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Credit: Betsy Devine
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Interview of Frank Wilczek by David Zierler on June 4, 2020,Niels Bohr Library & Archives, American Institute of Physics,College Park, MD USA,www.aip.org/history-programs/niels-bohr-library/oral-histories/44536
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In this interview, David Zierler, Oral Historian for AIP, interviews Frank Wilczek, Herman Feshbach Professor of Physics at MIT. Wilczek recounts his family background and childhood in Queens, and he describes how his early curiosity would come to inform the many intellectual pursuits he would take on later in his career. He describes his undergraduate education at the University of Chicago, where he enrolled at the age of fifteen, and he discusses his early interest in applied and pure mathematics. Wilczek describes the key influence of Peter Freund at Chicago, and his decision to pursue graduate work at Princeton. He explains how David Gross became his advisor, and he describes his idea to apply the renormalization group to theories of the weak interaction. Wilczek describes his decision to join the Princeton physics faculty immediately after his graduate work, and his developing interest in cosmological issues, as well as his ongoing efforts to extend models of the weak interactions. Wilczek shares his ideas on a grand unified theory and what he sees as the ongoing value of particle physics to cosmological inquiry. He explains what is known and unknown in the early universe, and how his training in philosophy informs those questions. Wilczek conveys his excitement at the possibilities of computers to move science forward, and he narrates the growing interest in his research which led to the Nobel Prize in 2004. He discusses the ways he has used the platform conferred by this recognition as a vehicle for him to pursue other interests. Wilczek discusses his interest in time crystals, and he discusses the origins of the Wilczek Quantum Center in China, and he explains the collaborative work he is pursuing at Arizona State University in neurobiology and expanding human capacity for sensory perception. At the end of the discussion, Wilczek explains how the concept of beauty has always, and continues to inform his scientific pursuits.
This is David Zierler, oral historian for the American Institute of Physics. It is June 4th, 2020. It is my great pleasure to be here with Professor Frank Wilczek. Frank, thank you so much for being with me today.
Oh, I'm looking forward to it.
To start, I know this is going to be a mouthful, but would you please tell me your title and institutional affiliations?
Well, I am Herman Feshbach Professor at MIT. I also am founding director of the TDLI—TD Lee Institute—in Shanghai, China. And chief scientist of the Wilczek Quantum Center at STJU—Shanghai Jiao Tong University—in China. And I also have a professorship, an honorary professorship, at Arizona State. And I'm a professor also at Stockholm University. So right now, I have four or four and a half positions.
And of course nowadays you're doing all of this from the comforts of your own home. [laugh]
Yes, I'm speaking to you from self-isolation in Concord, Massachusetts.
Let’s take it right back to the beginning. Tell me a little bit about your family background and your parents. Where are your parents from?
My parents are from Long Island, the northeast corner of Queens or the northwest corner of Nassau County, [laugh] where my father was born in Port Washington. My mother was born in Manhasset. Their parents were born in Europe, so they were immigrants, from Poland in my father’s case, or from parts of Europe that are now Poland in my father’s case, and from Italy in my mother’s case. And they met in that area. Manhasset and Port Washington are very close together. I was actually born at a hospital in Mineola, New York, [laugh] but lived the first three and a half years of my life in Port Washington. My parents lived with my paternal grandparents then. We moved to a place called Glen Oaks, an apartment in Queens, New York, in the very northeast corner. And that’s where I grew up, really, that I mostly remember, until I was 15, when I left for college at the University of Chicago.
What were your parents’ professions?
Well, my father didn't finish high school, actually. [laugh] But he was kind of a technician. They grew up during the Depression, so they really had very limited resources in their family. And he was a technician in the early days of radio, so kind of radio and TV repair guy, when especially TV was a pretty exotic thing. He went back and got his degree when I was growing up—his high school degree—but then also, when I was growing up, he was getting some college credits and learning—I'm not sure he actually ever got a degree at college, but he took courses in calculus and things that were relevant to his work. My mother was a homemaker. She worked for a few years in a bank before getting married, but basically, as was common at the time, she devoted all her efforts to the family.
Is your sense that with better economic prospects, your father would have pursued a professional degree and maybe even have pursued an intellectual life?
Yeah, definitely. He was a very smart guy. But he really had a very difficult childhood. Very limited circumstances. My grandparents came over from Europe, were not economically secure. I don’t know the full story, but somehow my father’s family was cheated or somehow lost their savings in the Depression. So they were left with very, very difficult circumstances. My father had to go to work. It was not a good upbringing for him. But for me, sort of the bright side in a way was that when I was a teenager, or slightly before, he was going to night classes and doing these things. Sort of catching up, learning calculus. And I read the same books at the same time.
[laugh] How would you describe your family’s socioeconomic position? Working class? Lower middle class? Middle class?
Somewhere between working class and lower middle class. Yeah, lower middle class, I guess I would say. Unlike my grandparents, who really did work with their hands, my father, as I said, was kind of a technician and repairman. He actually got very good at the job and was rising through the ranks.
What role did organized religion play in your upbringing?
Well, it was a very big deal to my grandparents.
Catholic, I assume.
Catholics, right. All Catholics. Although I should say on my mother’s side, the family was kind of intact and was closely tied to the church. My father’s side, I didn't say it, but it was kind of on the borders of things I was saying—the family situation was not stable. My grandparents eventually got divorced. My grandfather was an alcoholic. So there were real problems. So certainly he [laugh] was not religious in any way. And my grandmother I think was also not closely tied to the church. But my maternal family, again, was. My parents, I would say, had lingering influence from their childhood [laugh] of connection to the church, and communities where the church was a big part. But they themselves over time I think became less attached to it. So when I was growing up, I think largely for my sake, they went to church on Sundays. I went to catechism classes. I took it very seriously. But I think after I left, they kind of drifted away. I left, and their parents grew older, and they kind of drifted away. So it was part of the scene, but not an overwhelming presence, I guess, in my childhood, I would say.
Who was it that first recognized your intellectual abilities? Was it your parents? Was it a teacher?
I’d say it was in school, from very early on. Really basically from the moment I entered school, they wanted to put me in more advanced classes, send me to a different place.
And you excelled across the board, not just in math and science?
Yes. Yeah, I really did, in all modesty. [laugh] I definitely wasn’t a prodigy on the scale of someone like von Neumann, but clearly a step above most of my peers.
To the extent that intellect has a genetic component, have you ever thought about where this might come from in your family? From your father, perhaps?
Well, from both, I think. My mother had less opportunity to cultivate her talents, but she actually did very well in school. And my father I think was clearly potentially a very powerful thinker, but not well trained, and also kind of damaged, I think, from the family situation. But especially in later years, when I got to know him better, I really saw that he had a lot of bandwidth that didn't get used properly. [laugh]
I think to fast forward to your later career, you display such a fundamental curiosity about the world in such diverse areas, and I'm curious how you might have expressed that as a child.
Well, I read a lot. [laugh] I did funny things like dissecting animals that we found, dead animals that we found. I launched little rockets [laugh]. But mostly it was more—I enjoyed all kinds of puzzles and games. Maybe that was the most striking thing. All kinds of puzzles and games. So I made up games, board games, and I kind of just would never let any kind of puzzle book or something that I found go unmined. Yeah, and as I said, I was very interested in the books my father brought home with the math and calculus. I also saved up very early on—I had an allowance [laugh] which for a long time was a quarter a week. But that went somewhere in those days. And I saved up for a long time to buy a telescope.
But also my parents, very early on, would take me every week to a nearby toy store. I got to look at the toys and think about which ones I really wanted. Because I couldn't—so that was a kind of training [laugh] in planning and saving. I have to say, although our financial situation was kind of constrained, I never felt that. I certainly never felt in doubt about my next meal. That wouldn't even enter my head. [laugh] And they could see that I really loved toys, mechanical toys but all kinds of toys, and I got toys. [laugh] And my father especially encouraged me to buy books. But he had to approve of the books, or rather if he approved of the book, he would pay half the price. So in practice, I only bought books that he approved of, [laugh] because I wanted my money to go further.
So you said you finished high school at age 15.
And the plan was to get you to college as soon as possible?
Yeah. Well, that was certainly my plan. Yeah, I think my parents were on board with that, and the teachers thought that that was a good idea.
And looking back, you had the maturity to match the mind to be able to do something like that?
No. Well, I didn't. [laugh] I didn't, really. Well, yes and no. I was not sort of the modern ideal of admissions offices, of a well-rounded student. Definitely not. [laugh] I didn't have a long list of outside activities or anything like that. Especially when I went to college, I was very socially immature. So I didn't do a lot of the sort of dating and going to dances, that kind of social activity. But I did do a lot of sports. Just ad hoc touch football games [laugh] and things like—disorganized sports, I would say. Spent a lot of time outdoors.
There’s lots of really top-rate colleges closer to home in Queens. Why Chicago?
Well, I applied, if I remember correctly, to Queens College, Chicago, Princeton, and somewhere else. I didn't get into Princeton, which I held a grudge for many years. [laugh] (I'm just kidding.) So that wasn’t an issue. The decisive thing was that Chicago offered a really good deal. At that time, they had something called the University Scholars, which basically I think zeroed the tuition. There were still residence expenses and so on. So that was very important to our family. And also gave me a lot of freedom in choosing courses, and special attention and things. I think they had only a dozen or so each year. So it was a really good deal. Yeah, so that’s why I went there.
Was your plan to focus on math and science as a 15-year-old, or were you still openminded at that point about your course of study?
I was still openminded in the sense that I was pretty darn sure that I wanted to do something that used mathematics. I really liked mathematical thinking. But my ideas about what within that broad orientation I would do were much less clear. I was very, very fond at that time of mathematical logic and philosophy. I think what I really intended to do when I started college, insofar as it was more specific, was try to figure out how minds work, and what now would be called some mixture of neurobiology and computer science.
So even within mathematics, you were looking more in the applied realm?
Oh, absolutely. No, I didn't want to do pure mathematics. No. Well, unless it was sort of mathematics that had philosophical indications. Like if I could have been a mathematician like Kurt Gödel, I would have done that. Or Alan Turing. That kind of semi applied mathematics with a philosophical bent.
And you never lost that as your identity as a scientist, your comfort in exploring areas that had philosophical implications.
Oh, no, absolutely not. I've always had that at the back of my mind. I'm now actually going through the proofs of a book that I just finished, where I've really come back to that, in a full-throated way. [laugh] It’s called Fundamentals. And I've kind of taken what I've learned in this long journey that’s relevant to those kind of fundamental issues, tried to put it together in a coherent way.
Let me just jump ahead, because it’s on my mind with some of the other people that I've been speaking to. The idea that things like string theory should be criticized because they get to a point where science ends and the evidence ends, and that the criticism there is you can have these ideas, but you have to be careful what department you think you belong to, right?
So I'm curious just what your immediate reaction is to that general binary, and the people that sort of represent those two sides of that kind of a discussion or argument?
Well, there is, I suppose, a discussion to be had at the level of academic politics about which department it should go in, but I don’t think that’s very interesting.
That question is a nice way of asking, “Is what they’re doing science?” That’s what I mean.
Well, I’d be very cautious about that kind of binary statement. But I understand the sentiment behind it. And I would put it just more positively. And it’s something I've said consistently and felt consistently, going back to the times we were mentioning, when I resolved not to do pure mathematics, [laugh] which is—and maybe a way I could have put it— that the kind of semi-pure mathematics I could imagine myself doing would have to be algorithmic. It would have to be something that you can check, [laugh] and where it has tangible outputs. I would put it more positively. Pure mathematics is a legitimate enterprise. It’s beautiful. I still, to this day, enjoy my amateur study of number theory and so on. But to me, what makes physics at its best really special is that the world of concepts in mathematics is also the real world. Now, coming to the case of string theory, if string theory does lead to tangible advances in understanding the real world, I’d be delighted. But I don’t think we should hold it to a different or a lower standard just because it’s so clever. [laugh] We still need—it still is—how should I say? However clever it is, to me there’s another level when it becomes a description of actual concrete phenomena. So you can do very good work without describing the physical world, but it can always get better if it does describe the physical world. [laugh]
Frank, back to Chicago. Did you have a physics component to the math major? Were there requirements in physics classes?
There were small requirements. I don’t remember the details. I amply filled the minimal requirement and more. But I certainly didn't study physics at the level that, say, would lead—I don’t know even if Chicago had it at that time, a minor as well as a major. But I know at MIT, that’s very common. I didn't do enough to justify that.
But you stuck with mathematics through your master’s degree.
With mathematics, right. I put off my decision as long as possible. And maybe [laugh] a little longer. My choice of physics courses was very quirky. I basically skipped the undergraduate curriculum after the freshman year and went to Peter Freund’s course on group theory in physics, which was particle physics, basically. [laugh] I had big gaps in my knowledge that I just kind of tried to paper over. [laugh] But I should say, as an undergraduate, I did read—and even in high school, as they came out, I read the Feynman lectures. I certainly didn't—in retrospect, it’s very clear to me that I didn't understand a lot of it properly, but I thought I did at the time. [laugh] And I also read Dirac’s book on quantum mechanics. I had for a long time—even in high school, I read Einstein’s books and papers—Einstein was a big hero. I made it one of my goals to read with understanding his original paper on general relativity. And by the time I had entered college, I think I had done that. [laugh] So my education in physics was very unsystematic, and it was largely autodidactic, but it was not negligible. I knew things here and there. [laugh]
So you did not fully avail yourself of like the Fermi Institute or many of the legendary professors in the physics department?
No, I really didn't. No. Peter Freund played a big role in my life, though, because he taught this course on group theory, or symmetry in physics that—he was so enthusiastic, and he really gushed—and it’s beautiful material. Still to this day I think the quantum theory of angular momentum of one of the absolute pinnacles of human achievement. Just beautiful. So yeah. So that was when I was a senior. In fact, that was my last semester at the University of Chicago. And it was a very unusual semester, because that was the time of the student protests, I think connected with the Cambodian invasion at that time, and other local events in Chicago. And the campus was shut down. The classes and courses were kind of improvised [laugh] and voluntary. So I went to that course, and I knew I wasn’t going to get a grade, so there was no problem. [laugh] And it was really clearly a labor of love all around on his part and for the students involved, and it was very special. And although I went to Princeton right after that as a graduate student in mathematics, in retrospect, that experience really planted a seed that later sprouted. [laugh]
Besides the satisfaction of now finally having been admitted to Princeton, when you say that you were delaying ultimate career decisions, was the idea to continue on in math a way of sort of delaying the inevitable specialization in physics? Like you knew it was sort of there?
Yeah, it really was. Well, I still—no, my first couple of years at Princeton, when I was formally a graduate student in mathematics, was really a kind of intellectual crisis for me. Because I had to decide—following the path of least resistance, I would become a pure mathematician. That’s what [laugh] the program—you know, I sort of stumbled into this program where that’s clearly where the pressure was directed. But I didn't want to do it. I mean, I was afraid of doing something that I wasn’t tremendously enthusiastic about, first of all, and secondly that I didn't feel I had quite the special talent for that some of the people I saw around me did. [laugh] But I went to a lot of seminars in other subjects, and colloquia, in computer science and biology and physics, and just was kind of testing the waters in other directions. And I was very fortunate. Things could have worked out very badly, because I wasn’t really following the program.
I'm curious, on a cultural level, working-class kids from Queens—you're a 15-year-old going to Chicago, and an 18-year-old going to Princeton. Culturally, what was the more difficult transition for you?
Princeton, definitely. At Chicago, I felt right at home, really, right away.
It’s urban. It’s very academically oriented. And I was in this program. I got a lot of attention. Yeah. But at Princeton, it was kind of, “OK, here’s your chalk, and there’s the blackboard. Now do something.” [laugh] And I just didn't—I was just—I felt kind of rudderless, there. And Princeton itself has a kind of southern gentility to it, [laugh] and the influence of the eating clubs and things like that. And this was just totally alien to my experience. So I didn't feel at home there at all.
Was there a singular moment when you realized, “Time to go to the physics department”? Maybe that’s where you'd find your rudder? Or was that a gradual process?
Well, I would say somewhere in between. It wasn’t something that happened from one second to another that there was a phase transition. But sort of after a year and a half of just not finding my way there, I lucked into [laugh] the ferment that was going on in fundamental physics at that time. So in my sampling of all the things that were going on, that’s the thing where clearly there was a sense of excitement and direction. And I was very fortunate that the director of graduate studies was David Gross, who was this dynamic young guy. So that kind of made my choice for me—that clearly very, very exciting things were happening.
What was David doing during those years? What was his research?
Oh, well, he was working on what became asymptotic freedom in QCD. [laugh] He was working on trying to understand this problem of why—well, at a phenomenological level, why those Stanford deep inelastic scattering experiments sort of showed something that looked like non-interacting quarks, in the framework of quantum field theory, or to show that it’s impossible. David really wanted to show that it’s impossible. At that time, he wanted to look for something different. But the first step was to show that quantum field theory couldn't possibly explain [laugh] what was going on. So that was one big thread. That was what he was doing. But at the same time, Ken Wilson was visiting Princeton, and he was giving his lectures on renormalization group and critical phenomena. So these two things were kind of coming together.
So immediately you knew, as you were developing your own persona as a physicist, that it was going to be theory in which you were going to specialize?
Oh, yeah. Absolutely. There was no way that I had the training or the taste for experimental physics. Especially the training. I might have liked it if I had sampled it more. But going back to the Chicago days, as I said, when I entered college, my original intention was to study mind and neurobiology. My vision of myself was that I was going to bring mathematics to neurobiology and teach them how to do it properly. [laugh] But then when I actually encountered the state of the field, it was clear that it wasn’t really ready for mathematical treatment. And then when I went to the laboratory, I didn't like it at all. [laugh] It was very slow, very frustrating, meticulous.
So in terms of the training, would you say that your classical education in math, all the way through a master’s program, was actually an elegant precursor to theoretical physics?
Well, it wasn’t entirely useless. And I got some technical things that turned out to be useful. And the style of thought was definitely not antithetical to physics. Although in some respects, it is. We did proofs, and proving things that are obviously true. But the mental discipline was significant. There are worse ways of preparing for a career in theoretical physics than to study mathematics. That's for sure. And there are more efficient ways, too, in retrospect. But in retrospect, you can always find a shorter path up the mountain. But it was a path that definitely was always moving up. [laugh] Acquiring skills.
How did you develop your thesis topic?
Well, I went to these lectures by Wilson. I talked to David Gross. David and I talked about a lot of things. I wanted to do something independent for my thesis.
And you clicked with David personally?
Yeah, I absolutely did click with him personally. Yeah. So very early on among the things that were going on, clearly this stuff with renormalization group seemed to be very good, [laugh] and there were definitely open questions there. At that time, there was of course no common understanding, to put it mildly, of what the theory of the strong interaction should be, or even that such a thing was on the horizon. But the gauge theories of electroweak interactions were maturing. They were becoming kind of plausible. The neutral currents weren’t quite established yet, but it was in the air, and that was where people were focusing attention.
Anyway, so it didn't really take much of a bright idea—my bright idea was to apply [laugh] the renormalization group to these theories of the weak interaction, which were non-abelian gauge theories. And there was a big theoretical issue in electrodynamics of the so-called Landau ghost—vanishing of the coupling—at long distances as you tried to remove the cutoff, in modern language. But this behavior hadn’t been calculated for non-abelian theories. So I thought, “Well, there’s a good question.” I didn’t have in mind any practical application at the time, but I thought it would make a very good thesis project to do that calculation for the weak interaction, and see if these new theories of the weak interaction solved this conceptual problem of the Landau ghost. And that would make them, in a sense, more fundamental than the theory of quantum electrodynamics. They had the great advantage also that my spotty education was not really a barrier, because it was a calculation [laugh] that was mathematically well-defined. And the kinds of things that I really did feel comfortable with—relativistic quantum field theory and renormalization group—they were enough.
To the extent that graduate students think in such grandiose terms, I'm curious what fundamental questions you thought your dissertation contributed to.
The fundamental question was whether the new theories of the weak interactions were free of this conceptual problem of not making sense if you extrapolated to ultra-high energies. So that’s a less technical way of putting it. Quantum electrodynamics, although very successful, sort of notoriously broke down if you tried to extend it to arbitrarily high energies. It became internally inconsistent. So I wanted to see if that was still true—that was also true of the emerging theory of the weak interaction.
To what extent was your research reliant on experimentation?
Well, not in any direct sense. That proposed thesis project was not really, in any direct sense. The result of the calculation, that the coupling becomes weak at short distances, immediately suggested to us application to the strong interaction, where there are these phenomena that David was aiming to show couldn't happen [laugh], that it was inconsistent with quantum field theory. Suddenly it did seem like it was consistent with quantum field theory. Possibly. And so we very quickly turned from the weak to the strong interaction.
Who was on your thesis committee?
I don’t really—let’s see. Well, David, certainly, of course. And I think Arthur Wightman was on the committee? And an experimentalist. I think Pierre Piroué, if I remember correctly. But that didn't make a big impression on me. I had taken the oral exam and so forth. The thesis committee was kind of a formality, as it usually was. I should also mention that very crucial to that early stage of my career was Sidney Coleman. He happened to be visiting Princeton at the time. [laugh] He was a very, very charming figure, and we became friends very early. He was a great mentor, also. And it was very encouraging to me that he was so interested in what we were doing. I knew that David was a brilliant guy and so forth, but he was youg and junior himself—you know, I was 21 and he was 31. We were kids, in retrospect. And he wasn’t a tenured professor when we began the work. So the fact that here was this legendary figure from Harvard [laugh] who was on the same page really was very encouraging and very important to maintaining my confidence and interest in this particular line of investigation.
What kind of advice did you receive on the best steps forward after the thesis defense, in terms of postdocs or other opportunities?
I didn't take any advice, really. [laugh] My wife wanted to stay in Princeton.
When were you married?
We were married about the same time as the asymptotic freedom was discovered in 1973. It really all happened at the same time. She wanted to stay at Princeton. She had been a student there. Actually she still was a student there. And I didn't want to move. I thought things were going very well. I was interested in what I was doing. We had a new colleague, Tony Zee, come in, who was an assistant professor, and we got on quite well. And I liked Sam Treiman. And David was of course still a force of nature. And Curt Callan. So it was a great environment. I didn't want to leave.
And this was all in the physics department? You didn't have much interaction with the Institute?
No, no, not at all. Well, I mean, I knew it was there, and occasionally went there for seminars. But no, not really.
So you stayed on at Princeton for postdoctoral work?
Well, I didn't really do a postdoc. I joined the faculty.
You just straight joined the faculty.
It was an assistant professorship. I got tenure I think in ’79, so fairly standard.
Did you see your joining the faculty as an opportunity to continue on with the research from graduate work, or was it an opportunity to move on to new projects?
Oh, to move on, for sure. Although—well, OK, I should give a twofold answer. [laugh] The most naïve thing, which is the way I felt at the time was, OK, so now we've solved the strong interaction; it’s time to solve the weak interaction. [laugh] And the modern electroweak theory, with its kind of minimal structure and so forth, was by no means clearly the end product at that time. Nowadays, we don’t expect the weak interaction really to explain why the values of mixing angles are what they are. But at that time, we thought maybe extra symmetry or some additional insight would lead to a bigger and better theory of the weak interaction, which included more predictions. So that was the immediate thing I wanted to do. The logical thing would have been to try to take on confinement, and extend the theory of the strong interaction. But that looked too hard to me. I wanted to do something that was more within reach. But also, I just wanted to do things that I found interesting.
What was too hard about it? What does that mean?
Well, I didn't see how to make progress with it. [laugh] And I also didn't—how should I say?—if I think about the kind of work that we recognize as making big conceptual advances in understanding the physical world, it’s usually not a matter of solving hard applied math problems. [laugh] It’s usually a matter of getting additional concepts in there and working at weak coupling [laugh]. Or finding some expansion parameter that leads to a simple theory when it’s zero, but if it’s not zero, you can systematically isolate its effects. So I was looking for things like that, somehow. Well, yeah. I guess the other part of it is that it wasn’t clear to me that understanding confinement would lead to anything but justifying what we already knew, sort of. Justifying the quark model or something. Which is a laudable ambition, but in my own mind, I was after bigger game than that. [laugh] The weak interaction thing really didn't work out. I guess in retrospect, I could have—if I were cleverer or faster than I was—but it really would have been pretty extraordinary—I could have discovered the Kobayashi–Maskawa mechanism [laugh]. But I didn't.
But what did happen was that—two things. Well, several things. Several things happened rapidly around that time, actually. It became clear that this phenomenon of asymptotic freedom, it was clear to me very early on that it would enable you to study how matter behaves at ultra-high temperatures. And so you could actually do early universe cosmology in a way that you couldn't before. Like if you read Weinberg’s book, the Gravitation and Cosmology book, it was sort of just before we did this work which clarified the strong interaction. At the very end, he talks about the very early universe and how you can’t really say anything, because the strong interactions are strong and we have no idea what happens [laugh]—it gets totally speculative. I had read that passage, and it made a huge impression on me, because I was looking for unsolved problems, and that was one. And now we could address it. So the early universe sort of opened up. And that became a big interest of mine, and an abiding interest—what could we say, based on fundamental physics, about the early universe? Could we get more signatures of what might have gone on? Were more things explainable, understandable, than before? So things like why there’s more matter than antimatter in the universe. The possibility of cosmic phase transitions. Just describing the equation of state of matter at ultrahigh temperature. All those things became open to investigation, and that took up a lot of my effort in the ‘70s.
The other thing that happened was—well, I did, in retrospect, spend a lot of time not so fruitfully trying to extend models of the weak interactions. But one thing that came out of all those struggles was a few things that you could do. [laugh] One thing that—you couldn't really address the masses and mixing angles very well, but you could discuss the evolution of the different couplings, the strong—well, all the different couplings, [laugh] using the same techniques that we used to describe the evolution of the strong coupling. So we could and did apply that to the weak and electromagnetic interactions, and that led to this whole picture of unification, which works pretty well. Qualitatively in the sense that the couplings tend to converge at high energies, but also we discovered more quantitatively, if you include supersymmetry. I studied how you renormalize all kinds of couplings. So there were lots of nice calculations to be done. Trying to explain the delta I = 1/2 rule, which was a mystery. So there was a lot of work to be done at that point. And understanding phase transitions. I forget what the original question was, but I guess the original question was whether to build on my thesis or do something else.
And I guess the answer was both, because fortunately my thesis opened a lot of doors. So it was building on it but not in the sense of the thesis was a broad foundation, and you erected a pyramid on it. It was more like the opposite. The thesis was a point, and we erected an inverse pyramid [laugh] based on that point.
And when you say “we,” who were your most important collaborators during your Princeton years? Did you continue to work closely with David?
Not really, no, because he did pursue the confinement direction much more. I collaborated quite a bit with Tony Zee, Sam Treiman, and I also did a lot of this work on my own. I never actually wrote a paper with Steve Weinberg, but I did consult with him on some of these cosmological issues, and that was important to me. Yeah. So those were the dominant collaborations during the 1970s.
Did you take on graduate students right away when you became assistant professor?
Yes. Yeah, I had students from very early on. Doug Toussaint, Steve Wandzura, and some others.
And were they generally working in more narrowly defined areas than you were working on, or not necessarily?
Well, of course. [laugh] They had to do particular thesis problems and get up to speed and focus on them enough to learn the ropes, so to speak. Not everyone has the same style as I do, to put it mildly. My style is to try to do something important and then abandon it [laugh] and do something else. Most people, if they do something that they feel is important, they want to keep at it, to maintain ownership. When I have an idea that’s successful and popular, that to me is a signal that my work is done. [laugh]
But popular doesn't always mean scientifically relevant.
No, absolutely not. Right. [laugh] Well, popular means—it does mean relevant, in a sense. That it will absorb people’s attention and give them pleasure and lead to literature and so forth. Whether it leads to experimentally fruitful exercises or enterprises or technologies or things that become of interest philosophically [laugh] or to get beyond kind of an ingrown purely academic enterprise, that’s another issue.
Had you more or less let go of your earlier interests in biology and cognitive issues? Did they remain in the back of your mind?
Yeah, no, absolutely. I still follow that at an amateur level. And indeed, in recent years, at Arizona State, I've started to build up something that’s kind of—projects that involve expanding perception. So really gadgetry that’s aimed at helping people expand their perception. So it has gotten much—I always had in mind my early experience with my father. The other thing my father brought home, he brought home a lot of broken radios and televisions. [laugh] We had some very early televisions, like with two and a half inch screens and things. And he was kind of a hoarder, too, so we had all this stuff. Kind of a museum of early TV technology and radios. And I could see him; he derived great joy from working with those things. He didn't want me to touch them, unfortunately. [laugh] But I always admired—I think because of his clear admiration for and kind of the inventors and gadgetry and things like this—and I always aspired in that direction, although I didn't act on it until recently. [laugh]
Would you say that the 1970s and the early 1980s was a golden age of cosmology?
Yes. Clearly. Because of this—suddenly—although in the long run the direct influence of asymptotic freedom was limited, it really gave—it made a foundation for the whole enterprise. It made it intellectually respectable as well as technically possible to address what matter was doing during the Big Bang, very early on, and that enabled one to address whole new questions. I missed the boat on inflation. I really should have invented inflation, in retrospect. But I didn't. [laugh] And that was clearly the big, big thing. But there were other things. And no, I didn't miss the boat completely, I don’t think—this story isn’t finished—about the dark matter. We’ve been talking about cosmology and so forth, and on the one hand, and this links up to axions. I don’t think we got to axions, actually, but now we will. I was starting to talk about how I wasted time on the weak interactions, but some good things came out of it. [laugh] And axions are the high point. From this work on trying to understand the masses of quarks on the one hand, and implications of QCD in the early universe on the other, one thing came out is that—bya long chain of reasoning, which we could go through, but it’s a long chain that seems to be sound—we were led to predict a new kind of particle called an axion, and that it could make the dark matter of the universe. And it still looks good. It looks better than ever. So that has been a continuing thing. Right now, as we speak, I have active efforts, and there are active efforts all over the world, to detect axions as dark matter. I'm very heavily involved in that.
To what extent during those years did you think that your research contributed to the efforts to produce a grand unified theory?
Oh! Well. It did. I mean [laugh] the whole—how should I say? To this day, the really—the only—well, let me backtrack on this a little bit, but let me first state it. The only really quantitative evidence we have for unification—that it’s on the right track—is the fact that the strong and the electromagnetic and the weak interaction coupling converge at very high scales, and in fact at such a high scale that gravity also becomes a comparable strength. So this is by far the most compelling evidence for unification. The other evidence is that the different quantum numbers of fermions and of quarks and leptons fit very nicely into a unified group of SU(5) or SO(10). So that’s less—that’s not numerical, so to speak. It’s discrete choices as opposed to continuous choices. The only continuous evidence, which is sort of at another level of quantitative evidence, is this unification of couplings. And that points to a high scale. It’s absolutely central. And, well, I don’t know if you want to go through these technicalities of unification, but the fact that it’s a very high scale is what protects you, to some extent, from proton decay. It’s what gives you very small but not zero neutrino masses. So it’s the absolute core of the story.
And you were thinking in those days specifically about how to apply particle physics to cosmology?
Oh, yeah. In the ‘70s, already. Yeah, definitely.
How much were you thinking about black holes during that period?
A little bit. I mean, I studied Hawking’s work on evaporation of black holes, and I thought it was fascinating. And I was aware—well, that came later, really—I was aware that there was a possible problem with information loss. But—how should I say?—to me, at the time, there seemed to be more pressing issues than that. So I didn't really—I mean, my attention was mostly elsewhere. But I thought the phenomena of black hole evaporation or radiation was pretty fascinating, and still do.
If you had naming rights, would you have chosen the term Big Bang?
[laugh] Well, yeah, I think it’s a good name. I think it’s actually quite a good name. I like it, yeah. It captures people’s imagination.
What does Big Bang convey and what does it distort?
Well, the main thing it conveys is that the universe was once much denser and hotter. And it appeared as a kind of fireball such as you might get out of an explosion. So that much is true. Where it potentially misleads is that this explosion occurred everywhere, so it was not from a point in empty space outward. And we really don’t know whether the picture can be extrapolated all the way back. Probably not.
All the way back what? All the way back to what?
Well, we don’t know. An unknown kind of explosion, or something else [laugh].
But that suggests that there’s what to learn about what happened prior to the Big Bang?
I think it’s quite possible that that will turn out to be not a meaningful question. The whole concept of time breaks down in the early universe. This was Saint Augustine’s answer, by the way. [laugh] He said that at some level, time is what clocks measure, and if you don’t have clocks, you don’t have time. So it doesn't make to sense to talk about what happened before there were clocks. But anyway, these are higher-order worries to me. The Big Bang is a pretty damn good description of how the universe has looked for the last 13-ump-ditty-ump years. And the fact that we don’t know quite how to cap it off is—well, that of course from a philosophical point of view is very significant and vexing, but from the point of view of conveying the main message of how we got here [laugh], saying that the universe evolved from a Big Bang tells you a lot.
Does it also tell you that—or does physics tell you that the universe was able to create itself?
No, it doesn't—well—that’s a kind of strange question. [laugh] That’s the kind of question that my training in philosophy, my self-training in philosophy, has taught me to really examine critically, what it means. There are several ways you might interpret that question. One is whether we need something extra-physical to explain the physical world. Or can we make physical hypotheses that are within the bounds of the known laws of physics that we observe today that give a plausible account, when supplemented with some basic historical facts, give us an account of the physical world today that’s credible. I think, yes, it does. But does it answer all questions about ultimate origins? Certainly not. It doesn't tell us whether there might be other worlds far away that eventually will become visible to us. It doesn't tell us to what extent the laws of nature we observe are uniquely determined. So it certainly doesn't answer all possible questions, much less questions about what does it all mean. Was there any higher purpose to it? These questions do not get illuminated very much. At the same time, they get advanced a lot. They sort of change their character. But they certainly don’t get answered by our understanding of physical cosmology. Maybe it’s misguided to hope that they ever would be.
You could even say that such questions are unnecessary if you're confident that physics does explain how the universe could have created itself. Because then there’s no why.
Yeah, but the idea that the universe created itself, I don’t—that’s not—that to me is not a—that’s a—I guess it’s grammatical [laugh], but I'm not sure that it makes sense if you hold it up to examination. What is its operational content?
I guess the closest I could come to a sensible interpretation of that is we might find a formulation of physical laws that is consistent with everything we know that has tremendous circumstantial evidence that it’s on the right track, that is very, very difficult to change. So it’s rigid, in a sense, and also goes beyond what I think we have now. And one very clear way things might improve is that our understanding of laws now are basically always dynamical in the sense that they say, “If you have this at time T1, you'll have that at time T2.” But they don’t address the question of why do you have this at time T1. So you have to start it somewhere. But if you had a comprehensive account not only of the laws in the sense of dynamical laws but also included the kind of closure—so there’s only one history that seems internally consistent—then you could say that gives me an account of everything I observe. It can’t be changed very much without ruining it. And it also accounts for the history of the universe as we observe it, or at least it gives us a consistent picture—and then you could choose to call that future theory, “Well, the universe created itself.” I think that’s a kind of misleading way to talk about it. But in so far as you can make any sense at all out of the idea that the universe created itself [laugh] – that’s it.
Well, is it just as easy to say that there was nothing to create because the universe always existed?
Well, again, always—yeah. I don’t want to put it in any other way than the way I put it, which is [laugh] if you could have that kind of account that was intellectually closed, consistent with observations, and got beyond dynamics—then you could declare victory. OK, then I've understood it. Now, I don’t think we have that now, of course.
And I also don’t think such a theory be a complete account, of course, of everything we observe in detail. A profound lesson that we learn from our understanding of physical law is that it has a kind of irreducible stochastic element. In quantum mechanics, we learn this. An irreducible element where the wave function contains more than we actually observe, and what we actually observe is probabilistic treatment of the wave function. And also we learn that there’s extreme sensitivity to initial conditions. So as a practical matter, you can’t go from the laws—even if they include it in principle—a complete account of what the history should be—that wouldn't account for the history we actually observe, because you can’t calculate it, as a practical matter, or even in principle, because of chaos on the one hand, sensitivity to initial conditions, and also this irreducible stochastic element.
OK, so given that understanding, I think we could declare victory. It’s declaring victory in a strange sense. It’s almost—declaring this particular victory—at the same time, operationally, it means you declare defeat, because you say, “I'm not going to be able to do any better by thinking about fundamental laws. Those are the fundamental laws. I've done as much as a physicist can, so now it’s somebody else’s problem—we hand it over to the biologists and the historians.” [laugh]
And of course, Frank, another challenge is that we're necessarily limited by our own minds in conceiving of answers to these questions.
Well, we're not, actually, because we can use computers.
That’s where I was getting to. So to what extent do you see computers, supercomputing, and artificial intelligence really helping to answer these kinds of questions in the future?
Oh! Well, they certainly will help. I mean, we have existence proofs of that. Even my own mundane thing of QCD, we wouldn't understand confinement. We don’t understand confinement, really, in, I would say, a really profound way. But the reason that we're very comfortable—well, I certainly am—comfortable and convinced is because the computers have shown us that that’s what the theory produces. It produces not only confinement, but the actual particles we observe, and nothing else. So the computers have changed the nature of the theory—the way QCD is practiced is heavily, heavily, heavily reliant on the help of computers. The way modern high-energy experimental physics is practiced is totally reliant on computers. There’s no way in the world you could analyze what’s going on at the LHC without enormous amounts of data processing. So the influence of superhuman intelligence is not speculative. It’s already here.
Another aspect which is maybe more what you were aiming at is you could say, well, maybe the theories will—eventually the theories will have a qualitatively different character in the sense that they won’t be expressions that are tailored to the human mind. [laugh] The theory will be some physical object that produces the answers. Now, that might seem extravagant or strange or weird, but actually that’s the current state of chess and Go and things like that. The best theories of good Go playing [laugh] or good chess playing are not books of rules but certain patterns of connections in neural networks. They give the best answers. And there may be no simpler way of understanding it [laugh] “Well, here it is. This is the theory. This is how chess works.” [laugh] It’s a very possible, logical outcome.
That’s not the way physics has gone, so far. Physics has had this remarkable program if you look at it. We take it for granted now, but if you think about it abstractly, it’s an extraordinary program of trying to understand the world by understanding the really, really smallest things thoroughly [laugh] and then building back up. And it didn't have to work. [laugh] You know? And certainly I don’t think the Greek philosophers thought it would work that—maybe some of them did, at least in crude form, with atomism, but most didn't. And really this concept that you could understand the world deeply by understanding the simplest possible situations thoroughly is a very strange concept and didn't have to work. [laugh] That there are precise laws. That you don’t have to invoke supernatural influences or thought or the influence of distant bodies like in astrology. Not only don’t you have to, but that would muck things up, because the laws seem to work without all that, with extraordinary precision. So that’s the way it has gone. This program has been extremely successful so far. Not entirely successful, as we have mentioned. We don’t understand, roughly speaking, why the Big Bang had to be the way it is. We certainly don’t understand and probably can’t understand—we understand why we don’t understand [laugh] - history in detail. So if you want theories of biological objects and so forth, it may be that the theories—that deep understanding can’t be achieved by human minds. You really need objects that implement programs. But physics is a shining example of how structures, mathematical and logical structures that were tailored to human limitations allow us to get very far. [laugh]
[laugh] Frank, can you talk a little bit about how you see your research leading to the development of quantum chromodynamics?
Well, it was the turning point. We built on a lot of experimental work and theoretical modeling that led to people understanding that there was such a thing as the [laugh] strong interaction. That there was some phenomena that you could call a quark. It was kind of a little bit vague when we started, but that there was many phenomena, but the phenomena that turned out to be really crucial was the scaling behavior. So we built on all that. But I think it’s fair to say that we changed the situation qualitatively because we had a very precise proposal for what the theory should be. [laugh] And I think that was inconceivable just a few years earlier. In fact, I know it was—well, it was inconceivable, for instance, to Freeman Dyson. He gave a talk at Princeton—I think in 1972, but maybe it was 1970—anyway, where he said it would be 100 years before we had a theory of the strong interaction.
[laugh] At least he believed there would be a theory.
[laugh] Well—[laugh]—and it goes very much together with what we were just talking about—this amazing fact that looking at structures that the human mind is attuned to that have a tremendous amount of symmetry and kind of abstract simplicity—actually turn out to describe nature. So although the world of phenomena in the strong interactions appears to be extraordinary complex and diverse and hard to understand, once we got to a candidate theory and started working out from the candidate theory, it became a very different kind of enterprise. In a sense, we were very lucky, because we got to leverage all that prior knowledge. But I don’t want to be too modest about this. We changed the picture. [laugh] That was the turning point. No question.
And who’s the “we”?
Well, David Gross and I. And Politzer also did calculations that got asymptotic freedom.
Is this really a case of multiple independent discovery? Were you aware of Politzer’s work at the time?
When we were quite far along, we became aware that Politzer was working on this kind of problem, because Sidney Coleman told us. Sidney was—as I said, he was visiting Princeton at the time, and Politzer was his graduate student. So, he told us we should talk to this guy and make sure that we acknowledge him—Sidney was such a sweet person, and he absolutely wanted to avoid any kind of priority dispute or unpleasantness. So he brought us together so we could have simultaneous publication and check each other on the key calculation. So we became aware, but it’s pretty much when we were already done.
I'm so curious about the gestation period from research to recognition by the Nobel committee. So do you have any sense of why 2004, what the timing was that year?
Well, I don’t know why it was that particular year. I have ideas about why it took so long. [laugh] They may be wrong ideas; I don’t know. But I think several factors came into that. First of all, for better or worse, the theory made very precise predictions, and the Nobel committee is desperately afraid of giving prizes to work that later turns out to be wrong. [laugh] They really don’t want to do that. [laugh]
So they really kicked the tires with your research.
[laugh] Yeah. So the fact that it could be tested precisely meant that they would wait until it did get tested precisely. And really the crucial data started—the really incisive numerically precise data that could have falsified the theory, sort of the last chance to falsify the theory I would say, was when the LEP collider started gathering data. That was in the early ‘90s. So that was one thing.
Did that make you nervous? Not as a scientist, but as a person? The ego that is thinking, “This is real Nobel Prize-winning work. I hope this doesn't prove us wrong.” But as a scientist, you just want to know what the truth is.
Well, I'm not that scientific. [laugh] No, of course I want—you know, no, I wanted it to be correct. Just like now, I want the axions to be the dark matter as well. I don’t deny a personal interest in my babies. Come on. I'm a human, too. But in any case, by the time—how should I say?—by the time LEP came around, the evidence, although you might say it was circumstantial and only semi-quantitative, it was pretty damn overwhelming. So I think—how should I say?—maybe you could compare it to like the discovery of gravitational waves. There was no question—or better, the w and z bosons. There was no doubt that the theories were correct enough [laugh] to justify the predictions that underlay those experiments. So I don’t think there was much doubt about the result.
But it’s one thing to say that, and it’s another thing to actually do it. I can’t think of an example in the history of science where a theory that seemed so well-established turned out to be fundamentally wrong. I mean, you could say that the wave theory of light was fundamentally wrong or something, but it’s not really fundamentally wrong. It’s just incomplete. So yeah, I think by that time it was clear that QCD as we formulated, it was at worst incomplete. [laugh] The idea that it might be totally wrong just wasn’t credible. But anyway, for whatever reason, I think that was part of it. Another part was that there was kind of an intellectual history involved. So I think it would have been very difficult and arguably unjust for the Nobel committee to have given us the prize prior to giving a prize to the experimentalists who discovered the scaling behavior. So that was Friedman, Kendall, and Taylor. And also ‘t Hooft and Veltman, I would say, because their work really made gauge theories respectable [laugh] as quantum field theories. And we definitely relied on that. So those had to be first, I thought. Almost surely.
Do you have a sense of who were some of the key champions of your research in terms of promoting it to the Nobel Committee?
No. I know lots of people have told me they were [laugh] - but that’s a different matter! [laugh] I'm pretty sure—well, I'm 99% sure that Jerry Friedman was an advocate. But beyond that, a lot of people have told me they were, but I take it with a grain of salt. And I don’t want to know, really.
Frank, what was that day like? When did you get the call? And was it out of the blue, or was the buzz so loud that you knew this was coming?
Well, the buzz—I mean, once those two prizes were awarded—to Friedman, Kendall, and Taylor and ‘t Hooft and Veltman—I think that takes us all the way to 1999 or something like that. So not that long before. So at that point, I really thought, “Any day now.” Not any day, but any year now. So it was from year to year, I thought there was a very finite chance. And so every year at the appropriate time, I would study when the announcement was going to be, and kind of be psychologically worked up. [laugh] I couldn't help myself. And in fact, I knew the day so I would—so for two or three years before the prize was actually awarded, I literally…I wasn’t able to sleep the night before. Just wasn’t. And that included 2004. So I was from time to time checking my clock. We had ones of these clocks that are liquid crystal, red display, that show the time. I knew the announcement was going to be at 12 noon Stockholm time, which would be 6:00 in Cambridge, where I was, in the morning. So about 5:00, I looked at the—when I looked at the clock, I said, “Look, you're not going to be able to sleep, so why don’t you take a shower and get ready just in case?” And I did. So I went to the shower. But it was about ten minutes later, when I was just in the middle or towards the end of my shower, that my wife came in with the telephone and said—I hadn’t heard the ring of the telephone—when she came in and said, “Someone wants to talk to you.” [laugh]
So Frank, your timing was off. It wasn’t six a.m. They got you before.
Well, six a.m. was going to be the public announcement, but I didn't realize that they would call people before that. I guess I knew much less about the Nobel Prize then. But no, I didn't know they would call in advance. And well, I took the call of course, but I came right out of the shower. I didn't dry off. I was just soaking wet and took this call. And you know, Betsy knew about all this stuff, of course, and said, “It sounds like someone with a Swedish accent.” [laugh] “You should definitely take this call.” And I did. And it was, of course. It was the Nobel Committee. And the other thing I didn't realize was I thought when they did tell you that they’d just say, “Congratulations, you've won the Nobel Prize. Goodbye.” [laugh] But it wasn’t that way at all. Several of my Swedish colleagues wanted to congratulate, and gave little speeches. [laugh] The head of the Academy. And they wanted to give some advice about how to deal with the press. So this went on for about 20 minutes, and I was still soaking wet, and just [laugh]—my wife was trying to dry me off. [laugh] So it was quite an experience. And then when that was over, I guess—I think I put on some clothes, but then—but I right away—I wanted to call my parents right away, because I knew this would mean a lot to them. It would really mean a lot to them. As I said, they had grown up in difficult circumstances, and really were invested in my success. So I called, but when I called up, my father was furious. He said, “Do you know what time it is? What do you want? What are you trying to sell me? Whatever it is, I don’t want it!” [laugh]
So I explained to him what was going on, and it was a great moment. And then that takes us to about 5:30, I suppose. Then there was somehow a—I had half an hour of peace, more or less, to get something to eat and get properly dried off. But then there was a stringer for the AP who heard about this and right away was at our house [laugh], maybe even before the formal announcement, but certainly not long afterwards, and wanted to take pictures and so forth. And then the phone began ringing. Once the announcement was made, the phone began ringing off the hook. Took a few but then my wife took the phone off the hook. So that was the immediate experience. And then—well, it goes on. [laugh] But I guess what I didn't anticipate was kind of the outpouring of—I don’t know how to put it, except—love from my colleagues, some of whom I thought of as my rivals. But just the wave of congratulations and kind of the pride of the community. Because it’s recognition not only of individuals but also of the community’s achievement. The high-energy community, and people who had given us the leverage to do this.
And the fact that your colleagues were so happy for you probably speaks to how generous you've been with them over the years as well.
I guess so, although I didn't think of it that way. [laugh] But yeah, I try. Because—yeah. Well, this goes very deep, but part of it is my Catholic background, I suppose, but I think more than that, it’s what I've learned in my career in physics, and understanding the physics world, is a kind of—is two things that are complementary. One is humility. The universe is really big and really old and [laugh] really—we're a very, very small part of it. And that’s just true. That’s something you learn by understanding the world. But on the other hand, self-respect. Because we do manage to understand a lot, and although the world is big, that doesn't mean we're small. We have lots of atoms, time for lots of thoughts. And somehow that combination of humility and self-respect reflects itself, I think, in empathy and generosity in dealing with fellow human beings.
It probably also helped keep you grounded during those first few days after the announcement.
Yeah. Well [laugh] right. Well, it was another state of consciousness. It was really something else. So it wasn’t so much a matter—it was much too late to be thinking about things. It was just experiencing. [laugh]
I'm curious if, given the fact that you're being recognized for research that had taken place, in large part, earlier in your career—
—and because you had gone on to so many more diverse topics in physics and even sort of somewhat out of physics, I wonder if you ever thought about the fact that recognition at that level provides you with a voice or a platform to talk about all kinds of things that may have nothing to do with the research for which you were recognized. I wonder if you ever thought about that and you saw an opportunity to use that platform.
I'm very aware of that. Very aware. And again, there are two complementary aspects to it, I would say. On the one hand, it’s an opportunity, and I've tried to use that opportunity in a constructive way. You may know I write a column for The Wall Street Journal for instance, and previously I wrote columns for Physics Today, where I talk about—well, in the Physics Today, it was more directed towards the physics community, but in The Wall Street Journal, it’s also to the external world, but really about scientific subjects, things that are recognizably scientific. Maybe not theoretical physics, but closely related to theoretical physics, or subjects in which I really think I have unique knowledge—or not unique, but special knowledge that very few people have, and where I think our community has something important to tell people. And so I'm very comfortable with that.
On the other hand, I'm very uncomfortable with just overreaching in the sense of expressing—well, it’s not even a matter of overreaching; it’s a matter of debasing the currency [laugh] by talking about things where I don’t have such special knowledge or authority. So I wanted to—I have a Twitter account, for instance, but I don’t use it to express my opinions about music [laugh] or about politics. I could do that. I'm entitled to do that, just as anybody else is entitled to. But it would, I think, diminish from the message of the more valuable parts. So that’s the way I feel about it.
So what messages or areas of knowledge do you feel comfortable about using that platform?
I was going to say, on the third hand [laugh]—well, I feel pretty comfortable with most of science, almost all of science, and large parts of technology. So if you look at my Wall Street Journal columns, you'll see they're very diverse. I talk about things where I have not made major contributions, even sometimes things in biology, but where I feel I do understand things at a professional level and have something to add. But I was going to say, on the third hand, the other field which may not be so obvious but I feel is very important is kind of what brought me into this in the first place, as we sort of talked about earlier—is the kind of philosophical issues and things that border on theology or what goes into religion. Questions about the nature of reality and so forth. And although I don’t think science exhausts that by any means, I think that philosophers or theologians or people like that who express dogmatic opinions about the nature of reality really should learn some physics before they do that. [laugh] I think that god speaks through his works or its works, and that studying god’s work is the royal road to learning about what god is. And so I feel—especially in my new book, I'm taking that on.
You're using the term god as a narrative device, not to indicate any belief in such a being?
Certainly not an anthropomorphic belief, no. But sort of—the word is used very, very widely, and I just—no, I don’t—no. I just mean—how shall I say it?—topics that are usually associated [laugh] with god in most people’s minds, where I think science has a lot to say, that people should know about. So people talking about the meaning of the universe should know how big the universe is, and how old, and that it came from the Big Bang, and how complexity emerges, and that we really do have a causal description of many, many things that holds up well. It’s not true that anything goes. Things like that. So I think I'm very comfortable talking about those fundamentals and trying to get across these basic messages that I've learned about the issues that I really wanted to address as a teenager and pre-teen. [laugh]
Frank, to go back to the narrative a little bit, can you talk about your decision to move over to MIT and how that came about? Were you recruited?
Oh, yeah, I was definitely recruited. [laugh] They made a very nice compelling offer, and that was certainly part of it. There were family reasons. My wife’s family is based in New England. Both our daughters were going to school here at Harvard and MIT. So there were certainly personal factors. I also felt I could benefit from a kind of more broadly focused environment than the Institute for Advanced Study. The Institute for Advanced Study is a marvelous institution, but it’s small, and it’s cut off from experimental physics. It’s really—well, it has a brilliant faculty, but it’s very small. [laugh] So my interests were going more towards areas of physics that weren’t so much represented there and science that weren’t so much represented at the Institute.
And MIT was an ideal place to pursue those interests?
I thought it might be. As it turned out, I didn't really make optimal use of MIT, I don’t think. But yeah, the atmosphere was a little more down to earth.
In what ways were your research interests expanding during those years—the early ‘80s, mid-‘80s?
I was becoming much more interested in condensed matter physics, in particular.
Why? What was it about condensed matter that captivated you?
Well, part of it was just, for me, the novelty value. But more specifically was the realization—well, I had gotten interested before I came to the IAS, when I was at Santa Barbara, where that was really the dominant activity, I would say. And I found that the techniques that I had developed or we as a community had developed in high-energy physics to understand particles, those kinds of phenomena, and even cosmology to a certain extent, that those techniques could also be used to illuminate certain kinds of questions in condensed matter. As I mentioned to you, I always had at the back of my mind trying to do tangible things [laugh] that would be useful to people, not only intellectually but actually useful. And at least I got a little closer to that by thinking about condensed matter. But there were very specific things. At Santa Barbara, I took up directions of research that were suggested by what was going on in condensed matter physics, similarly to how almost a decade earlier, I had taken up the quantum field theory and renormalization group. And there was a kind of ferment in condensed matter physics around the ideas of fractional charges and Quantum Hall effect, and also to a lesser extent Berry’s phase. And I just glommed onto that. I really liked the—they were nice mathematical things.
Who were some of the key people in condensed matter that you wanted to learn from and work with?
Oh, well, Bob Schrieffer was absolutely key, of course.
What was his research at the time?
Fractions. Fractional charge on solitons. And he was interested in the Quantum Hall effect. It was very much stimulated by success. I was able to, with Jeffrey Goldstone, we found powerful ways of understanding fractional charge that were new to the condensed matter people. Well, that were new, period, and that opened up all kinds of doors, similar to the way asymptotic freedom did. But then there was a very concrete success with fractional statistics, anyons, where we were able to put together the ideas from Berry’s phase and basic theory of the Quantum Hall effect with kind of abstract ideas about vortices and charges and gauge theories to really start a new field of anyons and fractional statistics and so forth, which kept me busy for quite a while. And you may or may not know that the really first compelling observation was about a month ago now. [laugh] So that has been—
So something really big happened during the pandemic. That’s exciting to hear.
Yeah, yeah. Well, probably the experimental work was probably done before the pandemic, but it appeared in April 10th issue of Science. Of course it’s another case where there has been overwhelming circumstantial evidence, but it’s another thing to actually have very tangible quantitative experiments.
I asked you to compare your experience at Chicago and then to Princeton, but of course that’s difficult because you're at a very different stage in life as a young undergraduate and then a graduate student. But you might be better prepared to answer that question as a professor moving from Princeton to MIT. And that is, how was physics different at MIT?
Well, I have to be very careful about how I put this. [laugh]
You can always speak freely now and edit the transcript later, so—
[laugh] It was—noisier [laugh] in both a good and a bad way. It was noisier in the sense that it was open to more inputs. So there was just more going on. In the immediate environment, there was a very vibrant condensed matter group. There was a lot of interest in QCD and in calculational physics, which was also very interesting. But also in the penumbra of this, there was also all the engineering that goes on at MIT. So it’s a very rich environment. Whereas the Institute for Advanced Study is kind of an ivory tower. It’s very different. So it was noise in both the good and the bad sense, It was noise in the sense that [laugh] it got you out of ruts [laugh] but it was also more distracting. There were more things to do in terms of teaching and practical distractions.
When did you come up with the idea of time crystals?
Well, I came up with the idea in nascent form, I would say, in 2011. I was playing around with it in one way or another—dawdling, as I often do—for a year or so. And the original form of it was rather different from the final form—I mean, the semi-final form [laugh] that came out in 2012. Originally it was just—I was teaching a course in symmetry and group theory applied to physics, and I always strived to do something new and different, so I wanted to do—I mean, crystallography is one of the beautiful chapters of symmetry in physics and group theory. So I thought, “Well, is there some excuse for doing crystals in higher dimensions?” [laugh] And then I thought, “Well, time is a dimension, so we can do crystals [laugh] with time, also.” And so I started thinking about four-dimensional crystals, just really as sort of recreational mathematics. And then Al Shapere said—he was my former student and is now a valuable colleague—I was telling him about this, and he said, “Well, do you think this could be real? [laugh] How do you decide if it’s real? And at a more technical level, could you make a Landau-Ginzburg theory?” So that really got me thinking.
Is the question of real, is that really a question of is it measurable?
Yeah. Well, it could be—yeah. Well—[laugh]—philosophers could write books about what it means, but yeah, certainly things being measurable helps. [laugh] Then there are different kind of measurable. You could ask whether they occur as natural objects, whether they can be engineered, whether they can be numerically simulated and sort of numerically engineered. But yeah, the realer, the better. So then that was—and then I—you know, I got to realizing that the most interesting issue was whether—that these things could develop spontaneously. That summer of 2012, I guess, to celebrate my 60th birthday, which had happened—well, maybe it was 2011; I don’t remember—it probably was 2011—so I took a walk across England to celebrate. There’s a path where you can walk across England. It took about two weeks. A lot of walking. [laugh] A lot of time to think, and not much to think about. So during that, I decided—as well as interacting with my family—and then when it was just walking and thinking, I was thinking about this time crystal question. And I got to a point where I thought I had enough to really write something down, although I certainly didn't understand everything. But at some point—this is always the case—at some point, you have to decide, “Well, now I've got enough to write down.” Letting it languish any further is just going to make it seem stale, and you'll lose your enthusiasm and so forth. Also, you can get feedback from the world. So at that point, I sat down and started to write things down, carefully. And as always, when you write things down carefully, it leads in slightly unexpected directions. But that was the origin of it, basically.
And what was the idea that you had?
It was trying to teach this course, and then questions from Al Shapere that led to asking this crucial question of whether uniform behavior in time could be broken spontaneously. Because people had thought a lot about spontaneous breaking of all kinds of symmetries. The fractionalization that I talked about earlier played into that, kind of the intellectual background here. But no one dared to talk about time translation symmetry, because as I soon discovered, there are mathematical subtleties there that don’t exist for other symmetries, basically because of the connection between time translation symmetry and conservation of energy. Usually, when you talk about spontaneous breaking, the naïve understanding of why that occurs is that it’s energetically favorable. But if you're breaking energy conservation, you need to have another criterion. Anyway, it took some thinking to get to that, and to dare to put it out.
What are some of the larger questions that are begged as a result of your thoughts on time crystals?
To me, the biggest question—well, there are lots of questions, and very likely we’re not asking the right ones yet. But for me now, the biggest question is whether whether they can be put to practical use in improving atomic clocks. That, I think, is a great goal—when you can use time crystals, which are lots of atoms vibrating in synchrony. Well, atomic clocks are basically based on vibrations of atoms. Since atoms are frictionless, they can be very stable.
So this presumes that atomic clocks can be improved.
Oh, yeah. There’s no question that they can be improved. I mean, there’s no fundamental limit. Well, if there is a fundamental limit, that would be very interesting to know. But there doesn't seem to be a fundamental limit. Certainly not close to where we are now. But there are lots of engineering challenges and practical challenges. And basically the time crystal clock would use not just one atomm but many atoms working together, to improve the stability. So that’s kind of the motivating thought. But so far it hasn’t really been brought to fruition. That to me is the really—is the holy grail of the business, is can you improve atomic clocks. But there’s also just—there’s an exploratory aspect, which is, OK, so this is not just a new state of matter, but a whole new class of states of matter. [laugh] What are the quasiparticles like? Could they be good for something? Could they have some unanticipated practical use? So it’s just a new world to explore. So there’s an exploratory aspect. I don’t know particularly—the only really particular target that I know of, that I think is compelling, is these atomic clocks. But who knows what might come out of other things, just exploring the different states that could occur. As far as fundamental directions, these get more speculative, and they're sort of less and less connected to what we actually did. [laugh] But I think the whole question of whether in—for instance, in conditions of extreme curvature, or extremely rapid time variation of gravitational fields, whether space/time itself might have phase transitions, I think is really interesting. And that would be the other—the more fundamental direction that could use exploration. And I have spent some time on it, but so far, I don’t have much to show for it.
Now where does this fit within your previously stated pattern on working on a project until it becomes popular and then promptly abandoning it?
Well, that’s exactly what happened! [laugh] But as long as the fundamental problem of application of atomic clocks is out there, I think I could be induced to focus on that. I also keep an eye on what people are doing and look for opportunities. It’s not the top of my agenda right now.
How did the Wilczek Quantum Center come about, and why China?
[laugh] Well, it’s a product of Vincent Liu and Hongwei Xiong, who were—and Biao Wu—who—well, Vincent was kind of a postdoc that I mentored at MIT who has gone on to become quite a successful professor. And Biao and Hongwei were friends of his [laugh] in China. They saw an opportunity to do something in China. The original plan was much more modest. They basically asked me if I was OK if they used my name to make a proposal and form a little thing. Originally, it was going to be in Hangzhou. What I thought it was going to be like—you know, it would be like a plaque on a wall and a few offices. But then it just somehow metastasized [laugh] into now what’s—as things do in China—into a significant cluster of people and offices in Shanghai and part of a much bigger initiative, like basically a national lab by U.S. standards, called the TD Lee Institute, which they asked me to be the founding director of. And that’s another long story. It’s still in the making.
Is your sense that China is a pretty exciting place to be doing physics these days?
Yeah. Well, it’s exciting in two ways. It’s exciting at the kind of sociological level, because this is clearly going to be the source of a large part of the manpower and the womanpower in the physics world in years to come. And the institutions are just being built up, so it’s kind of exciting to see, and all this energy and optimism and dynamism. I don’t know whether to call it an honor or privilege or a burden [laugh] to be trying to help.
But as founding director, your duties are more than ceremonial?
Yes, they are. [laugh] Although I didn't quite realize that at first, but yes, they're very much—so that’s part of it. Then there’s the actual work that’s being done, which is uneven but certainly has some very high points and is very rapidly becoming better and better. I've really enjoyed collaborating with Biao Wu and with Jianwei Pan, who does experimental work for us. I mean, who has been inspired by some of our work, and we've actually written papers together, taking ideas to actual experiments. So it has been rewarding in that way, too. I forget what the original question was.
How that came about—the Wilczek Quantum—
Yeah, well, it came about because of the initiative of those guys, who kind of roped me in. At first, I was very skeptical of doing this, doing anything in China. But they made it sound [laugh] exciting and fun. It was a slippery slope.
I wonder if there were any geopolitical considerations.
Basically, no, is the zeroth order answer. My personal attitude is that I think of the science. My primary allegiance is to the science community, which is international. And I want to see the science community thrive. So I'm a citizen of the U.S., and I'm loyal to the U.S., and I certainly would never betray the country, but I'm not a nationalist in the sense that I feel jealous of China or feel that we have to keep them down. On the contrary. I'm a human being and a scientist first.
When did you develop the relationship with Arizona State?
Oh, I don’t know when it began, really.
I mean it’s a chicken and the egg question. Were you interested in expanding perception issues before or after your partnership with ASU?
Well, I had always been interested at some level. But no, no, this particular direction is only the last two or three years. And that’s a whole ‘nother story. But my connection to Arizona State is considerably longer. But it began as a very casual thing where every year we’d visit for a week. And then it became two weeks. And over, I don’t know, about a ten-year period—I don’t know when this began, but it was in the late 2000 noughts, and gradually grew. We really liked being there in the winter months, so it became one month, then it became—the last three or four years, it has been two months, and that’s the stable arrangement. And then I asked myself, “Well, OK, you're spending two months here. Why don’t you do something? [laugh] Other than what you usually do.” I was also caught up with the kind of entrepreneurial spirit at ASU. They're very open to the idea of new initiatives and very enthusiastic about the idea of serving the community and reaching out, interfacing, with the real world, in the sense of the public and business and so on. So the stars seemed to be aligned for this kind of initiative. And I stumbled into a really great collaborator there for this kind of thing, Nate Newman. I also should mention Anne Dominic, who you may have met, has been tremendous help in making things happen at ASU. So all those things fed into it.
What does it mean to you to be involved in research relating to the expansion of perception?
Well, I think the concept of expanding perception is a great concept. I mean, a marvelous concept. I don’t think we've done it justice yet, [laugh] but I do think it’s one of the really important directions that the science community could be pursuing, and is pursuing, but in a kind of disorganized way, and not sufficiently physical in my opinion, with virtual reality and augmented reality and all this stuff. But really integrating it into everyday life and letting people experience the visual world, the audible world, and worlds that we don’t ordinary experience at all more viscerally I think is a wonderful prospect.
And your interests in expanding perception are mostly technological, as opposed to pharmacological?
Yes. [laugh] Yes. Well, in principle, I'm open to pharmacological ideas, but that’s way outside my competence. [laugh] I haven't gone there, no.
In your view, how does technology help to expand our perception?
Well, our perception is very, very limited. We only see a small part of the electromagnetic spectrum. We don’t see polarization. Even in the part of the spectrum we see, we only take a sampling of three frequency averages, the colors. So there’s tremendous room for improvement in vision. Of course other senses, too. And there are things our natural senses don’t pick up on, like magnetic fields, the different chemical signatures of things, like the response to different fields, of resonance, and so forth. So our sensory systems were very much contingent [laugh] on how we evolved, presumably, and there were lots of opportunities that weren’t taken up that now have become economically and technologically feasible to do much better. Let’s do it.
I'm curious—in all of your decades of research thinking about the deepest possible thoughts in physics, if you were thinking about, maybe even frustrated by, our inherent lack of perception, and how this current research might have been useful 20 or 30 years ago to helping you maybe even come up with more profound ideas.
No, I don’t think so. The thing is, these—well, it’s conceivable, I suppose, but it seems far-fetched. Because the kind of fundamental physics that I've been involved in really as the frontiers today is mostly to do with very extreme or very contrived conditions [laugh] where perception doesn't play that big a role. Well, with one big exception, which is very relevant. Well, I don’t know. Actually, now that you mention it, maybe there is room for things. But usually, when you're talking about the quantum world or what happens in abstract spaces of high dimension and things like this, it’s so far removed from our normal senses. Also the rules are different. You have to unlearn a lot of things. Sort of default assumptions about how things work have to be removed. So our perception builds those in, so it makes the work harder in some ways. But on the other hand, and in fact part of the inspiration for wanting to expand perception is that we probably do want to be able to deal with complex datasets while making use of our visual apparatus, which, as humans, for better or worse, that’s the best tool we've got. That’s where humans have the most impressive performance in many ways, is being able to take in and process a lot of visual information in powerful ways, in parallel, and fast. So methods of visualization I think might have been helpful, although—how shall I say—the ideal is so far removed from what we actually have [laugh] that as a practical matter, I don’t see it. I mean, certainly it wasn’t a feasible thing early in my career and might just be becoming feasible now, to really have meaningful visualizations of the quantum world that you can see different parts of the wave function all at once and try to integrate them in your mind. That’s the kind of thing that might just be becoming possible now.
I wonder if you have even humanitarian dreams about what expanded perception might allow. In other words, a greater perception of the physical world—
Yeah, exactly. Well, expanded perception in the larger sense of not—OK, we've been talking in the last few minutes about perception in the very tangible sense of interacting with the world and seeing things and so on. But there’s another sense of perception which is more conceptual, which I experience every day and really is the way it’s like a spiritual experience is just to realize that the world is so vast, and contains so many things, has so many possibilities, that our experience of it just scratches the surface in many ways, and indeed is misleading in many ways. That our division between self and not self may be quite superficial. These perceptions of our place in the world I think could play a role in expanding people’s circle of empathy so that they see more commonalities between not only different people, but also people and animals, and just the world, and sort of a sense of perspective. These things of humility and self-respect that I mentioned earlier—those are powerful messages that I would love to convey to the world.
And the world deeply needs these things right about now.
It would be very helpful, I think. It would be very helpful. And they have the benefit of—I mean, the virtue of deep truth. They're not wishful thinking. They're not lies. It really is the way the world is. So I see it as a big part of my mission for the rest of my life, to try to convey that to people. [laugh] To get that message, which has taken me really my whole life to realize its power and put it together in a way that is coherent. So now I'm ready to share.
You've been unafraid in your career to identify things as beautiful.
And so it would certainly seem like this goal has beauty as its center.
Yeah. Beauty is certainly a big part of it. Right. Because it all hangs together in an aesthetically pleasing way, and can bring joy. And so that’s part of its appeal as well as its truth. And I also think there’s kind of a harmony to it that has a lot in common with musical harmony, and the harmony you see in other kinds of artistic creations. To see the world as a work of art is a really wonderful thing, and not crazy. [laugh]
Frank, I think that’s such a nice opportunity for I think what has become sort of the natural end of our wonderful conversation. And that is, you just said you want to devote the rest of your life to this. What does that look like for you? How do you go about accomplishing this very beautiful and noble goal?
Well, the main thing I can do, and which I have done now, is write a book. [laugh] I wrote a book. And I think I mentioned briefly I just got the proofs. So that’s one reason it’s on my mind. So we'll see where it leads.
But of course a book is just a thing that a few—a fraction of the population will read, and an even smaller fraction will understand, right?
Well, yeah, but—
In terms of the applications, the ways that these things can be shared with people on a broader basis than a monograph, what does that look like?
No, it’s not a monograph. Well it’s meant to be—[laugh] it may or may not succeed, but it’s meant to be the seed of a discussion that reaches a large audience. So that’s what I'm hoping for. It may or may not happen. I'm trying. [laugh]
But in terms of the technology, obviously there need to be advances in things that are available to people, and for that technology to be harnessed in the right way. That’s what I'm asking. What does that look like?
Well, that’s a much larger job than any one person can really take on. I would hope—and again, I come back to the same thing—I would hope that this message reaches a lot of people, but also sort of the right people [laugh]—people who are in positions of authority and positions of power, leaders of the scientific and technological world, and maybe even well-meaning people—in policy and in religion, and in popular culture. We can dream. [laugh] And we’ve got to start somewhere.
Right. And nowadays, it really feels like it is kind of a dream, because divisions seem much more powerful than the things that unify us these days.
Right, but you know, the world looked very different just a few years ago. So I wonder how deep this goes. I think there’s a chance we can overcome it. I think it’s a real chance. I think maybe things had to get really bad before they could get better. Like a fever that has to break or something. We'll see. Anyway. But despair never got anybody anywhere, so—
Frank, it has been so fun talking to you. I really appreciate the time you've spent with me.
It has been a joy. OK. Good luck with this.