The greatest weapons in the conquest of knowledge are an understanding mind and the inexorable curiosity that drives it on.

Inspect every piece of pseudoscience and you will find a security blanket.

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.

Surely, if we take on thinking partners - or, at the least, thinking servants - in the form of machines, we will be more comfortable with them, and will relate to them more easily, if they are shaped like humans. It will be easier to be friends with human-shaped robots than with specialized machines of unrecognizable shape. And I sometimes think that, in the desperate straits of humanity today, we would be grateful to have nonhuman friends, even if they are only the friends we build ourselves.

The significant chemicals of living tissue are rickety and unstable, which is exactly what is needed for life.

I have never written a book that didn't teach me far more than it taught my reader.

Today's science fiction is tomorrow's science fact.