The camera image swept away from the beach ball, away from the blank liquefied ground, and swept the sky.
Malenfant pointed. “What the hell is thatT
It was a blur of gray-red light in an otherwise empty sky. The firefly switched to infrared, and Cornelius cleaned up the image. Emma saw a rough sphere, a halo of motes of dim light that hovered, motionless, around—
Around what? It was a ball of darkness, somehow darker even than the background sky. It looked about the size of the sun, seen from Earth; the motes were like dimly glowing satellites closely orbiting a black planet.
Cornelius sounded excited. “My God. Look at this.” He magnified the image, picking out a point on the rim of the central ball, enhancing as he went.
Emma saw rings of red light running around the rim, parallel to the surface.
“What is it?”
“Gravitational lensing. Bent light. That means… It must be…” He scrolled through expert system interpretations, speed-reading. “We’re looking at a black hole. A giant.
“This is probably the remnant of a supercluster. Just as what’s left of a Galaxy after star evaporation collapses into the central hole, so galactic clusters will collapse in turn, and then the superclusters.
“That hole might have a mass of anything from a hundred trillion to a hundred thousand trillion solar masses, an event-horizon radius measured in hundreds of light-years.”
“I don’t understand,” said Emma. “Where did the Galaxy go?”
“Our Galaxy hole was surely carried to the heart of the local galactic cluster black hole, and then the supercluster.”
“And we were dragged along with it.”
“If it’s a hole it has no accretion disc,” Malenfant said.
“Malenfant, this thing is ancient. It ate up everything a hell of a long time ago.”
“So how come those motes haven’t been dragged down?” Malenfant said.
“Life,” Emma said. “Even now. Feeding off the great black holes. Right?”
“Maybe,” Cornelius said, grimly. “Maybe. But if so they aren’t doing enough. Even gravity mines can be exhausted.”
“Hawking radiation,” Malenfant said.
“Yes. Black holes evaporate. The smaller the hole, the faster they decay. Solar mass holes must have vanished already. In their last seconds they become energetic, you know. Go off with a bang, like a nuke.” He smiled, looking tired. “The universe can still produce occasional fireworks, even this far downstream. But ultimately even this, the largest natural black hole, is going to evaporate away. What are the downstreamers going to do then? They should be planning now, working. There will be a race between the gathering and management of energy sources and the dissipative effects of the universe’s general decay.”
Malenfant said, “You’d make one hell of an after-dinner speaker, Cornelius.”
The camera had panned again, and it found the Sheena in her beach ball.
“I think her movements are getting labored,” Emma said.
Cornelius murmured, “There’s nothing we can do. It’s cold out there, remember, in the far downstream. Her heater will surely expire before long. Maybe she won’t even suffocate.”
They watched in silence.
Sheena’s firefly, tethered to the beach ball, jerked into motion. It floated toward Emma’s viewpoint, across the eerily smooth surface of the liquefied asteroid.
It drifted to a halt and reached out with a grabber arm to touch its human-controlled cousin. In the softscreen image, the arm was foreshortened, grotesquely huge.
Then the firefly turned and drifted out of shot, toward the portal, towing the beach ball.
“Onward,” Emma whispered.
Another transition, another blue flash.
The camera performed a panorama, panning through a full three hundred and sixty degrees. The portal, a glaring blue ring still embedded in the asteroid ground, slid silently across the softscreen. There was the Sheena’s bubble, resting on the surface, lit only by the robot’s lights and by the soft blue glow of the portal itself. The Sheena tried to swim, a dim dark ghost behind the gold. But she fell, languidly, limbs drifting.
And then, beneath a black sky, there was only the asteroid surface, smooth: utterly featureless, rubbed flat by time.
“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.”