The Earth faces environmental problems right now that threaten the imminent destruction of civilization and the end of the planet as a livable world. Humanity cannot afford to waste its financial and emotional resources on endless, meaningless quarrels between each group and all others. there must be a sense of globalism in which the world unites to solve the real problems that face all groups alike.

At two-tenths the speed of light, dust and atoms might not do significant damage even in a voyage of 40 years, but the faster you go, the worse it is--space begins to become abrasive. When you begin to approach the speed of light, hydrogen atoms become cosmic-ray particles, and they will fry the crew. ...So 60,000 kilometers per second may be the practical speed limit for space travel.

[O]ur statesmen, our businessmen, our everyman must take on a science fictional way of thinking.

An atom-blaster is a good weapon, but it can point both ways.

It is the obvious which is so difficult to see most of the time. People say 'It's as plain as the nose on your face.' But how much of the nose on your face can you see, unless someone holds a mirror up to you?

I made up my mind long ago to follow one cardinal rule in all my writing — to be clear.

The easiest way to solve a problem is to deny it exists.