The history of exploration has never been driven by exploration. But Columbus himself was a discoverer. So was Magellan. But the people who wrote checks were not. They had other motivations. And there's Columbus - he couldn't even get Italy to pay for his voyage so he has to go to Spain.

What I’m saying is, when different experiments give you the same result, it is no longer subject to your opinion. That’s the good thing about science: It’s true whether or not you believe in it. That’s why it works.

It could be that these other civilizations, if they are far more advanced intellectually than we are, would not even measure our existence as a blip on the intelligence radar. They could be so advanced that we are to them what worms are to us.

Some claim evolution is just a theory. As if it were merely an opinion. The theory of evolution, like the theory of gravity, is a scientific fact. Evolution really happened. Accepting our kinship with all life on Earth is not only solid science. In my view, it’s also a soaring spiritual experience.

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.

Any astrophysicist does not feel small looking up at the universe; we feel large.

The universe for me was other planets and other star systems and other galaxies. I enjoyed tracking it, but it had no specific influence on my ambitions for that reason. It wasn't really far enough away from Earth to matter to me.