If we want to go to space with humans, that's for fun not for science. Human adventures in space are just sporting events.

It is in the long run essential to the growth of any new and high civilization that small groups of men can escape from their neighbors and from their government, to go and live as they please in the wilderness. A truly isolated, small, and creative society will never again be possible on this planet.

If you're in the business world, that's what's expected: You should go bust and then start again on something else. So it's a much more relaxed kind of a culture. It's also competitive, but not in such a vicious way. I think the academic world is actually much more destructive of young people.

Dropping of the atomic bomb was the main subject of conversation for many years and so people had very strong feelings about it on both sides and people who thought it was the greatest thing they'd ever done and people who thought it was just an unpleasant job and people who thought they should have never done it at all, so there were opinions of all kinds.

If you want to have a program for moving out into the universe, you have to think in centuries not in decades.

Scepticism is as important for a good journalist as it is for a good scientist.

The thing that makes me most optimistic is China and India - both of them doing well. It's amazing how much progress there's been in China, and also India. Those are the places that really matter - they're half of the world's population. They're the places where things are enormously better now than they were 50 years ago. And I don't see anything that's going to stop that.