Every mode of transport that we use - whether it's planes, trains, automobiles, bikes, horses - is reusable, but not rockets. So we must solve this problem in order to become a space-faring civilization.

The biggest mistake, in general, I've made, is to put too much of a weighting on someone's talent and not enough on their personality. And I've made that mistake several times. I think it actually matters whether somebody has a good heart, it really does. I've made the mistake of thinking that it's sometimes just about the brain.

If anyone thinks they'd rather be in a different part of history, they're probably not a very good student of history. Life sucked in the old days. People knew very little, and you were likely to die at a young age of some horrible disease. You'd probably have no teeth by now. It would be particularly awful if you were a woman.

The key test for an acronym is to ask whether it helps or hurts communication.

If humanity doesn't land on Mars in my lifetime, I would be very disappointed.

You need to live in a dome initially but over time you could terraform Mars to look like Earth and eventually walk around outside without anything on. ... So it's a fixer-upper of a planet.

I think there are too many smart people pursuing internet stuff, finance, and law. That is part of the reason why we haven't seen as much innovation.