Attempting to define science fiction is an undertaking almost as difficult, though not so popular, as trying to define pornography... In both pornography and SF, the problem lies in knowing exactly where to draw the line.

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

The inspirational value of the space program is probably of far greater importance to education than any input of dollars... A whole generation is growing up which has been attracted to the hard disciplines of science and engineering by the romance of space.

The only way to define your limits is by going beyond them.

Before the current decade ends, fee-paying passengers will be experiencing suborbital flights aboard privately funded vehicles. . . . It won't be too long before bright young men and women set their eyes on careers in Earth orbit and say: "I want to work 200 kilometers from home-straight up!"

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

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