Air poured out with a rush when he opened the stop-cock. There was two thousand pounds pressure to begin with. The tank had been in unshielded sunshine for more than an hour. The effective pressure of the air had tripled, at least, because of its rise in temperature. It made a rocket jet of gas. McCauley could feel its quick, sharp tug at him.
It went empty.
He put it under his feet and gave it the most violent of thrusts toward the Milky Way. Now he could see that he had given the discarded things all the momentum that had carried him away from the Platform, plus all he had taken from Sammy Breen. He was moving toward the Platform. It no longer dwindled as time went by. It grew in size with an intolerable, incredible slowness. But that slowness amounted to doom.
"You're headed back," said Randy's agonized voice in his helmet phones. "But it's slow, Ed! It's desperately slow!"
The blackness, which was Earth's own shadow cast upon its night-side surface, was now fully halfway from the rim of the world toward that halfway point which was the middle of the space that Earth occupied within the cosmos.
"There's about fifteen minutes left before totality," said McCauley with deliberation. "I've one more thing I can throw away. But I need to steer with it too, and I can't be accurate at this distance. I don't dare to use it from so far away. I've no space rope left to throw for you to catch. I have to throw that last thing away at the very last instant."
He heard confused sounds. Sammy Breen, back at the Platform, made incoherent noises. He probably gesticulated, because Randy understood.
"Yes," said Randy's voice harshly. "Make it quick. But take care! More than your own life depends on your being careful now!"
Sammy Breen gulped. McCauley heard him. Then silence again.
It was necessary to wait. McCauley was a tiny, glistening object in emptiness, a desperately long way from the equally glistening Platform. He turned slowly, foolishly, as he floated. Away off against a background of stars—but the sun moved momentarily nearer its edge—there was a shape that now was not quite half of a circle of brilliant light, and more than half of a circle of darkness like that of the Abyss. It did not look like Earth. It had not the least appearance of a world in which human beings lived and moved and breathed and loved and died. It was a monstrosity whose details changed their shape as half minutes and quarter minutes went by. And continually and implacably the darkness spread over more of it.