event was taking place out there.
Against the burning stars, Jupiter moved!
Jameson could only gape. The scale of what he was witnessing was almost beyond human grasp.
Slowly, ponderously, the colossal bulk of the planet stirred.
It sloshed.
Across its seething face, a great sluggish tidal wave of thickened hydrogen brimmed over hundreds of miles of atmosphere and lapped in an advancing wall that would have tumbled Earth like a cork.
It stretched.
It no longer was the oblate sphere that man had known since he started looking at it through telescopes. The thing spinning around its waist had given it a flying-saucer shape, a hatbrim of raging hydrogen fighting to pour itself into the circling maw of a gnat.
The gnat had strained and swallowed an elephant. By now, zipping around the captive giant at very nearly the speed of light, the robot probe had converted enough of the stolen hydrogen into Einsteinian mass to tug at the remainder of that tremendous corpse.
Just how much of Jupiter was left? To Jameson, it looked no smaller than before. Perhaps it had lost a few thousand miles of diameter, perhaps not. As its outer layers were stripped away, the rest of that compressed hydrogen, relieved of pressure, would tend to boil and swell. And even with half its bulk gone, Jupiter would still be the most massive object in the solar system other than the Sun itself.
“It won’t be there!” Kay said suddenly. “I just realized that from now on when we look up in the sky at night to find Jupiter, it won’t be there!”
Jameson looked around and was amazed to see tears running down her cheeks. “Sorry,” Kay said. “I’m just tired.”
“It’ll be our turn someday, Kay,” he said. “When we’ve used up everything else, we’ll start using up the planets.”
With trembling hands he swung one, of the stubby ship’s telescopes around in its gimbals and turned on the magnetic lens. The computer-controlled fields flexed transparent plastic, shaped a pool of mercury into a reflecting curve. A picture stirred itself into being on the photoplastic plate behind the eyepiece, held steady by the electronic image compensator.
A Cygnan ship stretched toward him like a claw. It had stopped rotating. The three long spars, with their buckets of life at the ends, spread motionless from the tip of the notched beam of the drive section. As Jameson watched, the buckets swiveled in their wishbone cradles and snapped into place, reversed. He tried to imagine what was happening inside those worldlets. Had the lakes with their queer bright sailboats been drained? Were the animals hushed in their cages, waiting for gravity to resume?
The spars folded inward, swinging through their fifteen-mile arcs. Jameson could see how their triangular cross sections and the three-sided buckets fit into the grooved sides of the starship, just as Pierce had said they would.
He lifted his face from the eyepiece. Jupiter was picking up momentum, like a stone rolling downhill. It moved past the stars, dragging its moons with it.
And us too, if we don’t fire our engines soon, he thought.
He called the observatory and got Maybury. She’d finished her work in the engine room a couple of hours go.
“Are you recording?” he asked.
“Yes, Commander.”
“How fast are they accelerating?”
“One gravity, same as before.”
“Their trajectory. Is it going to be what we figured?”
In the screen, Maybury bit her lip. “It’s too early to tell, Commander.”
“Keep tracking them.” He switched off.
Kay had returned to her console, taking instrument readings with Yeh and feeding questions to the ship’s computer. She looked up as Jameson returned to his seat.
“We’re going to have a lot of borrowed momentum when we break loose from Jupiter,” she said. “We may reach Earth in less than four months.”
Jameson nodded. “The astronomers are going to have a merry time figuring out what all that gravitational displacement will do to the balance of the solar system.”
Kay hesitated. “Tod, will … will the Earth be safe?”
Jameson drew a long breath. “We’ll know for sure in just a couple of days. That’s all the time it will take for them to cross Earth’s orbit.”
Before returning to his cabin to collapse in his bunk, Jameson sought out Maybury in the observatory.
The ship’s engines had been firing steadily for a couple of hours now; Mike and Quent, and the three Chinese fusion techs, were taking turns staying awake to monitor the boron-11 fusion/fission cycle. Maggie had calculated an escape orbit from the death-grip of Jupiter, which was now falling toward the Sun at more than a thousand kilometers a second. Enough maneuvering jets had been unplugged so that Kay had even been able to put some spin on the ring. The ship would live until it got back to Earth.
Provided Earth was still there.
Maybury looked up from a computer console as he entered. Her face looked dreadful: a wan porcelain mask with two great dark holes in it. Her head moved as though her neck had gone stiff.
“Still working?” he said.
“I thought I’d just set up some hypothetical programs to calculate gravitational stresses for Earth using various trajectories for Jupiter.”
“You don’t have to stay awake for that. There’s not a damn thing anybody can do to change things.”
“I know. It’s just something to do.”
He settled down in a seat next to her. With the engines firing, he had almost two pounds of weight.
“I found out where the two humanoids came from.”
She was all attention. “Where?”
“61 Cygni.”
She nodded slowly. “It could be. It’s roughly in the line of flight from Cygnus X-1.”
“And it’s
“That’s right. Eleven point two light-years away. There are only a dozen stars that are closer to us.”
“If Dr. Ruiz’s theory was correct…” He stopped till the pain disappeared from her face. “Then that must have been the Cygnans’ last stop before they headed for Earth. Our feathery zoo mates were the Cygnans’ most recent acquisition before us.”
“But 61 Cygni was never considered to be a prime candidate for life.”
“It is now.”
“It’s a double star, actually. The two suns are a K5 and a K7. Very weak. About six percent of the luminosity of our own sun. There wouldn’t be much of a biosphere for habitat planets. Are you sure you understood the humanoids correctly?”
“61 Cygni has a third component,” he prompted her.
“But it isn’t a star,” she said. “It’s a nonluminous body. A planet. Actually, one of the first extra-solar planets to be discovered. It’s a superjovian, with a mass about twelve times Jupiter’s. It…” She stopped. “Oh.”
“Exactly.”
She swiveled back to the computer console so quickly that Jameson had to press her shoulder to push her back in her seat. Her hands scrabbled over the keys. Words tumbled out of her as she worked. “Dr. Ruiz transferred big chunks of the Farside computer’s astronomical library to the ship’s memory before we left Earth. He wanted to be sure we had updated data. The third component of 61 Cygni was discovered over a hundred years ago when they noticed some irregularities in the proper motion of the binary. They started to discover a lot of extrasolar superjovians that way about then—most of them among the closer stars, of course. But nobody keeps tabs on them much any more. They get surveyed every few years in the automated sky sweeps, and if anybody wants to pull data out of the record for a graduate paper or anything, they can. Here we are. A check was made on it about five years ago, and then another just about a month before we launched this mission.”
