Pretending to know everything closes the door to finding out what's really there.

There's no shortage of people that we can put on, because science touches us all.

The history of exploration across nations and across time is not one where nations said, 'Let's explore because it's fun.' It was, 'Let's explore so that we can claim lands for our country, so that we can open up new trade routes; let's explore so we can become more powerful.'

Three and a half million years ago our ancestors - yours and mine - left these traces [indicates footprints]. We stood up and parted ways from them. Once we were standing on two feet, our eyes were no longer fixated on the ground. Now, we were free to look up and wonder.

Give a kid a book, and you change the world. In a way, even the universe.

After all, what nobler thought can one cherish than that the universe lives within us all?

My interest in the space program has a certain purity to it because I recognize the romance of it but I was never seduced by it. That allowed me to view it through a more purely scientific lens. My interest in space while in school came about through my scientific activities.