I realized very early in life what my abilities and limitations were, and foreign languages was definitely one of my limitations. With strenuous effort, I just barely passed my French class at Harvard so I could graduate.

One in 200 stars has habitable Earth-like planets surrounding it - in the galaxy, half a billion stars have Earth-like planets going around them - that's huge, half a billion. So when we look at the night sky, it makes sense that someone is looking back at us.

A hydrogen bomb, for me, was puny compared to the Big Bang - the creation of the universe. That's what I really wanted to work on - the nature of the universe itself, and that's what I do for a living.

I think Newton would be the greatest scientist who ever lived.

One day when I was 8 years old, everyone was talking in hushed tones about a great scientist that had just died. His name was Albert Einstein.

There's the caveman in us. The caveman in you says, "I want direct contact. I don't want a picture." The caveman in our body says once in a while, we have to go outside. We have to meet real people, talk to real people, and do real things.

No matter how beautiful the theory, one irritating fact can dismiss the entire formulism, so it has to be proven.