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.

I have a very high respect for professional comedians. What they do astonishes me. You have to be really smart and absorb everything, repackage it, bring it back to the person, and make them laugh at themselves. I can make people laugh during my talks because they didn't come to have me make them laugh. It's added value. So my job is way easier than that of a professional comic.

You say you're worried about kids? I'm not worried about kids, I'm worried about grown ups... Children are not the problem here... We spend the first year of their lives teaching them how to walk and talk, and the rest of their lives telling them to shut up and sit down.

We went to the moon and discovered Earth.

Like a snowplow in overdrive, a supernova shockwave might sweep away any gas clouds in its path.

We think scientific literacy flows out of how many science facts can you recite rather than how was your brain wired for thinking. And it's the brain wiring that I'm more interested in rather than the facts that come out of the curriculum or the lesson plan that's been proposed.

God is an ever receding pocket of scientific ignorance.