The entire sweep of human history from the dark ages into the unknown future was considerably less important at the moment than the question of a certain girl and her feelings toward him.

If such a thing had happened once, it must surely have happened many times in this galaxy of a hundred billion suns.

It was the mark of a barbarian to destroy something one could not understand.

We seldom stop to think that we are still creatures of the sea, able to leave it only because, from birth to death, we wear the water-filled space suits of our skins.

We always thought the living Earth was a thing of beauty. It isn’t. Life has had to learn to defend itself against the planet’s random geological savagery.

Many, and some of the most pressing, of our terrestrial problems can be solved only by going into space. Long before it was a vanishing commodity, the wilderness as the preservation of the world was proclaimed by Thoreau. In the new wilderness of the Solar System may lie the future preservation of mankind.

After their encounter on the approach to Jupiter, there would aways be a secret bond between them---not of love, but of tenderness, which is often more enduring.