The theory of evolution, like the theory of gravity, is a scientific fact.

... there is no shame in not knowing. The problem arises when irrational thought and attendant behavior fill the vacuum left by ignorance.

When Kennedy said, 'Let's go to the moon,' we didn't yet have a vehicle that wouldn't kill you on launch. He said we'll land a man on the moon in eight years and bring him back. That was an audacious goal to put forth in front of the American people.

I have a very high respect for professional comedians. What they do astonishes me. You have to be really smart and absorb everything, repackage it, bring it back to the person, and make them laugh at themselves. I can make people laugh during my talks because they didn't come to have me make them laugh. It's added value. So my job is way easier than that of a professional comic.

The caricature of science is that we hold tight to the theories we have, and shun challenges to them. That's just not true. In fact, we hold our highest rewards for those scientists who can prove others wrong. And by the way, they are famous in their own lifetimes. We don't wait until they're dead.

I can't tell you how many people say they were turned off from science because of a science teacher that completely sucked out all the inspiration and enthusiasm they had for the course.

Some air you inhale was exhaled by Cleopatra.