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]

In fact, one of the arguments for searching for intelligent life in space, elsewhere, is that we have no evidence that intelligence has any survival value. The most successful creatures on this planet are the cockroaches. They've been around, what is it, 100 million years or so and I suspect they'll still be there 100 million years in the future. Maybe intelligence is an evolutionary aberration which dooms its possessors in the way armor may have doomed some of the dinosaurs.

Whether we are based on carbon or on silicon makes no fundamental difference we should each be treated with appropriate respect.

You don't believe in organized religion, yet a major theme in so many of your works seems to be a quest for God.

Isn't killing people in the name of God a pretty good definition of insanity?

The time was fast approaching when Earth, like all mothers, must say farewell to her children.

Once you can reproduce a phenomenon, you are well on the way to understanding it.