“It’s just like the last stop,” Emma said. “As if nothing will ever change again.”

“Not true,” Cornelius said. “But this far downstream, the river of time is flowing broad and smooth—”

“Down to a sunless sea,” Emma said.

“Yes. But there is still change, if only we could perceive it.”

The camera tipped up, away from the asteroid, and the softscreen filled up with black sky. At first Emma saw only darkness, unrelieved. But then she made out the faintest of patterns: charcoal gray on black, almost beyond her ability to resolve, a pattern of neat regular triangles covering the screen.

When she blinked, she lost it. But then she made out the pattern again. Abruptly it blurred, tilted, and panned across the screen.

Now the triangles showed up pinkish white, very blurred but regular, a net of washed-out color that filled space.

“The firefly is using false color,” Cornelius said.

The pattern slid across the screen jerkily as the remote firefly panned its camera. And beyond the net Emma saw a greenish surface, smoothly curved, as if the netting contained something.

“It must cut the universe in half,” Emma said.

More of the framework slid through the screen, blurring as the camera’s speed outstripped the software’s ability to process the image.

“It looks like a giant geodesic dome,” Malenfant said.

Cornelius said, “I think it is a dome. Or rather, a sphere. Hundreds of thousands of light-years wide. A net. And there’s only one thing worth collecting, this far downstream.” He pointed to the complex, textured curtain of greenish light visible through the interstices of the dome. “Look at that. I think we’re seeing black hole event horizons in there. Giant holes, galactic super-cluster mass and above. They are orbiting each other, their event horizons distorting. I think the holes have been gathered in there, deliberately. They are being merged, in a hierarchy of more and more massive holes. I imagine by now the down-streamers can manage hole coalescence without significant energy loss.”

“How the hell do you move a black hole? Attach a tow rope?”

Cornelius shrugged. “I don’t know. Maybe you use Hawking radiation as a rocket. The details hardly matter. The dome seems to be an energy collector. Like a Dyson sphere. Anything still alive must be living on those struts, feeding off the last free energy: the slow Hawking radiation of the black holes. But it’s a damn thin trickle.” He glanced at his softscreen. “We can postulate strategies for survival. Maybe they eke out their dilute resources by submitting to long downtimes: hibernation, slow computation rates, stretching an hour of awareness across a million years…”

Perhaps, Emma thought. Or perhaps they are conscious continually even now, in this ruin of a universe. Frozen into their black hole cage, unable to move, trapped like Judas in the lowest circle of Hell.

Cornelius said, “It may seem strange to you how much we can anticipate of this remote time. But the downstreamers are walled in by physical law. And we know they will have to manage their black hole resources. The supercluster holes are the largest to have formed in nature, with masses of maybe a hundred trillion suns. But even they are evaporating away.

“So they have to harvest the holes. If you combine two holes you get a more massive hole—”

“Which will be cooler.” Malenfant nodded. “It will evaporate more slowly. So you can stretch out its lifetime.”

“They’re probably coalescing holes in hierarchies all over the reachable universe. This site, immense as it is, might be just a rung on the ladder.

“The engineering details are tricky. You have to bring the holes together fast enough that they don’t evaporate away before you’ve harvested them. On the other hand it mustn’t be so rapid that you form a hole so huge it evaporates too slowly and you are starved of usable energy… Remarkable,” Cornelius breathed, staring at the dim, ghostly images. “To think that mind has now encompassed the universe — that the future evolution of the universe actually depends on conscious choices — made by our descendants.”

Cooperation, Emma thought, spanning a universe, projects lasting millions, even billions of years. Whatever these people

have become, she thought, they are not human.

“Oh, Jesus. Look at that.”

Emma turned back to the screen, where Malenfant was staring.

Across a broad circular region the geodesic network was disrupted. It looked as if some immense fist had punched through it from the inside, ripping and twisting the struts. The tips of the damaged struts were glowing a little brighter than the rest of the network; perhaps there was some form of repair effort under way.

And beyond the damaged network she could see the event horizons of giant coalescing black holes — each, perhaps, the mass of a supercluster of galaxies or more — the horizons distorted, great frozen waves light-years long visible in their cold surfaces.

“What do you think?” Emma said. “Some kind of breakdown?”

“Or war,” Malenfant said.

“War? Here, so far downstream? That’s insane.”

“Maybe not,” said Cornelius. “These people have responsi-

bility for the whole of the future. They are managing the last

of the universe’s energy resources. With responsibility comes

tension, disagreement. Conflict.”

Malenfant said, “To have come so far, to see this. How depressing.”

“No,” Cornelius said irritably. “We have no idea what kind of minds inhabit these giant structures. They may inhabit hierarchies of consciousness far above us. Their motivations are probably so far removed from ours that we can’t even guess at them—”

“Maybe.” Malenfant growled. “But I’m just a poor H Sap. And if I lived in that dome, I’d want to survive,-no matter how huge my brain was. And it seems to me they are doing a damn poor job.”

Reluctantly, Emma asked, “How far have we come?”

Cornelius studied his softscreens again. “Even the e-systems

are giving up on me now.

“Suppose we’ve taken another scale-factor jump downstream of the same kind of size as last time. That puts us at around ten to power one hundred years remote. What does that mean?” He rubbed his forehead. “To these downstreamers, the early days of their empire — zoom factors often or a hundred or ten thousand back, maybe, when even medium-sized black holes could still exist — those days were the springtime of the universe. As for us, we’re a detail, back in the detail of the Big Bang somewhere, lost in the afterglow.

“Malenfant, I once asked you if you understood, really understood, what it would mean to carry your off-Earth colonization project through to its final conclusion: to challenge eternity. This is what it means, Malenfant. This.

“And the immensity of the responsibility. We have to spread across the universe, make it possible for human descendants of the far downstream to have the power to do this, to survive the winter as long as possible. Because this is the last refuge.”

“But this is a process without limit.” Malenfant frowned. “This is a strategy that offers the prospect of eternal life… doesn’t it?”

“No,” Cornelius said sadly. “At least we don’t think so. There’s a paradox. You have to have some kind of framework, a structure to gather your energy, house your souls.”

“The Disneyland sphere.”

“Yes. The structure grows with time. And even if matter is stable, which it may not be, the structure has to be upgraded, repaired. The maintenance requirements go up with time, because the structure is getting bigger, but the energy available is going down with time.

“It’s a squeeze, Malenfant. And it isn’t possible to win. This black hole management policy is a good idea — the last, best idea — but in the end, it’s doomed to fail.”