A World Out of Time

10 to the power 23 tons of hydrogen and hydrogen-compound ices were aimed to strike the sun at solar-escape velocity. Earth's oceans would boil...

The State did what it could. Tens of thousands of fusion bombs, Sol system's entire armory, were set off at the dawn side of Persephone, just above the atmosphere. A thick rind of the planet's atmosphere peeled away and streamed off like a comet's tail, its mass pulling at Persephone's dense core. A streamer of gas far more massive than the Earth broke free, and rounded the sun, and sprayed back toward the cometary halo.

If the bombs could have been placed earlier, Persephone's core would have done the same. It was rock and iron, yellow-hot, and it glowed X-ray hot as it streaked into the solar photosphere and disappeared.

The sun grew bright.

Oceans shrank, crops withered, tens of millions died before the State could place a disk of reflecting tinsel between Earth and Sol. It was a temporary measure. The sun's new heat was permanent, at least on the human scale of time. Fusion would run faster in Sol's hotter interior. The buried heat would leak to the photosphere and out.

The State had one chance for survival. It could move the Earth by the method Farside had used to stop Persephone cold in its orbit.

"Do you understand what you're seeing?"

Corbell made a shushing gesture. "Yeah."

"Good. We were afraid. The light show and the bottled memory are both very old. They date from the end of the rule of the Girls. They have been stored in zero-time for... perhaps a hundred thousand years, perhaps more. We feared they must have decayed," said Skatholtz.

"So you tried it on me." But his anger seemed impersonal, remote.

The State had had to abandon the Mercury mines: a serious industrial handicap. Nonetheless they were building something out there in the asteroid belt-something huge, like a starship big enough to carry the whole human race to safety. But no, that wasn't it. Corbell was fascinated. He knew it might be the memory RNA, but he was fascinated anyway. He hardly heard what Skatholtz was saying: "It was sensible, Corbell. The Girls who made the light show ruled the sky. You are familiar with such things. Do you know now who hurled a moon at us?"

"Not yet. Shut up and let me..."

They had finished the thing. Two tubes, concentric, each a hundred miles long; the i

Corbell said, "How do you climb down off an elephant?"

"Should I know that?"

"You don't climb down off an elephant. You climb down off a duck."

"Why?"

"It's so much safer. How do you move the Earth?"

Small wonder if the light show meant little to Skatholtz. Watching the construction of the motor-in the naked sunlight and sharp-edged, totally black shadows of space-was bewildering. The diagrams made sense to an architect, but they were only rotating lines to Skatholtz. But without bottled memory and without Corbell's career in space, Skatholtz was still bright enough to make some sense of what he was seeing.

"You move something else," Skatholtz said. "The damage done by the rocket's thrust and by mistakes you might make will not kill anyone if nobody lives on the working body. Then the working body can be moved until the world falls toward it as a rock falls to the ground. What was the working body? Ganymede?"

"Uranus. Can you stop the light show at that picture?"

The lecture froze on an "artist's conception": a blurred, curved arc of Uranus's upper atmosphere. The motor looked tiny floating there. Corbell said, "You see? It's a double-walled tube, very strong under expansion shock. It floats vertical in the upper air. Vents at the bottom let in the air, which is hydrogen and methane and ammonia, hydrogen compounds, like the air that the sun burns. You fire laser ca

"I don't understand all your words. Fusion?"

"Fusion is the way a star burns. You probably used fusion bombs against the Girls."

"Okay. The hydrogen fusions in the middle of the motor-"

"-and the explosion goes out and up. It's hottest along the axis, cooler when it reaches the walls of the motor. The whole mass blasts out the top, through the flared end. It has to have an exhaust velocity way higher than Uranus's escape velocity. The motor goes smashing down into deeper air. You see there's a kind of flared skirt at the bottom. The deep air builds up there at terrific pressure, stops the tube and blasts it back up. You fire it again."

"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."