If you're a scientist, and you have to have an answer, even in the absence of data, you're not going to be a good scientist.

The day we stop exploring is the day we commit ourselves to live in a stagnant world, devoid of curiosity, empty of dreams.

The very nature of science is discoveries, and the best of those discoveries are the ones you don't expect.

A common way to compute density is, of course, to take the ratio of an object's mass to its volume. But other types of densities exist, such as the resistance of somebody's brain to the imparting of common sense.

It's my duty to enlighten people.

We only recently figured out the origin of our own moon. And we have some idea of how the Sun and Earth formed, but that's only because modern telescopes empower us to see other stars and planets freshly hatched within gas clouds across the galaxy. As for the origin of life itself, the transition from inanimate molecules to what any of us would call life remains one of the great frontiers of biology.

I grew up in New York City where there is no night sky. Nobody has a relationship with the sky, because, particularly in the day, there was air pollution and light pollution, and you look up, and your sight line terminates on buildings. You know the sun and maybe the moon, and that's about it. So what happens is that I am exposed to the night sky as you would see it from a mountaintop, and I'm just struck by it. Suppose I grew up on a farm where I had that sky every night of my life - then you're not going to be struck by it. It's just the wallpaper of your nighttime dome.