One possibility is: God is nothing but the power of the universe to organize itself.

Any two particles in the universe attract each other through the gravitational interaction.

Just like an ordinary guitar string, a fundamental string can vibrate in different modes. And it is these different modes of vibration of the string that are understood in string theory as being the different elementary particles.

The revolution which began with the creation of quantum theory and relativity theory can only be finished with their unification into a single theory that can give us a single, comprehensive picture of nature.

Deep, persistent problems are never solved by accident; they are solved only by people who are obsessed with them and set out to solve them directly.

We know no more than we did in 1975 - and that's not good

The page of my notebook was filled with many messy integrals, but all of a sudden I saw emerge a formula for counting. I had begun to calculate a quantity on the assumption that the result was a real number, but found instead that, in certain units, all the possible answers would be integers. This meant that areas and volumes cannot take any value, but come in multiples of fixed units.