Haley stared at him stupefied.

“Can’t you understand?” the doctor went on. “You know that space, our ordinary three-dimensional space which makes up our cosmos, is not infinite but finite — is curved in a fourth dimension. It is so curved back on itself that it forms a great sphere, floating in the four-dimensional abyss.

“And you must know, too, that spherical space is expanding, stretching out like a great bubble being blown up. Why, Eddington and De Sitter and all those other old scientists of five hundred years ago knew that. The bubble of our space has expanded like that for ages and it has been getting too big! It has got so big, the strain on it so great, that now it is about to burst!”

DOCTOR RIDER’S thin face was colorless and his hands were trembling violently as he continued.

“I made this trip outside the Solar System in the Pioneer so that out here, away from the distorting gravitational forces of the sun, I could study this space strain. I’ve been studying it during all our outward trip.

"My observations and calculations show infallibly that the strain of expansion has become so great that our spherical continuum of space is going to pop like a breaking balloon. Space will be ripped to fragments at any moment, and those fragments will henceforward be separated from each other by a four-dimensional gulf in which there is no space!”