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.

Going out, naturally, the ships had lost angular speed as they gained
in height. Descending, they gained in angular velocity as they lost
height. They were not quite 30 miles apart as they sped with increasing,
headlong speed and rushed toward the edge of the world's disk. When they
were only 2,000 miles high, the Earth's surface under them moved much
faster than it had on the way up. When they were only 1,000 miles high,
the seas and continents seemed to flow past like a rushing river. At 500
miles, mountains and plains were just distinguishable as they raced past
underneath. At 200 miles there was merely a churning, hurtling surface
on which one could not focus one's eyes because of the speed of its
movement.

They missed the solid surface of Earth by barely 40 miles. They were
moving at a completely impossible speed. The energy of their position
4,000 miles high had been transformed into kinetic energy of motion. And
at 40 miles there is something very close to a vacuum, compared to
sea-level. But compared to true emptiness, and at the speed of meteors,
the thin air had a violent effect.

A thin humming sound began. It grew louder. The substance of the ship
was responding to the impact of the thin air upon it. The sound rose to
a roar, to a bellow, to a thunderous tumult. The ship quivered and
trembled. It shook. A violent vibration set up and grew more and more
savage. The whole ship shook with a dreadful persistence, each vibration
more monstrous, more straining, more ominous than before.

The four in the space ship ca