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.

Those who do good science do so because they choose problems that are suited to them.

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

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

Surprise is inherent in the structure of the world.