"Elegant," said Skatholtz.
"Yeah. Nobody's there to get killed. Control systems in orbit. The atmosphere is fuel and shock absorber both-and the planet is mostly atmosphere. Even when it's off the motor floats high for awhile, because it's full of hot hydrogen compounds. If you let it cool off it sinks, of course, but you can bring it back up to high atmosphere by heating the tube with the laser, firing it almost to fusion. Start the light show again, will you?"
Skatholtz barked something at Krayhayft. Corbell watched: Earth held out, barely. Heat-superconducting cables had to be run to the north polar cap to borrow its cold. The cap melted. Millions died anyway. No children were born; there wasn't shelter for them. It took over a century to drop Uranus into place, six million miles ahead of the Earth in Earth's orbit. The planet accelerated slowly, drawing Earth after it... and then sped up, to leave Earth behind, in a wider orbit. They lost the Moon.
The sun expanded via its own internal heat. Light was reddened, but the greater surface lost more heat to space... to Earth. By now the Girls had charge of Uranus and the floating fusion motor. They moved the Earth again.
Five times the Earth had to be moved. At one time it was circling precisely opposite Mars. Later, further out. Internally Sol's fusion furnace had stabilized; but the photosphere was still growing. And the Earth must be moved a sixth time.
With RNA-augmented intuition Corbell said, "Here's where they have their trouble."
The Earth was too warm. There is a region around any stable sun, a rather narrow band in which an Earthlike world can have Earthlike temperatures. But Sol's ideal temperature band had moved too close to Jupiter. The giant world would have pulled Earth out of orbit- perhaps into a collision course.
Put Earth in orbit around Jupiter itself? But the sun's heat output was leveling off. The Earth would suffer a permanent ice age-unless Jupiter could be made to shine hotter.
"I can't figure that last part," said Corbel. "Run it again."
Krayhayft ran it again. Two nearly identical astronomical scenes divided by a wall across space. Corbell watched Uranus pull away from Earth, drop behind Ganymede and coast outward. Ganymede fell... twice. In one scene it grazed Jupiter, flaring as it passed through the atmosphere a dozen times, and finally decaying in a prolonged burst of hellfire. In the second scene the fleck of light dropped straight in: one flare, and gone.
"Yeah. They tried to be clever," said Corbell. "They thought they were good enough to do a two-shot. They used Uranus to pull the Earth past Jupiter, slowed it to put the Earth in Jupiter orbit, then dropped Uranus deep into the moon system. The idea was to stop Ganymede almost dead in its tracks. Of course the maneuver fouled up a lot of lunar orbits."
"What went wrong?"
"I'm not sure. The Girls wanted a grazing orbit. Instead the moon dropped straight in. But so what?"
Skatholtz made no answer.
It was hard to think. The deep knowledge of giant fusion pulse-jets and Uranus's atmosphere and interstellar war hadn't been in his head until now. It let him understand the history tape, but when he tried to think with the new data it came out all jumbled. Damn Skatholtz anyway: Why should Corbell tell him anything? But the problem fascinated him. The RNA carried that fascination... and Corbell knew it... and couldn't bring himself to care.
"Let's see. Jupiter puts out more heat than it gets from the sun.
That's heat left over from when the planet fell in on itself out of the original dust cloud, four billion years ago-my years. So the planet could hold heat and leak it out for a long, long time. But the energies should be the same no matter what angle the moon fell at."
"This impact, would it cause fusion? Would Jupiter bum?"
"Jupiter's too small to burn like a star. Not enough mass, not enough pressure. But yeah, there'd be a hell of a lot of pressure in the shock wave ahead of Ganymede. And heat."
"Difficult to add up?"
"What?"
Skatholtz said, "The numbers of the heat made by a grazing fall should be simple. They knew the mass of Ganymede and the height of the fall. The Girls could add up just how much hotter Jupiter would become to warm the world just enough. But. The heat made by fusion is too complicated to add. The Girls made their numbers simple with the grazing orbit. Would the heat added be great?"
Corbell was nodding. "Look: The center of Jupiter is compressed hydrogen, really compressed, to where it acts like a metal. Ganymede drops straight in. The fusion goes on in the shock wave, and it adds, it builds up: The continuous fusion explosion makes the shock wave greater and greater. The heat has been leaking out ever since."
"I can't picture this, Corbell. Does it make sense to you?"
"Yeah. They lost a moon, and it killed them. Uranus was on its way into interplanetary space. The Girls couldn't bring it back in time. Their territory was too hot. They tried to take Boy territory."
Corbell became aware that the show had ended. New memories settling in his brain still dizzied him. But he felt like Jaybee Corbel. His personality seemed intact.
Skatholtz said, "Then the new moonlike object is Uranus. Some Girls must have survived. What can we do? We don't have spacecraft. We can't build them fast enough. Corbell, could we use your landing craft?"
"No fuel." Corbell laughed suddenly. "What would you do with a spacecraft? Ram Uranus? Or learn to fly it?"
"You're hiding something."
"I don't believe in your Girls. If they survived this long, they would have done something long ago." Uranus's arrival was too dramatically fortuitous. Such a coincidence had to be explained away; and Corbell had thought of an explanation. Well... try misdirection. "Could they have held out in the Himalayas? There's life in some of the high valleys. They'd be a long time building industry there."
"Your place names mean nothing." Skatholtz helped him stand up. "Can you point out this Himalayas place on a picture of the world? There was one downstairs."
Chapter EIGHT: DIAL AT RANDOM
I
The stairway was a long diagonal across the building's glass face. The bannister jogged to horizontal at six landings; otherwise it ran straight down to the admissions room.
Skatholtz and Krayhayft spat Boyish at each other. Corbell caught some of the exchange: Skatholtz telling the tale as it had come from Corbell, Krayhayft checking it against "tales" memorized over several hundred years of life. There was something Italian in the way their hands jumped and their mouths spat syllables; but their faces were blank. Scared, Corbell thought. The "tales" matched too well.
Corbell tried to set his thoughts in order. He'd been given far too much to assimilate all at once.
Girls could have survived this long. Peerssa had found pockets of life in isolated places. But they would have acted! Unbelievable, that Corbell could have returned just in time for their million-year delayed vengeance.
He had to escape. It had been urgent. It was more urgent now. Could Boys slide down a bannister? Unlikely that they'd ever practiced. But Corbell hadn't practiced recently...
"They were fools," Krayhayft was saying. "They should have chosen several smaller moons to drop one by one."
"You're the fool," Corbell snapped, surprising himself. "It would have taken too long to bring Uranus back each time. It would have fouled up too many orbits. We're talking about a planet ten times as big as the world!"