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.

Also, where does your identity come from? Your memory, of course.

I think we are all the sum of that which has happened in our lives. And if you're successful, it would be wrong to think that you'd be more successful had something been easier. That's not a given.

Going into orbit around Earth - where the space station is today, and where the space shuttles and John Glenn and all those folks go-that's three-eighths of an inch above a schoolroom globe, just FYI. That's not very far from Earth. Yes, you are off Earth, but you're not really going anywhere yet. The moon was the only real destination.

If we have the power to turn another planet into Earth, then we have the power to turn Earth back into Earth.

For me, the most fascinating interface is Twitter. I have odd cosmic thoughts every day and I realized I could hold them to myself or share them with people who might be interested.

God is an ever receding pocket of scientific ignorance.