The String Theory Backlash

In October 1984, it was announced that the Nobel Prize for Physics had been awarded to Carlo Rubbia and Simon van der Meer, for the discovery of the W and Z bosons at the UA1 experiment at CERN just the previous year. This was the capstone discovery in the establishment of the Standard Model of particle physics. The third generation of fermions had already been discovered (the tau lepton by Martin Perl in 1977, the bottom quark by Leon Lederman also in 1977), and the nature of the strong interactions had been elucidated by deep-inelastic scattering experiments at SLAC in the late 1960’s and early 1970’s. Unsuspected by many, particle physics was about to enter an extended period in which no truly surprising experimental results would emerge; subsequent particle experiments have only been able to confirm the Standard Model over and over again, including the eventual discovery of the top quark at Fermilab in 1995. (Astrophysics, of course, has provided substantial evidence for physics beyond the Standard Model, from neutrino oscillations to dark matter and dark energy.)

A month earlier, in September 1984, Michael Green and John Schwarz submitted a paper on anomaly cancellation in superstring theories. String theory had been around for a while, and it had been understood for ten years that it predicted gravity, and was a candidate “theory of everything.” But there were many such candidates, each of which had run into significant difficulties when taken seriously as a theory of quantum gravity. Most people who were paying attention had presumed that string theory would face the same fate, but the Green-Schwarz result convinced them otherwise. A brief article in Physics Today was entitled “Anomaly Cancellation Launches Superstring Bandwagon,” and theorists everywhere jumped to learn everything they could about the exciting new possibilities the theory offered.

So here we are, over twenty years later, still with no surprising new results from particle accelerators (although hopefully that will change soon), and still with strings dominating the landscape (if you will) of theoretical high-energy physics. And still, one hardly needs to mention, with no clear path to connecting string theory to low-energy phenomenology, nor indeed any likely experimental tests of any sort.

In the circumstances, it’s not surprising there would be something of a backlash against string theory. The latest manifestation of anti-stringy sentiment is in two new books aimed at popular audiences: Peter Woit‘s Not Even Wrong: The Failure of String Theory and the Continuing Challenge to Unify the Laws of Physics, and Lee Smolin’s The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next. I haven’t read either book, so I won’t presume to review them, but I think we’ve heard the core arguments expressed on this blog and elsewhere. I’m a firm believer that it’s good to have such books out there; I’m happy to let the public in on our internecine squabbles, just as I’m happy to keep them updated on tentative experimental results and speculative theoretical ideas. It seems unduly patronizing to think that we can’t reveal anything to the wider world until everyone in the community agrees on it.

But I don’t actually agree with what the books are saying. Here is the main point I want to make with this post, trite though it may be: the reason why string theory is so popular in physics departments is because, in the considered judgment of a large number of smart people, it is the most promising route to quantizing gravity and moving physics beyond the Standard Model. I don’t necessarily want to rehash the reasons why people think string theory is promising — I’m not positing an objective measurement of the relative merits, but simply an empirical observation about people’s best judgments. Rather, I just want to emphasize that, when you get right down to it, people like string theory for intellectual reasons, not socio-psycho-political ones. It’s not a Vast String Theory Conspiracy, funded by shadowy billionaires who funnel money through Princeton and Santa Barbara to brainwash naive onlookers into believing the hype. It’s trained experts who think that this is the best way to go, based on the results they have seen thus far. And — here’s the punchline — such judgments could change, if new results (experimental or theoretical) came along to suggest that there were some better idea. The way to garner support for alternative approaches is not to complain about the dominance of string theory; it’s to make the substantive case that some specific alternative is more promising. (Which people are certainly trying to do, in addition to the socio-psycho-political commentating about which I am kvetching.)

That is, after all, the way string theory itself became popular. Green and Schwarz labored for years on a relatively lonely quest to understand the theory, before they were able to demonstrate anomaly cancellation. This one result got people psyched about the theory, and off it went. It’s not a matter of impressionable young physicists docilely obeying the dictates of their elders. Read Jacques Distler’s (absolutely typical) story about how he dived into string theory as a graduate student, despite the fact that his advisor Sidney Coleman wasn’t working on it. In a completely different field, listen to Nobel-winning economist Gary Becker on the response to his ideas (via Marginal Revolution):

“There was a sea change. I began to notice it in the 1970s and 1980s. A lot of the younger people coming out of Harvard, MIT and Stanford were very interested in what I was doing, even though their faculty were mainly – not entirely – opposed to the sort of stuff I was doing.”

This is just how academics act. They are stubborn and willful (even at a charmingly young age!), and ultimately more persuaded by ideas than by hectoring from their elders. And it’s not just the charmingly young — if good ideas come along, supported by exciting results, plenty of entrenched middle-aged fogeys like myself will be happy to join the party. If you build it, they will come.

There’s no question that academic fields are heavily influenced by fads and bandwagons, and physics is no exception. But there are also built-in mechanisms that work to protect a certain amount of diversity of ideas — tenure, of course, but also the basic decentralized nature of university hiring, in which different departments will be interested in varying degrees in hiring people in certain fields. Since the nature of science is that we don’t yet know the right answers to the questions we are currently asking, different people will have incompatible intuitions about what avenues are the most promising to pursue. Some people are impressed by finite scattering amplitudes, others like covariant-looking formulations, others don’t want to stray too far from the data. The thing is, these considered judgments are the best guide we have, even if they are not always right. Green and Schwarz were lonely, but they persevered. If you want to duplicate their success, find a surprising new result! You can’t ask a department to hire people in an area they don’t think is promising, just because it serves the greater goal of diversifying the field overall. Crypto-socialist pinko though I may be in the political arena, when it comes to intellectual life I’m a firm believer in the free market of ideas, and would tend to resist affirmative-action programs for underrepresented theories.

The bandwagons come and go, influenced by both data and new ideas. When I was in grad school in 1990, things were in a lull in fundamental physics generally, and students were escaping to Wall Street and elsewhere. The discovery by COBE of temperature anisotropies in the microwave background re-invigorated cosmology, and attracted a number of bright young theorists. The Second Superstring Revolution in the mid-90’s did the same for string theory. There’s every reason to believe that the LHC will do the same for phenomenology — the leading indicators are already easily visible.

The thing that has kept string theory alive is that interesting results have kept coming, from the 70’s (gravity!), to the 80’s (anomaly cancellation, five critical string theories), to the 90’s (branes, dualities, black hole entropy, AdS/CFT). The last few years haven’t witnessed their own “revolution” (unless you count the landscape), but it would seem a little impatient to give up on that basis alone. If nothing else, string theory is extraordinarily fruitful and robust. Indeed, the AdS/CFT correspondence says you can’t really separate field theory and string theory. Take an ordinary gauge theory in flat four-dimensional spacetime, and make it as supersymmetric as possible without adding gravity. Then make the coupling very strong, and the degrees of freedom rearrange themselves — just as the strong coupling in QCD makes the quarks and gluons rearrange themselves into pions and nucleons — into Type IIB superstrings living in a ten-dimensional spacetime. How amazing is that? It’s not proof that strings are connected to the real world (which, as people sometimes forget, is not manifestly maximally supersymmetric, and does in fact involve gravity), but it’s the kind of rich structure that keeps people optimistic that string theory is on the right track.

Of course, you do have to make the case that your personally favorite approach is a promising one, to the public and to colleagues in other specialties as well as to graduate students. This is not always a job that string theorists have done well. Some of them, I’ve heard rumors, can even occasionally be a mite arrogant. Let’s admit, this is something of an occupational hazard among academics; if universities fired all the arrogant people, the remaining faculty would be stuck teaching twenty courses a semester. And, while I think that an enormous landscape of stringy vacua might very well exist, I think that supporters of the idea have dramatically failed to take seriously the difficulty of actually calculating anything on that basis. Discussions about these crucial issues have all too often degenerated into sophomore-level philosophy-of-science debates, which haven’t done credit to either side. The truth is, we’re not doing science in a new way, it’s the same old way — trying to come up with the simplest possible consistent and coherent framework that explains the phenomena we observe.

And (to add one more “of course”), needless to say we need to keep our eyes on the prize, which really is explaining those phenomena. Sometimes people do get entranced with the math, which is fine, but as physicists the ultimate arbiter of interestingness is a connection to data. String theory hasn’t done that yet, and might not do it for a long while, but in the end will have to, one way or another. It’s hard! But string theory will either progress to the point where its connections to reality become increasingly manifest and specific, or people will lose interest and work on other things. That’s the way the system works.

Update: Interesting reports from the Strings 2006 meeting in Beijing from Victor Rivelles, Jonathan Shock, and Dennis Overbye.

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226 Responses to The String Theory Backlash

  1. Mark says:

    Very nice job Sean. I agree with basically everything you say. I do think that the tension which exists regarding string theory at the moment could be eased if there were fewer people making outrageous claims rather than using the more modest “it’s hard, we’re working on it, stay tuned” line. But in the end, it is the science that matters and on the basis of which decisions are made.

  2. Rob Knop says:

    Sean — well said.

    One of the complaints I hear people making about String Theory is that it’s got no connection to experiment– and I do see and agree with this complaint. One way to say it is that String Theory is “good math, but perhaps not yet good physics.”

    I do agree with you that, so far as I can tell, it’s the best game in town when it comes to understanding quantum gravity. I don’t understand String Theory myself beyond the Elegant Universe level, but make the same observation that you do: smart people who do understand this kind of thing talk mostly about String Theory, and perhaps a little about Quantum Loop Gravity (about which I know next to nothing). And, I disagree with the extreme-curmudgeon point of view that if it doesn’t have a predicted experimental result that can be done right now, it’s not worth doing in a Physics department. But at the moment, String Theory seems to be such a long way from having any predicted experimental results that it’s difficult for me to get very excited about it from my level of understanding.

    When I give public talks on cosmology, I mention that before the epoch of inflation, all modern science can really say is that we don’t know what happened, and can’t even really predict what happened. Even inflation, now, has some predicted observations that have borne out… but before that, it’s “here be dragons”. I do mention that the string theorists may be working on it, but we’ll just have to wait and see what will come as science progresses.

    -Rob

  3. lmot says:

    Alot of the problem is in the way string theorists market their work to the public. Particle physicists in general are personally ambitious people and take their status as “king of the sciences” as a birthright. They are not content to work away quietly on some speculative ideas while other sciences grab all the headlines. Thus the longer the field goes on without any real fundamental discoveries, the more they feel the need to compensate by jumping up and down in front of any reporter or TV camera they can find and claiming they’ve found new dimensions and/or universes or whatnot.

  4. Peter Woit says:

    Sean,

    A few comments about your posting:

    1. What unleashed the First Superstring Revolution wasn’t so much the Green-Schwarz calculation as the fact that this calculation convinced Witten to start working full-time on superstring theory. It was that news that really got people interested (I was there). Superstring theory is an extremely complex subject, both in 1984 and much more so now. Few people understand it in enough detail to have a clear idea of what its accomplishments and problems are, so there’s a huge amount of mystification about this, with most people relying on what they hear from a small number of experts, not their own understanding. These experts unfortunately have been much more interested in explaining what they see as promising about the theory than in explaining the difficulties and how serious they are. I hope my book and Lee’s will give people a more balanced and realistic understanding of the situation.

    2. It’s certainly true that string theory remains as popular as it does largely because of the lack of many viable alternatives. My own view is that the highest priority of the theoretical physics community should be to think hard about what it can do to encourage people to find alternatives. I very often get e-mail from students and young researchers saying that they have looked into string theory, don’t like what they saw, want to work on some alternative, but don’t see how to make a career for themselves doing this. I have trouble knowing what to tell them. If someone is a grad student at Princeton like I was and wants to do particle theory, who can they work with there or at the IAS who is not doing string theory?

    3. When I first started publicly criticizing string theory, I was surprised by some of the reaction. Quite a few people contacted me to tell me how “brave” I was, something I found rather peculiar. My job and ability to do what I want to do don’t depend on the favor of any string theorists, and I knew many of them personally and had never had any problem discussing my skepticism about the subject with them. You make fun of the “Vast String Theory Conspiracy” and you’re correct that there are plenty of people with an unrealistic view of this, but over the last few years I have had some disturbing experiences. There are more than a couple string theorists out there who are not interested in having a free market of ideas in this area. Despite quite enthusiastically positive referee reports from some highly-respected physicists, two string theorist referees were able to stop Cambridge University Press from publishing my book a couple years ago, and they didn’t do it by pointing out anything incorrect I had written. The free market of ideas was not in operation there. The arXiv still censors links to commentary on my blog about preprints there, is that evidence of a free market of ideas?

    Most disturbing to me recently has been the string theory community’s toleration or even encouragement of the brutal bullying tactics Lubos Motl employs to try and suppress criticism of string theory. He’s made string theory look bad, but his intimidation has also been quite effective. Many people who write to me or post comments on my blog tell me to be careful to preserve their anonymity because they fear attacks from him or from others of his ilk. Often these people are string theorists themselves. Yesterday he managed to bully Christine Dantas into taking down a posting she had put up listing ten achievements of LQG, the most prominent alternative idea about quantum gravity. Part of his posting about this included a vicious attempt to humiliate some student at SFSU, purely because Lubos mistakenly believed she had a physics Ph.D. and wanted to make the point that some physics Ph.Ds (those critical of string theory) should not be listened to. Do you really think this is evidence of a healthy free market of ideas?

    Clifford and other string theorists object to all being lumped together with the likes of Lubos, but I don’t see any of them (except from time to time Aaron Bergman) ever being willing to forcefully condemn his tactics. When I’ve explicitly asked some of them to do so, the reaction I’ve often received from them has been that they think he is basically right about what he is saying, just “undiplomatic”.

    So, the fact of the matter is that there hasn’t been a functioning free market of ideas in this field. My book and that of Lee’s are attempts to start to change this. I hope you’ll read them, if the publisher hasn’t sent you an advance copy by now of mine, let me know. For one thing, you may find the book is rather different than what you expect. Out of 19 chapters, only one is about the sociological aspects of this.

    Peter

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  6. Sean says:

    Lubos’s tactics are disgusting and reprehensible. And that, I’m afraid, is the final word on the subject, as far as this comment thread goes; if anyone would like to delve into that particular bit of psychodrama, please do so on some other blog. Further comments will be deleted, even if they also say other interesting things. Surely there are more substantive issues to talk about.

  7. ed hessler says:

    This post is yet another reason I like CV so much and would think I’m missing matter if I didn’t check in daily or thereabouts.

    Mark’s comment is on point: it IS the science that matters and this science matters.

    For folks like me–a K-12 science educator–these essays and comments provide some light on what for me is very deep material. It helps me think about the nature of science no matter where it is practiced from biology to physics (I’m sure there is an “A” science and a “Z” science but I can’t think of one right now. Ah, one: arachnology. (I’m sorely tempted to invent a new one, for the symmetry, zebra science, the idea suggested by the title of an essay by the late Stephen Jay Gould: “Just Exactly What is a Zebra?” But I won’t.)

    It is a great summary and beautifully said.

    Cheers.

  8. fh says:

    Good post Sean. I agree very much with the “build it and they will come” mantra. In fact it’s happening. LQG for example is gaining this status by and by, it wasn’t taken seriously in HEP for a very long time because it doesn’t come from a particle physics background but from a bunch of GR based people (the first tentative connection to ordinary QFT was only made last year), also many of the tools that were available to Green and Schwarz to study strings had to be built from scratch so it’s been long in the coming. (and has come with it’s own share of serious problems)

    However, one caveat. As you said correctly, Green and Schwarz were working in a context where many potential theories were floating around. These days that’s not the case in the particle physics community. As such it is my impression that tolerance for loners just persisting to come up with the next great thing that will convince everyone is much lower in particle physics today. (Therefore most speculative developments are happening in a more relativist context)

  9. Yidun says:

    Dear Prof. Carroll,

    Very well said! I do agree with you on almost all of your points. However, from my humble point of view, I would think that the truth may not be in the hands of majorities. In other words, I would not think that if a theory under devoloping is good or not has much to do with the judgement of large amount of smart people.
    I strongly agree with on that the best way to attack or defend a theory is to show better results, either theoretical or experimental. So, either people working in ST or in LQG or in any other approach should just work hard, and harder.

    Sincerely, Y.

  10. fh says:

    Algebra to Zoology?

    Another point, thanks for the historical introduction I always enjoy those, as virtually all of this is before I was born. The pace of discovery up to the 80s culminating in the confirmation of the standard model is breathtaking compared to today.

  11. Doug says:

    Loop theories may be related to helical string theories if one considers that a loop has a zero helical angle.

    John Baez may allude to this possibilty in weeks 234 and 233 of ‘This Week’s Finds in Mathematical Physics”. He discusses Music Theory and sporadic Lie Gropus like the Monster and Mathieu subgroups.

    If the Monster has a complex-24-D, a string-D and a time-D, is it possible that both the string-D and time-D are also complex? A complex-helical-string-D may be equivalent to complex harmonic oscillators. A complex-time-D may be consistent with the Hawking imaginary time concept and possibly the Bars 2T-physics concept.

    Histrically there seems to have been 4 eras of string theory:
    1 – ‘PYTHAGOREAN HARMONY OF THE UNIVERSE’
    http://etext.virginia.edu/cgi-local/DHI/dhi.cgi?id=dv4-05
    2 – String Theory: They Are Winners Already [in music]
    http://www.oberlin.edu/con/connews/2003/string.html
    3 – Pauling [Chemistry Nobel 1954], Corey & Branson helices and pleated sheets – ‘The Structure of Proteins: Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain’
    http://www.pnas.org/cgi/reprint/37/4/205
    and the subsequent work of Crick, Watson, Wilkins [and Franklin] with the first three awarded Medicine / Physiology Nobels in 1962 “for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material”.
    http://nobelprize.org/medicine/laureates/1962/index.html
    4 – the current evolution of various string [including twistor] theories ushered in by Veneziano and Susskind.
    http://online.itp.ucsb.edu/online/colloq/veneziano1/
    http://www.edge.org/3rd_culture/susskind03/susskind_index.html

    One can visualize replacing Rovelli loops [with a zero helical angle] with springs or slinky-toys of the same periodicity as a means of possibly linking [unifying] loop and string theory.
    http://www.cpt.univ-mrs.fr/%7Erovelli/loop_quantum_gravity.jpg

  12. BG says:

    I very often get e-mail from students and young researchers saying that they have looked into string theory, don’t like what they saw, want to work on some alternative, but don’t see how to make a career for themselves doing this. I have trouble knowing what to tell them. If someone is a grad student at Princeton like I was and wants to do particle theory, who can they work with there or at the IAS who is not doing string theory?

    As someone who was recently a student himself, I can say my response was simply to start studying cosmology instead of particle theory. I think the “problem” is really as Sean has said – particle physics has been a bit stagnant the last decade or two, and as a result the field is simply already full of highly qualified people (both string cheerleaders and brilliant detractors). It’s simply not really a good time to want to do particle theory, period. If students are chased away and start taking up other fields rather than sit and wait for the LHC to deliver data, I don’t really see that as a huge problem. If the LHC turns on and finds something weird, I’m sure we’ll see a rapid influx of particle theory students trying out new ideas. Until then, it seems like most effort is best spent elsewhere.

  13. John Baez says:

    Sean writes:

    I haven’t read either book, [….] But I don’t actually agree with what the books are saying.

    Hmm. Maybe you’re disagreeing with what you think the books might say. Smolin’s won’t even be out until September. I suspect you’ll actually find it quite interesting.

    Rather, I just want to emphasize that, when you get right down to it, people like string theory for intellectual reasons, not socio-psycho-political ones. It’s not a Vast String Theory Conspiracy, funded by shadowy billionaires who funnel money through Princeton and Santa Barbara to brainwash naive onlookers into believing the hype.

    I don’t believe these books claim something like that.

    […]
    the reason why string theory is so popular in physics departments is because, in the considered judgment of a large number of smart people, it is the most promising route to quantizing gravity and moving physics beyond the Standard Model.

    I agree with that; the question is whether these people are right. And, I think both books make the case that they’re wrong. This is of course the key issue, which towers over all the sociological/political issues: is string theory right or not?

    I don’t necessarily want to rehash the reasons why people think string theory is promising […]

    Tiresome though it may seem, to really engage Woit’s and Smolin’s books, one has to discuss the reasons they think string theory is wrong, or misguided. And, more generally, to defuse the so-called “string theory backlash”, string theorists would have to talk to people who believe that string theory is wrong, or misguided, and convince them that it’s right, or at least on the right track.

    A single verified experimental prediction would probably suffice.

    But until that comes along, string theorists should accept that lots of smart physicists will doubt string theory – because in their considered judgement, they believe it’s not the most promising route to quantizing gravity and moving physics beyond the Standard Model. These physicists have detailed, precise reasons why they believe this. And, it can’t hurt physics to have a discussion these reasons.

    Preferably with a minimum of heat…. but I suppose I’m a dreamer.

    By the way, I really like your blog, and I’m sorry my first (?) post is a bit argumentative.

  14. Aaron Bergman says:

    At the risk of this turning into yet another LQG/String discussion:

    [LQG] wasn’t taken seriously in HEP for a very long time because it doesn’t come from a particle physics background but from a bunch of GR based people

    I don’t really think this is true. A fair number of people (myself included) have looked into various aspects of LQG and not found it particularly appealing. This has nothing to do with some sociology of GR people rather than particle theory people; it’s an honest disagreement on the merits. To couch it as some sort sociological difference in perspective isn’t fair to the people who have honestly considered the issue.

  15. Sean says:

    John, I think I completely agree with everything you say. I’m sure that both books do try their best to make the physics case that string theory is not the most promising route forward, and the arguments therein should be addressed seriously and substantively. Which, not having read either book, I can’t do right now. (I do have a copy of Lee’s book, obtained through surreptitious channels. Peter, nobody has sent me yours, but I’d be happy to take a look if someone were to do so.)

    Therefore, I specifically chose to focus here on a certain peripheral claim, which I know I’ve heard before, and which I suppose might be absent from both books. Namely, that we should make some extra effort to support work in alternatives to string theory, because it is so dominant and it hasn’t yet made direct connection to experiment. On this issue I am a staunch classical liberal, and feel that we should let the market decide. In other words, it is only on the basis of substantive physics arguments that people will or will not make their decisions to work on string theory or anything else. If people want to support alternatives, the best way to do so is to generate exciting new results within those approaches, not (to be somewhat unfair in the cause of an irresistible rhetorical flourish) to complain that the Man is keeping them down.

    Glad you like the blog, and always extremely happy to welcome sensible argumentation.

  16. EU says:

    here in Europe the topic “failure of string theory?” is informally discussed since 8 years at least. Discussing this topic turned out to be much less dangerous than what I was alerted. Although a few string theorists prefer avoiding discussing this issue, most string theorists agree with the main points. The ones that successfully moved towards less stringy physics didn’t kill their academic career.

  17. fh says:

    “To couch it as some sort sociological difference in perspective isn’t fair to the people who have honestly considered the issue.”

    No that was not what I meant. I didn’t mean it sociological at all. These are genuine disagreements over physics! I think someone with a GR background will have a very different idea what’s crucial in physics then somebody with a particle theory background.

  18. island says:

    Looks to me like the process is working just fine. Thanks to the “complaining”, etc… kids coming into the field will now be aware that string theory isn’t *necessarily* the most promising avenue of cutting-edge pursuit, so they won’t be so fad-oriented toward it as the will now have a grain-of-anti-hype to go with the hype.

    It’s the healthy approach… 😉

  19. Aaron Bergman says:

    These are genuine disagreements over physics! I think someone with a GR background will have a very different idea what’s crucial in physics then somebody with a particle theory background.

    If this is leading towards something with the initals BI, I really don’t see that as a substantial philosophical difference. The main difference as I see it has to do with the nature of QFT. Rather than talk about GR vs. particle physics backgrounds, I get the feeling that AQFT vs. pragmatic-QFT (for lack of a better term) is much more relevant.

  20. fh says:

    I think there is a list of topics (and it’s by neccesity idiosyncratic), AQFT vs pragmatic-QFT is one of them (and one that’s close to what got me to look in this direction, which certainly wasn’t BI). But this is getting rather off topic for this thread I guess.

  21. John,

    Last fall, I wrote a series of posts (I, II, III) which I hoped might be a springboard for exactly the sort of sober discussion you’re talking about.

    I’m still surprised at how little disagreement there was in the responses. I was hoping that someone would pipe up and explain why I was wrong.

    More generally, I’m with Sean. These are scientific questions, which ought to be decided on their scientific merits, rather than on the basis of who can write the most popular book for the general public (or, conversely, on the basis of whose blog postings are most obnoxious).

  22. Santo D'Agostino says:

    Sean writes:

    Rather, I just want to emphasize that, when you get right down to it, people like string theory for intellectual reasons, not socio-psycho-political ones. It’s not a Vast String Theory Conspiracy, funded by shadowy billionaires who funnel money through Princeton and Santa Barbara to brainwash naive onlookers into believing the hype.

    It’s not a conspiracy, but it bothers me that there is hype at all. There should be no need for hype; a theory should be able to thrive on its own merits. One could usefully compare this situation to the NBA draft, where players are drafted based on their “upside,” or in recent years on their “upside potential.” Plenty of players with “tremendous upside potential” end up being busts.

    I’ve met lay people at parties who have been convinced by the hype that string theory is already well-confirmed and established. This IS a socio-psycho-political issue, and it certainly bothers me. In popularizing physics for lay-people, the first criterion ought to be honesty.

    A math colleague has a high opinion of string theory because “string theory predicts gravity.” I’ve had conversations with string theorists, and it bothers me that they play fast and loose with the concept of prediction. The fact that the theory doesn’t make one single prediction (which some people have tried to soften by saying “sharp prediction”) makes the hype that much more bothersome.

    I have no objection to anyone working on string theory; however, there is a general public misunderstanding about the status of string theory, and this misunderstanding also extends to some members of the scientific community. Any efforts to correct such misunderstandings ought to be applauded.

    Santo

  23. QUASAR9 says:

    Well Sean, you got an invite to read both books, and possibly review on them. Excellent post, and civilised, sensible debate or arguments in the comments section.
    This is what I understood blogging to be about. I’m a socialist cum for the common good commie, open to a ‘free’ market of ideas or thought, and cannot be shouted down by other more radical views from the left or the right, nor mistaken to be a supporter of the errors or failures of the various forms of ‘ruthless’ and authoritarian government(s) or communism. Good to see that ‘theoretical’ physics is a wide subject and open to interpretation, and no more concrete (finalised) than ‘theoretical’ ideology politics/economy. There is still much room for debate. Q

  24. Sean says:

    Let me just second Jacques’s suggestion of his earlier posts on quantum gravity and UV fixed points. They are for experts, but do a very good job at explaining one particular difficulty with quantizing gravity that I personally had been vaguely aware of but not really appreciated.

  25. MoveOn says:

    I read all the time the word “alternatives” to string theory.

    Let’s have a look at hep-ph for inspiration, where there is a whole crowd of particle phenomenologists busily at work doing non-stringy physics. In fact there is a whole sub-community of extra-dimensional model builders, who are proud not to be string theorists. All this started with Randall-Sundrum, and to my understanding their work really was meant to bypass/be an alternative to string theory. In a way, it’s quantum gravity and extra dimensions for the poor guy. Anyone can enter the field and produce new models right away, there are almost no consistency requirements (apart from anomalies) to be respected (yes! we are not doing string theory!) The art is to combine as many results as possible from other people in a new way, in order to create “better” models. Hence new models abount, all sorts of GUT groups being revived, but this not only in 4 (as in the past), but now in 5,6, you name it, dimensions. Branes are put here and there at will, and supersymmetry is split or not, etc. Then there are ex-nuclear physicists doing “phenomenological quantum gravity”.

    So that’s how particle physics beyond the standard model “sans cordes” is starting to look today – and this is where the hype is coming from. It’s definitely not coming from the string physicists – there may have been a good deal of hype in the past, but in the last couple of years, not really (apart from a few isolated people). At least I can’t remember having heard something disproportionate from the leaders in the field. Strominger? Nope. Maldacena? Nope. Polchinski? Nope. Douglas? Nope. Vafa? Nope. Gross? Perhaps a bit. Susskind? Perhaps a bit. Witten? Nope. Seiberg? Nope. And so on.
    (ordering, omissions = random, no pun)
    So what, please, are people complaining about?

    On the contrary, it’s actually the string physicists who keep the intellectual and scientific standards high – despite of the spin doctors trying to claim the opposite. Anyone not believing this is invited to check out hep-ph first before criticising hep-th.