At times, I get very lonely because people are afraid to talk to me or don't wait for me to write a response. I'm shy and tongue-tied at times. I find it difficult to talk to people who I don't know.

In the last 200 years the population of our planet has grown exponentially, at a rate of 1.9% per year. If it continued at this rate, with the population doubling every 40 years, by 2600 we would all be standing literally shoulder to shoulder.

Time travel used to be thought of as just science fiction, but Einstein's general theory of relativity allows for the possibility that we could warp space-time so much that you could go off in a rocket and return before you set out.

There is a real danger that computers will develop intelligence and take over.

We are very, very small, but we are profoundly capable of very, very big things.

My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.

A few years ago, the city council of Monza, Italy, barred pet owners from keeping goldfish in curved bowls... saying that it is cruel to keep a fish in a bowl with curved sides because, gazing out, the fish would have a distorted view of reality. But how do we know we have the true, undistorted picture of reality?