My best teachers were not the ones who knew all the answers, but those who were deeply excited by questions they couldn't answer.

The idea that there could be other universes out there is really one that stretches the mind in a great way.

Science is very good at answering the 'how' questions. 'How did the universe evolve to the form that we see?' But it is woefully inadequate in addressing the 'why' questions. 'Why is there a universe at all?' These are the meaning questions, which many people think religion is particularly good at dealing with.

In essence, we string theorists have been trying to work out the score of the universe, the harmonies of the universe, the mathematical vibrations that the strings would play. So musical metaphors have been with us in science since the beginning.

The number of e-mails and letters that I get from choreographers, from sculptors, from composers who are being inspired by science is huge.

Over the centuries, monumental upheavals in science have emerged time and again from following the leads set out by mathematics.

Einstein's theory of relativity does a fantastic job for explaining big things. Quantum mechanics is fantastic for the other end of the spectrum - for small things.