Going from PayPal, I thought: 'Well, what are some of the other problems that are likely to most affect the future of humanity?' Not from the perspective, 'What's the best way to make money?'

If you think back to the beginning of cell phones, laptops or really any new technology, it's always expensive.

The primary means of energy generation is going to solar. It will at least be a plurality, and probably be a slight majority in the long term.

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.

If something's important enough, you should try. Even if you - the probable outcome is failure.

Mars is the only place in the solar system where it's possible for life to become multi-planetarian.

Entrepreneurship is like eating glass and walking on hot coals at the same time