One can imagine a time when men who still inhabit organic bodies are regarded with pity by those who have passed on to an infinitely richer mode of existence, capable of throwing their consciousness or sphere of attention instantaneously to any point on land, sea, or sky where there is a suitable sensing organ. In adolescence we leave childhood behind; one day there may be a second and more portentous adolescence, when we bid farewell to the flesh.

I'm sure we would not have had men on the Moon if it had not been for Wells and Verne and the people who write about this and made people think about it. I'm rather proud of the fact that I know several astronauts who became astronauts through reading my books.

Human judges can show mercy. But against the laws of nature, there is no appeal.

The more wonderful the means of communication, the more trivial, tawdry, or depressing its contents seemed to be.

If we have learned one thing from the history of invention and discovery, it is that, in the long run-and often in the short one-the most daring prophecies seem laughably conservative.

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

Creationism, perhaps the most pernicious of the intellectual perversions now afflicting the American public.