Lee Smolin’s The Trouble With Physics is probably the hot physics book of the year. Granted, that’s not saying very much, relative to whatever Oprah’s reading this week, but it’s led to no end of discussion among physics types. And also, frequently, the spectacle of people with Ph.D.’s squabbling like children, so reviewing it is a subject that I approach with some trepidation.
I’m coming to this late enough that it’s hard to talk about the book without also talking about the various responses to the book. I’ll do my best to split that material off into a separate post (if I post it at all), and keep this more or less a straight book review.
So, The Trouble With Physics. Previous complaints about the title aside, this is a very good book. It presents a very clear and thought-provoking argument about the nature and practice of modern science, with a minimum of technical jargon. I don’t agree with every detail of it, but it’s written very coherently and persuasively, and is a surprisingly good read for such a weighty subject. If you read only one string theory backlash book this year, this should be the one.
The book divides into three main parts. As is traditional for pop-physics books, it opens with a history of physics up through the Standard Model. This is followed by a description of string theory and the problems with string theory, and then the book ends with an exploration of the sociology of modern academic science. I have minor complaints with each of these sections, but none of those complaints are really fatal for the book, or for the overall argument.
Smolin takes a fairly unique approach to the historical overview, choosing to cast everything in terms of “unification” of elements previously thought unrelated. This is obviously intended to set up the modern concerns of unification of forces, and while his description of Maxwell’s electromagnetism, relativity, and the Standard Model work very nicely in this context, I think it’s kind of stretching a point to call Newton’s first law “the unification of motion and rest.” It’s clever, but I’m not sure it’s useful.
When the story turns to string theory, he does a very nice job of laying out the basic questions that the theory is intended to address, and describing the successes and failures of the theory. I’m not really in a position to evaluate the technical details of his claims, but as he presents it, the picture is pretty damning. String theory looks less like a theory making real progress than a shaky model accumulating epicycles– Peter Shor’s Amazon review is a fairly amusing summary that isn’t too far off the history presented here.
There’s a sort of interlude at the end of this section in which he presents some highly speculative alternatives to string theory as a path to a theory of quantum gravity and unification of all forces. This is probably the shakiest part of the book, and the bit most susceptible to “gotcha” games, but given what he’s doing, I don’t think it’s a real problem. I think he’s a little too accelerator-focussed when talking about experimental constraints– as I’ve said a dozen times here, some of the tightest constraints on new physics come from table-top experiments like the EDM searches run by Dave DeMille, Larry Hunter, Dima Budker and others, which have already ruled out some versions of supersymmetry, and are poised to do much more in the very near future. There’s also a passing mention of the phenomenal short-distance gravity measurements done by Eric Adelberger and his group in Washington, which I think probably deserve more than one paragraph.
In the final section, he turns his attention to the sociology of science, and asks whether the modern academic system might not be stifling the innovation needed to find a way past the problems plaguing the quantum gravity field. He provides an unflattering but instantly recognizable description of the string theory culture, and suggests that the structure of the field, combined with the incentive system in modern academia, puts young theorists in a position where they have to do string theory or else.
I actually found this the weakest part of the book. Most of the problems he identifies in the string theory community are not unique to string theory. Every field of physics, and probably all of science, is full of people who are supremely confident and convinced that their own work is absolutely the most important thing going on in physics at the moment. That’s more or less how you get a Ph.D., after all– you pick some problem, and focus on it to the exclusion of all else for a period of several years. You pretty much have to think that it’s the most important thing going in order to finish. And when you move out on your own, you have to at least present your work as critically important in order to get and keep the funding necessary to make progress.
He also blasts the field for susceptibility to fads, but again, I don’t see this as unique to string theory. Even in experimental atomic physics, which has considerably more inertia than string theory, you see signs of this sort of thing. One year’s DAMOP meeting is nothing but vortices, the next is wall-to-wall degenerate Fermi gases. It happens everywhere.
String theory may suffer from these problems more strongly than some other fields, but the difference is one of degree, not kind. Everybody in physics has a little of the attitude he discusses. As previously noted, Smolin has his own narrow-focus problem, as he consistently talks about quantum gravity as being the only interesting problem in physics, when in fact it’s a pretty narrow subset of physics activity.
I’m also somewhat skeptical about his claims about the academic system. It’s not that I disagree that the tenure system puts some strange pressures on people– as I may not have mentioned in the past fifteen minutes or so, I’m currently up for tenure– but, rather, I don’t think those pressures are really responsible for choking off innovation.
Smolin’s claim is that the tenure and promotion system in modern academia is set up in a way that really doesn’t allow young people to work on ground-breaking approaches to deep and fundamental problems. The pressure to quickly produce grants and publications for tenure tends to rule out working on such projects, which are necessarily long term enterprises. And similar incentives continue even after tenure, meaning that a research program pursuing foundational issues is probably incompatible with conventional academic success.
I think this is probably true as far as it goes, but I doubt it’s the whole story. For one thing, it’s not even a new problem– as Smolin himself notes, Einstein wound up working as a patent clerk because nobody would give him an academic job. (Institutional anti-semitism probably played some role there, too, but I’m not all that up on Einstein’s history.)
Beyond that, though, I’m not sure that the lack of conventional academic success is a real disincentive for the sort of people who are likely to make fundamental breakthroughs of the sort Smolin is after. I mean, do you really think that a different academic system would have Grigori Perelman both proving the Poincaré conjecture and chairing the math department at Princeton? Maybe the claim is that a different system would’ve freed up more people to attack the problem, and the solution would’ve been found by somebody a little less goofy, but I’m not so sure.
I think the set of people who are truly capable of finding novel ways of attacking the sorts of foundational issues Smolin is interested in is not a large set, and that those people are not likely to be motivated by conventional academic success, or demotivated by having it denied to them. I’m also not terribly confident in the ability of the general physics community to identify such people. If Smolin wants to use the Perimeter Institute to support people who he thinks have the potential to make those kind of breakthroughs, more power to him, but I don’t think there’s really a pressing need for a complete overhaul of the existing academic system.
Whatever you think of his various arguments, though, this is a very well-done book. It’s carefully structured, clearly written, and very measured in its tone. Smolin goes out of his way to express respect and even admiration for people in the string theory community, and some of their work, even while laying out a (fairly compelling, at least to me) case that they’re going badly astray. It’s not a vicious polemic, but rather a carefully phrased and extremely coherent argument. Whether he’s right or not will likely remain untested for a good many years, but in the meantime, he’s given physicists a good deal of material to think and talk about.