Fifty years," I hackneyed, "is a long time." "Not when you're looking back at them," she said. "You wonder how they vanished so quickly.

I am not responsible for what other people think. I am responsible only for what I myself think, and I know what that is. No idea I've ever come up with has ever struck me as a divine revelation. Nothing I have ever observed leads me to think there is a God watching over me.

All of a sudden, space isn't friendly. All of a sudden, it's a place where people can die. . . . Many more people are going to die. But we can't explore space if the requirement is that there be no casualties; we can't do anything if the requirement is that there be no casualties.

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

People who think they know everything are a great annoyance to those of us who do.

It's humbling to think that all animals, including human beings, are parasites of the plant world.

It is always useful, you see, to subject the past life of reform politicians to rather inquisitive research.