Physicist Eugene Commins was born in 1932, the same year that James Chadwick made the first observations of a neutron: the third subatomic particle discovered. Eighty-two years later, when I spoke to Professor Commins in his sun-dappled office, researchers had recently detected the Higgs boson at CERN (see BSR issue 24, “Hunting down the Higgs”), the last particle left to be verified in the Standard Model of particle physics, a model that is sometimes called “the theory of almost everything.”
In the 1920s, which Commins called “the first golden age of physics,” scientists incorporated a new understanding of particle behavior into the classical physics we all learn in high school, giving rise to the field of quantum mechanics. Classical physics is an ancient way of understanding the world, and deals with the behaviors of macroscopic, everyday objects. Quantum mechanics describes what happens at infinitesimal scales, where atoms and sub-atomic particles exhibit a split personality, at some times acting like discrete units, and at others like waves of energy. Technological advances during World War II caused another paradigm shift, where the necessary equipment was available to validate quantum theories. As an experimental physicist, Commins used low-energy atomic beams to test the predicted behaviors of subatomic particles.
Throughout his career, Commins relied on curiosity and intuition to guide him. “I’m a sleep-walker,” he told me, “I just wander through the world.” By the time he started graduate school in physics at Columbia University, a professor in his department, Tsung-Dao Lee, and his collaborator Chen Ning Yang, had made the discovery that would shape Commins’ entire research career: parity violation (described by Commins below). To complement his research accomplishments, Commins is also known as a talented teacher, mentor, and artist. Nobel laureate and former US Secretary of Energy Steven Chu writes, “One of the best things about being mentored by Gene was that he allowed me to be different from him.” Currently, Commins is writing a textbook on quantum mechanics, a course he has taught more than 20 times here at Berkeley.
TL: Could you describe your research?
EC: In our present state of knowledge, we understand that there are four fundamental interactions in nature: gravity, electromagnetism, which is at the heart of everyday physics and chemistry, and the strong and weak nuclear forces, which have to do with nuclei and particle physics. The weak interaction governs the decays of unstable radioactive particles. Most particles obey parity, which means they are symmetric to spatial inversion. (TL: I must have looked a little nervous at this point, because Commins gives me a wry smile.)
Now, I’ll explain what that means. Imagine that you see some process in nature, and you look at it in a mirror. You’d see the same process happening, but inversed. If the probability for what actually occurs and what you see in the mirror is the same, then parity is conserved. For years, we assumed that all particles obey the rule of parity, no matter what fundamental interaction they obey.
At Columbia, Lee and Yang theorized that the weak interaction, alone among all interactions, violates parity. They proposed this in 1956, and won the Nobel Prize just a year later. That was a big discovery, and I was fascinated by it. Although I didn’t intend it to be that way, almost every experiment I did here at Berkeley was studying parity violation in one way or another. I spent my whole life doing that.
TL: What piqued your interest in experimental physics, instead of theoretical?
EC: I think that decision is made partly by the way people are trained, and partly the outlook they have on the world. I’ve always liked working with my hands, but I was kind of schizophrenic in that regard. My knowledge of theoretical questions has always influenced the problems I chose to study.
TL: What is the experiment you’re most proud of?
EC: Oh, the last one we did. I don’t work in the lab anymore. I’m too old for that. I decided that I was too old during the last experiment I did, with a gifted student, Chris Regan. But I’m very proud of that project, putting a limit on the electric dipole moment, which we published in 2002. It was a good, hard experiment, and required a lot of ingenuity. The magnetic field from the BART trains was interfering with our measurements, so we had to work when they weren’t running, between two o’clock and six o’clock in the morning!
TL: You’ve seen huge changes in the field over your career. What are the biggest differences?
EC: I think that physics is the victim of its own success. Here’s what I mean: when I was born, Chadwick discovered the neutron using an apparatus that probably cost him less than $10. He did it all by himself, the paper he wrote was crystal-clear, and the results were as persuasive and clean as they can be. Even when I was at Columbia, most experiments were modest and human-scale. You could read physics journals and understand most of the papers, even those not in your field.
But nowadays, the problems we’re tackling have become complicated and ultra-specialized. All the easy questions have gotten solved, and people moved on to much more difficult questions. Now you see lists of authors longer than the papers themselves, and those experiments cost millions of dollars. I don’t really know if this is sustainable.
TL: You’ve been a musician and painter for most of your life. Do you think that your interest in art has affected your outlook as a scientist?
EC: I feel that music and science go hand in hand. I love music and I love physics. There is great aesthetic appeal in the equations of physics. Maybe that’s in the eye of the beholder, but I think that there’s great beauty in finding an elegant, symmetrical solution to a very difficult problem. For example, relativity is an enormously elegant solution to a subtle, complicated problem. Or quantum mechanics; it’s very mysterious, and therefore very beautiful.
TL: Many of your students have mentioned your strengths as a graduate advisor. What was your mentoring philosophy, and how did you develop it?
EC: Like so many other things I’ve done, I haven’t really known what I was doing. I did everything by the seat of my pants. There’s no hard and fast rule when it comes to mentoring. You have to see what the student needs, have some intuition about what works, and most importantly, you need to pay attention to them. When it comes to my students, I’ve always been surprised by their brilliance and their ingenuity. They kept surpassing anything I expected of them, which is really a wonderful thing to see. Seeing a student become a scientist in their own right: that’s probably given me more satisfaction than anything else.
TL: What advice do you have for current students?
EC: Well, you have to take the long view, and you need to have self-confidence. But I think the most important thing is courage. When you try to do something interesting, it will certainly be hazardous. There’s a high likelihood it won’t work. You see, if you choose something that’s sure to work, it’s not going to be interesting. But if you choose a problem that’s really interesting, then chances are it’s not solved, and there’s always going to be danger in that. But it’s really worth it, in the end, isn’t it?