A billion could live off the earth; 6 billion living as we do is far too many, and you run out of planet in no time.

This programme to stop nuclear by 2020 is just crazy. If there were a nuclear war, and humanity were wiped out, the Earth would breathe a sigh of relief.

I would only have been too pleased if someone had asked me for my data. If you really believed in your data, you wouldn't mind someone looking at it. You should be able to respond that if you don't believe me go out and do the measurements yourself.

Life does more than adapt to the Earth. It changes the Earth to its own purposes.

I put up my thumb and it blotted out the planet Earth.

We'd never have got a chance to go outside and look at the earth if it hadn't been for space exploration and NASA.