Feynman at 100

The past month has seen quite a few events and articles celebrating the 100th anniversary of Richard Feynman’s birth (see for example here, here, here and here). Feynman was one of the great figures of twentieth century physics, with a big intellectual influence on me and on many generations of particle theorists. In particular, his development of the path integral formulation of quantum mechanics and the Feynman diagram method for calculating and understanding what quantum field theories are telling us are at the center of how we have learned to think about fundamental physics and apply it to the real world.

When I first started studying physics, in the seventies, Feynman was a major figure to physicists, but not that well-known outside the subject. After the 1985 appearance of the book of anecdotes “Surely You’re Joking, Mr. Feynman!” and his 1986 role in the report on the Challenger disaster (followed by more anecdotes in the 1988 “What Do You Care What Other People Think?”) Feynman became a huge public figure. The Physics section of any book store that carried science books would often have nearly a whole shelf of books by and about him, with the only competition the shelf of books about Einstein (the Hawking shelf didn’t get going until a bit later).

I avidly read the Feynman anecdote books when they came out and was suitably entertained, but I also found them a bit disturbing. Too many of the anecdotes seemed to revolve around Feynman showing how much smarter he was than someone else. I hadn’t thought much about this, but was interested to read historian of science Melinda Baldwin’s piece Feynman the Joker this month at Physics Today. It ends with:

But Feynman’s charm and brilliance were only one side of his personality. His writings, and the accounts of those who knew him, reveal a man whose faith in his own brilliance could veer into self-absorption and the mistreatment of others, particularly those whom Feynman didn’t consider his equals. Even people who admired Feynman’s intellectual gifts could become exasperated with his antics, and some important professional and personal relationships went off the rails when that happened. Feynman’s legacy reminds us that it’s important to have fun with physics—but to make sure those around us are having fun too.

I think this is an overly harsh take on Feynman, but do think that his later career suffered from the sort of self-absorption Baldwin points to. She links to an interview with Gell-Mann, which includes:

One of your best-known interactions was with Richard Feynman at Caltech. What was that like?
We had offices essentially next door to each other for 33 years. I was very, very enthusiastic about Feynman when I arrived at Caltech. He was much taken with me, and I thought he was terrific. I got a huge kick out of working with him. He was funny, amusing, brilliant.

What about the stories that you two had big problems with each other?
Oh, we argued all the time. When we were very friendly, we argued. And then later, when I was less enthusiastic about him, we argued also. At one point he was doing some pretty good work—not terribly deep, but it was very important—on the structure of protons and neutrons. In that work he referred to quarks, antiquarks, and gluons, of which they were made, but he didn’t call them quarks, antiquarks, and gluons. He called them “partons,” which is a half-Latin, half-Greek, stupid word. Partons. He said he didn’t care what they were, so he made up a name for them. But that’s what they were: quarks, antiquarks, and gluons, and he could have said that. And then people realized that they were quarks, and so then you had the “quark-parton” model. We finally constructed a theory—I didn’t do it by myself; it was the result of several of us put together. We constructed the right theory, called Quantum Chromodynamics, which I named. And Feynman didn’t believe it.

He didn’t believe that the theory was correct?
No. He had some other cuckoo scheme based on his partons. Finally after a couple of years he gave up because he was very bright and realized after a while that we were correct. But he resisted it, and I didn’t understand why he had to be that way. Partons…

Looking at Feynman’s career, his great accomplishments were in the years 1947-58, and it’s somewhat surprising that he didn’t make major contributions (besides the partons…) to the development of the Standard Model in the years from 1958-73. One contributing factor may have been his insistence on “What I cannot create I do not understand.” John Preskill recounts in a recent talk:

Feynman often told students to disregard what others had done, to work things out for oneself. Not everyone thought that was good advice. One who disagreed was Sidney Coleman, a Caltech grad student in the late 50s and early 60s. Coleman says: “Had Feynman not been as smart as he was, I think he would have been too original for his own good. There was always an element of showboating in his character. He was like the guy that climbs Mt. Blanc barefoot just to show it could be done. A lot of things he did were to show, you didn’t have to do it that way, you can do it this other way. And the other way, in fact, was not as good as the first way, but it showed he was different. … I’m sure Dick thought of that as a virtue, as noble. I don’t think it’s so. I think it’s kidding yourself. Those other guys are not all a collection of yo-yos. Sometimes it would be better to take the recent machinery they have built and not try to rebuild it, like reinventing the wheel. … Dick could get away with a lot because he was so goddamn smart. He really could climb Mont Blanc barefoot.”

A related aspect of Feynman’s working method was a sizable amount of hostility to any abstract mathematics. In his talk at the Caltech Feynman 100 event, Lenny Susskind makes a great point of this, seeing Feynman’s insistence on physical intuition rather than mathematics as a key to his strength. For some problems though, as Sidney Coleman realized, refusing the mathematician’s toolbox may just make it impossible to do what you need to do.

A peculiar aspect of the Caltech scientific symposium was that the two talks on particle physics (by David Gross and Hirosi Ooguri) spent a great deal of time promoting something that Feynman detested. While Gross described a major legacy of Feynman as “a healthy disrespect for authority” and “a total aversion to BS”, those characteristics led Feynman to have a very negative view of string theory, up until his death. He was known to remark that “string theorists don’t make predictions, they make excuses”, and in a 1987 interview stated:

Now I know that other old men have been very foolish in saying things like this, and, therefore, I would be very foolish to say this is nonsense. I am going to be very foolish, because I do feel strongly that this is nonsense! I can’t help it, even though I know the danger in such a point of view. So perhaps I could entertain future historians by saying I think all this superstring stuff is crazy and is in the wrong direction.
What is it you don’t like about it?
I don’t like that they’re not calculating anything. I don’t like that they don’t check their ideas. I don’t like that for anything that disagrees with an experiment, they cook up an explanation – a fix-up to say “Well, it still might be true”. For example, the theory requires ten dimensions. Well, maybe there’s a way of wrapping up six of the dimensions. Yes, that’s possible mathematically, but why not seven? When they write their equation, the equation should decide how many of these things get wrapped up, not the desire to agree with experiment. In other words, there’s no reason whatsoever in superstring theory that it isn’t eight of the ten dimensions that get wrapped up and that the result is only two dimensions, which would be completely in disagreement with experience. So the fact that it might disagree with experience is very tenuous, it doesn’t produce anything; it has to be excused most of the time. It doesn’t look right.

Asked at the end of his talk what he thought Feynman would say about string theory today, Ooguri responded with an argument that string theory had made a lot of progress since Feynman’s time, was much better understood, and was the only known consistent way to do things. He said he was very curious to know what Feynman would say, but I think it’s extremely clear what that would be: he thought it was BS back in 1987, and thirty years of lack of any progress towards making any predictions has shown that he was right back then.

I’m still an admirer of Feynman’s work and career (and sorry that I never got a chance to meet him), but at the same time think it’s a good idea to acknowledge that he, like any scientist, had his limitations. Adopting his hostility to abstract math and trying to climb Mont Blanc barefoot is likely a bad lesson to draw from his career. On the other hand, a really good lesson to learn from Feynman would be the importance of recognizing when theorists have nothing but excuses and are engaging in BS. There’s no question at all about what Feynman would have thought of the current mania for the string theory multiverse.