If you have somebody who's brilliant and highly creative with a different point of view than you have, and a very different intellectual background, great things can happen.

I think that the future of the human race is to spread through the universe, and now is the time that we should be laying the foundations for that.

Whether you can go back in time is held in the grip of the law of quantum gravity.

'Closed timelike curve' is the jargon for time travel. It means you go out, come back and meet yourself in the past.

If you think that the distance from the Earth to the nearest planet where we could live comfortably... is being, like, from New York to Australia... what we've achieved so far, in going to the moon, that's about two-and-a-half inches. So that's the challenge.

A big misconception is that a black hole is made of matter that has just been compacted to a very small size. That's not true. A black hole is made from warped space and time.