But the time arrived when they knew they were losing control of their reaction sphere in the sky. The hard radiations increased inexorably in spite of all the coolants they could generate and send aloft. They had to admit that the day would come when they would be destroyed by the very instrument that had given them an extra hundred millenniums of life.
At the end of time—the Xlarnans, pressed against a wall, the reaction sphere, from which came hard radiations, burning them. The ethnic urge to survive in the face of swiftly approaching death. Necessity mothering invention. And then—
The Chronotron....
Electronic envelopes speeding faster than light. Three dimensional nature rejecting the envelope. Only in Time can anything be in two places—along the duration line.
The Chronotron—planting new Cause in the beginning of Effect. And there is alternate time.
Large numbers of Xlarnans, through the Chronotron, back to the beginning of the reaction sphere era, an already advanced race with the course of another hundred thousand years to run before facing the threat from the sky once more.
The first cycle ends, and at the last extremity of alternate time veritable super beings achieve immortality. With immortality, less procreation. And at last, sterility.
Still the deadly threat above them. The daily promise of sudden and complete devastation. Now there are rockets at last, but certain techniques and necessary discoveries in the fields of chemistry and metallurgy elude them. Attempted space flights end in collisions with meteors or death due to radiations in the outer void—but escape velocity never achieved.
Then came—THE THEORY....
Very vague and unidentifiable fossils discovered in astoundingly deep strata. Nothing definite, but a bothersome hint of high development. Hypothesis evolved into theory; Xlarn had known a complete geological cycle before the Beginning, perhaps when the Great Ring around the planet had been a moon! Granted this previous cycle, one might assume a complete evolutionary development. If such a world had existed on Xlarn previously then perhaps some highly intelligent race had evolved. They might have been threatened by some cataclysm in their own time and found a means of getting away from the planet—perhaps even to another solar system!