Deep beneath the surface of the Sun, enormous forces were gathering. At any moment, the energies of a million hydrogen bombs might burst forth in the awesome explosion.... Climbing at millions of miles per hour, an invisible fireball many times the size of Earth would leap from the Sun and head out across space.

In this single galaxy of ours there are eighty-seven thousand million suns. [...] In challenging it, you would be like ants attempting to label and classify all the grains of sand in all the deserts of the world. [...] It is a bitter thought, but you must face it. The planets you may one day possess. But the stars are not for man.

I have great faith in optimism as a guiding principle, if only because it offers us the opportunity of creating a self-fulfilling prophecy.

Any sufficiently advanced technology is indistinguishable from magic.

I will not be afraid because I understand ... And understanding is happiness.

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.

I am an optimist. Anyone interested in the future has to be otherwise he would simply shoot himself.