Obviously, in order to get back to Earth they headed away from it in fleet formation. They pointed their rounded noses toward the Milky Way. The upward course was an application of the principle that made the screen of tin cans and oddments remain about the Platform. Each of those small objects had had the Platform's own velocity and orbit. Thrown away from it, the centers of their orbits changed. In theory, the center of the Platform's orbit was the center of Earth. But the centers of the orbits of the thrown-away objects were pushed a few miles--twenty--fifty--a hundred--away from the center of Earth. The returning space ships also had the orbit and speed of the Platform. They wanted to shift the centers of their orbits by very nearly 4,000 miles, so that at one point they would just barely graze Earth's atmosphere, lose some speed to it, and then bounce out to empty space again before they melted. Cooled off, they'd make another grazing bounce. After eight such bounces they'd stay in the air, and the stubby fins would give them a sort of gliding angle and controllability, while the landing rockets would let them down to solid ground. Or so it was hoped. Meanwhile they headed out instead of in toward Earth. They went out on their steering-rockets only, using the liquid fuel that had not been needed for course correction on the way out. At 4,000 miles up, the force of gravity is just one-fourth of that at the Earth's surface. It still exists; it is merely canceled out in an orbit. The ships could move outward at less cost in fuel than they could move in. So they went out and out on parallel courses, and the Platform dwindled behind them. Night flowed below until the hull of the artificial satellite shone brightly against a background of seeming sheer nothingness. The twilight zone of Earth's shadow reached the Platform. It glowed redly, glowed crimson, glowed the deepest possible color that could be seen, and winked out. The ships climbed on, using their tiny steering rockets. Nothing happened. The ships drew away from each other for safety. They were 50, then 60 miles apart. One glowed red and vanished in the shadow of the Earth. The other was extinguished in the same way. Then they went hurtling through the blackness of the night side of Earth. Microwaves from the ground played upon them--radar used by friend and foe alike--and the friendly radar guided tight-beam communicator waves to them with comforting assurance that their joint course and height and speed were exactly the calculated optimum. But they could not be seen at all. When they appeared again they were still farther out from Earth than the Platform's orbit, but no farther from each other. And they were descending. The centers of their orbits had been displaced very, very far indeed.