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 cabin knew torture. Weight returned to them, weight more violent than the six gravities they had known for a bare fourteen seconds at take-off. But that, at least, had been smoothly applied. This was deceleration at a higher figure yet, and accompanied by the shaking of bodies which weighed seven times as much as ever before--and bodies, too, which for weeks past had been subject to no weight at all. They endured. Nothing at all could be done. At so many miles per second no possible human action could be determined upon and attempted in time to have any effect upon the course of the ship. Joe could see out a quartzite port. The ground 40 miles below was merely a blur. There was a black sky overhead, which did not seem to stir. But cloud-masses rushed at express-train speed below him, and his body weighed more than half a ton, and the ship made the sound of innumerable thunders and shook, and shook and shook.... And then, when it seemed that it must fly utterly to pieces, the thunder diminished gradually to a bellow, and the bellow to a roar, and the roaring.... And the unthinkable weight oppressing him grew less. The Earth was farther away and moving farther still. They were 100 miles high. They were 200 miles high.... There was no longer any sound at all, except their gaspings for breath. Their muscles had refused to lift their chests at all during the most brutal of the deceleration period.