Space can be mapped and crossed and occupied without definable limit; but it can never be conquered.

The best measure of a man's honesty isn't his income tax return. It's the zero adjust on his bathroom scale.

It may be that the old astrologers had the truth exactly reversed, when they believed that the stars controlled the destinies of men. The time may come when men control the destinies of stars.

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.

Two possibilities exist: Either we are alone in the Universe or we are not. Both are equally terrifying.

The moon is the first milestone on the road to the stars.

I don't think there is such a thing as as a real prophet. You can never predict the future. We know why now, of course; chaos theory, which I got very interested in, shows you can never predict the future.