A physicist is an atom's way of knowing about atoms.

The great questions are those an intelligent child asks and, getting no answers, stops asking.

Evolution advances, not by a priori design, but by the selection of what works best out of whatever choices offer. We are the products of editing, rather than of authorship.

I am growing old, and my future, so to speak, is already behind me.

If the germ plasm wants to swim in the ocean, it makes itself a fish; if the germ plasm wants to fly in the air, it makes itself a bird. If it wants to go to Harvard, it makes itself a man. The strangest thing of all is that the germ plasm that we carry around within us has done all those things. There was a time, hundreds of millions of years ago, when it was making fish. Then ... amphibia ... reptiles ... mammals, and now it's making men.

I think I know what is bothering the students. I think that what we are up against is a generation that is by no means sure that it has a future.

A scientist should be the happiest of men.