If we want to solve a problem that we have never solved before, we must leave the door to the unknown ajar.

Victory usually goes to those green enough to underestimate the monumental hurdles they are facing.

In its efforts to learn as much as possible about nature, modern physics has found that certain things can never be "known" with certainty. Much of our knowledge must always remain uncertain. The most we can know is in terms of probabilities.

When you get as old as I am, you start to realize that you've told most of the good stuff you know to other people anyway.

In those days, in Far Rockaway, there was a youth center for Jewish kids at the temple.... Somebody nominated me for president of the youth center. The elders began getting nervous, because I was an avowed atheist by that time.... I thought nature itself was so interesting that I didn't want it distorted like that. And so I gradually came to disbelieve the whole religion.

We have been led to imagine all sorts of things infinitely more marvelous than the imagining of poets and dreamers of the past. It shows that the imagination of nature is far, far greater than the imagination of man. For instance, how much more remarkable it is for us all to be stuck-half of us upside down-by a mysterious attraction, to a spinning ball that has been swinging in space for billions of years, than to be carried on the back of an elephant supported on a tortoise swimming in a bottomless sea.

Some people say, "How can you live without knowing?" I do not know what they mean. I always live without knowing. That is easy. How you get to know is what I want to know.