But when you predicted the quark in 1964, you realized it was not just another “cousin” particle, right?
That’s right. Looking at the table of known particles and the experimental data, it was clear that the neutron and proton could be made up of three particles with fractional charges, which I called quarks. [Until then all known particles had charges that were a whole multiple of the charge in a proton.] Quarks were permanently confined in the neutron and proton, so you couldn’t pull them out to examine them singly. The neutron and proton were no longer to be considered elementary. It was not a difficult thing to deduce. What was difficult was believing it, because nobody had ever heard of making the neutron and proton composite. Nobody had ever heard of these fractional charges. Nobody had ever heard of particles being confined permanently inside observable things and not directly attainable.

As time goes on, physicists seem to find more and more particles. Could there be an infinite number of them?
All of us theorists believe in simplicity. Simplicity has always been a reliable guide to theory in fundamental physics. But the simplicity may not lie in the number of named particles. It may be that the theory, expressed simply, gives rise to huge numbers of particle types. The particles might go on forever, but you detect only the ones that are light enough to play a role in your experiments.

Now researchers are pinning a lot of hope on finding yet another set of predicted particles in experiments at the Large Hadron Collider. Do you think this will bring some clarity?
Well, there is another possibility, that they find some phenomenon that is utterly unexpected. It would upset us if they found something totally new, totally mystifying, but that’s what would be most exciting.


You were thought of as a math prodigy as a child, but math wasn’t your only passion, was it?
I remember when I was around 5, I looked through my father’s books. He had had a very substantial library, a huge library. And when the bad times struck—the Depression—he had to get rid of them when we moved to a tiny apartment. He had to have the furniture taken away. He couldn’t sell it; he had to pay to have it removed. He paid somebody five dollars to take away his library. Heartbreaking. But he had a few books left, 50 books or something like that. One of them was a book that gave etymologies of English words borrowed from Greek and Latin. So I learned all these Greek and Latin roots and how they went to make up English words. It was exciting. That started me on etymology, and I have loved etymology ever since.

I was always OK in math. Actually I loved math, loved studying it, loved using it. I loved history. I was particularly in love with archaeology and linguistics. And I could discuss anything with my brother—archaeology, etymology, anything at all. He never did anything with it, but he was very, very intelligent and very knowledgeable about all sorts of things. He was passionate about birds and other living things. Not so much the scientific principles of ornithology, but just seeing the birds and identifying them and knowing where they were, and what kind of nest they had, and what songs they sang. Going with him on a bird trip was the best thing—the best thing—I did in those years. My brother taught me to read from a cracker box when I was 3.

When you were going into college, you were interested in studying archaeology, natural history, or linguistics, but your father wanted you to make money as an engineer.
I said I’d rather be poor or die than be an engineer because I would be no good at it. If I designed something it would fall down. When I was admitted to Yale, I took an aptitude test, and when the counselor gave me the results of the exam, he said: “You could be lots of different things. But don’t be an engineer.”

Then how did you settle on physics?
After my father gave up on engineering, he said, ‘How about we compromise and go with physics? General relativity, quantum mechanics, you will love it.’ I thought I would give my father’s advice a try. I don’t know why. I never took his advice on anything else. He told me how beautiful physics would be if I stuck with it, and that notion of beauty impressed me. My father studied those things. He was a great admirer of Einstein. He would lock himself in his room and study general relativity. He never really understood it. My opinion is that you have to despise something like that to get good at it.

Why is that?
If you admire it sufficiently, you’ll be in awe of it, so you’ll never learn it. My father thought it must be very hard, and it will take years to understand it, and only a few people understand it, and so on. But I had a wonderful teacher at Yale, Henry Margenau, who took the opposite attitude. He thought relativity was for everybody. Just learn the math. He’d say, “We’ll prepare the math on Tuesday and Thursday, and we’ll cover general relativity on Saturday and next Tuesday.” And he was right. It isn’t that bad.

You’ve known some of the greatest physicists in history. Whom do you put on the highest pedestal?
I don’t put people on pedestals very much, especially not physicists. Feynman [who won a 1965 Nobel for his work in particle physics] was pretty good, although not as good as he thought he was. He was too self-absorbed and spent a huge amount of energy generating anecdotes about himself. Fermi [who developed the first nuclear reactor] was good, but again with limitations—every now and then he was wrong. I didn’t know anybody without some limitations in my field of theoretical physics.

Back then, did you understand how special the people around you were?
No. I grew up thinking that the previous people were the special ones. Even though I knew most of them. I didn’t know Erwin Schrödinger [a pioneer of quantum mechanics]; I passed up a chance to meet him for some reason. But I did know Werner Heisenberg fairly well. He was one of the discoverers of quantum mechanics, which is one of the greatest achievements of the human mind. But by the time I knew him, although he was not extremely old, he was more or less a crank.

How so?
He was talking a lot of nonsense. He had things that he called theories that were not really theories; they were gibberish. His goal was to find a unified theory of all the particles and forces. He worked on an equation, but the equation didn’t have any practical significance. It was impossible to work with it. There were no solutions. It was just nonsense. Anyway, it was interesting that Wolfgang Pauli [discoverer of the exclusion principle], who did not go in for particularly crazy things—at least not in physics—was taken in by Heisenberg’s stuff for a little while. He agreed to join Heisenberg in his program.