Don't mess up the environment until you're quite sure what you're doing.

Training was one thing, reality another.

I think in the long run the money that s been put into the space program is one of the best investments this country has ever made . . .This is a downpayment on the future of mankind. It's as simple as that.

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]

... chemistry is a trade for people without enough imagination to be physicists.

Some dangers are so spectacular and so much beyond normal experience that the mind refuses to accept them as real, and watches the approach of doom without any sense of apprehension. The man who looks at the onrushing tidal wave, the descending avalanche, or the spinning funnel of the tornado, yet makes no attempt to flee, is not necessarily paralyzed with fright or resigned to an unavoidable fate. He may simply be unable to believe that the message of his eyes concerns him personally. It is all happening to somebody else.

Many, and some of the most pressing, of our terrestrial problems can be solved only by going into space. Long before it was a vanishing commodity, the wilderness as the preservation of the world was proclaimed by Thoreau. In the new wilderness of the Solar System may lie the future preservation of mankind.