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

I want to be remembered most as a writer - one who entertained readers, and, hopefully, stretched their imagination as well.

The exploration of the planets is now closer to us in time than the exploration of Africa by Stanley and Livingstone.

The piece of equipment I'm most found off is my telescope. The other night I had a superb view of the moon.

It is not easy to see how the more extreme forms of nationalism can long survive when men have seen the Earth in its true perspective as a single small globe against the stars.

A man who grows that much hair,' critics were fond of saying, 'must have a lot to hide.

One orbit, with a radius of 42,000 kilometers, has a period of exactly 24 hours. A body in such an orbit, if its plane coincided with that of the Earth's equator, would revolve with the Earth and would thus be stationary above the same spot on the planet. It would remain fixed in the sky of a whole hemisphere ... [to] provide coverage to half the globe, and for a world service three would be required, though more could be readily utilized. (1945) [Predidicting geosynchronous communication satellites]