"Which hypothesis do you believe?"
"There may be some truth in both," replied Gazen. "The two processes might even go on together. What if meteorites are simply frozen nebula? It is certain that the earth is still growing a little from the fall of meteoric stones, and that part of the sun's heat comes from meteoric fuel. Most of it, however, arises from the shrinkage of his bulk. Five or ten million years ago the sun was double the size he is now. Twenty or thirty million years ago he was rather a nebula than a sun. In five or ten million more he will probably be as Jupiter is now—a smoking cinder."
"And the earth—how long is it since she was crusted over?"
"Anything from ten to several hundred million years. In that time the stratified rocks have been deposited under water, the land and sea have taken their present configurations; the atmosphere has been purified; plants and animals have spread all over the surface. Man has probably been from twenty to a hundred thousand years or more on the earth, but his civilization is a thing of yesterday."
"How long will the earth continue fit for life?"
"Perhaps five or ten million years. The entire solar system is gradually losing its internal heat, and must inevitably die of sheer inanition. The time is coming when the sun will drift through space, a black star in the midst of dead worlds. Perhaps the system will fall together, perhaps it will run against a star. In either case there would probably be a 'new heaven and a new earth.'"
"Born like a phoenix from the ashes of the old," said I, feeling the justice of the well-worn simile.
"I daresay the process goes on to all eternity."
"Like enough."
The sublime idea, with its prospect of the infinite, held us for a time in silence. At length my thoughts reverted to the original question which had been forgotten.