We account for all the matter and energy that we're familiar with, measure up how much gravity it should have, it's one-sixth of the gravity that's actually operating on the universe. We call that dark matter. It really should be called dark gravity. We don't know what that is.

Science is a fundamental part of our existence.

It'd be a shame to talk about the universe and not show some images of it, because we have some of the more stunning representations of our field relative to any of the sciences. But I don't use the imagery as a substitute for the insights and wisdom I can convey so that when you leave you say to yourself, "Wow, I'm a little more deeply connected to the universe, and I want to learn more."

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.

Computers have proved to be formidable chess players. In fact, they've beaten our top human chess champions.

Modern science is under no obligation to satisfy the expectations of your five senses.

There's nothing a teacher likes better than ten minute videos. It's not the whole class, but it's not too short, it's enough to wrap a lesson plan around.