Notice: We are in the process of migrating Oral History Interview metadata to this new version of our website.
During this migration, the following fields associated with interviews may be incomplete: Institutions, Additional Persons, and Subjects. Our Browse Subjects feature is also affected by this migration.
We encourage researchers to utilize the full-text search on this page to navigate our oral histories or to use our catalog to locate oral history interviews by keyword.
Please contact [email protected] with any feedback.
Credit: Phillip Cheung for Quanta Magazine
This transcript may not be quoted, reproduced or redistributed in whole or in part by any means except with the written permission of the American Institute of Physics.
This transcript is based on a tape-recorded interview deposited at the Center for History of Physics of the American Institute of Physics. The AIP's interviews have generally been transcribed from tape, edited by the interviewer for clarity, and then further edited by the interviewee. If this interview is important to you, you should consult earlier versions of the transcript or listen to the original tape. For many interviews, the AIP retains substantial files with further information about the interviewee and the interview itself. Please contact us for information about accessing these materials.
Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event. Disclaimer: This transcript was scanned from a typescript, introducing occasional spelling errors. The original typescript is available.
In footnotes or endnotes please cite AIP interviews like this:
Interview of Lee Smolin by David Zierler on April 1, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Interview with Lee Smolin, Founding and Senior Faculty Member at the Perimeter Institute with faculty appointments at the University of Toronto and the University of Waterloo. Smolin narrates the origins of the Perimeter Institute and he describes his unorthodox views on what exactly cosmology is. He describes loop quantum gravity and the notion of a “theory of everything” and why he has much love for string theory despite perceptions of the opposite. Smolin explains the utility and trappings of the Standard Model and he searches for deeper meaning in the origins and societal impact of the pandemic. He recounts his childhood in Cincinnati and his early appreciation for physics and the circumstances that led to his undergraduate education at Hampshire. Smolin explains his attraction in working with Sidney Coleman at Harvard, and why he saw a grand plan in his desire to learn quantum field theory. He describes meeting Abhay Ashtekar and his postdoctoral work at UC Santa Barbara and then at the Institute for Advanced Study. Smolin describes his formative relationship with Chandrasekhar at Chicago, his first faculty appointment at Yale, and his tenure at Syracuse where he found a strong group in relativity and quantum gravity. He explains his reasons for transferring to Penn State and his involvement in loop quantum gravity achieving a mature state amid a rapidly expanding “relativity community” throughout academic physics. He describes his time at Imperial College, where he developed a quantum gravity center with Chris Isham and he historicizes the technical developments that connected his theoretical work with observation. Smolin describes his book "The Life of the Cosmos" and his foray into thinking about biology and why he identifies as a self-conscious Leibnizian who tries to connect cosmology with the concept of a god and the centrality of astrobiology to these issues. At the end of the interview, Smolin explains why he continually returns to quantum gravity, and he conveys his interest in keeping philosophy at the forefront of his research agenda.
Okay. This is David Zierler, Oral Historian for the American Institute of Physics. It is April 1st, 2021. I'm delighted to be here with Professor Lee Smolin. Lee, it is great to see you. Thank you for joining me.
Thank you very much, and I didn't realize it was April Fool’s Day.
There you go. Lee, just to state on the record, I'm so glad I'll tell you, I got to Sean Carroll from Alan Guth who said, "You've got to talk to Sean," and after my epic conversation with Sean, he said, "You've got to talk to Lee." So, that's sort of the academic tree for how we connected, and I'm so happy for it.
Well, you'll get some good recommendations from me if you want. I'm very excited. Sean is somebody I like very much; I admire very much. As you see, he's fully articulate, very well read, very well educated, and we disagree on absolutely every point.
That's what makes science so beautiful.
Lee, to start, would you please tell me your titles and institutional affiliations? I pluralize everything because I know you have many.
I don't have all that many. First of all, I'm Founding and Senior Faculty Member at Perimeter Institute, which means I was one of the first three faculty hired. I also have some position, I understand, at the University of Toronto in the graduate philosophy department. It's called a status only position, and I think it's an adjunct position. They tell me I can supervise PhD students and sit on committees and so forth. And I'm an adjunct at the University of Waterloo, which means that I can sit on and chair thesis committees and have PhD students.
Now, at the Perimeter Institute, is that also a place where you can supervise graduate students and sit on committees?
No, we are not a degree granting institution. So, we have programs, like we have a master's program, but they're all officially done through universities, and all of our PhD students are registered as PhD students at a university.
This is such a great opportunity, since you're a founding member. Tell me about the origins of the Perimeter Institute. How did it all get started?
This is going to add a lot of time, but sure. There are lots of stories, and I don't know which ones you've gotten. Here's one way to tell the story. I'll start with my experience, and then I'll go back and contextualize it. So, one day, I get an email from somebody called Howard Burton. At this time, this was fall 1999, or early the next year, I moved to Imperial College for a visiting position. I've taken with me a number of post-docs. I'm intending to stay and was negotiating to stay in London, as part of a donor funding a research group or center that I would lead.
I get this email from this guy. He says, "I can't tell you who we are or where in the world we are, but we want to start an institute, and we want one of the fields to be your field. Can I come talk to you and get your advice?" So, he was in advice seeking mode. And at that time, Fotini Markopoulou and I are recently married. Although it was to be a very short marriage, punctuating a long-term friendship. It was in the midst of that, but she was in Berlin working under Renate Loll at Max Planck -- the Albert Einstein Institute. Howard also contacted her, and we all got together and met in Berlin for about two days and talked.
But just to fill in how it happened from the other side, Howard was a new PhD in quantum gravity at the University of Waterloo who had decided not to go on with academic research. He had a broad background. He had done some economics and some philosophy of science at LSE, and in Amsterdam. His wife is Dutch. And he writes a letter to Research in Motion in Waterloo, which is the company that invented the smart phone, and says, "This is who I am. I've got lots of different talents. One of them is not frontier research in physics. Can you give me something interesting to do and save me from Wall Street?" or Bay Street, which is the Canadian equivalent. Mike Lazaridis, who was the inventor, and co-CEO of the company, called him and said, "Look, we can certainly interview you here at RIM, but if you're really crazy, meet me tonight for dinner."
They met at this little Greek place, and Mike showed out this fantasy, that he was very recently very wealthy, and he was smart enough to understand that the money wasn't really his because he could never spend it, and he wanted to use it for good. He was a college dropout who had always wanted to be a physicist, so he introduced the idea of donating $100 million (CAD) to start a physics institute. They threw around ideas, and for some reason, Howard Burton, new PhD, no academic experience, nothing but a PhD, was exactly the right person to lead this, and somehow Mike knew that.
So, they talked for the evening, Mike offered him a job, he said, "I'll go home and discuss it with my wife." Mike said, "Well, go home and discuss it with your wife. You have the weekend, because if you say yes, this will be the last free weekend you have in several years." And they began this crazy venture. It's very difficult now to communicate how nuts this was, because now we're very established, and people consider us as important and established. We have a huge -- this is very important, we have a beautiful, modernist building designed by great architects, and we feel somehow substantial. We have twenty-something tenured faculty, although tenure was not part of the original design. The original design was much more radical in the sense of being non-hierarchical. There were only two academic jobs, which were post-doc and faculty. The question was just what your term of renewal was. There are a lot of stories to tell about the evolution of Perimeter, but it's been so interesting and so much fun. We've all learned infinitely much.
Here's a simple one, Lee. What's the origin of the name Perimeter?
Oh, that's a multiple pun based on Research in Motion, which is the name of the company. RIM, the perimeter, pi, the measure of the perimeter.
Ah. And Lee, when everything was in conceptual mode, were there any models that people were looking to, like the Institute for Advanced Study, or the Santa Fe Institute, or things like that? Or was this really a blank slate? Let's not pay attention to other enterprises, and let's just build this entirely on our own?
Oh, they were smart. They put together a very smart board. They got some very smart people to advise them academically. There was an advisory committee, although we learned very quickly -- by the way, it was months before Fotini and I were actually offered jobs. For a long time, we were operating under the idea that we were staying in London, or Europe anyway, and we were advisors to this project. I’ll skip over our own personal stories.
The Institute for Advanced Study, where I spent, I think, a total of three years, from the point of view of Howard and my -- they visited everywhere. They talked to everybody at all levels of the hierarchy. The Institute for Advanced Study was certainly something to learn from. From my point of view, it was an anti-model. The second week I was there, after I'd gone for the sixth time to the particle physics table for lunch -- the only other time was when Freeman invited me just to have lunch with him privately. And I said to Steve Adler, "Do we always have to eat lunch with the same people? I mean, I hear there are some historians and some mathematicians." And Steve said, "I've been sitting here at the same table since 1964," or whenever it was. I'm not here to criticize the institute, but they were, in many ways, an anti-model for many of us.
Lee, in terms of the niche that Perimeter had from the beginning and enjoys to this day, of course, the institute has, as you noted, scholars who are not physicists. What is unique about the Perimeter Institute that doesn't exist elsewhere?
Well, our philosophy was very -- there were several aspects of it. One of them -- and these came from Howard, to my understanding. A lot of it came from Fotini, who had thought a lot about these issues of hierarchy, and so forth, in science. Some came from me; some came from Rob Myers. We were the original people. What we cared about, and this is still true to this day, is discovering new science, i.e., making breakthroughs. No fakes, no consolation prizes, no lots and lots of citations, no secondary indications of progress. The real thing.
Two, we're interested in the fundamentals and the foundations, and we deliberately support a variety of competing lines of work, research agendas or programs, towards those aims. So, if the subject is quantum gravity, we support several approaches to quantum gravity. If the subject is quantum foundations, we support several approaches. We were among the first because just at the same time, quantum information and quantum computing was becoming recognized. We were among the first people to put substantial effort into that. That became a separate break-off of our institute, which is the Institute for Quantum Computing.
Of course, academic freedom, but even more than that, we encourage both mainstream and non-mainstream, orthodox approaches and non-orthodox approaches. No crackpots or amateurs. Not the kind of people who show up to your door with, "This is the right theory." We were interested in rebels, but only well trained and educated rebels from within the scientific community. We wanted to have breadth, we wanted to have a broad portfolio, and we wanted to have a spirit which is friendly and supportive, but at the same time, nobody got away with anything. Serious question.
In other words, you can't go to the meeting and say, "So-and-so has just left, so we have to hire next year's X to fill their place." Every search is competitive, every motion is the real thing. Within that, we give a lot more autonomy to post-docs and young people in general. So, post-docs are not tied to a group or a field. They have their own autonomy, their own visitors’ funds, their own travel funds. It is very important to us to raise the status of post-docs. And we try to break up the silos, which researchers often tend to fall into-- we're always looking for a way to get people to communicate with each other across the different boundaries. We're all theoretical physicists, and we introduce the idea of “interdisciplinary” as kind of a joke when you're talking about a condensed matter physicist and a cosmologist. They ought to be able to talk to each other, and we try very hard to make that happened.
Lee, as the name suggests, obviously, the focus of the Perimeter Institute is on theoretical physics, but today, because so much in the world of astrophysics and cosmology is being driven by observation, what is the interface with Perimeter Institute (ed. we refer to it as “perimeter institute, not THE perimeter institute”) with the world of observation? How does the perimeter institute involve itself and learn from what's going on in observation?
By having people who are very involved in the experiments. For example, Kendrick Smith is very involved in the CHIME experiment, and is, in fact, the person who figured out how to make CHIME so useful to find fast gamma ray bursts. So, we have a range from very philosophical foundations to mathematical physics. A range which includes people who are deeply involved with experiment. And we have lots ways to send one of our scientists away to visit an experimental group or invite experimentalists to visit us.
Lee, I'd like to ask a very broad question that I think is going to animate much of our discussion. I love asking this question of eminent physicists at various stages in their career, and so just for context, if we can define a generation in physics in decades, physicists who are in their 30s, 40s, 50s, 60s, 70s, and 80s, this is a question I've posed to in their 80s, Steve Weinberg; in their 70s, Joe Silk; in their 50s, Sean Carroll; and to you in your 60s, I'd like to ask you this question. What do you see as the boundaries between cosmology, astrophysics, and astronomy, and have those boundaries shifted over the course of your career?
Oh, no, but that's not the most interesting question.
Well, let me start with that. We'll get to the most interesting question.
My point is that I’ve always understood those boundaries to be different than most of my colleagues. For example: the boundary between physics and cosmology. For me, a cosmological theory is one that is structured in such a way that it could be a theory of the whole universe. All of our standard theories-except general relativity with spatially closed boundary conditions are structured in such a way that they require that they describe only a part of the universe, that is there must be things in the universe that the theory assumes are there but are not described by the theory-such as reference frames and observers.
From my perspective, cosmology is about can we have the ambition to have a theory which is a theory of the whole universe, the whole system? Which means, and I've developed this idea quite a lot, that it's very different from quantum mechanics, theory of relativity, and so forth, which only make sense operationally as theories of part of the universe. So, for me, and I wish I had convinced more people of this, the job is to invent a new kind of theory. I spent a lot of time and a lot of ink in the books arguing what that kind of theory would be, which could be a cosmological theory. It's not just astrophysics on a live scale.
Another difference is that I believe that the time is fundamentally real and also that the laws evolve. This results in a new role for astrophysics- like in biology it becomes possible to make functional explanations in astrophysics. I believe that my colleagues and I are the first to realize the implications of this.
To what extent does this require the integration of gravity into the Standard Model?
Oh, totally. But that is very much just a first step. My thinking is way beyond that. I'm worried about things like biology. I'm worried about things like the extent to which, in cosmology itself -- when we apply physics to biology, we use a mix of methodologies. We're sometimes reductionists, we're sometimes functionalists, to explain why a particular protein exists in the biosphere. It's not enough to be one or the other. You have to be both, and it's very intricate how they work together. I'm working with a group of people, and we believe that the same is true about cosmology. That is, the right kind of explanation is a mix of reductionism and functionalism. This is Marina Cortes, Andrew Liddle, Stu Kauffman. We have three papers which have been on the way for about a year, but that's because this is a very hard, serious question. Arguing that kind of question as well how biology and cosmology really address each other, as well as physics. I think most people are lost in the dust in my point of view. As far as astrophysics is concerned, I love astrophysics. I love the kind of science it is. I love to hear about it. It played a particular role in the development of my ideas, because when I invented the idea of cosmological natural selection, it raised biological sounding questions about astrophysical processes, which I had to learn how to think about. In my career, there's been a great turning point. The issue, of course, is time. I began my career thinking that time was emergent and there was a level of reality we could ascend to where it simply didn’t exist.
In LQG we saw how time could emerge from the-- from the Wheeler-DeWitt equation. Since Ted and I, and then Carlo and I, had found an infinite number of exact solutions. My own view is that time in the sense of causal relations and growth and passage and presence, and all of those ugly things that many people don't like to talk about, is the most fundamental thing.
Lee, just to clarify, when physicists, perhaps string theorists, talk about searching for a theory of everything for unifying all the forces, are you saying that biological functions can exist in that unified theory, or are you talking about a theory that's more fundamental that encapsulates both within it?
Many string theorists, and also some people working on other approaches such as LQG, are working within a 19th century methodology which assumes reductionism is all that is required for scientific explanation. The notion of “unification” they are interested in is essentially the one dominant in the more atomistic of the 19th century theorists such as Maxwell, Gauss, Faraday etc.
I am convinced that, one: those notions of explanation our outdated and inadequate. We need new methodologies which allow it to be sometimes the case that functional explanations are needed to enrich and complete the reductionist explanations. I mention biology for two reasons. One: because biology offers us many examples on which to try out and get comfortable with functional explanations. Two: There are good reasons to believe that an important question for cosmology is why the laws and history of our universe are hospitable for life. There's a lot to say about string theory. If you actually read, which a lot of people haven't, what I wrote in What Is The Trouble with Physics in 2006, you will see that I have a lot of affection for string theory.
But string theory has a big problem which is an infinite number of “vacua” each of which correspond to a different set of elementary particles, moving in spacetime backgrounds of different dimensions and topology. I learned about this problem from Andy Strominger, who has been for many, many years, a friend. In about 1988 when he wrote a paper called Torsion Solutions in String Theory, in which he talked about this, and he was very dismayed because there were so many solutions to string theory, so many to expand around, that the idea of doing phenomenology and predicting anything about the Standard Model was ridiculous. There would be vast numbers of solutions that agreed with the Standard Model and vast numbers of solutions that don't. So the theory would make absolutely no predictions.
I understood immediately that Andy was right. At the time I was reading a lot of popular evolutionary theory - Richard Dawkins, Steve Gould, etc. The solution for anyone who knew that literature was that we had a landscape of theories, and we needed a dynamical principle to explain how a population of theories evolved on the landscape. In biology natural selection serves well as an explanatory methodology. I asked myself if I could invent a cosmological scenario that would explain the spectrum of the Standard Model, by evolving a population of theories on a landscape of theories. In those days I kept a Tasar sailboat on Lake Skaneateles, near Syracuse, and I sometimes thought about physics problems as I sailed. In July 1990 I challenged myself to invent a scenario for cosmological natural selection, and I succeeded. It wasn’t hard, it was a one sail problem. I started to work on this idea right away, finally publishing it in 1992. I had to learn a lot of astrophysics to turn this into a viable, testable theory.
The timing of summer 1990 is tied down by an unfortunate circumstance. One of my closest friends at that time was Dr. Laura Kuckes, who was the only person to have studied simultaneously for an MFA at Yale Drama school and a medical degree at Yale. The summer of 1990 she worked for the Innuit Health Service in Point Barrow Alaska. That evening she called and among other things she asked me to pick her up at Syracuse airport when she next flew back to her family home in Ithaca. I told her of my new idea and she advised me to write a book about it. Laura and a friend drowned off Point Barrow on August 5,1990, when their boat capsized in heavy wind on her way to the tiny local airport where she was to start her journey home. That book was of course Life of the Cosmos, dedicated to her.
Very few colleagues expressed interest in this idea. I remember describing it in a conference talk where Lenny Susskind was in the audience; Lenny argued with me afterwards that the structure of vacua of supersymmetric theories would not work with my idea.
It was then a bit of a surprise when some string theorists 13 years later in 2003 rediscovered the idea that the string theory vacua could be picked out by a dynamical mechanism operating on a “landscape of string theories.” Now I didn’t mind their late interest in the idea of a dynamical principle to pick the laws. But I do mind their adoption of a version-based on the anthropic principle, which could be easily shown to be untestable. Such an enormous amount of wasted time could have been avoided had they just stopped to think through what kind of distributions on landscapes lead to testable theories. This would have been obvious for anyone who read either the population biology literature or my paper. Which is the second thing I mind, almost never being cited for the idea. I love Lenny, so I'm going to be a little bit pejorative.
Lenny Susskind, you're talking about.
Yeah. I mean, he hates me in some way, and in some way, we love each other. But he was certainly a role model at the time I met him my first year of graduate school. But he missed this for a long time. It wasn't that -- I tried to tell him on a number of occasions. The whole point is there's this landscape, which is a word I stole from theoretical biology and population dynamics. There's a landscape of theories which is so vast, the question is not what's the theory. Just like in biology, the question is how did the theory arise, through what process? Understanding the process is the harder physics, not the last five digits on some constant Standard Model. Some of that is meaningful, and some of it is accidental, just like in biology. I've been thinking from that point of view since that conversation with Andy. And I was reading the theoretical -- evolutionary theories, like Margulis and Dawkins and Steve Gould, and so forth. And it immediately came clear to me that the only way physics was going to progress was by embracing something of those methodologies, for the same reason that it works in biology.
So, I think an interesting thing about my career is that I've been, in some sense, on my own track, for now quite a few numbers of years. I'm in a rather different place and very happy about it. I have a feeling that a number of people are looking around and catching up. Maybe that sounds pejorative and egotistical, but that's really how it feels. They got onto the landscape in 2003 with the discovery of the dark energy and so forth. But from my point of view, a completely non-productive point of view, because they were tied to timeless inflation, eternal inflation, and various ideas about that which led them to completely miss the key question, which is what is the methodology? How do you ask answerable questions? How do you make really testable predictions when you're in a situation like biology where there's something like a landscape? They never thought it through.
Lee, to delve a little further into the constraints imposed by the Standard Model, of course, how much misapprehension was there really? In other words, the Standard Model was never created to be an alter upon which physicists prayed. From the beginning, it simply established some parameters that were designed to be broken, to find physics beyond the Standard Model. So, to what extent was this misapprehended in the way that you describe Andy Strominger's work and your subsequent work, about the need to not just move beyond the Standard Model, but move beyond even broader debates within physics?
Well, let me tell you what I observed. I was a kid for some of this. I started graduate school in '75-'76. The year before I went to graduate school, I happened to be at a conference in Boston where Abraham Pais spoke. He said something that made a huge impression on me then. He said that the Standard Model is wonderful, and gauge theories are wonderful. We understand so much physically about the forces and the nature of the interactions. But there are these twenty parameters. There were nine more to come because of massive neutrinos, but at that time, there were twenty parameters. Not only do we have no understanding of where they come from, we've never in the history of modern physics ever explained one such parameter, no matter what the context, going back to the discovery of the mass and charge of the electron. Bram later became a very good friend, which is another story, based on our mutual love of modern art. But I was really impressed by that, that there was a range of questions that all of this excitement about gauge theory didn't address, and it's still the case.
The thing that I'm dismayed by, that's putting it too strongly, but I try to mention, let's put it that way, is that we have very good people from elementary particle theory at Perimeter. I know a number of people in the theory, and this question of what accounts for the values of these parameters is just out of bounds. Lenny and others made this big try for the landscape and anthropic principle, and it was clear, if you can think clearly at all, and I can go through the steps, it was clear the anthropic principle by definition could not lead to any testable prediction.
Please go through the steps.
Okay, I'll do that in a minute. So, they immediately got on the wrong track. It didn't work, very predictably. Let me criticize the standard argument about how the interactions were supposed to work. I'm very bad -- this is a thing maybe about being sixty-five, or maybe I've always had it. Oh, Hoyle, this is Hoyle's argument. Hoyle said that life depends on carbon and oxygen, but let's focus on carbon. The universe is full of carbon. It's one of the most common of the chemical elements. That requires explanation. You know something, as that generation developed the physics of interior stars and how the stars go from fusion to fusion to fusion to fusion, eventually getting to carbon, and carbon somehow sticks and is stable. Therefore, because we know there's a lot of carbon, the universe somehow must have been tuned so that all those nuclear reactions have the right rates, because carbon gets produced in plentiful amounts but it's also very stable.
So, that's Hoyle's argument. Now, the first line which says that carbon is essential for life is nowhere used in the logic of the argument. It's just there to stand for some religious hope about being part of the universe. That's the mistake. But many people have drawn the conclusion from the success of that argument that you can have an anthropic argument that makes a prediction. But there was no anthropic argument there. There's simply the observation that the universe is full of carbon, and that requires explanation. I can reproduce that in whatever, however many contexts.
What have been some of the responses to this criticism?
Well, from philosophers, they say, "Of course." There's even a name for the fallacy, which I don't remember right now. But I mean, it's so well understood that it's named, and all you have to do to a professional philosopher of science is say the such-and-such fallacy, and they say, "Oh. yes." I can get that name for you. Martin Rees is somebody -- for some reason, I don't understand why he's so friendly to me, because I see him as way, way, way up there, but I love Martin. He sometimes gets in touch, and we talk, and we argue about this, and it's friendly. I don't understand his thinking, but he's certainly a much better astrophysicist than I'll ever be. I don't have your job. It's not my job to explain how other people think.
Lee, let me ask a sort of less highfalutin question, and that is, something that we've all been dealing with over the past year, if I may, the caricature of a theoretical physicist might suggest that this year of the pandemic, and physical isolation, might be at time of incredible productivity, of having more bandwidth to work on complex equations that you might not otherwise have been able to. Alternatively, perhaps, not being in physical proximity with your colleagues, not being able to work out problems on the white board, has been damaging to the kinds of the things you might have wanted to do over the past year. So, in general, how have you done?
Oh, me? Fabulous. I mean, at the moment, if you look at the archive, there's a big gap for a year, but sitting on my desk are six manuscripts, all almost ready to go, and some of them in the process of going, which are much braver and I say this, and people will laugh, for me, these are scary papers. Intimidating papers for the idea. These have been brewing, these different collaborations I've been involved with, have been brewing for some time. The whole picture together makes a revolution, if I'm allowed to say that, and it's not just me. It's about the issues of time, the nature of law, the question about the right methodology for doing cosmology.
So, this has all been a very fruitful time. I am also going crazy. I want to get out of here. Last March 14th, we had tickets to Paris. I don't love the traveling at the rate that many of us professional academics do it, but I'm very rooted in Europe because of the years I spent there. That's actually part of the physics story, because the early developments in loop quantum gravity are, in a certain sense -- again, if this doesn't sound too egotistical -- the story of a friendship with Carlo and Abhay and I. I'm sure there are many stories like that. I'm not sure it's worth writing down, but it's a story of friendship among three people which always will be complicated. Most of that was actually physically carried out when I basically moved to Verona at the invitation of Carlo's father. That is, he gave me an apartment to draw me to Verona so that his son would come home.
Lee, because you are alive to biology, to philosophy, even to the sociology of science, how, if at all, has this year in the pandemic, changed your thinking at the broad level?
I've been searching for some -- I know the kind of wisdom I don't have. It's very flattering for you to say that. I have the deep feeling that there's stuff we're all missing. The story is scary enough, and many of us have been very brave. It's really been much harder than it looked at the beginning than it looks day-to-day. But I also have the feeling, this thing about going back to normal is just going to fade away and we're going to find ourselves somewhere else. That will be, in some ways, a much better place, in some ways, a much worse place. I wish I had the wisdom to think about that. I have some friends who I think might, who I talk to. It's been great for my family and my personal life in a different way. Some of which are stories that are easy to tell; some are not. It's difficult.
And for the institute, it's been basically -- it's hard to tell, but I'm worried, and the reason why I'm worried is that what we learned as we built Perimeter, and as it grew from the first -- you know, very much like a tech startup. We were in this sort of restaurant post office. Very handmade, very simplified. Not much technology compared to the level of technology that we could have thought about. And we found that the most important thing is cramming a bunch of people into an office in front of a blackboard and talking to each other. Sometimes getting angry, sometimes laughing, whatever. That very active, beautiful sense is what made Perimeter work and what makes any place that makes this kind of science work. We have a lot of communication over Zoom and other things. I really thought we should have put the whole thing on Second Life, and reinvented the building in Second Life so we all went to our offices there, and so forth. But we haven't seen each other, many of us, in a year.
I have students who haven't touched anybody in a year and complain to me about it. Yes, I'm your advisor, but you're here from another country with no family, you're sitting alone in your little one-bedroom apartment. Compared to that, I'm having a very normal life. But they're all aspects of it. One of the things is that you can't hide. I used to have a schedule. I've had it for years, and this goes back several jobs. There's been a way in which I lived in a city and went to work a few days a week in a less urban setting. At Penn State, when I lived in New York; at Syracuse, when I lived in New York. And here, I live in Toronto, which is a great city, by the way, if we get onto that.
But now, everywhere is the same. It's like there's a sort of quantum gravity. In quantum gravity we imagine that everything is really -- space is not essential. Everything is really causal relations amongst events that happen and grow this pattern now of that which is existing now. At a certain level, space emerges, and we understand that in some of the recent work I've done with Marina Cortes, very, very well in detail what it means to say space emerges. And then, you find yourself very far away in space from some things, and very close to other things. So, we went through the reverse of that phase transition. We had all these ways of being in touch, and then we also had airplanes. And it's like they took away the airplanes. Now, it doesn't matter. Sometimes, during each day, I'm sometimes talking to somebody in Brazil, or Rome, or Paris, or London, or across the park. We have some friends who live across the park. You see what I'm saying. I can't say, if you want to talk to me, make an appointment next Wednesday, because that's when I'm at Perimeter. Every day is the same, and I don't know that that's really helping. Anyway, long story short, for me personally, it's been a very productive year, and if we get out these papers and I still have a job, it'll be a credit to the broad mindedness of Perimeter.
Well, Lee, let's engage in some oral history now. Let's start first with your parents. Tell me a little bit about them and where they're from.
My parents were both born in the Bronx to Jewish/Eastern European immigrants. My mother, Pauline, who died two and a half years ago, was a moderately successful playwright. She was a professor of English at the University of Cincinnati. They both had huge influences on me, but in some sense, through her, I grew up in the theater. I was born in New York City, started life, the first ten years in Manhattan, the upper westside, and then for some reason which I can go into but won't, my parents move to Cincinnati and I lived in Cincinnati with them. And then my life was in and out of New York from different places. Certainly, through her, I had an exposure to the theater, to literature, to the theater world that is to these crazy actors that kind of hang around. They're so much fun. My father, who died of COVID in December, unfortunately, very recently, and has touched us very closely, was an environmental and chemical engineer, and certainly had a huge influence over me. We read together when I was eight or nine, that book, One, Two, Three, Infinity. Is that Gamow?
Yeah. My parents were very loving and very supportive of me, and what they let me get away with, now that I am a parent of a teenager, is just incredibly. I dropped out of high school. I met Buckminster Fuller and followed him around for a little bit, and wanted to be an architect, as a high school dropout.
Lee, what neighborhood did you grow up in?
In Cincinnati, Walnut Hills.
And did you go to public schools through high school?
Yes, I went to Walnut Hills High School.
Did your father involve you in his work to the extent that you had a pretty good idea of what it meant to be a scientist, even as a kid?
No. He was an engineer, but no. For me, wanting to be a scientist came at me like a blast from nothing, because I was -- very briefly, my parents had a friend, Dr. Larkin, who was a professor of mathematics at Xavier University, which is a small Catholic college there. They bought a computer. It was a little IBM 1620, or something like that. And when I was nine or ten or eleven, Dr. Larkin gave me permission to play with the computer, to write programs which were then, of course, hand coded in Fortran. I enjoyed that experience. Now, it's ridiculous. Now, there are five year old kids that went way beyond how far I got, but it was unusual to give a young kid of that age access to a computer and just let them play with it.
As a result of that, and almost being thrown out of the high school, I was not allowed to take advanced courses in math. When Dr. Larkin heard of this, he challenged me to take the whole pre-calculus sequence in night school at Xavier. I did this partly to show up the high school. It was all an act of rebellion, and we together challenged the principal to let me into the advanced math program once I took pre-calculus at the night school. So, in tenth grade, I did calculus. I did the AP standard thing, and then for the next two years, I studied somewhat on my own.
So, then when I heard about Buckminster Fuller, I knew enough math to actually dream of how to do structural calculations on the domes that I was trying to design. I went to the public library, where I found books on tensor calculus. All of which had chapters on general relativity. That led me back to the library, where I found a book edited by the philosopher, Schlipp, called Albert Einstein philosopher scientist. I read Einstein's essay, and autobiographical note, one evening, as a high school dropout sitting on the front porch in the spring. Somehow, something spoke to me, and even though I had never taken a physics course -- in fact, I had been forbidden to take a physics course because of my political activism. I know that doesn't make sense, but it's what happened. So, I knew no physics whatsoever, but something just spoke to me. I saw Einstein's aspiration to make sense of quantum mechanics and unify it with space and time and gravity. And this voice said, "Oh, I could do that." I had never met a physicist. I had no knowledge of it, but there's just this calm voice that said, "That's it. That's what I'll do." And that is what I've done. It's insane.
Lee, was your family Jewishly connected at all, growing up? Were you members of a synagogue? Did you get bar mitzvahed? That sort of thing.
I got bar mitzvahed. We were members of a reform synagogue. An important thing to say is that my parents were also members of the Gurdjieff Work, and that had much more influence on my early years. I don't know if you know what that is.
Gurdjieff was a Russian-Armenian who went to the east. He's a very controversial figure. This is early in the 20th century. He traveled to Iran, Iraq, Persia, India, Tibet, Japan. He claimed to be a carpet trader, among many things, and there are even rumors he was a spy. In any case, as he traveled, he sought out teachers of esoteric or mystical teachings. He returned to Moscow in about 1905, 1906, and abstracted from his studies, what he claimed was a synthesis, of the different esoteric traditions, suitable for teaching to Westerners.
He began teaching in Moscow but had to leave due to the revolution. He set up camp in a large house just outside Paris became a very influential teacher among a small group of artists and intellectuals, first in Paris and then in London. It was never very well known, and it was never like the things that I grew up with, like Arika or transcendental meditation that attempts to spread a bigger -- it was very almost secretive. What it claimed was that if you worked in the sense of certain physical and psychological exercises, for many, many, many years, you might be a little wiser, and have a little clearer vision of your situation. So, it was a sort of tough love kind of thing. My parents were heavily involved with that until I was about fifteen or sixteen and then they fled that organization.
As a high school dropout, how did you get back on the academic track? How did you go about figuring out how to pursue an undergraduate degree?
In two steps. One of them is since my mother was a professor at the University of Cincinnati -- I was a weird high school dropout because I was very rebellious, and I helped make an experimental high school and joined it. The first week that we were in session -- it was called Morning Lights Schools, or something like that -- the teacher said, "We feel that the knowledge that we seek is in the community, and we want you to go home and think carefully about where in the community is the knowledge you seek, and we'll help you to go there." So, I came back the next day and said, "The knowledge I seek in university. So, I don't need you guys. My mother’s on the faculty. I can sign up for any course I want. So, bye." And I started taking courses at the University of Cincinnati. I met Paul Esposito, who was a relativist on the physic faculty, and started studying with him. He was teaching a graduate course in general relativity and I took it. That's the first course in physics I ever took. Meanwhile, I was very inspired by the idea of Hampshire College, which fit very well my rebellious –
Yes. I was going to say, not to be teleological, but it sounds like you were destined for Hampshire based on what you're telling me so far.
Well, they turned me down twice. The third time I applied, they said, "You can't apply. We're like 20 to 1 and we're going crazy. You can't apply three times." I said, "You haven't talked to me." I don't know where I got the arrogance or confidence. It's not the kind of person I was, but I insisted on borrowing my parents' car. I couldn't drive, but my girlfriend could drive. We drove up to Hampshire and insisted on getting interview for each of us. He was the only physicist. I knocked on the door and I said, "I want to come study physics here. What would that involve?" And he said, "What do you know?" So, we spent the afternoon talking about general relativity, with him pretending he didn't know it and having me teach it to him. He is a very, very good physicist, who unusually had dropped out of the post-doc track and wanted to teach at a small college. I knew that I had met my teacher. Indeed, had I not met him I don't know what would have happened. I would have been one of these kids at who makes free phone calls from a payphone, to London, then Paris, then Vienna, Milano etc., and back to the payphone next door.
Lee, besides you detecting that your out of the box approach would fit well with Hampshire's out of the box teaching philosophy, did you ever have any concern that not being at a large research university, like MIT, might hamstring your studies if you wanted to pursue graduate work in physics?
It never occurred to me. Herb was really, really hard on me, and he always expressed doubts about my education, which I needed. I mean, what he did would be illegal now. He made the grader in the classes I was going to take each semester, and then he would grade my work. He would call me up at like one in the morning and pretend to be angry with me and say, "Look, you thought you were a scientist or a physicist? That's disgusting and disgraceful. That's unimaginable." And he would hang up. He's a really nice guy to everybody else. I never understood. Then he would call at seven in the morning and say, "Meet me in my office in an hour and show me how to do those problems." For three years, he was nasty, demanding, never said a nice thing, and I was horrified and terrified. And then, I said, "Do you think I possibly could go to graduate school?" And his sequence, it started with quantum mechanics and got on from there. So, I never had elementary and particle physics. So, he said, "You think you can go to graduate school? Go to the board," and he gave me an incline plane problem. And he said, "Maybe it's possible." So, I applied, and I got in everywhere.
Lee, as an undergraduate, did you have any access to laboratories, experimentation? Did you involve yourself in that world at all?
No. There were laboratories. There were things, but I was not very good at that.
What kind of advice did you get, if any, in terms of where to go and possibly who to work with?
At Princeton, in the office, they showed me my file. They said, "There's some letters missing. Why don't you look through your file and see which letters are missing?" I looked through my file, of course, and there was a letter from somebody I knew, and there was a big circle around a paragraph that said I was philosophical. It said, "This is just the boy for Johnny." And I met Johnny and couldn't understand him. I was not sophisticated enough to understand John Wheeler and what he would have offered me at that stage. So, I didn't go to Princeton because I didn't want to be Johnny's boy. At Harvard -- well, I already had a strategy. I was following the mission that Einstein gave me. So, I was working on quantum foundations and general relativity. I was learning quantum field theory. And it was very clear to me that what I needed was to be somewhere where there was all this excitement about gauge theories.
Somehow, I had this intuition, and this turned out to be right, that what I could bring to trying to quantize gravity was what the gauge theorists knew. So, if I wasn't going to Princeton, I went to Harvard. There's also my girlfriend at the time who decided to go to Harvard, although she broke up with me the second week we were both there. I went, and I talked to them at Harvard, and Sidney Coleman, who became my advisor, we talked, and he said to me, "Look, don't come here. We're really hard on people. We're nasty. We're not interested in those deep philosophical questions. Your right thing is to go to Princeton, and work with people there." So, of course, I went to Harvard since Sidney told me that, and it was the right thing.
Did you have a sense already that Sidney was an incredible lecturer and that he might be an excellent mentor for you?
He wasn't an excellent mentor, but he knew enough -- he was a great lecturer, and I took that famous quantum field theory course. What I learned at Harvard, wow! The first year, I had quantum field theory from Sidney Coleman, quantum field theory and quantum gravity from Stanley Deser, quantum field theory from Gerard 't Hooft, weak interactions from Álvaro de Rújula. And then I went across to the math building and hung out with Raoul Bott and talked about -- just was one amongst some graduate students who were hanging out with Raoul Bott. So, it was a tremendous education, genuinely. Sidney left me alone. He said, "I'll give you two or three years to do something in quantum gravity. Otherwise, I'll put you on a QCD problem." He put me under the supervision of Stanley, who was really my main mentor.
What was Stanley working on at the point you connected with him?
Supergravity. He just invented supergravity.
What was so exciting about this at the time, from your vantage point?
Oh, it wasn't exciting. It was interesting. I didn't get the aesthetics. It's ugly. But I, and a friend from Hampshire, who I had graduated with and he had gone to Maryland, John Dowd, which was more a relativity group, we worked together and tried to make sense of a geometrical setting for supergravity. We wrote a paper about that, and I wrote another paper about it. So, it was interesting, but it didn't seem to me -- it still seems to me like maybe it's there, maybe it's not there. It doesn't address the core issues that I'm interested in, but it might be there. But Stanley was very interested in it. Stanley was very interesting. I learned a lot from him. Nobody -- 't Hooft took some attention to me, I guess, which was nice. He gave a course on the Standard Model, etc., and everything that he'd done. The first day, there were two hundred people in the lecture hall. He was a terrible lecturer, and by halfway through, there was only me and two others. And it turned out that I was the only one who was actually registered for the course. He was really lovely, and I certainly appreciated him.
I learned a lot from the post-docs. Steve Shenker, especially. It became clear to me -- it was abundantly clear that they had this beautiful idea of loops ad evaluating gauge theories through loops. I had heard lectures from Polyakov and visiting lecturers, Ken Wilson, and a few other people like that, and it just was crystal clear to me that's the way we quantize gravity. We use those loops. So, I was a conscious thief. I learned all that stuff in order to steal it and apply it to quantum gravity. That was my first paper. And then, Abhay and Sen discovered this beautiful structure, and I knew that was like a lock clicking.
Where did you meet Abhay Ashtekar?
I think I met him in Oxford. I spent two summers in Oxford. There was a -- I don't know what, a workshop or something like that, sponsored by some foundation on quantum gravity. I think I met Abhay there. I'm not sure.
Lee, to the extent that physics goes through trends over the decades in its subfields, where was general relativity at Harvard when you were a graduate student? Was it considered a hot topic? Was it considered a backwater?
Yes, it was a backwater. Both classical and quantum. I basically took what they could teach me, and then I switch communities, from a sociological point of view. We can talk about how and why I did that. Although that took some years. That went through ITP and IAS. But after that, I was at Chicago in the relativity community.
Did you have any interaction with Bob Dicke as a graduate student?
Oh, I wish. No. I met Quine. I met Feyerabend. That was the really influential thing. I wish I had met Dicke. They were certainly there, and I was aware of them.
What about Steve Weinberg? Did you have any interaction with him?
A fair amount, because he came to me one day and he said -- I love Steve. Let me back up. Harvard was a nasty place. Seriously nasty. Would be totally illegal now. People got screamed at. People got called names. Women got -- it was high pressure, because this was the real thing. Steve never participated in that. When he asked a question, somehow, it was because he didn't know the answer. He wasn't trying to play any kind of game. Which doesn't mean he was warm and friendly, but he was in some sense, serious, and probably understood a lot of what was going on.
Anyway, he came to me one day and said, "Have you read this book by Hawking and Ellis about these topological methods and singularity theorems and so forth?" And I said, "I've read some of it." He said, "I have a proposal for you. I feel uncomfortable that I have a textbook that I've written in general relativity, but I don't understand that book which is supposed to be the cutting edge. Could we meet once a week, and you teach me on the board what's in that book?" I said, "Yes." What I never told him is I went across the street to Bott-- to Bott, who I was pretty friendly with, and I made him a challenge. I said, "This is what Steve Weinberg challenged me with. Why don't you and I meet a few days before and we can decode Hawking and Ellis and then I can take what I learned from you back to Steve Weinberg?" And Steve was polite, but the entire time I would be talking, there would be a rip, and he would be opening his mail and sorting it. And he would occasionally ask a question. So, we talked some, and I certainly admired him and what he had achieved.
Lee, what was your dissertation topic ultimately on, given that you were sort of all over the place in your interests?
It was called Studies of Quantum Gravity, deliberately. Quantum gravity on the lattice was in it, and the two papers on supergravity, geometrical formulation of supergravity. I think the calculation -- I did a calculation for Hooft's class. He said, "I've got to give you credit for something, so do something related to the course." So, I did a one loop calculation in quantum gravity related to spontaneous symmetry breaking. They were just pasted together, but then I wrote a long essay on what the problem is with quantum gravity. I included stuff that nobody around Harvard was talking about, the Unruh effect, with acceleration and radiation. I tried to really think about what was important in the field of quantum gravity. That preprint got to Bryce DeWitt, and that's why I was hired for the KITP program, by Bryce and Cecile.
Who was on your thesis committee?
Oh, it's funny. Steve, Stanley Deser, certainly Sidney. I think there was another one. It might have been Mike Peskin. Here's how my defense went: I was told to stand up and present the results. I started talking. After about two minutes, Sidney looked around and said, "Gentlemen, have we heard enough?"
Was this a good sign, or a bad sign, as far as you knew?
I'll just tell you what happened. Steve Weinberg looked up and said, "Wait a minute. I've got eight pages of questions." And Sidney, in the acknowledgements, he thanks me for a lot of things, but never for enough time, and I've heard enough, and I'm the chair, and this thesis defense is over. And Stanley Deser said, "You can't do this, Sidney. We have to critique the work." And Sidney says, "Stanley, on your own time." So, it was over in five minutes.
Were you hoping for a longer discussion?
I don't know what I was hoping for. I was glad for that. And Steve took me out in the hallway, and we sat down somewhere, and he spent an hour taking me through his questions, as did Stanley.
Was your sense that Steve was more interested in pedagogy, or in actually picking your brain?
Oh, Steve was, and he gave me some advice, which was actually good advice. He said, "My advisor was T.D. Lee, and I'm going to pass," -- I don't know if that's actually true, but -- "I'm going to pass on what T.D. Lee said to me when I got my PhD. What T.D. said to me is that abstract stuff is interesting, but every few weeks, spend a day and think about the weak interactions." He smiled a cool smile, and he said, "That worked for me."
That's great. Lee, after you defended, obviously, we know what you ended up doing, but what was available to you? What post-docs were compelling for you?
I got two offers. One was from Steve Hawking, and I already had a rather negative view, not of Steve as a person, but of his research direction. I didn't think he understood quantum field theory well, and he had these ideas about instantons and quantum gravity. It's a funny thing to say, but I didn't think he knew what he was doing. And I was also a coward.
I had visited the group in Cambridge twice. I think, once for a conference, on lattice quantum gravity, that I was kind of the star of because I had done the first work in, and the other was just to kind of drop in and give a seminar. Both times, Steve was very warm. It obviously wasn't easy to communicate with him, but I didn't turn him down out of lack of friendliness, or whatever. I was terrified of the regime of taking him to the bathroom and feeding him, because before they had any money, that's what it meant being a post-doc with him. He was on a pedestal, and I didn't like that atmosphere. I didn't like the, oh, let's go see what Steven has to say.
Lee, this might be a difficult question, but was your sense that part of the reason that he was on a pedestal was because of his disability?
Do you think he was aware of that himself?
I don't know. I didn't get to know him really well. Let's put that to the side. Maybe we can come back to it.
Also, during this time, Lee, I know he was a few years ahead of you, but did you have any interactions with John Preskill at this point?
Yes. He was a year or two ahead of me. I had some interactions with John Preskill. Paul Steinhardt was in my class and Paul was -- we weren't friends, but there were a couple things about which he was very kind to me. I've always liked him and admired him. There were a number of other people I could try to think of. As soon as I went to Santa Barbara, I made very good friends with Andy, who I mentioned, with Ted Jacobson. I was already good friends with John Dell, who was there.
So, Santa Barbara was your first post-doc. That's where you went first?
And there was this group on quantum gravity. I took it, and then they called me and said, "We're not going to be ready to open until January. So, we set up a situation where you can go to the institute for four months." And I said, "Have you checked with them, because they turned me down?" Whoever it was said, "No, that's fine." So, I went to IAS for four months, and then went out to Santa Barbara for a year and a half, and then went back to IAS for another two years, which they added, which was nice.
So, you started at the institute for four months. Who did you work with at that point?
Nobody. I talked with a lot of people. I think I was working some with John Dowd, because we were continuing. I don't think I worked -- you can check my papers, but I think they were solo papers.
Was this four month stint where you had this humorous understanding that you didn't want to be stuck at the same lunch table with all the other theorists?
Yes. And I had a great lunch with Freeman.
Yeah. What was it like to talk to Freeman one on one?
Well, I'll tell the story. Freeman was a gentleman, and certainly, I miss him. He said to me -- I'm sure he was doing what he did for all the new post-docs. He said, "Are you happy here? Are you comfortable? Do you have what you need? Is there anything I can help with?" And I said, "There is one thing, Freeman, that I'd very much appreciate if you could do." And he said, "Sure." And I said, "Can you tell me what Einstein was really like?" And he said, "No, no, no. I'm sorry, I can't. I never met him." I don't remember the conversation. I'm making it up, half, but I've told this story so many times and basically, I said, "Freeman, that's impossible. How could you not meet him?" And he said, "I'll tell you. When I came here, I wanted to meet Einstein, so I understand. I went to Helen Dukas and made an appointment to have tea with him on Friday."
Helen was Einstein's secretary.
Yes. "And then, the day before, I was nervous because I didn't know what I'd talk about. So, I went back to Helen and asked for some papers on Einstein to study. I took them home and looked at them and realized they were garbage. What he was doing with his unified field theory was junk and would never work. And then I woke up with a dilemma in which I couldn't go and see him and not tell him that what he was doing was nonsense, but I couldn't tell him. So, I called in sick and spent the next years until he died, not meeting, avoiding him." And I said to him, "Didn't you understand --" and he interrupted me. He said, "No, what you're going to say is true. Einstein could have easily defended himself to me and I would have learned something. But by the time I understood that I was much older than you are now, and Einstein had been dead for years."
The other question that you might have asked Freeman -- I'm not sure if you did, but this all presumes that Freeman's approach was unique. That no one else could have or would have alerted Einstein to the possibility that he was very much on the wrong track.
Sure, but this was a theme that Freeman often spoke about, about his generation being conservatives because of the overreach philosophically of the previous generation. So, he and his friends, Freeman and his friends, thought that they were better, that they were focusing on doing real physics. But there's a lot to explore in there. Since you're a historian, you know who David Bohm was.
Did you know that David Bohm and Freeman were close, close friends, and had dinner together every night for two years?
No, I did not know that. Huh. I'll just note, editorially, that there are certain parallels between Freeman's interactions with Einstein, and perhaps, yours with Steven Hawking.
I don't know. I mean, surely, there's an issue for me about Steven. Maybe we'll leave it at that for now.
Now, when you went out to Santa Barbara, it was the ITP. It wasn't Kavli at that point. Who were some of the people there? This is in the relatively early years. Who was there at that point? Who were the key people?
Well, we were the first class. Among the other post-docs, I think I've mentioned the ones who became good friends. Steve Shenker I already knew through John Dowd, because they were friends in high school. Andy was a very good -- we're still very friendly, but we were really good friends in those days. Ted Jacobson, who became a very, very good friend. I'm not remembering many other people. Per Bak was there, the person who revolutionized condensed matter and critical phenomenon. We became friends much later when we were both in London together. Am I missing somebody?
No, no, but I was going to say, just to fast forward to your excitement in the initial part of our conversation about Perimeter Institute, and looking at the institute as sort of an anti-model, going from a place that is as establishment, it is the apotheosis of the establishment as the institute, even at this point as a young scholar, was part of the attraction of the ITP that you wanted to disassociate with the establishment, that you wanted to be in a place where there might be some intellectual freedom that you might be afforded that's not possible at a place in Princeton?
I don't think that was an issue. No. And the institute -- I mean, it wasn't for me to stay in an establishment place. There was a kind of underworld at the institute. There was a security guard who was probably bipolar. His name was Dominic. He had all sorts of stories of hanging out with Gödel, and then taking wild drives through the countryside, because Gödel was totally insane. There was a logician who had gone mad, who slept on Freeman's floor and was always hanging out. There were a couple of people from the weapons program who somehow ended up with positions at the institute who we used to hang around with. I was then living with a woman who was deeply insane, and an artist. That added a certain whatever to it. There was -- oh, god, what's his name? There was a very good topologist, John somebody. It'll come to me. He's one of the famous topologists of Princeton, and his wife, they used to hang out with us. And there were some art historians. So, I just didn't take it -- there was great physics there, and I liked being there. Steve was the closest person I had, and later on, I realized we were both interested in quantum foundations.
Yau and I used to go fishing together. We used to go walking around and fishing together. So, I was comfortable there, and somehow just ignored the stuffiness. I didn't hang out only with the physicists. The person I've had a long difficult relationship with was, of course, Edward. Part of that took place there, because he was a faculty member.
He was at the university, though. He wasn't at the institute at that point.
Yeah, but we knew each other. He had been a post-doc at Harvard. The woman that he married, Chiara Nappi, is somebody that I was very friendly with. In fact, I met him through her. Of course, So, I felt kind of integrated, socially. There wasn't a social issue, at least not that I remember.
Was your time at the ITP productive?
Who did you work with there?
Still? It's a theme.
Yeah, I do a lot of single papers. But I took a long time over a very foundational paper, trying to understand the Unruh effect, and the Hawking radiation, which is probably my best paper. It's called something like quantum and thermal fluctuations. That took years to get right. It is an amazing paper, when I go back and look at it.
How long were you at the ITP?
And what did you do next?
I went back to Princeton for another two years.
Did you have any misgivings about that?
No. No, I liked it there. I was vaguely aware that the other post-docs were in a big competition to get faculty positions, and they were all working on Standard Model, Standard Model extensions, QCD. And they were really smart, and I hung out with them, but I was in my own little world working on quantum gravity and quantum foundations. They had invited me to be there, so I felt welcome.
Lee, the chronology, I think, puts you at the Institute right around the time of the superstring revolution.
Yes, I was there at the talk where Edward changed his mind. The talk where John Schwarz, whatever his name was –
Tell me about that. How did he announce that he had changed his mind? What was the thinking?
Just by his presence. And then he began saying to people these ridiculous things like, "You've got to stop whatever it is you're doing, and join us and work on string theory, because we're going to have it all wrapped up in 12 to 18 months, and you're going to miss the boat."
This struck you as ridiculous from the beginning.
The hype was ridiculous. The next place I went was Chicago, and I remember Chandrasekhar making fun of the string theory hype. Chandrasekhar was reporting on a recent visit to the institute. Chandra reported, Edward said to him, "You've got to stop whatever it is you're doing, and join us and work on string theory, because we're going to have it all wrapped up in 12 to 18 months, and you're going to miss the boat."
Chandra turned to Edward and said, "Look, young man, I knew Heisenberg pretty well and I can assure you that Heisenberg would never have done such a thing as to turn to somebody and say, you should be doing quantum mechanics because that's the big thing. Especially, talking with an elder of yours who has been doing physics for 50 years." But I was interested in it because my key idea was the vibrating loops, and that idea went into loop quantum gravity, and it went into string theory.
So, Lee, let's just freeze the narrative for a second, because it's obviously more complicated than you simply going to a talk that Witten gave in 1984. So, to go back five years, even ten years, were you aware of what people like Schwarz and Green and Veneziano were doing? Was this on your radar at all before 1984?
Before 1984, vaguely. I don't think I read any of the papers. What was more on my radar was conformal field theory, because Steve told me, "You really got to pay attention to this." Steve Schenker, when I was at Chicago, and he was a young faculty at Chicago.
It's very important also, at this point, that what you're emphasizing, the pushback that you're emphasizing right now, is not so much that there were problems with string theory. It was sort of the sociological bandwagon-ism that this is where the truth is, and either get on or miss entirely. That's the thing that you're pushing back on from the beginning.
No. There were substantial things. It was in a fixed background; it was strings moving in Minkowski spacetime crossa torus or a sphere. It was not -- since I've been thinking about the dynamics of loops of fluff of gauge fields as the basis for the quantum theory of gravity, it wasn't that far from what I'd been thinking about, but what I'd been thinking about had no background metric. That was the key difference. I understood, already, this issue about background independence. And there are other things which I had mentioned in the note I wrote you. I had by then a pretty decent introduction to philosophy, and especially, starting in the summer of 1980.
Julian Barbour was a very important influence on my thinking. I was also thinking a lot about quantum foundations. So, I'm already because of those two things, I'm in a partly -- I'm hanging out with friends involved in the string stuff, but I'm also going every time I can get to hang out with Julian Barbour, and background independence, and so forth. So, I'm sort of accidentally between these different communities. And it meant that the -- it wasn't so much a lack of interest on string theory on my part. It was a lack of interest from the string theorists in the ways I wanted to develop it, because what I thought would happen -- I mean, I somehow knew they were really ambitious and smart, and I had a conflictual relationship with Edward because it started through a friendship with his wife. His father, also, Louis Witten, was a professor at the University of Cincinnati. Edward was very hard on me, as he was on many people. And I took that personally. That hurt my feelings. So, it wasn't simple by any means. But I had my road I was going down, and it wasn't Edward's road, and it wasn't anybody else's. If they knew me well enough, they were discouraging. I think some of it is my fault. I don't think I explained myself very well.
As if the ITP and the institute did not provide enough of an intellectual contrast for you, I wonder what Chicago was like, what the research culture, the intellectual culture was like when you arrived there.
Some of it was really good. Bob Wald and Bob Geroch made a culture which was very high level, and really in the classical general relativity world, which is the world that Abhay came from. Abhay was their student. There was a personal tension in the group, which I don't know why. I can speculate, but Bob Geroch and Chandra never spoke to each other. And Bob Geroch didn't produce much, although he was a fabulous pedagogue. I had heard some great lectures by him on Asymptotic Structures of Spacetime, at a conference at the University of Cincinnati.
In Chicago I also met Louis Crane, who was doing a PhD in mathematics, specializing in three and four dimensional topolology under Karen Uhlenback. We became close friends and wrote some good papers together; and he was to make important discoveries about the mathematics of loop quantum gravity. I’ve always felt he was very much underappreciated. He's a story which there is a lot that I regret. He's one of the few friends I've had who is no longer a friend. I also think that he's been vastly -- his contribution to loop quantum gravity has been vastly understated and underappreciated. During that time I also met the knot theorist Louis Kauffan, a mathematician at the University of Illinois, Chicago. He was teaching a course on knot theory for artists at the Art Institute of Chicago, where my girlfriend, Penn Stallard was doing an MFA-on holography.
How much interaction were you able to have with Chandra?
A lot, at his request. He would come by and say, "Smolin, come talk to me." And I would go to his office and we would talk, sometimes about science, and sometimes he would just pass on wisdom.
Like what? What kind of wisdom did you get from Chandra?
He said most people in this kind of work burn out after ten or fifteen years, and that's because they either have a big success and they get too attached to it, or they fail, and they get discouraged. He said, "The way to avoid that is do what I do, which is I pick a subject, I learn it, I make a contribution, I write a book, and then I put it all in a box and put it on a shelf." He had a row of these. "And I look around for something completely different to work on."
You internalized that, obviously.
No, I've been working on quantum gravity. In a way, but in a different way.
What was he working on when you interacted with him? What was the last thing that he had put on the shelf?
I was there when he got the Nobel Prize. I was interested in quasi-normal modes and he recommended reading a chapter of his book on that. A few days after that he was awarded the Nobel Prize. I ran into him in the hallway the day after and I said, "Chandra, what are you doing here? You should be relaxing and celebrating." And he looked at me like I was a Martian. And he said, "Have you studied page 243 to 256 like I told you to?"
This is a great man.
He was a great man, yeah. He went on to say that “if you read those pages you will understand that what I do there is a thousand times more important, than the work they gave me that silly prize for.”
When did you go on the job market? When did you start thinking, okay, time to get real? I need to become a professor.
Oh, from the beginning. It was clear when nobody was getting a job. Of course, that's always the way it is. So, I was told from the beginning.
So, Chicago was another place for you to hide out until opportunities opened up.
It was explicitly that. I had been a post-doc for something like four years. It was understood I was getting tasked, too. Chicago's offer to me was explicitly while you're looking for a faculty job. I was fortunate enough to get the one at Yale, which had been already turned down by two people. I had been the third person it was offered to.
They opened up a new line for you, or this was somebody that you were going to replace?
It was not a line as far as tenure. They didn't tell me this, but there were no tenure lines associated with it. They only told me that three years later when -- so, now loop quantum gravity is invented, and that's taking off and I'm taking off. I get an offer from Syracuse where Abhay is, and Rafael Sorkin, who was a very dear friend.
Wait, let me get this straight. You come to New Haven thinking you're on the tenure track. Three years later, they tell you that you never were. What was your response to that?
To leave. But not until Feza Gürsey came and told me to. I get an offer from Syracuse, which is where Abhay and several other people I admired very much –
I'm sorry to come back to this, but did you make a stink about this? Did you consider legal action?
I didn't consider legal action. I get this offer, I went to Tom Appelquist, the chairman, and I said, "I have this offer. Can I be put up to tenure?" And he says, "We'll go into a meeting and discuss it." And I say, being very confident, because loop quantum gravity has very quickly become a big thing, "I'll stay at Yale," I say foolishly, "if you will write me a letter that says there's a date where I'll have a fair evaluation for tenure." And he goes into a meeting a week later, and comes back and says, "We can't do it." Feza Gürsey comes and sees me an hour later. He was very much a gentleman, and he closes the door, and sits down in my office and says, "Do you know the real story?" And I say, "No, tell me about it." And he says, "You never had it. There was never a line." It didn't occur to me that -- this is the first time. But I also learned that this is not just me. It was the standard operating procedure. They explained to me that to make my assistant professorship into a tenured professorship, they would have to eliminate three other assistant professors. And that this was the way the university functioned. It was not the physics department. It was standard. I had friends in different departments, and they all agreed. It was what Yale was -- I don't know if they still do that, but –
And Abhay was already at Syracuse at that point, and he said, "Come on, we've got something for you."
Well, Abhay and I -- we didn't always have a smooth friendship, but we were very good friends at that time.
You came to Syracuse with tenure?
Not exactly, but I came to Syracuse with a verbal promise that I would get tenure in the first year.
What was happening on the faculty at Syracuse at that point?
It was a great group in relativity and quantum gravity. There was Josh Goldberg, who represented the older generation. Abhay -- we should talk about Abhay later, but he's a fabulous scientist. There's Rafael Sorkin, who's a fabulous and important scientist.
And Gaby Gonzalez, that comes later, right? This is after you were gone.
She and Jorge come to Syracuse; she is at that time a PhD student. Originally, Gaby wanted to do quantum gravity. I think for a few weeks she was my student, but very quickly she changed her mind. There was Peter -- I forget his last name -- who was doing gravitation radiation.
There was some excellent work that was happening at Syracuse.
How long did you stay?
I think four years.
It was a good time, overall?
And you were productive during this time.
What else were you working on?
That was the -- I mean, the launch of loop quantum gravity -- so, we're back to '86. So, there was -- I know you didn't ask me that question, but just to note from there. There was a semester-long program at ITP on quantum gravity organized by Abhay and Ted Newman, who I don't know if you know, unfortunately, just died. Abhay invited me to that program. I had seen Sen's paper, which Abhay built on, and I already from Sen's paper knew that I could do a lot with these techniques about loops and operators based on loops, and so forth. And then, Abhay came and gave a seminar at Yale in December of '85. Then, it was clear, and I started right away working on this thing. And then we all came to Santa Barbara. Ted Jacobson was there; Paul Renteln, who was a PhD student at Harvard; Abhay and Ted and Roger was there sometimes. That six months was a very important period. Basically, I put the knowledge of these loop operators and variables in, and there was a lot I had to learn about thinking of relativity in these Ashtekar variables, and it just took off.
Why did it take off? What was your sense of the circumstances?
There were many results, and the way to the quantum theory, the first key result was with Ted Jacobson, and it was that he could easily solve the Hamiltonian constraint. Usually, in quantum theories of gravity, the Hamiltonian constraint, or the Wheeler-DeWitt equation was very non-linear and very hard to solve. And using these loop techniques, it just happened in 10 or 15 minutes on a blackboard. And then we had to do a lot of checks, and regularization procedures, so as to make it really honest, and not just to multiply infinity by infinity. And it worked. That was the big result, from my point of view. Then, the problem was to solve the vector of the diffeomorphism constraint. And at that time, we were working with the connection representation or states of functionals of Abhay's connection. That, and we couldn't solve the diffeomorphism constraints.
Louis became an assistant professor in math at Yale, and we worked on it together, and pretty much convinced ourselves it wasn't possible. And then Carlo showed up. Carlo, I had met during a program in Santa Barbara, and invited him to come Yale to work with me. He had money for U.S. travel, and he went to Syracuse and came to us. And he had been in London with Chris Isham. Chris had taught him about non-canonical representations in quantum mechanics, where the algebra you represent is not the canonical algebra. I mean, there's a cute side of the story, where I taught him those nine to do, we were stuck, and we went sailing, and Carlo told me about his girlfriend who left. There's all that sort of cute stuff, but basically, three days after Carlo arrived and I explained the situation to him, he came into my office and said, "I can solve all the problems. We transform to a new basis with the states that functions as loops." And it worked.
Did Abhay get to Penn State before you did?
No, the Penn State physics department got a donation that would support four faculty, and they wisely decided to put them in one area and decided to think about quantum gravity as that area. So, they started with Abhay. They invited Abhay to form a center. I was, although I think he regretted it later, the first person he asked to come and make the center with him. We invited Jorge Pullin to come, and we left the -- if I remember right, we left the fourth one open, originally. Or who am I forgetting? Anyway, so Abhay and I and Jorge went and opened up the center at Penn State. Abhay and I had been very close friends, but immediately there were some unexpected personality conflicts when we got to Penn State. So, the next few years were not very comfortable.
These were personality conflicts within or beyond the physics department?
They were just between Abhay and I, and they were stupid. Well, some of it was that Abhay -- I, of course, as I had already been doing at Syracuse, was already living in New York and coming out, and I kept doing that at Penn State. Abhay felt that didn't represent total commitment. That offended him.
What was your defense to that?
First of all, I said, "I've been doing this for several years, and I come to every meeting, and I'm there whenever I need to be there. Nobody's ever complained." I went immediately to the chair, Banavar, and said, "You're my chair, do you have any problems with this?" And I think some of it -- there was a misunderstanding between Carlo and Abhay and I. The misunderstanding was that Carlo and I thought we were the three troubadours, and it was a three of us, and each of us had put in something essential. Abhay had put in the classical formulation; I had put in all the technology about loops and flux; Carlo had put in the last thing that you have to go the representation. So, it felt like three friends on an adventure. Carlo was a year younger than me, and Abhay is five or six years older, and I think Abhay's perspective was that he was the leader, and we were his first followers. Somehow, that had never crystalized before Penn State.
Meaning that if he expressed displeasure about you exerting energies elsewhere, he would have expected that you would have listened to that.
Yes, and there was also a kind of priority issue, and it went like this. Ted and I first, and then Carlo and I published these papers with these results, like solving the Wheeler-DeWitt equation. And from a mathematical physics rigorous point of view, we were making it up as we went along. There were subtle questions about what inner product does this limit that we use for regularization converge. And I was trained to be a particle theorist. I was not trained to be worried about those questions, and I took the view that that was for other people to worry about.
And Abhay tried, when Carlo and I found first the solutions to all the constraints -- this was probably the turning point -- Abhay came to us and said, "Don't publish that. Don't put it on the paper." And we said, "Why? That's the real result." And he said, "For mathematically minded people, it's not a result, and you're making us all look bad. Wait, and I'll work with you, and we'll turn it into a real result." And we said, "No, it is a real result." So, he worked with some other people who were mathematical physicists like him, and they published a rigorous version of our results-indeed the exact same with the same results, but as real theorems and real mathematical physics. And they didn't cite us. That was very hard to take. We said, "You must cite us." And they put a little note that saying, "These results have some inspiration from the work of Rovelli and Smolin," but it's hard to see a connection. So, I still don't know what that was about, but it was hard to be as friendly -- let's put it that way -- after that.
Was loop quantum gravity, at this point, achieving something like maturity after being at the cutting edge for a while at this point?
There was more stuff that happened. A very important thing -- so, this is '92, '93, '94, probably. There was the invention of spin foam models, the path integral formulation, and that came from several people at once.
Were you involved in that at all?
Yes, but not in the most central development. There were several different approaches. The first one was Mike Reisenberger's. The second was around Freideland Krasnov and friends. The one I was involved with, and it wasn't my idea, was Fotini Markopoulou's, which was based on merging loop quantum gravity with causal sets, which was basically her PhD. I got interested in that one. I still think it is the best approach.
Lee, to orient us in the chronology once again with where string theory is by the mid-1990s, of course, going back to Witten's exhortation that everybody should drop everything and start working on this, ten years later, we start to see the ramifications of this on the faculty level, where there's all of this interest that only new hires should be string theorists. Of course, Shelly Glashow, famously or infamously, declared his intent to make faculties string free. Where were you on these academic political debates? If we can set aside the science to some degree, where were you on this idea about how many string theorists there should be at any given one department, circa the mid-1990s?
I think this needs some contextualizing. There was already a schism in American theoretical physics between what was called gravitational physics and high energy physics, going back to the 1950’s. It would be very interesting to unravel the politics of this.
One story is that the high energy theorists grew out of nuclear physics which was very well funded coming out of the war-because their community had made the weapons. At the same time, a decision was made in the late 1940’s to have civilian control over science not connected to making weapons, and hence the NSF was born and most physics went through the NSF. But there remained a grey area which was developments of fundamental (taken to be high energy) physics, that might plausibly lead to new kinds of weapons. So, there was also a funding stream for high energy physics through the DOE. Further complicating the picture is that the relativists had some funding sources of their own coming from the air-force and perhaps other agencies. There was no good national security justification for these, apart from fantasies of alien science powering flying saucers, or using quantum non-locality to communicate with submarines. (To put yourself in this state of mind, recall that the gravity research foundation was originally founded to fund anti-gravity devices. Meanwhile the CIA was funding experiments in remote viewing, justified by misunderstandings of quantum theory. As were their Soviet counterparts.) Sometime in the sixties a separate division of the NSF was set up for “gravitational physics.”
Because it was small, autonomous and agile, the directors of the gravitational physics division had a lot of freedom to use their judgment to choose which theorists were NSF supported. They sent proposals out to reviewers they selected, but made decisions using their own judgments, without the politics of panels.
I personally believe I had a good career solely because Richard Isaacson believed in me and made sure department and search committee chairs knew that. I suspect the same is true of a number of my colleagues including Ted Jacobson, Rafael Sorkin. It was also solely due to Richard’s taste that the gravitational physics program supported a diverse set of excellent researchers and subjects, from mathematics, to the early forays into computational general relativity, foundational thinkers, cosmologists, classical and quantum gravity. There were perhaps a dozen research centers, each with on or two postdocs and two or three professors: Austin, Baton Rouge, Berkeley, Brandeis, Cal Tech, Chicago, Maryland, Pittsburgh, Penn State, Princeton, and Yale. Of all this there remains now only the centers at Baton Rouge, Penn State, plus a few individuals such as Ted Jacobson.
This was the American “relativity community”, excellent, dynamic but fragile. And indeed, this creative world was destroyed in a few years, not by string theory, but by the NSF betting the house on the LIGO experiment. So, first, I played no role in whatever discussions of the NSF led to the decision to sacrifice the relativity community for the LIGO project. Kip Thorne was nice enough at a diner during a visit to Penn State perhaps in 1997, to explain to me the whole picture, with the consequences. I was confirmed in my search for a position outside the US. I also played no role in the debate among high energy theorists as to what portion of their faculties or postdocs should be string theorists versus “phenomenologists; I was not in their community, funding wise. Some people in the US and UK claim that TTWP gave ammunition to the physicists whose funding priorities were other than string theory. I have no direct evidence of that. In any case, it was never my view that the number of people working in any particular direction should be set. What I have always argued for is a much greater diversity of ideas and research programs to solve fundamental problems. I am against “premature paradigms.” I am most of all in favor of the first-priority for hiring be the unusual young people who pursue their own ideas, who have the creativity, intellectual independence and ambition to push forwards until we find the rue explanations to what puzzles us.
This was brought about -- I don't know all of the history of it, but the high energy theorists came out of World War II very aggressive, and they had a lot of money to spend, because they were an adjunct of the high energy experimentalists. Speaking to you, as a historian, it will be very important to know this history. Somehow, the division of gravitational physics got invented in the NSF, which was like a home for wayward deep thinkers. It was directed by Richard Isaacson, and he took an unusually personal interest in the development of the field, and the young people in the field. I was hired because Richard Isaacson went to the chair at Yale, and said, "He is among the people that if you hire, I will make sure he's well-funded." And this is, of course, before LIGO and numerical relativity were big. So, there was this kind of small corner of the world, which was well taken care of, and it had a variety of people doing everything from numerical relativity which Bryce developed with Steve Christensen, and some other people down in Texas. The Syracuse group was started by a student of Einstein, Peter somebody.
So, the relativity world had control of the few groups that Yale, Princeton, NYU, Texas, Santa Barbara, Berkeley, Chicago. And I was in that group, even though I wasn't trained by them. They generously considered me one of them. Meanwhile, the high energy physicists went about hiring string theorists. We challenged that, and they challenged us, and there was a sense of a rivalry, and there was a sense that the members overwhelmed us. It was a little bit different in Europe, and this is very important, because in Europe the most prestigious positions go in competitions where the field is not very important. Try to find the brilliant individuals, like the CNRS, or the Max Planck Society scholarships. So, we were thriving, and those people related to what we were doing were thriving. Maybe it's jumping ahead, but one thing that I'm proud of in my career is that there are about twenty people who did a PhD with me so far, and seventeen of them are faculty now.
That's a pretty good batting average.
Yeah. And those seventeen were a high proportion -- at one time, I don't think this is true anymore, but there was a moment when they were like a third of the untenured faculty in quantum gravity. I don't quite know how we did it, but somehow -- and Abhay is certainly a grand strategist, and Carlo isn't bad, and I'm not so bad when I'm needed either. Somehow, we managed to establish a stable sociological field against the pressure of all the string stuff.
And you specifically saw it in those oppositional terms?
Yes, because people explained it to me in those terms.
You're talking about both scientifically and in terms of faculty hires?
There was something else. This is not the whole picture. The problem was not really the string theorists coming out of the group of the relativity, the gravitational physicists. At some point, Richard Isaacson told me that the bulk of funds coming out of his office were going to go into numerical relativity and the experimental program. Kip Thorne sat down and told me, "If you can, you should leave the United States because we have this big experiment, and we're going to take all the money, and you're going to get screwed over if you stay in the United States." And I left. That was one of the reasons I went to England.
You resigned your position, or you went on leave?
I went on leave because I went to England for two years. I intended to negotiate a position at Imperial College. There was, under discussion, a center for quantum gravity which Chris Isham and I would run, which would have been funded externally, and I would have had a chair at Imperial College as a result.
And this is brand new territory for Imperial. Is anybody working on these things before you arrived?
Sure, Imperial was a very important place for quantum gravity, Chris Isham among them. So, it was a natural thing for Imperial College to do, and I was very excited about it.
What were your impressions when you got to Imperial College?
It wasn't what it should have been. There were some very, very good people there. One of them became an important collaborator and close friend, Joao Magueijo, who's a very provocative person in cosmology. We did some very good work together on what became called relative locality, and doubly, special relativity. Chris was a very important and very influential person in quantum gravity in those days, and I had three post-docs with me. We were nicely set up there. I had to make the decision, and it was not an easy to decision, to pull the plug there. By the time I made that decision, I didn't have an offer letter for the whole thing from Imperial, but it was being negotiated. I pulled the plug on all that and took Perimeter's offer, which I'm very, very glad I did.
So, you could have stayed at Imperial. You could have gotten what you wanted.
I don't know. Who knew? Maybe.
So, we talked about this at the very beginning, but by the time you were pulled in with Perimeter, how mature were the discussions up until that point? In other words, when you became aware of this, what opportunity did you have to shape these existential questions about what kind of institute it would be?
We were at the very beginning. There were very formative -- I mean, Howard Burton had a very clear mind about what he wanted to do. Howard had, when he had gone home that weekend to discuss with his wife, he had written a long email message to Mike Lazaridis, which laid out the whole structure, the timescale, the different fields, which fields to prioritize, the governing structure. The whole thing. So, that was all previous to Rob, Fotini, and I. But we were certainly the first faculty. I felt like I had a very important role.
Lee, given the situation at Penn State, and the fact that your future at Imperial was uncertain, to what extent was jumping in with both feet at Perimeter risky or not?
It was risky, and I'm usually a very risk averse person, but it seemed like the right thing to do. Can I speak personally?
It was a crazy time, somehow, for me personally. Fotini and I were divorced very quickly, although we remained very good friends, and remain to this day very good friends. Somehow the marriage/romance thing was a mistake, and we got over it. So, we went to Perimeter together to make it as friends. I think that confused some people, but we weren't confused. But obviously my life was changing. I was living in New York, sharing a loft in Tribeca with -- do you know who Jaron Lanier is?
With Jaron, and we're very good friends. My plan was basically to stay in New York and fly up four days a week to Waterloo and be part of launching perimeter, but keeping New York as my base, and probably buying something there.
You just liked being in New York, or you had some institutional connectivity there?
I had had visiting positions at Rockefeller, NYU, Columbia. There's a little flirtation story, or big flirtation story with each of them, which had not worked out. But I'm a New Yorker and if I wasn't going to go to Europe, I was going to be in New York. But nothing in the end of that worked. September 11th happened in the middle of that move. I was in London packing up the flat, otherwise I would have been in New York that day. So, I then came back to Canada, and we launched Perimeter, and I was going back and forth to New York. I eventually decided to explore the idea of Toronto being my home. That was the right thing. I met the person who's now my wife in the midst of all that, Dina. So, Perimeter seemed so much like -- there was a strong sympathy between my vision of what a research environment could be, and Howard and Mike's plans as they laid it out, that I felt like that was the right thing. That was a once in a lifetime chance.
Lee, during this time, of course, you yourself are working on string theory, or at least some of the background that informs string theory.
In the late nineties, I was working mostly on trying to bring together string theory and loop quantum gravity, which was always what I was thinking should happen. I was also starting to work on quantum gravity phenomenology.
People that were more naturally inclined toward this in the field, what were they not doing where you felt this need that this work needed to be done?
Nobody was interested. There was so much polarization, and accidentally, I was friendly with some of the string theorists going back, so I had no problem talking with them. Some of it was this schism with Abhay which got serious, and I wanted some room. I didn't want to fight with Abhay over the leadership of what direction we were going to go in loop quantum gravity. I was happy to seed that. And I had some ideas, very concrete ideas, some which worked out and some which didn't work out, about how to use matrix models to bring together loop quantum gravity in string theory. The last two years I am working again on matrix models in a collaboration with Jaron Lanier, Stephon Alexander and others.
Lee, was this work most formative intellectually for what would become The Trouble with Physics?
No. I'll tell you the story of The Trouble with Physics, if you like. But let me just say something else. The matrix models I played with then, there's a paper that Jaron Lanier and Stephon Alexander and I and some other people at Microsoft researched, I've just finished, which is on an analogy between quantum gravity and machine learning, logistically. It's a lot more than that. It's a long paper, and it may end my career. It's a crazy paper. But that is a development from working on the matrix models for unification, only connecting it with machine learning, and so forth. That's with Jaron, who I was sharing his loft when New York got attacked, and so forth. So, there is a lot of connections like that.
The story of The Trouble with Physics actually starts with the friendship with Jaron. Jaron and I used to compare the situation in physics with that in computer science, and we saw in both cases a premature institutionalization of research programs. And he was very concerned with the program of strong AI. He has written a lot against the hypothesis that human beings are anything like digital computers. We felt, as we talked, that that idea had taken over the field of computer science in an analogous way to the way that string theory had taken over the world of fundamental theoretical physics. We planned a long paper on that, and there were some other examples we were looking at. Of course, we never wrote it, but that became the original proposal for what is now called The Trouble with Physics. As originally outlined, that would have been a more academically oriented book.
It began with a lot of theoretical stuff about research programs and the role of controversy in science and the development of science, which I had been very interested in since meeting Feyerabend. So, it more had the flavor of an academic methodology of science book, i.e., a academic book in philosophy of science. There were a number of case studies, and string theory was one of the -- there was sort of the general stuff and a number of case studies, and string theory was one of the case studies. My agent for all the books I write is John Brockman, and I sent this to John, and he called me and said, "Are you crazy? I can't sell this. It's an academic book. It's fine with me if you write academic books. Send them to University Backwater Press, and they'll publish four or five copies. I'm a businessman, so don't bother me with it." John has certainly become a dear, dear friend. I said to John, "Look, you're my agent. We have a contract. Your job is to present that book and sell that book to a publisher." And he said, "Okay, I'll try," and I don't know what he did.
Soon after that -- so, I guess this was 2003 -- was the one time I went to the TED conference, and I was invited to give a talk, and John was there. He told me he didn't manage to sell this book. And he said, "Listen, let's take a walk." And we took a walk and because he is a great agent, he said, "Tell me what's important to you. Why do you want to write this book?" And we talked for a while, and he said, "Listen, here is the book. You take the case study on string theory, which is really your life, and you can animate it, and you put that in the front. And then you put all this academic stuff that nobody cares about, about abstract theories of how research programs develop and resolve conflicts. And nobody will care. You just put that in the back. The editors won't ever read it anyway. That, I can sell."
That resonated with you.
I wanted to write the other book, because that's the book that has always been in my head. So, when it became controversial, I'm like, huh. This is an academic study of the problem with how research programs compete and the importance of competition amongst research programs.
Lee, to what extent could you extrapolate broadly from the specific case study of string theory, and to what extent did you stay in that particular lane and not branch off into other topics?
Well, I certainly was invited to. I got lots and lots of phone calls and emails saying, "I work in X field," whether it was biology, or literary studies, or different medical issues. "And we have the same sociological issues going on in our field. Can you come and work with us?" I thought about that, and I realized that, because the original thing was so controversial, that I don't enjoy controversy. So, I just put a stop to it. That is, okay, it's obvious that the issue is generalized, but that's not my job. I did my job. There were people who went on this string wars thing for years, and I didn't want to do that. I wanted to do science. I regretted the anger it caused and the friends I lost, most of whom I think I've gained back. So, I just got out of that, and I didn't go to the conferences about fighting out the string wars. I had done my bit.
Do you think that you enjoyed some level of credibility, for example, in a radio debate with Brian Greene, where you can say, "Look, I've done string theory. I'm not an outsider looking in. I know where you're coming from." To what extent was that academically and intellectually useful to you?
I think it was not just useful, but from a point of view of integrity, it was necessary. That's why I couldn't write a book that said The Trouble with Cardiac Treatment, or something like that. I'm sure there's a lot of stuff for somebody to write -- or I don't know. I was in my element, and it's very important to be able to say that if you took Brian's book of about the same period and took my chapters on string theory and lined them up, they would tell the same story. Not exactly, but almost exactly. I also did things professionally. I don't remember how many, but I have somewhere in a notebook everyone's name who I sent to or offered to send, an early draft. I sent it to key string theorists, most of the really famous ones, more than once and said, "Could you please comment?" There was an issue which was really important to get clear, which was the claim of finiteness of string theory to all orders in the perturbation theory. I had dug up the fact that that proof had never been completed. Very few people knew that was the case, so that was something that I had to take a long time over.
Lee, to what extent did you grapple with the idea of the sociological issue of patience with string theory? In other words, on one end of the spectrum, you have people that say, "Look, this field's been around for twenty-five, thirty years. Show me that it has any relevance in the real world." Of course, on the other end of the spectrum, people saying the field is growing, there's something innately beautiful about it, keep giving us resources. Exciting things are coming. To what extent did you grapple with the sociological issue of scientific patience?
I've never heard that issue mentioned. But let's look at what has happened. What's happened is that -- I work at this research institute, and we don't have formal groups, but we have areas, and we have an area in quantum field theory and strings. We don't have a strings area, although we used to. And we have some good people in that area. Very, very good people. What they do is mostly variance of different approaches to quantum field theory. They do very little that actually depends on working out the amplitude for a string to propagate, something that up to 1995, the string theorists would have said is the main problem in string theory. It's all good work. Some of it is progressive, and some of it, in my view, is not very. But basically, if you go to the string conference, which I've only gone to a few of them, but if you look at the topics now, there's a lot going on, but there's very little that could be called string theory in any formal sense. If you look at Perimeter, the two people who have grappled with the real issues in making string theory work are Laurent Freidel and myself, who are both, quote, in the quantum gravity area. So, I think that string theory was an interesting idea and it made interesting progress. Mostly, it's died and turned into other things, without changing the sociology. That's the interesting trick. That is, there's still a community which identifies as you're in this community or not.
Do you think that the field has moved away from an interest in proving long-term its testability? Has it delved further into mathematical issues?
Some people have gone that way. What we're looking into at Perimeter, and what interests me -- I don't know if this will really pan out, but there's an area that has come out of general quantum gravity, loop quantum gravity, string theory, classical general relativity, having to do with boundaries and boundary conditions. There are some extraordinary young people in this area, and you can't classify then. And I love this. Some of them come from Harvard in terms of their PhD. Some of them come from more classical relativity places in Europe, like Brussels. My hope is that five or ten years from now, the young people they train won't understand that there was this schism. But we'll see. There's a lot of stuff we're skipping, but my own involvement with loop quantum gravity has been deliberately ambivalent for a long time. That is, sometimes I work on a problem related to making that theory work, or some version of it that I think is interesting. I have my own research program, which I've set out and delineated very clearly in the last several books and talks and papers. It starts with a set of principles, and it goes on to discuss a set of models that several people have been kind enough to work on with me. I’m very excited about that, and whether it's loop quantum gravity -- there's a sense in which loop quantum gravity is closer to its origins.
Lee, when did you get involved in thinking about ways in which loop quantum gravity, or quantum gravity generally, might be understood through experimentation?
I got interested in the late '90s in the idea that there were observations of very high energy astrophysical phenomenon that tested Lorentz invariance at the Planck scale. This is an area that was started by a few people in the '90s. The one I'm most closely connected with is Giovanni Amelino-Camelia, who is in Napoli. He just moved from Rome to Napoli.
When I started working with Giovani, we were interested in whether a theory with a highest energy – presumably the Planck energy – could be consistent with special relativity. The problem is that if this energy is a threshold-beyond which quantum geometry begins to arise – do all observers agree on when a particle is on or over the line? The basic issue is if you say that there's a length which is a Planck length, below which there's this quantum geometry which is different. In whose reference frame is that threshold, because it could Laurents transform? That's a meaningful question, and there are three possible answers: The first is that there is a preferred frame of reference in the world. Lorentz invariance is broken. This has consequences for observations of gamma ray bursts and whether the speed of light is dependent or not on energy. That is testable and has been tested since the late '90s in the present time, by some of the Fermi observations about gamma ray bursts. The present view amongst experts, which I am not is that this first possibility is not in agreement with the experiments.
The second possibility is that there is no preferred frame-but Lorentz invariance is modified. Giovanni was, I believe, the first person who made a version of this work and deserves credit for it. But Joao Magueijo and I were closely behind with a different version, as I believe was Jersy Kowalski-Glickman. The idea is that the Planck length, or the Planck energy, could be an invariant the way that the speed of light is an invariant, so that you change all the other transformation laws. This is an idea we now call relative locality. It has a different set of predictions for those experiments. So, before I left Imperial, I had started working occasionally on this. You can look it up, but something like that -- a few papers in that area. Then, there was the invention of doubly special relativity. And then ten years after that, we discovered there was an issue with locality, and it became relative locality. So, that's been my involvement so far.
Lee, where is LIGO in all of this?
LIGO is in a very interesting place, because they're under some hypotheses which are basically the sort of incoherence of the ground state. You imagine that there are all these virtual blackholes down at the Planck scale, and it's this foamy thing that doesn't have a clear dimensionality. That would affect the propagation of high frequency light through space in a way that caused some background oscillations in the kind of measurements that you want to make at LIGO. That is, there would be some noise which would be due to quantum fluctuations in geometry. Dimensionally, noise is valued in square root of hertz, and the right square root of hertz is 10^-23 in the second, which is the square root of the Planck frequency. I'm not being clear. These very rough models predict noise at the square root of the Planck frequency. Interestingly enough, that's where LIGO has some sensitivity to noise.
So, there's a story about this. The GO down in Hanover, I don't know if it was ever actually published, but there were talks where they showed graphs of this noise, and Giovanni got very excited about it, and I got very interested in it. Again, since they didn't publish, we didn't publish. Now, the LIGO people seem to be saying that there's some inexplicable noise in the detector. Again, I'm told this second hand. I don't think they've published. So, it may be an approach to quantum gravity, or it may not be, but it's interesting. Something that I'm very interested in is recent ideas Chiara Moletti. (and I'll think of her collaborator in a minute) And some other people have also contributed similar ideas, that you can test whether the gravitational field is non-classical by taking a quantum state interacting with the gravitational field, which then comes over here as a gravitational wave and interacts with something here. It has something like teleportation. There's a possibility of transferring quantum coherence through the gravitational field. But if that is possible, then the gravitational field carries the quantum phase and it's not classical. These experiments are the inverse of experiments that Roger Penrose and some other people have been proposing for years about looking for the breakdown of quantum coherence in the interaction of classical masses. These experiments look like they may get made, they may get done. We may not be that far from that. So, I've been following this. I've done nothing to contribute to it, but I've been following it. We'll see.
As you rightly point out, we have skipped over a few things, and one of them that I'd like to come back to, of course, is the previous book, The Life of the Cosmos, which if I understand correctly, you were specifically thinking about reaching out to a non-technical audience. So, first, tell me some of the intellectual origins of that book, and why specifically you wanted to broaden out who would be exposed to these ideas.
That was my first book. I started to think about using biological evolutionary ideas in physics, in cosmology. I had this vision, or this scenario, called cosmological natural selection. It made two predictions, and I thought that was decent. It was interesting that there were predictions. I published a paper about that in '92, and I started to sketch a book about that in 1990. It was clear to me that already there was a kind of crisis in fundamental theoretical physics, and a slowdown of progress, due to our inability to make any new predictions. I had been alerted to this issue already by the talk of Abraham Pais I had heard at a conference in Boston in around 1974-75. So, by 1990 I had been concerned that physics was in a crisis for many years.
I was concerned with that. It's basically the book that I wrote. I was also interested in complex systems applied to astronomical issues like galaxies and dark matter. I got interested in this idea of landscape and the laws of physics evolving on the landscape. And the idea of the laws of physics evolving in general. What I didn't know is that Charles Sanders Peirce had, in the 1890s, speculated about these. But this seemed to me to require really thinking about it carefully, and that seemed to me like a book project.
Were you talking to biologists? Were you talking to people that had expertise in evolutionary biology, or were you sort of an autodidact on these issues?
Both, but as the book was worked on I became more and more aware of these people and their writings. I'll tell you this story. I talked to them more, but I think I was talking -- maybe not. Maybe it was after the book was written. I was reading all those people, certainly. I don't think I met any of them until –later. My ideas about cosmological natural selection were written about by Paul Davies in the Independent. John Brockman saw that. He called me and said, "That sounds very exciting. Do you have a book about it?" I said, "I happen to be writing a book, yes." There's a funny story I can tell about the next few hours – the publishing world works a lot faster than the academic world, and seemingly ten minutes later, I had a book contract. It was actually two weeks.
I took the idea of writing a book seriously. Remember that my mother was a writer and a playwright, so I was raised with the sense that writing a book was the greatest thing one can do. As I described before, the book I wanted to write was not a straightforward popularization. I had literary and philosophical interests I was exploring. So, that book had a rocky development. It was dropped by the original publishers and then taken up by Oxford University Press, New York City.
While writing the book I met many people whose ideas were interesting to me, and a few became good friends. One of these was Stuart Kauffman. Unlike the trade publishers, Oxford had readers, and Stu Kauffman was one of the readers. We met as a result. He called me up and we talked for a bunch of hours, and he then flew out a few weeks later to Penn State, and we talked for days. We became, and we are, really good friends. He's eighty-one now, and drives me crazy, as he always did. And then the book was published and in that period after the book was published, I met Lynn Margulis, which was a great honor. She's somebody I really admire. And I met Richard Dawkins; I met John Maynard Smith.
In your discussions with Dawkins, is your sense that he understands physics pretty well?
I don't think I ever talked about physics with Richard. I don't know. I don't have to talk about everybody. I don't really know him very well.
But did your ideas sit well with him? The idea that there are evolutionary biological concepts that can be applied to understanding the universe.
Yes, he supported that. I think he wrote a few things. It was a great thing, and it was something that I'm very, very thankful for. First of all, that I felt embraced by this community so. For example, Dan Dennett, who I disagree with numerous things about, but he sure is bright and articulate. He wrote about the idea and embraced it. I was very, very grateful. John Maynard Smith chaired a discussion in London when the book came out, where Martin Rees and Richard Dawkins were discussants. That was one of the greatest evenings of my life. I felt like I'm this kid from New York, and here I am in London with these great scientists talking about this idea I had. What could be better? So, I felt really embraced, and that became a kind of community, or a basis to find some friendships. So, John's intervention in my life was very important. I made a lot of friends through it. Among them, Jaron. I have a bunch of friends who are artists, who are really serious artists. They became friends through John and Katinka. So, this idea of third culture intellectuals, and so forth. Some of it is hype and sell, because John is a great salesman, but there is some reality to it. But it was a great thing for me to find myself as part of a larger community who thought about these kinds of ideas.
Lee, this is an intellectual history question, and we can root it in the chronology wherever you think it belongs. At what point did you start to realize that the philosophical implications of these ideas had to be dealt with systematically?
That is a good question: Certainly, at our first meeting in 1980 Julian Barbour made me aware of Leibniz and the history of relational ideas. So I understood then that philosophy had a lot to offer those of us who are trying to do fundamental physics. But you are asking something else: when did I become aware that “that the philosophical implications of these ideas had to be dealt with systematically? I.e. when did I see clearly that there was work to do in philosophy-that was essential for philosophy itself? I think the answer to that is when I started working with Roberto Mangabeira Unger. I always knew some philosophy. I did some undergraduate studies in philosophy. During my graduate studies I met two first rate philosophers who also knew a great deal of physics: Abner Shimony and Paul Feyerabend.
I began meeting philosophers in my own generation a few years later. There was a community of mostly English philosophers of physics who were very well educated in physics and philosophy. People like Simon Saunders, Harvey Brown, Jeremy Butterfield, David Albert, Tim Maudlin. These were powerful intellectually, and they knew physics in detail.
There was a quantum gravity conference in England, somewhere in the Northeast of England. Four or five of these philosophers were there and set up a discussion every evening so that we physicists got to talk to them. Of course, I was already in very close touch with Julian, and I was a few times a year for some period in Julian's farmhouse, staying there and working with Julian and talking with Julian. So, Julian was a big influence on me.
Another philosopher I got to know was Drucilla Cornell who was a feminist philosopher of law, and also a playwright. We dated briefly at some point in the story but became very good friends. She gave me a kind of education. She introduced me to Derrida, and I had some conversations with Derrida. She introduced me to several of the most eloquent feminist philosophers such as bell hooks. I also dramaturged her play about string theory called Background Interference. I was also friendly with Evelyn Fox Keller, whom I met through Amelia Rechel. She forced me to read some Heidegger.
And then I met Roberto Mangabeira Unger, and he, to me, is one of the most phenomenal, powerful intellects I have ever encountered in any context. I don't know if you know anything about him, but he's scary. So, we met kind of accidentally through Drusilla. She was a reader on The Life of the Cosmos, and said, "You know, there's this guy, Roberto Unger, and he was saying similar things from a very different point of view." So, I went and looked it up and quoted him. And I had heard him give a few lectures at Yale, so I was kind of aware of who he is. My brother is a law professor. Although my brother comes from the Christian Right, ideologically, he was very interested in Roberto's work. So, all of this kind of led to my meeting Roberto and discussing the similarities of our ideas about evolving laws and laws changing the nature. And he said to me at that time, one of the things he said is he said, "Should we write a book together?" And I was very -- I said, "Sure." And then he said, "You know, your thinking is just logically completely messy and incoherent. Half the time you're doing this quantum gravity stuff, and you think in time emerged, and the other half of the time, whatever you're thinking about, laws changing in cosmology." He basically said, "You need to renovate and think about the conflicts between those things." That book that we wrote together went through a long process, because two of the years in the middle, Roberto was appointed to the cabinet in Brazil. We didn't make much progress during those years. Anyway, Roberto certainly played a very, very important role.
Lee, to the extent that in philosophy, more than in science, it's important to ascribe to a particular intellectual tradition. Did you think about that? Did you think about who key influencers might have been going deep back into history? Philosophers, even during the time of The Enlightenment, who tried to think about the way that nature and human interaction interacted.
Sure, I'm self-consciously, a Leibnizian. I believe in a basic relational framework that Leibniz argued for. This is inherited from Julian. Also, many people who have thought seriously about foundations of physics, I think, feel rooted in Leibniz. Somebody I haven't mentioned is David Finkelstein. He's somebody who was enormously a role model.
Let's go back to Leibniz for a second. Why is Leibniz so compelling to you?
Because he's trying to solve the problem of how to make a quantum theory of gravity, which is background independent.
How possibly could Leibniz have been aiming to do that before any of these things were understood?
Because that's what the Monadology really is about. Since I'm not a professional philosopher, I'm allowed to just say something like that. I'm not a scholar. I haven't read volumes and volumes and volumes.
But you're saying, if you got in a time machine, and you went back and talked to him about all of these things, he would get it.
Oh, sure. But there's a tradition that starts there which Julian communicated to my generation. The obvious places are Mach, Einstein, which are the importance of thinking of filling the principles that Leibniz put forward in his debates with Newton and Newton's representatives. Of course, Roberto, who is much better educated, would say, "You shouldn't go around labeling yourself as a Leibnizian. You're probably better than that. You should wait and let your enemies describe who you are." Roberto's recommended that. But certainly, I feel like my work -- I situate my work in the context of the discussions between Leibniz and Newton and going forward. And that helps me think. That helps me also feel a little freer.
I'll refine the question, Lee. In what ways does the philosophical background assist you as a physicist to better understand space and time as concepts?
Because there's a history of people trying to do exactly that, and their ideas and their failures and their successes carry lessons for us. So, when there was this, quote, fight between string theory and loop quantum gravity, and people started throwing around different words, it was clear and it is clear that to a large extent, it's a continuation of the argument between Leibniz and Newton. It's what do you mean by an observable? Is it anchored to the world to some fixed structure, or is there no fixed structure so everything is defined with respect to everything else? And the reason why I'm in a different community than the, quote, string theorists, is clear. They're a community of people who don't have that influence and don't think about those ideas. As far as I can make out, we have the same technical training, but I'm working in a context in which these concepts and criteria are very important.
There are different ways to stress it, but let's talk about the technical. When we, quote, solved the Wheeler-DeWitt equation and the other constraint equations, we didn't just throw some equations together and naively get the answer, because this is quantum field theory. It's a different kind of quantum field theory because it's invariant under diffeomorphisms of space rather than under just translations and Lorentz piece. But you've got to do the same thing in quantum that you have to do in any other quantum field theory. That is, operators live at points and they're highly divergent objects. And if you multiply two operators together at the same point, it doesn't mean anything. So, you have to give it a definition by something like pulling them apart and taking them together at a controlled rate, or changing the dimension, or something like that. You've got to intervene in the definition of the theory to make that product of operators make sense. All the preparatory work that I did between graduate school and meeting Abhay and learning about his work, gave me a bunch of techniques to understand those kinds of limits and those kinds of products in a way in which was invariant under diffeomorphisms. So, if you actually look at those papers, that's the technical work of those papers. The technical stuff, I kind of developed from the techniques that Polyakov and Wilson, and so forth, used, adopted to be diffeomorphism ready. But the philosophy of why to do that came from Julian.
To go back earlier in our conversation where the theories that you're after now are much bigger, even, than unifying the forces, to the extent that the philosophical implications of your interest in, for example, quantum mechanics, where you're looking much beyond that. To what extent is there a bit of a red herring in terms of people saying that quantum mechanics really is a final theory? In other words, would Niels Bohr have said quantum mechanics is a final theory, or has everybody, to one extent or another, recognized that these things are pieces of a much larger puzzle?
I don't know. I think different people have different ambitions, and different things they want to do. It surprises me, the field of quantum foundations used to be very, very small, and consisted mostly of people who did other things and then developed their interest in foundations as kind of a hobby. That was how John Bell lived, and to some extent Bohm, and so forth. There were very few people who were purely working on quantum foundations. The field got professionalized because of quantum information and quantum computing. Now, there are actually people who are trained to work in quantum foundations, quantum information. There's a whole vocabulary, methodology, and so forth. In some sense, that's very good, but in another sense, they don't ask the same questions that us un-professionals ask, which is, does it make any sense? Does it need to be replaced by something else that makes sense?
For example, in the context of Perimeter, I hang out. I like them very much. We have a very good foundations group, and I hang out with them, and I'm sometimes in their seminars and vice versa. But there's a way in which we're on different paths. If they're not directly after making the technology work, they're after a way to understand quantum mechanics through change in formalism and language. Maybe I'm exaggerating that. I don't know. There's another thing that Chandra didn't tell me, but Saint Clair Cemin, who's one of the artists I made friends with through John and Katinka, told me. Actually, he was great. He's one of those people whose very good with words. He said what he's learned as a sculptor, and he's a very good, successful sculptor, is that either you keep questioning and keep building and keep going, or you stop, and you begin just making copies of your own work. What I didn't realize is that you could actually get to a point where it's pretty lonely -- there are some people there to talk to -- but it's a weird place to be. I don't know. Maybe I should think about where I'm going with that.
Lee, of course, you haven't shied away from the most fundamental questions at the intersection of physics and philosophy, and that is, the room to which cosmology can allow for a creator, a god, and then also the room to which cosmology can allow for the existence of multiverses.
So, let me address each of those, because in some sense, they're the same question. Formally, they're the same question. That is, in explaining what's in the universe, are we allowed to make reference to something that may be outside the universe? With Roberto, we decided at the beginning of our work together that we would just accept as axiomatic that there is one universe, and it could have been different, and it is this particular solution to whatever equations. It has this particular stuff in it and not this other stuff. So, there are a lot of features of it that are contingent. And that's the world we're interested in. We make, as a principle, that any scientific explanation just involves things in the world. That way, we don't have to think about either multiverse or a god. I think that makes us better scientists, if we're forced, at some point, to do that.
Because I came up through the Gurdjieff work, although I'm not at all practicing. We're originally Jewish, but my brother is a very devout Roman Catholic now. I'm not one of these people who feels life is a conflict between science and religion and science has to win for the future of rational civilization. I think Dawkins is very wrong. I don't think that's the right fight. I think that life is challenging and difficult, and there are very important things that science is learning and knows, and there are also mysteries. I'm not going to make one of these appeals to whatever, but I respect people who take any consistent, coherent path with integrity, with good faith, to try to make life more comprehensible.
Religion is not my way. In some sense, I believe in nature very deeply, but I think that science has to do a lot better job. We scientists, in my view, represent a kind of -- what we actually know is how to find mistakes in our world. We have a whole bunch of tools; we have toolkits which let us find mistakes. That's all we have. Everything else is contingent, hopefully we'll improve, we'll get deeper. So, it's as much a moral commitment to be a scientist as it is to be a priest or a rabbi or something, I imagine. I respect people, who with integrity, make those other choices.
Lee, this idea sounds very consistent with what you were conveying in The Trouble with Physics, where your lack of interest in picking fights with the religious communities seems to be fundamentally about freedom of expression, about not allowing any one group -- in fact, we could go even deeper than that. Just go back to your very strong reaction to Ed Witten telling people what to work on or not. There seems to be a continuity here.
If you take The Trouble with Physics, and you look at chapter seventeen, which in the original book was the second chapter, that's where I stated the principles that I was going to examine in these test cases. I mention two principles which could be the basis of a diverse community progressing together. One of them is that we agree that when there is rational deduction from public evidence that resolves a question, we agree that it's resolved, even if we don't like it. I have examples of that. I don't really like inflationary theory. I hope it's wrong, but I credit the fabulous success of their predictions. I have to, otherwise I wouldn't be a scientist. On the other hand, if there are questions that cannot be settled from rational deduction from public evidence, we have to be tolerant of people who hold different views and take different bets. For me, that's what ties democratic societies together. That's what science is, and that's why science and democracy are related. So, that's what The Trouble with Physics was really about.
Lee, on the question of your admiration, if not yet complete acceptance, of the inflationary theory, specifically, I'm curious if you can comment on the proposition that there is only one universe. Well, if there's anybody who can most seriously challenge that, it would have to be based on the testability, the notion of the testability of the multiverse, which as you well know, Andrei Linde believes he's well on the way to achieving. So, what is your reaction to that, both as an assertion of scientific probability, and as a philosophical concept, if you're coming from at least two intellectual traditions that might reject the notion of a multiverse out of hand?
Oh, poor Andrei. I wish -- no, because I don't know Andrei very well, but there are a number of times Andrei has come up to me while I was giving a talk or at a conference, and seriously screamed at me and said, "Eternal inflation is right, and you know it, and we know it. If you don't admit it, you're a liar." He's totally unprofessional and off the rodeo, or whatever. At least, in his interactions with me. But there are alternatives to inflation. There are bouncing universes of various kinds. In quantum gravity, we like to make models in which the singularities bounce. And a number of the people I work with are very good cosmologists, like Andrew Liddle, and Marina Cortes, and [Stephon Alexander and Joao Magueijjo. So, there are alternatives, and to me, it's an open question.
But I have to take that -- I have to say that they made some predictions. Somebody will come back and say that when the observers thought that omega was .3, Andrei Linde had no problem making a revised version of inflation, in which omega lambda turned out to be .3. And that's true. But nonetheless, there's a lot of data points in those curves of the microwave background, including the polarization, that are just spot on. That's impressive, and I've seen that develop -- I mean, the COBE experiment is within my career, so the first test point -- what am I trying to say? The first peak wasn't even known then, and now they go six or eight peaks, and its spot on. You have to be impressed by that I think. It might be wrong, but it's impressive.
Lee, to go to the other side entirely of the timescale, to what extent have you found a philosophical basis useful in considering cosmic eschatology?
What is cosmic eschatology?
The end of it all.
Oh, I don't think about that much. You mean, like, how the universe will end?
Or if the universe will end?
Yeah, I know. I'm interested in what happens in blackholes. I don't know. Maybe it's a fear of thinking about -- it's a fear of-- a fear of death, or something. I don't find it very interesting to go there. One reason why is that if you tell me some crazy thing is going to happen, my reaction is that its five million times more probable is that the theory is going to turn out to be different from what you think, and that's not even going to be a stateable option in the theory in 500 years, which is a long time before these riffs appear, or whatever you're worried about. You know, we all build our boundaries of what we're not willing to think about, and sometimes they change a little bit. But I don't see what I would learn by going there.
We've touched on this briefly with regard to academic politics, but I wonder the extent to which you've thought about larger macroscopic social issues with regard to your advocacy of principles for an open future, where of course, there is a clear intersection between science does the right way and an adherence to basic democratic principles, particularly at time when science feels to be under attack.
I have made speeches like that; I've given talks like that. I think that it's important for thinking about the future. This is, of course, what got me in touch with Roberto Unger, who's a social and political theorist. To think about the world which has as open a future as he needs for his political theorizing. He needs that world to be in a physical universe where the laws are not fixed. I can see that, and in different ways, including just emotionally and personally, I'm all the way to, at the physics level, what do we mean by the laws being changeable? It's a hard issue for me to think about, but it's important. This paper I mentioned with Jaron Lanier and people, which may turn out to be just insane, postulates that -- so, in The Life of the Cosmos, and the papers with that, I talk about the universe evolving, and not only this, the natural selection. It's possible to imagine a scenario for the quantum field theory vacuum could constitute the landscape where that would make sense. So, we're trying to do something hard enough, which is ask if the dynamics of the vacuum of a quantum field theory could behave like a machine that learns in the sense of these AI machine learning things. We have a formal analogy which may get us all fired, but -- so, I am thinking about these things. And there are some things that are too hard. Consciousness is too hard. I've written two papers on consciousness, and I think it's very hard. It's a tough, tough, tough problem.
Do you think approaching consciousness as a quantum mechanical system is a useful avenue of pursuit?
Not initially, but there could be some surprises. A more attractable problem is the natural thing that one would say not is that the brain is warm and chaotic, and you don't expect there to be quantum coherence in the brain. I'm sure you're familiar with all these discussions. And if you talk to people who are working on quantum materials, they have a whole bag of tricks for making coherent quantum states in different kinds of materials for having protected channels, it's sometimes called. It's not impossible if you -- this is not an optimistic statement. I'm not convinced that it's impossible that something like that isn't happening in some aspects of biology. There are a few attempts to do that which are not obviously wrong, or obviously -- and I think about that every once in a while, but mostly I think it's too hard.
Lee, while we're in the neighborhood of philosophy and quantum theory in the mind, I'd like to run a specific question by you, because it gets at all of these things, and it's something that we're going to have to deal with as quantum computing becomes more and more of a reality. That's this: the biggest boosters, or even the biggest hype masters of quantum computing emphasize that it's a game changer, that computation is going to mean something fundamentally different, and what we get from it is also going to be different. It's not going to be just a bigger or an exponentially larger or faster version of classical computing. So, on that basis, I just want to get your reaction to a scenario that may well play out. If we're operating under the assumption that the SSC will never be built, and that the LHC will never operate at high enough energies to see real physics beyond the Higgs, to see supersymmetry, things like this, can we get to a point where quantum computing can simulate real world experiments that will yield data that hard-nosed scientists will accept as if those experiments were actually carried out in real life?
It's a good time to bring out my "I don't know" side.
But I can ask you from a philosophical position if that sits well with you or not, the very notion of decoupling ourselves, decoupling science from the world of experimental deductive logic.
That doesn't -- I hope not, let me say. I'm just checking that I'm not somewhere -- yeah, okay. I'm sorry. That's not my scenario. Here's my wild scenario about quantum computing and experiment, and this comes out of the theories that I've been studying and publishing about foundations in quantum mechanics. In any situation where you're looking for a new theory to supersede an old one, there's a parameter where the old theory, the limit of that parameter goes to zero, and the new theory is the other limit. That parameter is a parameter somewhere in the middle. What would that parameter be if it was something beyond quantum mechanics, something like a non-local invariable theory?
So, I have constructions where the quantum state is an ensemble of things that really exist. If you have a water molecule and it's in some quantum state, there's really an ensemble of other water molecules throughout the universe that they communicate with non-locally. I told you this was feasible. And which explains the behavior of that quantum state. The N is the size of that collection, and the universe is very big, so for most things that we study quantum mechanically, that N is very large. For some things we know about, like ourselves, the N is 1, and the theory that I write down to describe that being the other limit is very different from quantum mechanics. Then, you want to know if you make some ion traps, and try to construct some kind of entangled state or coherent state amongst those ion traps, how many other places is that taking place in the universe? And that leads to a sane thought and a crazy thought. The sane though is not many, and you're going to see exactly how quantum mechanics breaks down. And I have predictions for that in some of the papers about this. So, there are actually things to measure.
The insane possibility, and I can't believe I'm saying this, but the insane possibility is that among the 10^22 planets that are out there, there are other beings who are playing with ion traps, and this is how we're going to get in touch with them. But the most probable thing to happen -- so, I'm in touch with people who play with quantum devices, and it's an interesting thing to ask how would the kind of breakdown of quantum mechanics that comes out of this theory I'm studying look in their experiments. That's productive. But I'm not writing a science fiction book. I'm not going around saying to people we could use these devices to communicate with people over large distances. But most probably, that's completely silly, but there's a future in which that's the only intelligent thing I've ever said.
Lee, on a totally different topic, you've had a long-standing affiliation with the NASA Astrobiology Institute. In what ways has thinking deeply about the possibility of life, even complex lifeforms out there in the universe, improved your abilities to contribute both in physics and philosophy?
So, first, the premise is wrong. I don't have a long interaction with the NASA Astrobiology Institute. I had a long association with the Santa Fe Institute, so that may be what you're thinking of. I know some of the people at the Astrobiology Institute. But I have been -- my friendships with Stu Kauffman, with Per Bak with other people who work in the world of complex systems, has changed my thinking about many things in fundamental physics. One of them is this thing I mentioned at the beginning about the role of different kinds of explanations. Reductionist versus functionalist, and whether that might play a role in cosmology. That work feeds into the work, the collaboration at Microsoft Research with Jaron and so forth, where we're trying to think about -- I mean, the question that that work comes out of is what does it mean to learn? Everybody seems to think they know, but can you give some criteria, some rules under which you could say that a physical system was learning? And is it necessary that that thing be alive? So, those two things feed into each other. The idea of seeing the universe as a complex system is useful, anyway, it's part of my worldview. I don't think it's an accident that there's as much complexity in the world as we see.
Do you consider Einstein's Unfinished Revolution a magnum opus? Not that it doesn't present new ideas, but does it anthologize all of the things that you've been thinking over the course of your career?
No. No. It does some. That book that does that, I'm not thinking of writing. I just got too much -- I'm in this weird place in which there's, and maybe this is related to the pandemic, but there's so much to do. I don't feel like summing up.
What were your motivations with the Einstein book?
To write a book about foundations in quantum mechanics, which is very important to me and was the one thing that I hadn't written. The books are all partly driven by my own need to work out some kind of question or puzzle. So, I realized I hadn't written a book about foundations of quantum mechanics, and that was dear to me. So, I took it as a subject. Then there was this very new work which came at the end. Books are hard. No. I'm not at the point where I want to sum up. But if somebody wanted to sum up, you should just take the epilogues of all of those. They all have epilogues and put them together. No, I want the real thing. I want a breakthrough.
Lee, we started at the beginning, how the pandemic has been remarkably productive for you in many areas. So, intellectually, what are the things that you've been motivated most to write about?
Well, to write these papers. One of the things I've been doing differently is to collaborate a lot, and with larger groups. And it's bloody hard. I don't know about what you do, but people -- the way that I seem to collaborate mostly is through making friends and having many, many conversations, which lead to a discovery of shared ideas, which lead to a project. Many of the people in these collaborations are friends at that level and have been. Like, this work with Stu and Marina and Andrew has been going on for years, and we have yet to finish anything. There are three papers in draft, and they've been in draft for more than six months. It's just so frustrating. But they're turning into good papers. You mentioned a kind of impatience with string theory. I don't have an impatience with string theory, but I have an impatience with the whole area of quantum gravity. I really, really, really want there to be some breakthrough that coheres sufficiently and is sufficiently surprising and impressive that it might be right.
What would that breakthrough look like?
What I'm doing now plus three or four things I don't want to say, because I don't want to be measured against them.
What about observationally? Is there anything going on right now that would contribute to this breakthrough?
Sure, the stuff we talked about tabletop scale quantum gravity experiments. A number of people are thinking about that. I'm very hopeful. And something like the breakdown of quantum mechanics at small end, as I was talking before, would be very helpful. And there could be a lot of surprises still in cosmology. But the problem is -- my understanding of how science progresses is that there's an element of surprise. So, we don't know. And the element of surprise can come directly from experiment, or it could come from theory in the form that is a different theory which makes some observation that would have been previously ordinary and meaningless all of a sudden meaningful because it's testing something that distinguishes a new idea from the old idea. So, I'm very much hoping for surprises like that.
Is the fundamental disagreement between Einstein and Bohr, do you look at that as settled, or is it provisional in the world of surprises?
Oh, it's very provisional. One of the things I'm thinking, a surprising paper that it never occurred to me I would write a paper about this. We just finished it with a friend, Clelia Verde. It says that the distinction between past and future is central for quantum mechanics, and it really is the distinction between the classical macroscopic world, and the quantum microscopic world. The right way to draw that distinction is between the past and the future. The quantum world is the future, and the classical world is the past. We're not the first people to say this, it turns out. Heisenberg said things like this, and Freeman Dyson said things like that. You can't even say this if you haven't been revising your idea about time so that it's meaningful to talk about the difference between the past and the future. I said these papers are scary. This is definitely scary, but it has a logic, and there is this thing, sometimes you just let the logic go, and then you decide whether to publish it or not.
Lee, now that we've worked up to the present in terms of the chronological narrative, for the last part of our talk, I'd like to ask a very broad question that's going to tie together all the things that you've worked on up to this point, your current interests, and where all of this might be headed. So, we'll return right back to the beginning of our talk, where really, at this point, the things that you're focused on for your future are really quite ambitious and grand, both politically, academically, and scientifically, where you're looking to unify theories even beyond the way that physicists have traditionally thought about unifying theories. So, the question is, how does one go about doing that? What are the blockages currently in place in terms of academic departments, in terms of pedagogy, in terms of funding, in terms of careerism? What are the things that need to change so that this revolution that you're a part of, to bring these vast areas of reality together into one unified understanding, what's standing in your way in order to get there?
I don't think much, which doesn't mean we're going to get there. My personal situation is exceptional. I mean, Perimeter, at some point, decided to install tenure, so I have tenure even if that wasn't the original design of the institute. I have a good situation in every way you might imagine. I have time. I have people who are supportive that I'm working with. So, it might work, and it might not work. And there always is this thing of time and getting older, which is there, but my feeling is that that's there, and come what may, I'm going for it. We'll see what happens. Personally, I'm in an exceptionally good situation, and I'm very, very, very grateful for that. Beyond that, it would be nice to spend a little bit more time with some of the people I find most provocative, or compelling, in terms of their ideas. So, if I had anything to complain about, it's that we're locked down, and it would be nice to work with people in a room again. And it may be time, and it may not be time. Ultimately, I've focused mostly on quantum gravity. I think I'm proud of what I've done, but nothing that any of us have done has been enough to get to the point that you keep emphasizing correctly, that you're testing ideas experimentally or observationally. That's certainly close to mind all the time, and we'll see. There are no promises. And I hope that if I really reach the point where I don't think I can make a contribution to that, then I can do something else, like write a novel, or a play, or a good book of philosophy, or something like that.
Lee, how would you even articulate this theory, if and when it comes to fruition? What would it look like and what medium would you choose to convey it?
It's conventional. Postulates, formulas. There are things which are on the edge, like if you believe that time is real, then your understanding of what a mathematical formula is in its relation to what's real has to be different. You can't believe this myth of the mathematical object, which is the mirror of nature, as Richard Rorty put it, for which every theorem about it is a fact about the history of the universe. You can't expect that if you think that the world is change upon change upon change, and time is real. Because the one thing that no mathematical object has is anything that corresponds to "this is the real moment." But you look for the best explanation. David Deutsch, I disagree with him about a lot of things, but what he has to say about science providing the most compelling explanation is right, I think.
Well, Lee, on that note, this discussion has been even more epic and fun and wide ranging than I could have hoped. I'm so glad we connected, and I'm so glad we were able to do this. So, thank you so much.
Thank you very, very much.