Asteroids have us in our sight. The dinosaurs didn't have a space program, so they're not here to talk about this problem. We are, and we have the power to do something about it. I don't want to be the embarrassment of the galaxy, to have had the power to deflect an asteroid, and then not, and end up going extinct.

These are two different exercises. One of them is, "You don't know and I know, so just shut up and listen," and the other one is, you're curious and you're learning, and I have a way where you can learn this so you'll know it as well. And when you know it, and know why you know it, then you don't have to reference me ever again because you take ownership of the knowledge, and you can then share it with someone else.

The persistent failures of controlled, double-blind experiments to support the claims of parapsychology suggest that what's going on is nonsense rather than sixth sense.

Why can't Pluto be a planet? Some people like Pluto. And if it doesn't exist then they don't have a favorite planet. Right? Please write back but not in cursive because I can't read cursive.

If we have the power to turn another planet into Earth, then we have the power to turn Earth back into Earth.

I think everyone should have a personal mission to leave the Earth a better place for them having lived in it and let Earth then take it from there.

Astronauts are the only kind of celebrity I know who can have a line of people waiting for their autograph, even if the line of people does not know in advance the astronaut's name.