Sheldon Lee Glashow

I came to graduate school at Harvard University in 1954. My thesis supervisor, Julian Schwinger, had about a dozen doctoral students at a time. Getting his ear was as difficult as it was rewarding. I called my thesis 'The Vector Meson in Elementary Particle Decays', and it showed an early commitment to an electroweak synthesis.

What the string theorists do is arguably physics. It deals with the physical world. They're attempting to make a consistent theory that explains the interactions we see among particles and gravity as well. That's certainly physics, but it's a kind of physics that is not yet testable.