I have experimental evidence that time travel is not possible.

Our population and our use of the finite resources of planet Earth are growing exponentially, along with our technical ability to change the environment for good or ill. But our genetic code still carries the selfish and aggressive instincts that were of survival advantage in the past. It will be difficult enough to avoid disaster in the next hundred years, let alone the next thousand or million. Our only chance of long term survival, is not to remain inward looking on planet Earth, but to spread out into space.

If a superior alien civilization sent us a message saying, 'We'll arrive in a few decades', would we just reply, 'OK, call us when you get here - we'll leave the lights on'? Probably not - but this is more or less what is happening with AI.

I have sold more books on physics than Madonna has on sex.

Although quantum mechanics has been around for nearly 70 years, it is still not generally understood or appreciated, even by those that use it to do calculations.

Among physicists, I'm respected I hope.

Thirty years ago I was diagnosed with motor neurone disease, and given two and a half years to live. I have always wondered how they could be so precise about the half.