The realisation that our small planet is only one of many worlds gives mankind the perspective it needs to realise sooner that our own world belongs to all its creatures.

I don't believe in astrology; I'm a Sagittarius and we're skeptical.

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.

I sometimes think that the universe is a machine designed for the perpetual astonishment of astronomers.

When I start on a book, I have been thinking about it and making occasional notes for some time... So I have lots of theme, locale, subjects and technical ideas... I don't worry about long periods of not doing anything. I know my subconscious is busy.

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]

One of the great tragedies of mankind is that morality has been hijacked by religion.