We are in danger of destroying ourselves by our greed and stupidity. We cannot remain looking inwards at ourselves on a small and increasingly polluted and overcrowded planet.

Equations are just the boring part of mathematics. I attempt to see things in terms of geometry.

Some people would claim that things like love, joy and beauty belong to a different category from science and can't be described in scientific terms, but I think they can now be explained by the theory of evolution.

I thought Eddie Redmayne portrayed me very well... At times I thought he was me.

Although September 11 was horrible, it didn't threaten the survival of the human race, like nuclear weapons do.

We are only the temporary custodians of the particles which we are made of. They will go on to lead a future existence in the enormous universe that made them

Speech has allowed the communication of ideas, enabling human beings to work together to build the impossible. Mankind's greatest achievements have come about by talking, and its greatest failures by not talking. It doesn't have to be like this. Our greatest hopes could become reality in the future. With the technology at our disposal, the possibilities are unbounded. All we need to do is make sure we keep talking.