“Right. That’s the Schwarzschild solution to Einstein’s equations. Spherically symmetric—”
“But if you spin the hole, things get more complicated.” It was called the Kerr-Newman solution. “The event horizon retreats in, a little way. And outside the event horizon there is another region, called the ergosphere.”
The ergosphere cloaked the event horizon. It touched the spherical horizon at its poles, but bulged out at the equator, forming a flattened spheroid.
“The greater the spin, the wider the ergosphere,” Gage said. “The hole ahead is four miles across. It’s spinning so fast that the depth of the ergosphere at the equator is a hundred and forty yards.”
Mackenzie looked thoughtful. “So?”
“We can’t enter the event horizon. But we could enter the ergosphere, or clip it, and get away safely.”
“Um. Inside the ergosphere we would be constrained to rotate with the hole.”
“That’s the plan. I want to flyby, clipping the ergosphere, and slingshot off the black hole.”
Mackenzie whistled. Pixels fluttered across her face, as she devoted processing power to checking out Gage’s proposal. “It could be done,” she said eventually. “But we would have a margin of error measured in yards. It would require damn fine piloting.”
“I’m a damn fine pilot. And we can take a lot of stress, remember.” It’s not as if we have to protect anyone living.
“Why do you want to do this?”
“Because,” Gage said, “the missile will follow me through the ergosphere. But after we’ve passed through, the hole will have been changed. The missile won’t be able to work out how…”
“We’ll have to get consent to this from the others. The eighty—”
“Come on,” Gage said. “Most of them have retreated into their own Virtual heads. There’s hardly anybody out here, still thinking, save you and me.”
Slowly, Mackenzie smiled.
For Gage’s scheme to work, the speed of Chiron would have to be raised much higher. When Chiron flew by the hole it would need an angular momentum comparable to that of the hole itself. So the drones ravaged Mackenzie’s frozen ocean, hurling the stuff of Chiron into the GUTdrives.
Chiron approached the lightspeed limit asymptotically.
By the time the hole approached, Chiron’s effective mass had reached about a tenth of the Sun’s. For every second passing in its interior, a hundred years wore away outside.
Ahead of her, the radiation from the black hole’s accretion disc was Doppler-shifted to a lethal sleet. Massive particles tore through the neural nets which comprised her awareness. She felt the nets reconfigure, healing themselves; it was painful and complex, like bone knitting.
Behind her the redshifted emptiness was broken only by the patient, glowering spark of the Squeem missile.
The black hole was only seconds away. She could make those seconds last a Virtual thousand years, if she wished.
In these last moments, she was assailed by doubt. Nobody had tried this maneuver before. Had she destroyed them all?
Gage let her enhanced awareness pan through the bulk of Chiron. Years of reaction-mass plundering had reduced the ice dwarf to a splinter, but it would survive to reach the lip of the black hole — and so would its precious cargo, the awareness of eighty downloaded humans, the canister containing their clutch of frozen zygotes. That canister felt like a child, inside her womb of ice.
Enough.
She reduced her clock-speed to human perception. The black hole flew at her face—
The misty giant companion star ballooned over Gage’s head, its thin gases battering at her face.
Chiron’s lower belly dipped fifty yards into the ergosphere. The gravitational pull of the hole gripped her. It felt like pliers in her gut. She was hurled around; she was a helpless child in the grip of some too-strong adult. The fabric of Chiron cracked; Solar System ice flaked into this black hole, here on the edge of the Galaxy, flaring X-radiation as it was crushed.
Then the gravity grip released. The hole system was behind her, receding. The pit dug in spacetime by the hole’s mass felt like a distant, fading ache.
She watched the patient GUTspark of the Squeem missile as it approached the hole. It matched her path almost exactly, she saw with grudging admiration.
The missile grazed the lip of the hole. There was a flare of X-radiation.
The GUTspark was gone.
It’s worked. By Lethe, after all these years, it’s worked.
Suddenly Gage felt utterly human. She wanted to cry, to sleep, to be held.
Cydonia, her home arcology, was an angular pyramid, huge before her, silhouetted against the light of the shrunken Sun. The ambient Martian light was like a late sunset, with the arcology drenched in a weak, deep pink color; against its surface its windows were rectangles of fluorescent light glowing a harsh pearl gray, startlingly alien.
Her boots had left crisp marks in the duricrust.
Gage wasn’t nostalgic, usually, but since the hole flyby she had felt the need to retreat into the scenes and motifs of her childhood.
Moro and Mackenzie met her on this simulated Martian surface.
“It was simple,” she said.
Mackenzie smiled.
Moro growled. “You’ve told us.”
“We took so much spin from the black hole that we almost stopped it rotating altogether. It became a Schwarzschild hole. Without spin, its event horizon expanded, filling up the equatorial belt where the ergosphere had been.”
Chiron had clipped the ergosphere safely. The missile, following Chiron’s trajectory exactly, had fallen straight into the expanded event horizon.
The long chase was over.
“I guess the missile wasn’t an expert on relativistic dynamics after all,” Mackenzie said.
“But we’re not so smart either,” Moro said sourly. “After all we’re still falling out of the Galaxy — even faster than before the hole encounter, in fact. A million years pass for every month we spend in here; we might be the only humans left alive, anywhere.” He looked down at his arms, made the pixels swell absurdly. “If you can call this life. And we don’t have enough reaction mass left to slow down. Well, space pilot Gage, where are we heading now?”
Gage thought about it. They could probably never return to their home Galaxy. But there were places beyond the Galaxy, massive stars and black holes that a pilot could use to decelerate, if she was smart enough.
And if they could find a place to stop, they could rest. Maybe Gage’s awareness could be loaded back into some flesh-and-blood simulacrum of a human form. Or maybe not; maybe the role of Gage and the rest would simply be to oversee the construction of a new world fit for her child, and the other frozen zygotes.
She smiled. “At this speed, we’ll be there in a couple of subjective months.”
“Where?”
“Andromeda…”
Even under the oppressive Squeem occupation, humans learned much.
They learned, for example, that much of the Squeem’s high technology — their hyperdrive, for instance — was not indigenous. It was copied, sometimes at second or third hand, based on the designs of an older, more powerful species…
“It was the first time,” Eve said, “that the name ‘Xeelee’ entered human discourse.”
I shuddered.
The Xeelee Flower
I still get tourists out here, you know. Even though it’s been so long since I was a hero. But then, I’m told, these days the reopened Poole wormholes will get you from Earth to Miranda in hours.