Greg Egan - Incandescence

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 turn 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.

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

Emory F. Bunn,

Some events in this novel depend on the detailed behavior of the plasma accretion disks that are present around black holes, and several aspects of this subject remain uncertain. For example, precisely if and when an accretion disk with given physical characteristics would be forced to lie in the equatorial plane of a rotating black hole (a phenomenon known as the Bardeen-Petterson effect) is a matter of controversy, because determining this theoretically depends on complex computer simulations, and direct observational data is inconclusive. See, for example: