Lee Smolin, The Trouble With Physics

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.

Comments

  1. #1 Aaron Bergman
    October 10, 2006

    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.

    The question worth asking at this point is, why do so many people choose to work on string theory. I want to emphasize that this is a choice; the idea that people are forced to work in string theory because there are no alternatives is nonsensical. Even if you’re dead-set on ‘fundamental’ish theory (there’s plenty of cool condensed matter theory out there after all), the job prospects are better in cosmology and phenomenology.

    String theorists aren’t any different from other people who end up in physics. There’s the no shortage of skepticism, obstinance and iconoclasm. Why would anyone choose to work in such an obviously dead-end field?

    Lee’s answer is that everyone is either stuck in ‘groupthink’ or perhaps just a ‘calculator’ as opposed to a ‘seer’. First of all, this is tremendously insulting. It’s also self-serving on Lee’s part. He presents himself with this air of affected sadness; he was a string theorist, you see, but he managed to break free of the cult. If only the rest of us could see so clearly.

    Lee doesn’t give much weight to the possibility that everyone involved here is doing their damndest to do the best job they can trying to solve very hard problems. Most people just happen to disagree with Lee on which directions have the best prospects. Apparently there is no room for this honest disagreement; the fact that people disagree with Lee is instead indicative of some structural or psychological flaw.

    He also dishonestly presents many of the issues involved. The one that is a serious bugaboo for me is the all too common narrative that string theory is born of particle physics while Lee and his friends are the defenders of Einstein and ‘background independence.’ This is simply false. I’m half-tempted to call it a lie, but I can’t escape the feeling that Lee actually believes this and can’t be convinced otherwise.

    I wish Lee would spend more time listening to his fellow physicists rather than telling us how he thinks we should do our job. He shows up online occasionally, but always seems to disappear as soon as the discussion gets technical. It is tremendously frustrating and aggravating.

  2. #2 Alejandro Rivero
    October 10, 2006

    Perhaps we should then to discuss which are the goals of the academic system, particularly of the subset of the academic system related to mathematical physics, gravity and particle theory.

  3. #3 Chad Orzel
    October 10, 2006

    Perhaps we should then to discuss which are the goals of the academic system, particularly of the subset of the academic system related to mathematical physics, gravity and particle theory.

    Can you unpack that a little?
    I’m not sure exactly what you mean.

  4. #4 Uncle Al
    October 10, 2006

    General Relativity works, weak field (GPS) to strong field (astro-ph/0609417). GR will not quantize. String theory maths are interesting (duals) though string theory is a disaster.

    Physics demands isotropic space, Lorentz invariance, and the Equivalence Principle from Galileo to GR and quantum field theory. Everything that differs (Weak force) after spatial inversion is inserted as exceptions. No theory can defend its postulates. If the vacuum is intrinsically asymmetric to parity transformation, then EVERYBODY is wrong and improved theory already exists.

    Rederive physics a la Cartan and Weitzenböck, allowing parity transformation asymmetry. Test for disjoint consequences – an EP violation for opposite geometric parity test masses. The best composition Eötvös experiment, nuclear binding energy of Ti vs. Be, is 0.2398% net active mass. A parity Eötvös experiment, left- versus right-handed quartz, is at least 99.97% net active mass. Is a 416-fold amplification of signal source in the only remaining untested EP violation supported by existing theory meaningful? Somebody should look.

  5. #5 Evan
    October 10, 2006

    I’m working on an Uncle Al Text Generator based on the Dada Engine. Could the real Uncle Al please post once more? I almost have enough sample text to write a working script…

  6. #6 cvj
    October 10, 2006

    Chad,

    Physicist sociological habits aside for the moment, Lee Smolin and Peter Woit are both seriously misrepresenting the actual research effort in the field. They both leave out a significant percentage of the types of problems that people are trying to solve using strings. Some of these problems involve real experiments taking place today. These applictions may not be successful, but it is puzzling to me how one can give a fair presentation to the general public about the research effort in a field -and condemn it so strongly- if you do not include the research effort of a significant percentage of the community. You and I have discussed the potential string theory applications to physics at RHIC, here on your blog…. do you remember? That’s part of what I am talking about.

    Happily, after some effort, some of us have managed to get Smolin to admit that there’s quite a bit missing about this from his book (actually, the little he does say about it is very wrong in parts), although he seems to justify that omission by saying that is “not fundamental”. (Peter was too , er, busy to respond. See earlier, nearer the start of the thread.) I find this odd, since these books are attacking strings for having nothing to do with Nature. So Smolin seems to be advocating redistributing resources from all these “non-fundamental” lines of research. That means you too Chad. Watch your back. ;-)

    -cvj

  7. #7 cvj
    October 10, 2006

    Hi,

    Here’s that earlier post of yours, with the comments from myself and Moshe on the bottom. Moshe gives extra information in the form of links to some blog posts about the subject. My point (one more time) is that this sort of work on applying string theory to understanding gauge theories (and hence the strong nuclear intereactions and new forms of matter being discovered in real experiments) occupies a lot of the string community. It may or may not be successful…. we do not know yet, but to leave it out in a characterisation of the efforts of the field at large seems to me a major misrepresentation on the part of Smolin’s and Woit’s books.

    Cheers,

    -cvj

  8. #8 Chad Orzel
    October 11, 2006

    Happily, after some effort, some of us have managed to get Smolin to admit that there’s quite a bit missing about this from his book (actually, the little he does say about it is very wrong in parts), although he seems to justify that omission by saying that is “not fundamental”. (Peter was too , er, busy to respond. See earlier, nearer the start of the thread.)

    Yes, I’m aware of that thread.
    As hinted above, I had been planning to write a second post on the reviews and responses to Smolin’s book. While researching links for it, though, I ran across and read that thread, which changed my mind. I’m fairly disgusted with the whole subject at the moment, and don’t plan to write any more about it for a while.

    And note that this is not just a comment on Lee and Peter– you and Jacques haven’t covered yourselves in glory, either. As far as I’m concerned, the four of you deserve each other.

    And that’s my final word on the topic for now. Any comments attempting to start an argument on this blog about who misrepresented who will be disemvowelled with extreme prejudice.

  9. #9 Jamie Bowden
    October 11, 2006

    So, if I recall correctly, Aaron’s a Super String Theorist (at least, that’s what I seem to recall his ancient posts on Usenet referring to his PhD work as such)…does this means he wears a cape and tights and aids Little Old Physicists in distress?

  10. #10 Aaron Bergman
    October 11, 2006

    Just the cape. I never liked tights.

  11. #11 dark-matter
    October 11, 2006

    If string theory (ST), after >25 years of intense effort, managed to produce even a single verifiable scientific result, folks like Woit and Smolin won’t write and sell their books on it. One cannot defend ST by attacking these authors. Instead it only reinforces the sorry state ST is in.

    The tripping point that prompted above authors to respond forcibly was caused by the string researchers themselves. Some prominent researchers tried to excuse ST failures by inventing the ridiculous Landscape (10^500 universes for each of 10^500 ‘solutions’), by suggesting it is the failure of the scientific method itself that is the problem, by invoking religion-inspired anthropic principle as the core principle of ST, by falsely linking ST to the Standard Model, by inventing a horribly patch-up model to cover up ST failure to predict/explain the positive value of the cosmological constant, by offering no physical explanations for the requirement of 10/11 dimensions after 20 years, by offering not even a single well-formed conjecture on why the so-called M-theory should exist after 10 years, by offering no basis for why all those fancy mathematical dualities should exist in the real world, and last but not least, by predicting vacuum energy in the order of 10^50 – 10^120 higher than measured, which is no better than the particle theory that it supposed to replace. This is more tragic than a joke.

    So we have the dominant, well-funded, enterprise of string research presents the above to the public after some 30 years of spending public money. Perhaps the string community should do some serious soul searching instead of rejecting/attacking those who points this out? After all, it is the careers of string theorists and the money/time invested that are at stake. Perhaps string theorists don’t care about their zero chance of winning the Nobel Prize as things stand. But the public will not tolerate the situation continuing because we are talking about fundamental physics research, the knowledge that will form the basis of future technological society. This is not a game. Sting theorists can start producing credible results, or they can continue to fool themselves until the NSF/DoE decides the public interests are not served by this enterprise.

  12. #12 Aaron Bergman
    October 11, 2006

    No theory of quantum gravity has produced anything verifiable towards that problem for the fifty or sixty years that people have thought about the problem. It’s hard. I’m sorry we haven’t done better.

    I’ve said my piece elsewhere, so to save Chad some additional aggravation, perhaps I should leave it at that.

  13. #13 Chad Orzel
    October 11, 2006

    I’ve said my piece elsewhere, so to save Chad some additional aggravation, perhaps I should leave it at that.

    If people want to discuss the book as a book, or the theories themselves, I have no problem with that. Provided the discussion keeps a civil tone, go nuts.

    I will not tolerate arguments about the character and motives of the various people involved, and who insulted who first. There are plenty of other blogs more or less devoted to that project– pick one.

  14. #14 Coin
    October 11, 2006

    I have a question. It is possible this question is stupid, or that this is not the right place to ask it, or both, but I am unsure how to go about finding answers correctly. The question is:

    Why do we need a theory of quantum gravity anyway?

    It seems to me the really big underlying problem, the biggest reason why we “need” string theory or the debate over it, is that we’ve had such a hard time formulating any theory of quantum gravity. How do we know gravity *is* quantum, though? Is it possible that the ultimately correct way to describe gravity is fundamentally non-quantum?

    My extremely shaky understanding of the subject is that our desire for a theory of quantum gravity is not based on any evidence-based reason to believe a theory of quantum gravity exists (the way the original electromagnetic quantum theories, which were adopted to explain specific physical phenomena, were); rather the justifications I have seen for why we want or need a theory of quantum gravity mostly have to do with the idea that it would be convenient for the “integration” of theoretical physics, for example because certain mathematical tricks that we use to make QM work stop working if gravity cannot be quantized. This seems to me like a very poor justification for quantum gravity (enough so I imagine there’s some better justification out there which I am simply ignorant of).

    Is there some evidential basis for expecting that some theory of quantum gravity applies in the real world, that I just don’t know about? On the other hand, is there some fundamental reason why we can’t just suppose gravity works in a fundamentally different way from the other forces, and set about trying to find ways to integrate the forces into a single theory without forcing gravity into the quantum framework we use for other things?

  15. #15 Chad Orzel
    October 11, 2006

    Is there some evidential basis for expecting that some theory of quantum gravity applies in the real world, that I just don’t know about? On the other hand, is there some fundamental reason why we can’t just suppose gravity works in a fundamentally different way from the other forces, and set about trying to find ways to integrate the forces into a single theory without forcing gravity into the quantum framework we use for other things?

    Two possible answers:

    1) There’s no good reason why gravity shouldn’t be quantum. We live in a quantum world (QED is tested to something like 13 decimal places), and everything else is quantum, so it would be surprising for gravity not to be.

    2) There are limits in which you just can’t get sensible answers from classical gravity– the interior of a black hole, etc. That suggests that there ought to be some other theory that handles those cases. Admittedly, those aren’t limits that anybody has observed, but it does suggest that there ought to be something else.

    I wouldn’t stake a great deal on either of those as a really compelling answer, but I’m not all that concerned about electroweak unification, either.

  16. #16 Aaron Bergman
    October 11, 2006

    The problem is that gravity is a classical theory, but everything else is quantum. If you want to keep gravity classical, you have to find a way to couple it to quantum matter. You could imagine something like

    G = < T >

    The problem, as Jacques says here, is that this makes your quantum mechanics horribly nonlinear. No one knows how to handle that.

    Roger Penrose speculates occasionally that macroscopic superpositions just don’t exist and that gravity and collapse of the wavefuction are somehow all related. He hasn’t been able to turn this speculation into a sensible theory, however.

    The point is that our current situation is untenable. Either the left side or the right side of Einstein’s field equations must be modified (or both).

  17. #17 Chad Orzel
    October 11, 2006

    (I fixed the HTML, and deleted two redundant posts. For the record, the original problem was that you typoed “rt” for “gt” in the brackets. Other than that, it was fine.)

  18. #18 ThoJ
    December 7, 2006

    Evan,

    check usenet or Uncle Al’s website. You can find a lot of things that sound like sorta like science under his name there.

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