Berkhoff said, 'Well, you've got to make this choice.' And I knew I didn't… I knew I was not going to be able to be a creative mathematician. I didn't want to be a math teacher, I didn't know what I was going to be. So I said, well, I guess I'll go into physics. I walked into the Physics Department and said, 'Well, I want to transfer to physics'.

And I had essentially no physics courses. I mean, look at my record, and you've got a C in sophomore physics or something and I'd taken Schwinger's course and I had a B or something or maybe some A or A minus or something. And I really didn't know any real physics. I knew some of the mathematics of physics. With George Mackey, I had studied Hilbert space and one thing and another. So they said, 'Well, yes, you… we'll accept you. But you have to take an exam in experimental physics or something'. I said, 'Oh'. They said, 'In order to train for this exam, we want you to work for a summer at the Harvard Cyclotron Lab, and you can learn how experiments are done'. I said, 'Oh, all right.' Well, actually, unless you're actually doing the experiment, the assistants do the donkey work. You pile lead bricks, you cut down bits of Styrofoam for targets. You don't learn any physics. I didn't learn any physics at all. I learned how to pile lead bricks.