getting harder, though," Roi replied. "And more perilous." Not only was the slower wind and the thinner Incandescence limiting their pace, if they ended up too far from the Hub there would be no hope of sustaining the crops. To survive the Wanderer only to die in a famine would be the worst thing she could imagine.
"The other choice is to take a different gamble," Kem said. "It's not too late to put ourselves in an orbit where we're constantly shielded by the Hub. The Wanderer's closest approach to the Hub is closer than we are now, but its furthest distance is still outside our present orbit. We can match orbital periods with it, and try to lock ourselves into a relationship where the Hub protects us as much as possible."
"Then what do we do when the Wanderer's orbit shrinks further?" Roi said. "We can't follow it back down toward the Hub in order to keep our orbital periods the same." She had had the idea, long ago, that perhaps Bard should have carved tunnels through the garmside as well as the sardside, granting the Splinter the ability to travel in either direction. If it came to a slow, drawn-out famine because they were too far from the Hub, that might yet be their only salvation, but there wasn't the slightest prospect of creating those tunnels in time to chase the Wanderer.
Nis held up the message sheet that contained Cho's observations. "Look how much brighter it's becoming already, just from the slight increase in weight when it reaches the close
st point to the Hub along its orbit. When its orbit shrinks. "
He trailed off, but Roi didn't need him to complete the prediction. Either the process that was driving this radiance would come to a halt by destroying the Wanderer, or it would keep growing in the same spectacular fashion, and it would make no difference where the Splinter was. Unless they were shielded by the Hub, this light would be strong enough to outshine the Incandescence and sear them all to death.
Roi rejoined the geometry-calculators for one more task. Since the Splinter's orbit was essentially circular and the Wanderer's was not, they couldn't hope to track its motion perfectly, keeping themselves always in the center of the safe zone that lay roughly — but thanks to the twist, not precisely — on the opposite side of the Hub. However, they could find the orbit that gave them the greatest protection possible, given that the Wanderer's brightness was reaching its ominous peaks with perfect regularity.
In effect, they would try to hide the Wanderer behind the Hub, to make it disappear from view. As the instructions flowed from the calculators to the sardside tunnel, and the observations flowed from Cho to the calculators, Cho's data began to reveal a modified cycle. As well as dimming and brightening from its own mysterious dynamics, the Wanderer was now growing more or less obscured by the Hub, which was swallowing varying portions of its light. As the Splinter eased into its new orbit, the two cycles slipped into the desired, antagonistic relationship: the Wanderer's dazzling bursts were cut short by the Hub's intervention, and when the imperfect alignment of the orbits most prevented the Hub from hiding the Wanderer, it was, of its own accord, at its least radiant.
Roi signaled Bard to close the tunnels, and told Tio to let the calculators rest. There was nothing more to be done. If the orbits started slipping further out of alignment, moving further from the Hub would only worsen the disparity. Their fate was at the mercy of the Wanderer now.
Roi sent word to evacuate the edges, to bring everyone as close as possible to the center of the Splinter. Her first instinct had been to move people to the sard edge — doubling the amount of rock between them and the Wanderer compared to the center — but Kem had pointed out that while pure light straight from the Wanderer couldn't reach them from the opposite side, a flare might wash behind them while radiating heat and light of its own, rendering the sard edge vulnerable.
Cho refused to leave his observation point, as did the light-messengers who linked him to the center. Roi sent a message to him.
"Let me replace you." She was older, it was her time.
Cho replied, "This is my work, not yours."
It was a bad argument, his skills might yet be needed for some future task they could not imagine, but Roi lacked the strength to make the journey to the garmside to plead with him in person.
The evacuees poured into the crowded center, bringing stores of food, pushing carts, herding susk.
Roi left her post and moved from chamber to chamber, seeking out people she'd known. Gul had come with a new class of hatchlings. She greeted him fondly, and played for a while with the children, but some restlessness drove her on. Ruz was nowhere to be found; eventually she heard that he'd taken the place of one of the light-messengers.
She stumbled across Bard in a crowded tunnel, pressed against the rock, his heart laboring despite the lack of weight.
He was dying. She said, "You moved the world, brother. You gave us our chance. Be at peace." He was too weak to reply. She looked around for food to bring him, but the influx of people had scraped the rock bare.
She had wanted to find Haf, but the crowd around her had become impassable. What could she have done for him, anyway? Sheltered him beneath her carapace? Offered him words of comfort, which would only have made him more certain that death was upon them?
Roi found a place beside Bard. She had planned to return to her post to wait for news from Cho, but the only news that mattered now would come to them all, soon enough, without the need for instruments and calculations.
She looked around at the people covering the walls and ceiling. They had worked hard, all of them. What was the nature of the world, what was the meaning of work, when so much struggle could end in obliteration?
She was tired now. She wished she could have gone as Zak had, when there was still so much hope. This was unbearable.
Bard stirred, and drummed something faintly.
Roi said, "I missed that."
"I think we've all been recruited," he said.
Roi caught his meaning and chirped softly. They really were one big team now. She turned the bleakly funny notion over in her mind, and felt the answering buzz of cooperation. Living or dying, she'd be doing the same as everyone around her. How could she not be happy with that?
Light replaced the crowds, the rock, the world. Roi ramped down her vision as fast as she could, fleeing from its intensity, trying to burrow into the safety of her mind to reach a painless black sleep. The light wouldn't let her escape: it overtook her, then reached into her eyes with lacerating claws.
There was only pain, heat, and brightness. She willed death, but the light kept slicing into her, playing with her, refusing to deliver mercy. Every time the sameness of it softened the blows, the thing turned her over and cut her somewhere new.
I can't do this, she pleaded, though she didn't know what she was addressing. Something broke, something weakened, and there was distance between her and the brightness. Finally. She relaxed. This was death: like sleep.
The pain welled up again, but the darkness remained. She thought she slept, three or four times, but there was no waking into light, either savage or gentle. Only waking into pain.
Roi flexed her legs, and felt her claws scrabble against rock. It hurt her to move, but it was not impossible. The only thing impossible was vision.
She waited, and heard movement around her, then plaintive drumming. She was blind, but she was alive, and others had survived alongside her.
There was work to do; she had to learn everything about the new situation. She called out to her team-mates, "Can someone tell me if the light is gone?"
Haf said, "I have some interesting news."
Roi put down her template frame.
"There's rock in our orbit," he announced. "I think we should stay here, or at least close by."
"Rock? What do you mean?"
"The void-watchers can see it with their light-gatherers. Pieces of rock, orbiting the Hub."
"You mean. other Splinters?"
Haf hesitated. "I don't think so. The shape's not the same. And the rock isn't exactly like our rock."
Roi let the puzzling news sink in. No mythical cousins, but that had always been a fanciful notion. To have rock, or something like it, not far away might be useful. She had no idea how they would reach it, but she was sure Haf would find a way eventually.
The death of the Wanderer had replenished the Incandescence, thickening it to the point that they were threatened not with famine but corrosion from the wind. They had reopened the tunnels and started moving out again, searching for the right balance. They had reached a point where the wind was not too strong but the crops would still be plentiful, and now they had this unexpected boon.
"I agree," she said. "We should stay here."
The Wanderer had killed a third of their people, and blinded another third. Bard, Cho, Ruz, Nis, Tio and Jos were all gone. Nobody understood what had happened, what had given the Wanderer's disintegration such force. Perhaps in a dozen generations someone would find a way to explore such mysteries; there might yet be something simple beneath it all.
Haf mused, "Rock's a good start, but I really don't think it will do for the wall."
"What wall?" Roi knew exactly what he was talking about, but she enjoyed teasing him.
Haf rasped annoyance. "The Hub is a dangerous place. Once we've left it behind, nobody should get close to it ever again. If they come this way we should send them back, the way you guide a hatchling away from danger: just pick them up and tur
n them around."
Roi chirped with delight. "First a wall, and now. what? A great machine for herding hatchlings who are hurtling through the void! Do you know how many spans it is around the Hub? In thirty-six times thirty-six generations, we could never build anything that began to do what you describe."
"Perhaps you're right," he conceded, but he didn't sound the least bit sincere.
She heard him approach and pick up one of her frames.
"Can I check your calculations?" he asked.
"That would be good."
The Wanderer's death-throes had given their orbit some elevation again: a return to light and dark, she'd been told, and a chance to see out into the void once more. She had been calculating a manoeuvre that she hoped they could perform with the tunnels to maintain the tilted orbit indefinitely. The opportunity to look out at their surroundings was too precious to lose again.
Haf worked in silence. Roi listened to the clicking of his claws against the stones, and felt herself drifting into sleep.
Afterword
The "weight and motion" of objects in the Splinter follow from Einstein's theory of general relativity; many of the effects described also occur in Newtonian gravity, but observations within the Splinter are sufficient to discriminate between the two theories. The best general reference on this subject is:
Gravitation by C. W. Misner, K. S. Thorne and J. A. Wheeler,
W. H. Freeman, New York, 1970.
The most comprehensive treatment of the particular space-time geometries discovered by the protagonists is:
The Mathematical Theory of Black Holes by S. Chandrasekhar,
Oxford University Press, Oxford, 1992.
"Zak's principle" is essentially Einstein's equation in a vacuum, that is, the version that applies when the matter in your immediate vicinity has no significant gravitational effect. The general equation, which allows for the presence of matter, is described in terms that are almost as simple in this excellent account:
"The Meaning of Einstein's Equation" by John C. Baez and
