Let us not fool ourselves into thinking we went to the Moon because we are pioneers, or discoverers, or adventurers. We went to the Moon because it was the militaristically expedient thing to do.

There are as many atoms in each molecule of your DNA as there are stars in the typical galaxy. This is true for dogs, and bears, and every living thing. We are, each of us, a little universe.

In physics, opinions don't matter, only demonstrated experiments. The day the fellow succeeds, if ever, he won't need anybody else's opinion.

I have yet to see a successful prediction about the physical world that was inferred or extrapolated from the content of any religions document.

Claiming there is no other life in the universe is like scooping up some water, looking at the cup and claiming there are no whales in the ocean.

We in astrophysics we think of the universe all the time. So to us, Earth is just another planet. From a distance, it's a speck. And I'm convinced that if everyone had a cosmic perspective you wouldn't have legions of armies waging war on other people because someone would say, "Stop, look at the universe."

If you want a nation to have space exploration ambitions, you've got to send humans.