Incandescence

Parantham said, "It wouldn't have had much of a head start, though, before all the rocks came tumbling after it. Collisions between the debris would redistribute its momentum, creating some fragments that would outrace the pack. You couldn't avoid a serious peppering, at the very least."

"I suppose they could have made more than one ark, to improve the odds," Rakesh suggested. "The others might have been destroyed by debris, or captured by the neutron star."

Parantham let out a long, reproachful moan. "Captured by the neutron star?"

Rakesh was bemused. "You don't think that's possible?"

"Of course it's possible. And that's exactly what they wanted! This one's the failure, the one that was left behind!"

"How is it a failure to get left behind?"

"The giants' stellar wind," she said, "has a greater energy density than middle-aged starlight, but there's something that would give it even more oomph: the gravitational field of a neutron star. The neutron star would have drawn the wind into an accretion disk around it, far richer in energy than anything else in sight. The Arkmakers saw this monster coming, and thought: if it's going to pulverize our home, better to learn to drink from that whirlpool than skulk around in the ruins waiting for the next disaster.

"This ark, and everything in it, was designed to survive in an accretion disk. The asymmetrical flow-through would have given it a kind of buoyancy, pushing it back out into larger orbits if it ever sank in too deep." Parantham ran a model, and piped the output to Rakesh. "The wind in the disk would have been strong enough to keep the fungus alive almost everywhere, to support the food chain throughout the ark."

Rakesh absorbed the model's results. Parantham's conclusions were hard to dispute.

"So this place was starved from the beginning?" he said. "When they missed the neutron star, they had no hope?" The children of the Arkmakers, designed to escape the fate of their planet-bound parents, had found themselves stranded with the wrong biology, trapped inside an ingenious machine for extracting energy from an exotic new source that was receding into the distance at a few hundred kilometers a second.

Parantham said, "No hope for themselves. But I can't believe this was the only ark. There could have been a dozen, there could have been a thousand. If they really saw no prospect of fleeing from the neutron star, every resource on the planet would have been used to maximize the chances of hitching a ride."

Rakesh looked around at the ruins of this desperate strategy, and tried to picture the same tunnels teeming with life while the hot wind from a neutron star's accretion disk whistled through the walls. Perhaps the extraordinary gamble could have paid off, if they'd repeated it a sufficient number of times.

"If they hitched a ride, where did it take them?" Rakesh asked. When he and Parantham had first realized what it was that had created the asteroid belt, they had run dynamical models and checked the maps, but they'd been unable to locate the neutron star that had done the deed. The only thing that had been clear was the general direction of its motion.

"Toward the center," Parantham replied. "Deeper into the core."

12

As the work team gathered in the Calculation Chamber, Roi caught sight of Neth and proclaimed hopefully, "Sixth time brings success!"

"Sixth?" Neth replied. "Surely this is the third?"

"It's one task to frame a hypothesis, then another to test it," Roi insisted. "So that's six separate acts."

Neth was too polite to object, and perhaps too serious to understand that Roi was only joking. If the proverb was worth anything, it certainly wasn't worth taking literally. It did encourage persistence, though, and Roi had a feeling that their persistence was finally going to be rewarded.

Since Neth's discovery that orbits around the Hub might become unstable, a dozen or so members of Zak's original team had left to educate hatchlings into the secrets of weight and motion, and a dozen more had headed for the sardside, with the even more ambitious aim of recruiting a new team to build Bard's tunnel. The task of those who remained was to find a geometry for space and time that satisfied Zak's principle, in the hope of learning more about the dangers the Splinter would face in the future.

Tan had refined his ideas for characterizing geometry to the point where he could calculate the natural paths — the closest things to straight lines — on any curved surface. The vital step that remained, though, was to find the correct way to move from the geometry of space alone to a version that included time.