God is an ever-receding pocket of scientific ignorance that's getting smaller and smaller and smaller as time moves on.

If aliens did visit us, I'd be embarrassed to tell them we still dig fossil fuels from the ground as a source of energy.

You gotta be a good sport! So when I would lose, I would say, "That guy was better than I was; what do I have to do to be better next time?"

I'm not as famous as Stephen Hawking, but certainly in the U.S., I have a very high profile for a scientist. It is an awesome responsibility, one that I don't shoulder lightly.

The solar system should be viewed as our backyard, not as some sequence of destinations that we do one at a time.

I have thoughts every day that are themselves tweets.

You know, there's black holes and what - could there be wormholes? Could - might there be a multi-verse? These are all fascinating frontiers. What is the nature of dark matter and dark energy? And what was around before the universe? And do we have access to higher dimensions?