The String Theory Backlash

By Sean Carroll | June 19, 2006 12:26 pm

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.

CATEGORIZED UNDER: Science
  • http://blogs.discovermagazine.com/cosmicvariance/mark/ Mark

    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.

  • http://brahms.phy.vanderbilt.edu/~rknop/blog/ Rob Knop

    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

  • lmot

    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.

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    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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  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    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.

  • ed hessler

    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.

  • fh

    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)

  • http://www.wanyidun.com/blog_r2u Yidun

    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.

  • fh

    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.

  • Doug

    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

  • BG

    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.

  • http://math.ucr.edu/home/baez John Baez

    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.

  • Aaron Bergman

    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.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    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.

  • EU

    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.

  • fh

    “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.

  • http://www.anthropic-principle.ORG island

    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… ;)

  • Aaron Bergman

    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.

  • fh

    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.

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    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).

  • Santo D’Agostino

    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

  • http://quasar9.blogspot.com/ QUASAR9

    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

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    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.

  • MoveOn

    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.

  • http://www.pieterkok.com/index.html PK

    I do not know a lot about string theory beyond the Elegant Universe, but I do know bandwagons and hypes (I work in quantum information theory). Hypes are largely generated in the media, who latch on to specific results, even though their popular representation might not be completely correct (“string theory predicts gravity”, “quantum computers are superfast”). There is then a feedback mechanism that may turn a hype into a bandwagon.

    Still, the bandwagon needs to be pushed along. The fact that there is a hype is a sign of a healthy discipline (both in terms of results and funding). Even the size of the backlash is a measure of the success of string theory.

  • Aaron Bergman

    I think the whole issue of hype misses an important point. ‘Hype’ to me implies some disingenuousness. NBA picks, for example, are hyped by agents in the hope of increasing the paycheck later on. What people call hype in physics, I see as people being excited about their work. People are in physics because they think it is fun, and they want to share their new ideas. There is an inevitable distortion coming out of this, but it isn’t restricted to string theory. LQG, braneworlds, ekpyrosis, etc. have all gotten their articles in the Science Times, too. Science journalists are trolling the arXiv for the next new thing, and most scientists are willing to talk to them. Maybe in a better world, all such articles would have their needed share of caveats, but that doesn’t make the greatest copy. In the meantime, I tend to think that people being excited about their work and wanting to share their ideas is overall a good thing,

  • http://theory.uchicago.edu/~sjensen/research/StringIntro/ Steuard

    Thanks for a good post, Sean. For my part, I got excited about string theory after reaching grad school and worked awfully hard for the chance to work in the field. I won’t say that nobody has ever felt “trapped” into doing strings, but that notion is entirely foreign to my experience.

    The thing that has always puzzled me about the “string backlash” is what exactly string theory’s detractors would like to see string theorists do differently. (I am happily ignorant of any “reprehensible” tactics used by anyone in the debate, so of course these comments apply only to the overwhelming majority of decent people out there.)

    Do they want us to leave the field? We won’t, not until we find another idea more compelling. (And if it turns out to be wrong, hey, it’s our careers on the line, not theirs.) Do they want us to stop telling the public about our work? We won’t: public outreach is part of science, and sharing things that one finds exciting is part of being human. Do they want us to make it clear when we speak that our work is tentative and not yet verified by experiment? We already do. Or at least, I always emphasize it, and most of the string talks that I’ve seen do the same. (We don’t include disclaimers on every slide,of course!) What more do they want from us?

    In the end, I find the “backlash” rather frustrating. I’m just following the physics I find most interesting, and somehow that generates not just scientific objections but what feels like actual resentment. I’m glad to have “lots of smart physicists” doubting string theory and pursuing other ideas that they consider promising! Why should I have to convince them to abandon those other possibilities entirely (by convincing them that strings are “on the right track”) before they will cease what feels like active hostility?

    Why do we need popular science books dedicated (or half-dedicated) not to sharing some exciting new idea but rather to cutting one down? Has anyone written a popular science book that’s mostly about why, say, technicolor is wrong? Or about why the resonant valence bond model of high Tc superconductivity is wrong? What makes string theory such a unique target for this sort of broad public criticism?

  • http://blogs.discovermagazine.com/cosmicvariance/joanne/ JoAnne

    MoveOn, it is statements in your comment, such as:

    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.

    that keep this endless discussion irritating rather than substantive. Quite frankly I am tired of string folks spouting that any other area of particle theory is simply not good theoretical science (yes, I’ve had some string theorists say this to my face). It grows tedious when one resorts to name calling in a debate rather than basing their position on facts.

    As to whether string theory is correct or not, the science will eventually decide, as Sean says. Personally, I think it is rather conceited of us to think that we are special enough to be able to accurately extrapolate 16 orders of magnitude – without any knowledge of the science that takes place within that energy range – and be able to describe nature at the Planck scale. Doesn’t mean that we shouldn’t try – we learn alot by trying – but we need to keep our feet on the ground while doing so.

    Speaking of hep-ph, there is much excitement there these days with alot of stimulating model building, breathtaking tour de force higher order calculations, collider physics is energized, there is a new level of precision in lattice calculations, and new effective theories being developed to describe heavy flavor interactions. All of this work is developed under the arduous constraints of being consistent with the full global data set – I can tell you that is not trivial. All of this work is also developed knowing that it will be tested and proved right or wrong soon. Very soon.

    Lastly, for all future Princeton graduate students who would like an alternative to string theory, I note that Lian-Tao Wang – a talented collider phenomenologist – is arriving as an Assistant Professor this Fall.

  • Moshe

    Excellent post Sean, I think you are right on the money in highlighting this interesting issue, even people who do not care much for string theory would probably not like the self-managing style of the scientific community compromised in any way.

    Steuard, my sentiments exactly.

    JoAnne: the list you make is really interesting, I don’t recall any of these issues discussed in popular or semi-popular press, but of course with blogs one does not need those…

  • http://wanyidun.com/blog_r2u Yidun

    Dear Steuard,

    Yes, you may not need those public science books that are against string theory. However, the whole society needs them, the society needs different voices. In fact, you are doing something of impelling interest only to you and a group of people. The theory you are working on is still under development. There is not solid evidences showing that it will be ultimately true. Moreover, since you think advertising the theory to the public is part of the science, why couldn’t you allow others to have opposite points of view? And those others are scientists as well. Actualy, the more an approach is advertised, the more criticism it’ll receive.
    If you are working on some well established physical areas, you may get less criticism for sure. From my humble viewpoint, however, a theoretical physicist who works for his own dream should not be afraid of criticism, public or private, as longs as those criticisms are scientifically rational but not emotional, because they are healthy for our scientific air at all.
    I would apologize if I misunderstood any of your points.

    Best, Y.

  • http://eskesthai.blogspot.com/2005/09/uv-fixed-point.html Plato

    From a layman who works hard to understand.

    Not that it matters, but seeing “in the ways” Jacques continued efforts to educate and speaks about, is refreshing reminder of the strange world you scientists are working in.

    “Dynamical triangulation” John? :) Monte carlo models, to flipping on quantum gravity methods?

    I have not heard to many from the likes of Steuard, who give their opinion on it from the inside. The talk Mark relayed on “negativity” would have been a good thing, if the insight and opinion were given from scientific stance, as was the discussion linked to cosmic variance, by Jacque in “I.”

    Aaron and Lee rebuttals, as well as the stand Peter Woit and Lubos(I won’t hold character against anyone as long as their willing to share perspective?) took to debate the sustenance string theory has for the future? Did character from either hurt this move to debate from a “negative stance” reveal other information? :)

    Creating the situations for advancing our understanding. How appropriate :) Supersymmetry conference, Anthropic debate, etc. Advancing the positions of all who understandly speaking from their respective models, who know, that such a forum may have initiated new ideas?

    I think laying aside the “conspiracy theory” would be a good thing.

    Oh Yes, this is a good post too Sean.

  • http://arunsmusings.blogspot.com Arun

    JoAnne,

    Whenever you have some time, would you mind telling us more about the breathtaking tour de force higher order calculations and the new level of precision in lattice calculations?

    Thank you!

  • http://arunsmusings.blogspot.com Arun

    Moshe wrote:

    …even people who do not care much for string theory would probably not like the self-managing style of the scientific community compromised in any way.

    Agreed. I certainly hope so. But I fear the hope is unrealistic. So far the natural sciences had objectivity on its side, so the funders of science were content to let this be so. The facts spoke for themselves. If the main justification for a line of research is that a lot of smart people think it worthwhile, then the hands-off attitude may change.

  • A.J.

    Why do you think journalists don’t write articles about the questions that motivate quantum gravity theorists? There’s not much data available right now, so it’s not a good time to be writing articles explaining the nature of the universe; scientists have many useful partial explanations, but our whole picture doesn’t hold together yet. We’ve got some neat hints though, so it’s a great time to ask questions. That’s really where most of the fun in quantum gravity is anyways: in wondering, for example, why black hole entropy doesn’t seem to scale with volume. (That susygravity and strings offer a framework for asking questions of this form is one of the things that makes it interesting to theorists. That it makes it comparatively easy to do so is cause for celebration or suspicion, depending on your levels of cynicism. :)
    But there are some good science articles to be written about the questions in quantum gravity. And it’d probably give people a better idea how science works and what theorists do during the day, aside from posing in white labcoats.

  • bizarre

    i’d just like to 2nd arun’s post #33 above asking joanne to tell us about some of the phenomenology being done at the moment. it seems like a lot of the particle theory blogosphere is string-based (i know this isn’t 100% true), it would be great to hear about theoretical work being done that is more closely tied to experiment (tevatron, lhc etc,).

  • lmot

    “‘Hype’ to me implies some disingenuousness. NBA picks, for example, are hyped by agents in the hope of increasing the paycheck later on. What people call hype in physics, I see as people being excited about their work.”

    As a counterexample, I offer to you Professor Michio Kaku. Highly disingenuous by any standard (I’ve heard him on the radio), and he has a clear paycheck motive: hawking books and various media appearances.

    I suppose you could argue that he’s not a real practicing physicst, he just plays one on TV.

  • Aaron Bergman

    I suppose you could argue that he’s not a real practicing physicst, he just plays one on TV.

    Yeah, pretty much.

  • graviton383

    I second the comments of JoAnne above. I’d be the last person to suggest that both serious model builders and phenomenologists have not been greatly (and positively!) influenced by ideas that arose from string theory. Hell, my last paper was on signatures of extra-dimensional, non-commutative Tev-scale black holes at the LHC. But there is much, much more to phenomenology than this. Overall, it is a very broad yet under-valued field and has been for some time, since the death of the SSC back in ’93. Many of us have had some of the same bad experiences that JoAnne mentioned re the interactions of stringers and phenomenologists. There is some sense that this is changing perhaps due to the advent of the LHC next year.. particularly when you talk to the younger graduate students. I hope so..for the sake of the future of our field…but it may all depend what happens at the LHC.
    Perhaps we’ll have this conversation again in 2010-11.

  • anonymous

    This is all rather tiresome. Why is there so much vitriol directed at string theory? For understanding the theoretical underpinnings of quantum gravity and cosmology, most physicists who have thought about it have decided it’s the best answer. If people want more physicists working on “alternatives” like LQG, they should go into LQG and produce interesting results to persuade people to switch, not rail against some imagined injustice. The fact is, many physicists have, at least briefly, looked into LQG and decided it is not interesting. The reason is quite clear, when you look at, say, Lee Smolin’s comments on Peter Woit’s blog, where he was totally unable to provide any explanation of how (or whether) LQG matches onto a unique low-energy Wilsonian action reducing to Einstein gravity in the IR, and evaded the question with wishful thinking that “deformed special relativity” would somehow enforce renormalizability. If someone has a true alternative and can sensibly answer basic questions about how it overcomes long-standing problems, people will notice and take interest.

  • Kea

    A nice topical post, Sean. I agree that good alternatives need to be built before people should take them seriously. How long will that take? Who knows?

  • Santo D’Agostino

    Aaron,

    Yes, hype implies disingenuousness to me, too. I’ve been involved in (and observed on blogs) plenty of arguments involving string supporters that were loaded with hype. For example, certain string supporters will not admit that the current state of string theory does not allow one single prediction to be made. Despite this complete lack of experimental support, the most lavish claims are made about string theory. That I would call hype.

    Of course, I am not suggesting that you personally engage in hyping the theory, Aaron. I find your comments to be quite reasonable.

    I also agree that other ideas are hyped, but none more than string theory. And this brings me to Steuard, who asks what string theorists ought to do differently. No, I don’t want you to stop doing string theory. No, I don’t want you to stop communicating with the public. But please have some perspective when communicating with the public.

    Rather than oversell string theory, as is often done, this is a wonderful opportunity to let the public in on how science develops. Bend over backwards to let the public know that this is a theory in development , and that there is no experimental support yet, so that it is extremely tentative. Emphasize that the foundations of the theory are not well-established, but that we are groping around in the dark, trying to find fruitful ideas. Let the public know about some of the most difficult unsolved problems that are currently occupying researchers, don’t just try to impress them with higher-dimensional razzle-dazzle. Let them know how murky and difficult is the task of theory-creation, and they might catch the excitement of science too.

  • Chris W.

    From the post:

    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 [emphasis added] that keeps people optimistic that string theory is on the right track.

    Sean,

    Could you explain more fully why the appearance of this rich structure—the AdS/CFT correspondence—is taken as an indication that string theory is on the right track? What reasons do we have, independent of string theory itself, to suppose that this rich structure is of physical, and not just mathematical, significance? Certainly it indicates that field theory can be recast (with certain caveats) in a very different form, but what does this really mean for physics?

  • http://blogs.discovermagazine.com/cosmicvariance/joanne/ JoAnne

    Arun & Bizarre: you bet! I’ve been completely snowed under the past few months and somehwat neglecting my blogging duties. However, this summer is looking better and I will do a series of posts on the current excitement in particle phenomenology.

  • anonymous

    Let me propose two completely compatible statements:

    1) String theory is the most promising route for unifying gravity with other fundamental forces.
    2) Trying to unify gravity with other fundamental forces is NOT the most useful way for most particle theorists to spend their time, since the lack of experimental predictions, massive extrapolation in energy, and top-down approach impede real progress.

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    Steuard,

    “Why do we need popular science books dedicated (or half-dedicated) not to sharing some exciting new idea but rather to cutting one down?”

    String theory is not an “exciting new idea”, it’s one that has been around for nearly 40 years, and for the last 22 years has completely dominated particle theory and consumed much if not most of the resources dedicated to the subject. It’s long past time for an honest evaluation of what results have been achieved by all this work, and what the prospects are for future progress.

    “Has anyone written a popular science book that’s mostly about why, say, technicolor is wrong? Or about why the resonant valence bond model of high Tc superconductivity is wrong? What makes string theory such a unique target for this sort of broad public criticism?”

    The other ideas you mention haven’t been overhyped for twenty-two years, and been the subject of an endless and ongoing flood of popular books, radio and TV programs while getting ever farther and farther away from any success or contact with the real world. The ratio of amount of effort and hype that has gone into string theory to actual progress towards its stated goal (unification of particle physics and gravity) is enormous and historically unprecedented.

    The story of what has been going on in particle theory over the last quarter century is one that deserves at least one or two books that approach it in some other fashion than through over-enthusiastic repetition of what the hopes for string theory have been, books that acknowledge that these hopes haven’t worked out and examine why. John Baez is right that one important thing that my book (and Lee’s, I gather) do is to lay out in detail what the scientific argument is that string theory-based unification hasn’t worked and most likely can’t work. It’s a complicated subject, not suited to a summary in a blog comment. I look forward to discussions about it with any string theorists willing to actually read what I have to say, rather than to just complain about the fact that I’ve chosen to say something they don’t want to hear.

  • http://math.ucr.edu/home/baez/ John Baez

    Jacques Distler writes:


    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.

    The first of your posts is dated September 1st, 2005. By chance, it was the day before, August 31st, that I wrote an issue of This Week’s Finds where I said I was sick of thinking about quantum gravity. So, that’s my excuse for not joining that discussion. But, thanks for tackling some of the big issues.

    I’m still sick of thinking about quantum gravity. Someday someone will figure it out, but not me.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Chris W. — What I said was that it “keeps people optimistic,” which I think is accurate. It’s not just that the theory can be written in various different forms; it’s that those various forms are reminiscent in interesting ways of the real world. The bad news about string theory is the lack of detailed confrontation with experiment; the good news is that, even without such help, we’ve still learned a remarkable amount about the theory (and about ordinary field theory).

    Admittedly, it could very well be all just an accident, and the fact that N=4 super Yang-Mills is dual to a ten-dimensional theory of gravity could have nothing to do with the fact that there is gravity in our real world. But string theory could have simply gotten stuck in the 70′s after people realized that it predicted a massless spin-2 graviton, and it very definitely hasn’t. People keep discovering new and unanticipated features of the theory, which is taken as a clue that it might be on the right track. It would be a shame, in some sense, if all that tantalizing structure were there, so obviously related to things we observe in nature (gravity, gauge theories, etc), and yet it all just be an accident. Clues are no substitute for hard evidence, of course, so we’ll have to keep plugging away.

  • hackticus

    Re: the lack of respect for phenomenologists among string theorists. I’ve known alot of string theorists, and one belief that I have found almost universal is that if phenomenology ever becomes “interesting” again, they (the big-brained theorists) will be able to jump right in, thank their smaller-brained phenomenologist friends for keeping the bench warm, and start cleaning up in the phenomenology business. Admit it! I’m talking to you Shamit! Personally, I think they’re fooling themselves.

  • Aaron Bergman

    How does one get on these free book distribution lists, anyways? I’d be happy to say something about either book, but I can’t see myself shelling out 27 bucks a pop for the things.

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    By chance, it was the day before, August 31st, that I wrote an issue of This Week’s Finds where I said I was sick of thinking about quantum gravity. So, that’s my excuse for not joining that discussion.

    I totally respect your being tired of thinking about quantum gravity, just as I respect those, like Howard, who believe that thinking about quantum gravity was waste of time from the ‘git go.

    In fact, were string theory not providing striking insights about a diverse range of other things, I would seriously wonder whether so many people should be working on a niche subject like quantum gravity.

    But, thanks for tackling some of the big issues.

    Hmmm. Thanks.

    Doesn’t seem to have had a noticeable impact on the blogospheric food fight (coming soon in paperback!). But at least I can say that I tried.

  • http://blogs.discovermagazine.com/cosmicvariance/joanne/ JoAnne

    Hackticus: Indeed, they have not kept such thoughts secret. However, they will be watching the fun from the sidelines!

  • anonymous

    as MoveOn says, about 20% of hep-ph is about speculative models that sometimes try mimicking stringy physics. In my opinion this kind of activity is not more interesting than counting the entropy of black holes. However, we expect that the speculative sector of hep-ph will become very interesting after LHC starts.

    To make just one example of the remaining 80%, the twistor tecniques proposed by Witten turned out to be slower than less celebrated teniques that QCD experts had developed for doing collider computations in the real world.

  • Lee Smolin

    Dear Sean,

    The argument you address is not the main argument in my book, but if I may I will address it on the terms you raise.

    Given your argument that string theory is worth doing because it is, in the considered judgment of a large number of smart people, thought to be promising, would you extend that to other research programs that large numbers of other smart people have decided, in their considered judgment, also hold promise? Given that there are a number of smart people who work on different approaches to quantum gravity and unification it becomes a question of how resources are to be divided up. How would you do it?

    There are roughly 400-500 theorists at recent string meetings and 150 theorists at recent meetings on background independent approaches to quantum gravity. By your argument, shouldn’t positions and resources be distributed in roughly these proportions? If these are the proportions by which smart, knowledgeable people divide their interests, but 95 % of resources go to one direction, isn’t there a problem analogous to an investment bubble in which “the market” is behaving irrationally? Or do you believe that the 150 smart people are not as smart as the 400, or that their considered judgment is not as worthy?

    The people who make investment decisions analogous to questions of which research programs to support, such as venture capitalists, do not believe in a simple “let the market decide” philosophy by which investments go only to the largest and most successful companies. If you talk with very successful venture capitalists and investment bankers you will find that they have quite sophisticated views and strategies about these kinds of questions. Among the things they talk about are distributing risk over a portfolio. They do not put all the investment in Microsoft, even if that is currently the most successful company, they make sure that there are healthy resources for competitors and start ups. Successful investment managers make sure to distribute their risks and investments because they acknowledge they are not able to predict the future. This is not because of moral principles, but because this has been shown to maximize rate of return. Even if you favor Microsoft you fund competitors and startups because this is in the long run essential for the success of Microsoft. Should we in science not also distribute our resources invested in very risky areas over the range of views that very smart, knowledge people have come to, so as to maximize the rate of progress in science?

    The argument, at the level you discuss, is not about whether string theory is one area worth supporting. It is about whether string theory should be the only approach to quantum gravity that should be supported, while very smart people who have thought just as carefully about the problem and come to the conclusion that other directions are more promising are starved of resources. If the situation were reversed I would for sure be arguing to distribute the risks and fund some of those starving string theorists-as indeed I do to support people in the non-string quantum gravity world who are not working on LQG. The reason is not to be nice, it is because in a situation where we don’t know the answer the rational thing to do is to distribute the risk and invest in the whole range of ideas that smart, thoughtful people have invented.

    Lee

  • Part-time Quantum Gravity Theorist

    Lee,

    You have clarified perhaps the principal criticism that yourself and Peter have of the present situation with string theory. Your figures, 400, 150, 95% – could you tell us exactly what these figures are and where you obtained their values? I think that would help focus attention onto the specific irrational market behavior that you are concerned with.

  • Lee Smolin

    PtQGT,

    The 400-500 is the attendence at the last and current string meetings. The attendence at LOOPS 05 was 150. The 95% is a guess, here is one fact: to my knowledge, apart from one position at Penn State, the last time there was an assistant professor appointed to a US research university working in a non-string approach to quantum gravity was around 1990. Most likely there have been more than 20 assistant professorships in the US given to people who work on string theory since then.

    Thanks, Lee

    ps again, this is not my principle argument.

  • http://www.canonicalscience.com Juan R.

    Aaron Bergman said:

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

    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.

    Without the risk… but I still remember string theorists claiming that LQG researchers were “taking GR too seriously” when latter claimed that string theory would be not correct (for a full quantum gravity theory) because GR was not a 2-spin over a flat static background (in despite of many Witten efforts to claim that string theory predicts gravity).

    Only after decades, string theorists changed the chip and now broadly agree that string theory is not sufficient and that loop theorists and GR comunity in general was correct. Now those basic ideas are introduced in future M-theory (which is NOT a string theory).

    i remember that also from (stringy) talks was claimed that LQG was “obviously wrong” (without proof of the claim) now we can heard to people as B. Greene claiming that LQG could be partially correct whereas we heard to people as Vafa stating that LQG if true may be part of “string” theory.

    Juan R.

    Center for CANONICAL |SCIENCE)

  • anonymous

    dear AR, while being a post-doc I wanted to learn some new topic: the main options were cosmology and string theory. Without knowing these two subjects, I had to rely on “experts”. At that time there were no dissident voices such as Peter Woit, and I chose string theory. Only after one year I realized that its lack of contact with physics is a real problem.

  • http://backreaction.blogspot.com/ B

    Sean: 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. [...] The thing is, these considered judgments are the best guide we have, even if they are not always right. [...] 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.

    Sean,

    you fail to realize how the situation in science has changed within the last decades. I totally agree with you on the build-in mechanisms that do protect science from getting completely stuck. These mechanisms however, might work better or worse. You, as many others, are talking about the individual search for truth of the single researcher. Theoretical physicist are, and have always been, driven by curiosity and the aim to understand nature, which seems to work with or without any method.

    Now we are in a situation where large groups of people are working together on research projects. They get hired to do so. Work together internationally. Produce papers in amounts that nobody can really read them all. The single researcher in his search for truth is faced with the demands of a community that he has to survive in (or drop out).

    The problem is that the ‘free market’ you praise is not protected by any means, and a community that grows larger runs in danger to loose its diversity by being heavily dominated through the most influential groups.

    Capitalism, left on its own, tends to fail on the same grounds. Monopoles lead into a dead end – Though I would say, the build-in mechanism (hopefully) eventually leads to a ‘revolution’. This, however, might take quite some effort, wastes time, and does not protect us from repeating the same mistakes again.

    Sean: 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.

    It could work much better than it currently does.

    I too would say you should read Lee’s book.

    Best, B.

    PS: btw, I noticed repeatedly that it’s quite annoying I can’t copy and paste text from the posts.

  • http://arivero.ciberpunk.net Alejandro Rivero

    Does anybody worry about the belief that any field theory is an effective theory (in the sense of being a non-fundamental approximation)? Perhaps this was the real argument driving these snart people to embrace strings. They believed in the non-fundamentality of quantum field theory (a dogma postulated already at undergraduate level) and then they were forced to reject the only theory that actually makes contact with the experiments.

  • http://backreaction.blogspot.com/ B

    MoveOn said… 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”.

    In case the last sentence was not meant as a personal attack, I apologize in advance.

    You might be interested to hear that I originally studied mathematics. Just that the maths department was broke, whereas the physics department offered me a position. So I became a nuclear physicist. Working on semi-theories like brane world models certainly was not my fist choice. Friends know that I actually worked on other stuff for some years, before I realized that would never get me anywhere, and I made my PhD about Extra Dimensional models. Which, for reasons that I found quite suspicions, were kind of interesting at this time.

    I am very grateful to the nuclear physicist for their support, and their open mindedness, despite the fact that I never really understood what a pomeron is.

    I totally agree on your criticism about the ‘production of new models’ without consistency requirements, see e.g. my post Paper Recipe. That does not mean though that everything done on the field is crap. The world is not just black and white.

    Best, B.

  • Torbjörn Larsson

    I was going to comment generally on the market of ideas that Tony and Lee sees problems in – but B scooped me. I also think that in a market analogy we naturally have some concentration and that is not a sign of problems as such. (B, I can cut and paste from posts, at least in Reply mode.) Neither are the amount of time passed nor any changes in theory. Look at evolution – I believe it took many years before the correct among Darwins ideas were solidly validated, and they had to be subsumed with other evolutionary forces in the modern synthesis.

    Tony,
    Coming specifically back to your situation, perhaps the market analogy is that your product has been refused by the retailers before even being exposed on the shelves for regular customers. Now you are trying to sell over internet. The evaluation you ask for lies implicit in the lack of interest you seem to observe. This situation is a risk for any product, even ideas. It’s not uncommon or wrong. In short, I don’t see why the market of ideas is vacuous and not working generally and specifically for you.

  • Torbjörn Larsson

    Since it is “jump on Distler” day for some unfathomable reasion, I should take the opportunity to say that as a layman I have enjoyed Distler’s posts, including the ones he refered to.

    They, together with some of Motl’s early posts IIRC gained me a sceptical view towards the LQG and similar efforts. I don’t think he especially succeeded in dispelling the ad hoc nature that string theory initially seemed for me to have. I think it was finding a historical review on the subject that did that for me. As a layman you have to find the simplest explanations in some murky waters. :-)

  • http://arunsmusings.blogspot.com Arun

    Tobjorn Larsson wrote:

    “Neither are the amount of time passed nor any changes in theory. Look at evolution – I believe it took many years before the correct among Darwins ideas were solidly validated…”

    The refinements to evolution came from increasing accumulation of the working of organisms, including how inheritance works.

    HEP is in a different situation today. The analogy with evolution would work if Darwin lived as a hermit on the moon, unable to get off its surface, and was theorizing about what happens on earth based purely on the seasonal changes in albedo.

  • Nigel

    Peter Woit, in “Not Even Wrong” (Cape, London, p259) you write:

    “As long as the leadership of the particle theory community refuses to face up to what has happened [the failure of the superstring theory to connect to physics] and continues to train young theorists to work on a failed project, there is little likelihood of new ideas finding fertile ground in which to grow.”

    This leads to the reason why string theory can proliferate without any facts or checkable evidence behind it. Judging by Clifford Johnson’s remarks elsewhere on this blog, string theory may be almost totally decentralized.

    Edward Witten and Lisa Randall might actually make a case that they have just put forward some ideas, and that if others join their bandwaggon and follow them down into a dead end, that is unintentional. “Victory has a hundred fathers, but defeat is an orphan” – J. F. Kennedy on responsibility for the “bay of pigs” failure in 1961.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    I cleaned things up by deleting some comments that were either personal attacks or repsonses thereto. Can’t a guy get a little sleep without worrying about the internet misbehaving?

    B, I have no idea why you’re having trouble cutting and pasting — it works fine for me.

  • Taxpayer

    As a one of the taxpayers that helps financing you guys I have three remarks:

    1) At least nobody is accused of being lazy, so we are getting good value for our money. Also, we trust you that you will resolve your differences over time.

    2) I like the NBA analogy. The best part is that compared to NBA players you guys work practically for free. Of course, watching you scribble away in your notebooks is way less entertaining. And – just as those NBA players – we like our theoretical physicists to behave themselves in public. You know, the kids are watching and we don’t want them to think superior intelligence is an excuse for bad manners.

    3) Apparently, current blogging technology does not allow for hard physics (I don’t see any formulas with lots of integrals and subscripts). Therefore, physics blogs will always tend to be more about the sociological/psycohogical/historical/outreach aspects of the field.

    Now go back to your notebooks.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Lee (and B, also) — no, I don’t think that taking ratios of the number of people at meetings and dividing up the resources that way makes much sense at all.

    When we’re talking about “resources,” there are two very different main issues: grant money and jobs. Where grants are concerned, people who work at the funding agencies and serve on review panels do make an explicit effort to take into account diversity of what they are funding as well as pure intellectual merit; at least they did when I was serving on those panels. Obviously, some people will be more inclined to think that sending all the money to their own field is the best approach, but in my experience most people aren’t actually like that.

    When it comes to jobs, I don’t see a better way to do it than the present system. Individual departments make decisions about who to hire, based on their own impressions and the advice of outside experts. If you think that more of them should be hiring people in a certain field, you have to convince them that the field you have in mind is interesting, and the best way to do that is to get exciting new physics results.

    But I think both of you are overestimating the “stickiness” of one’s research specialty. String theorists are not created in specially-designed pods in the basement laboratories of other string theorists. They are just physicists who look at what is going on and decide that string theory is the most interesting thing to work on. (So it is not really like a monopoly — try as you might, you won’t convince the Microsoft corporation to switch to selling Apple software.) If you don’t agree, convince them otherwise! Get an exciting physics result that persuades people who are now working on string theory that they should switch to something else. That is the only way to ultimately make progress.

  • http://yourdailyllama.blogspot.com wolfgang

    Sean,

    I completely agree with you, except for one minor detail. Microsoft does sell software for Apple computers 8-) The free market (of ideas) works not only for physics …

  • Doug (not the Doug above)

    What is so interesting to me about this entry is that commentators such as Sean, Peter, John, Lee, Jacques, and other professionals, as familiar, if not as prominent, are participating. Imagine a blog post where these people, along with the likes of Witten, Gross, Wilzeck, t’ Hooft, Gell-Mann, Weinberg, Atiyah, Penrose, Hawking, and other influential mathematicians/theoretical physicists, were inclined to participate in the discussion. How fascinating would that be?

    If Sean, the cosmologist, were to bring together, on the web, the chief theorists of the world to discuss the fundamental physics that are the foundations of cosmology, it would have to be “news fit to print,” don’t you think? However, Sean, I think that if you are to write a well-articulated blog entry, on which more of the missing notables above cannot resist commenting, the discussion will undoubtedly have to be much more elevated. Nevertheless, just think of the possibilities! You are making blog history here, you know? How far can you take it? I hope you will give it a shot.

    I think you could even build on the momentum here, by raising the level of the present discussion, from the “stringy theorists versus the particle theorists” debate, to the discussion of “inventive science versus inductive science.” You could even quote Lee’s statement to launch the discussion:

    The argument, at the level you discuss, is not about whether string theory is one area worth supporting. It is about whether string theory should be the only approach to quantum gravity that should be supported, while very smart people who have thought just as carefully about the problem and come to the conclusion that other directions are more promising are starved of resources. If the situation were reversed I would for sure be arguing to distribute the risks and fund some of those starving string theorists-as indeed I do to support people in the non-string quantum gravity world who are not working on LQG. The reason is not to be nice, it is because in a situation where we don’t know the answer the rational thing to do is to distribute the risk and invest in the whole range of ideas that smart, thoughtful people have invented.

    Isn’t this the real strategic challenge of venture capitalists? If the strength of our scientific/academic complex is to be based on free market principles, then the innovation and creativity that stems from the brightest intellectuals makes them the most valuable assets, right? If so, then certainly the task of the government and the philanthropists may indeed be to recognize that the “rational thing to do is to distribute the risk” and cover all bets, since no one knows, which inventor is going to be phenomenally successful. But then what would be even better, I think, is to motivate intellectual venture capitalists, with their uncanny intuition for finding the winning ideas, and link them to intellectual entrepreneurs! Surely, the same free market forces that have lead to the world’s astounding development of technology will likewise prove fruitful in developing the theories that unlock the mysteries of nature, don’t you agree?

    Hmmm, this may or may not be a sound conclusion, though, depending on the chances that inventive science, as opposed to inductive science, works at all. Maybe we need to invite the world-class specialists on the philosophy of science to weigh in on this, before we place our bets. Usually, inventive science replaces inductive science, when the work of the experimenters/observers (ok, phenomenologists, grrrr!) out paces the work of theorists, and demonstrates that the past generalizations from experience are not working. Since this seems to be true in mathematics as well as physics, where the foundations of these two disciplines are so intimately and inextricably intertwined, and at the same time, inexplicable, perhaps we would be better off, if we were to seek new generalizations from experience that are derived from our ability to think and reason from first principles, instead of reaching into our fertile imaginations for those flashes of possibilities that might prove to be the key we seek.

    For instance, we might start with a new look at imaginary numbers! Ha! Imagine the audacity of such a suggestion in this day of sophisticated string theory? In one recent instance, where I barely mentioned the suggestion on Peter’s blog, he evidently deleted my comment. I don’t know why, really, and I don’t have a copy of everything I wrote to help me figure it out, but think about it a minute. How bizarre sounding is it to suggest that “the biggest, single, invention of the human mind in history,” according to Atiyah, shows up as indispensable in quantum mechanics? The suggestion that the need for such an invention may be suspect is certainly more than enough to get you labeled as a crank these days. Since Peter has more than his share of these accusations to contend with on his blog, it may be the reason why he deleted my comment, I don’t know.

    The point is, though, the suggestion is not a presentation of a crackpot invention, but a plea to the heavy weights to examine the bonafides of what may be the acceptance of the greatest crackpot invention in history. Ohh, the heresy here is palpable, but doesn’t it stand to reason that the pathology found in abstract algebra, where the so-called complex numbers, quaternions, and octonions, lose their algebraic properties, one by one, might be connected to the pathology of particle physics, where zero, the same zero at the origin of the complex plane that appears in the complexes, quaternions, and octonions, wreaks the havoc that string theory originally sought to address in physics?

    Maybe, by returning to inductive reasoning, instead of resorting to inventions of the human mind, in desperation, John might even be persuaded to take another look at quantum gravity. Especially, if in doing so, he found a way to explain why the octonions are related to the concept of dimension through Bott periodicity! But, I don’t know many venture capitalists that are likely to be willing to fund John’s intellectual ventures, do you?

  • http://www.wanyidun.com/blog_r2u Yidun

    Dear Prof. Carroll,

    I also have the problem Bee has. It seems that I can’t select or copy anything in every post. But I can do copy in the comments.
    Best,Y.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    My only guess is that you might be using Internet Explorer rather than Firefox. You can hardly blame us for that, can you?

  • http://www.anthropic-principle.ORG island

    Sean wrote:
    B, I have no idea why you’re having trouble cutting and pasting — it works fine for me.

    This really is strange… I’ve had the same problems as B in the past but now it works just fine for me too.

    Tobjorn Larsson wrote:
    I believe it took many years before the correct among Darwins ideas were solidly validated…

    I believe that Lynn Margulis and others would tell you that they still don’t have it right.

  • MoveOn

    @JoAnne:

    “Speaking of hep-ph, there is much excitement there these days with alot of stimulating model building, breathtaking tour de force higher order calculations, collider physics is energized, there is a new level of precision in lattice calculations, and new effective theories being developed to describe heavy flavor interactions. All of this work is developed under the arduous constraints of being consistent with the full global data set – I can tell you that is not trivial. All of this work is also developed knowing that it will be tested and proved right or wrong soon. Very soon.”

    I have a high respect of phenomenologists doing hard core collider physics etc. But my aim was the model builders who view themselves as doing “alternatives” to string theory; this is mostly ad hoc non-sensical guesswork without any deeper principles – as the models (like GUT groups, brane configurations) are chosen at will, there is no real prediction these guys can make either. Namely, if the data don’t fit, they change the model by putting in more Higgs, etc. This is much much worse than string theory’s lack of predicitivity, as that is at least a highly constrained framework with some underlying principles. And “excitement” is of no value to me – we are in here for science, not for entertainment.

    So far, so good. Anybody is invited to do what it is within his/her capabilities. What bothers me is the attitude of those practitioners of “alternatives”, as they pretend to be morally on higher grounds. I don’t think there is a cheap way towards grand unification and quantum gravity, and getting into this field requires many years of hard work, but there seems to be some growing attitude that “string theory has failed” and so we ought to do “alternatives”, but without really intending/able to do any hard work (nor having any compelling, predictive, better idea than string theory). Summarily declaring failure without achievements on one’s own is a pretty cheap way to avoid going through the agony of trying to understand something and the pain of cumbersome calculations; and I find this quite arrogant.

    Yes, there is a lot of arrogance on the other side. Or how would you call the behavior of people with little or zero knowledge who produce themselves to give advice and tips to “misguided” experts? It’s sometimes so absurd that I don’t know whether to laugh or cry – see B’s remarks a while ago on how string physicists should be slowly educated to “think different”.

    And hype as well – wasn’t there even an embarassing press conference called by Lee Smolin a while ago, with the claim that certain observational data would support his theories? (As far as I know, all was within the error margins, ie, meaningless). The hype from this direction in form of books and Scientific American articles etc is at least as bad as string hype was during its high times.

    As I said, I don’t see much of unduly hype from the string physicist’s side since quite a number of years (I mean the relevant leadership here and not ppl like Kaku who is in the media business). But on the other hand,the way things are twisted and doctored and misrepresented today on the web and in form of a book is not just a strong form of (anti-)hype in its own, but a really malevolent attack on a community of people trying to do their best and come to grips with really difficult problems.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Being arrogant and dismissing the work from people in other specialties is both counterproductive and a waste of time. At the same time, complaining about the arrogance and over-hyped nature of the work from people in other specialties is likewise counterproductive and a waste of time. Do good work, and then do your best to help other people understand the good work you’ve done. Despite occasional appearances, we are all on the same side here.

  • http://backreaction.blogspot.com/ B

    Lee (and B, also) — no, I don’t think that taking ratios of the number of people at meetings and dividing up the resources that way makes much sense at all.

    I never suggested that, and I don’t think it’s a good procedure either. I can’t give you a recipe to improve the situation. What I am trying to say is that I am convinced it IS possible to support researchers in way that is more effective than it is now.

    But that won’t happen by sitting around and complaining about who wrote in which book/article/blog something insulting about someone (this does not refer to your post).

    When we’re talking about “resources,” there are two very different main issues: grant money and jobs. Where grants are concerned, people who work at the funding agencies and serve on review panels do make an explicit effort to take into account diversity of what they are funding as well as pure intellectual merit; at least they did when I was serving on those panels. Obviously, some people will be more inclined to think that sending all the money to their own field is the best approach, but in my experience most people aren’t actually like that.

    Fortunately, also in my experience most theoretical physicists are quite intelligent and reasonable people. Did you ever consider that they might just not be aware of the cause, and possible solutions, to the current problems? That’s why I say one has to analyze the situiation, and think about ways to improve it.

    Best, B.

    PS: I am using MS internet explorer and can’t mark text in the post, I can do so in the comments. I just checked with Safari, in this case both works.

    PPS: It’s sad that only MS and Apple survived. I don’t want to see physics research being devided up between strings and loops, no matter in what ratio.

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    MoveOn,

    It sure sounds to me like you’re denouncing a book you haven’t read. “a really malevolent attack on a community of people” would characterize your comments here, but the book I wrote criticizes scientific ideas, not the people working on them.

  • http://www.wanyidun.com/blog_r2u Yidun

    Dear Prof. Carroll,

    Yes I cannot. However, if any of you would claim that he/she is good at programming, I guess I would be able to blame, wouldn’t I? :-) ;-)

    Best, Y.

  • http://www.geocities.com/meopemuk Eugene Stefanovich

    Dear string theorists,

    just calm down and look at the big picture. Admit to yourself that your field (following the laws of free market) passed (or still passing) through a bubble expansion and now is about to burst. I am not talking about the bubble of ideas, theories, etc. I am talking about the bubble of public perception, hiring, and funding. There is a full analogy with the recent dot-com bubble. I know next to nothing about strings, but one doesn’t need to be an expert to see this. The dot-com bubble was created not by experts and computer programmers themselves, but by general share-consuming public and venture capitalists who where tricked by the hype. The same with string theory. The role of investing public in this case is played by hiring commitees, funding agencies, and expert panels, who often represent other fields of physics and make their decisions based on the general buzz.

    Admit that you were (understandably) overexcited in 1980′s and 1990′s when the great superstring revolutions roared. You promised “the theory of everything”, and you (in particular, Brian Greene and Michio Kaku) publicized this idea to the fullest extent. For some time you, string theorists, were able to convince the general public and panelists that yours is “the only game in town”. They trusted you and wrote you a blank check for a few decades. Now time passed and the blank check has expired (or about to expire). Please understand that these are not deeds of some evil antistringy types like Woit or Smolin. In the absence of deliverables, sooner or later the field would come to the same point even if Peter and Lee didn’t write their books and blogs. Like with the stock market, the public support of your field depends on public perception, and this perception started to change. People became tired of waiting when you deliver the promised “theory of everything”. I fully understand that majority of you, string theorists, never made such stupid claims. Yes, this is true. But it is also true that the public didn’t hear your reasonable voices on the high background of hype. You failed to stop people like Kaku (maybe you even found them convenient at that time?), and this is your fault.

    The final straw that made many people (including Woit) angry was when some of your colleagues tried to cheat and instead of promised stringy “theory of everything” they began to sell what suspiciously looks like anthropic “theory of nothing”.

    My prediction is that the string bubble will burst. Again, I am not talking about the bubble of ideas, but about the bubble of hiring and grant funding. This doesn’t mean the end of string theory. After all, many dot-com companies that survived 2000-2001 will live happily everafter. This simply means a redistribution of resources, what Lee was talking about. Of course you, string theorists, don’t like this. You would like to have the blank check for a bit longer. Who wouldn’t?

    Please understand that Peter and Lee are not your enemies, they are just messengers of the inevitable change. Please appreciate the fact that the message was delivered early and you have some time to make a graceful exit out of this situation. Don’t shoot the messengers.

  • adam

    It’s all a bit fuzzy, isn’t it? How would you guys quantify returns on the investment in string theory research? Presumably there has to be a point where funding ramps down unless [something] even if, say, quantum gravity isn’t better explained by some other approach or even that there isn’t a more promising approach (that might be claiming to solve the problem if only it got some more money). Maybe quantum gravity’s time isn’t now.

  • Haelfix

    Just to chime in. Jacques Distlers series of posts are in my opinion the only plausible and reasonable starting point for a sensible discussion of the merits of different approaches to QG.

    You *have* to refute or circumvent that logic in order to be taken seriously, b/c as I see it, they are fundamental and there is simply no way around them. Incidentally they are stated in other equivalent forms in several other places (including famous textbooks on quantum gravity)

    That these ideas are obvious to people versed in particle physics, but maybe less so to a GR oriented crowd is irrelevant. It is what it is.

    Physics isn’t a laundry list of pseudo political top ten ideas from x field versus y field. It is about what you *cant* do, rather than what you can.

  • http://christinedantas.blogspot.com/ Christine Dantas

    Peter Woit wrote:

    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.

    Bully? :) (Ok, Webster helped).

    Well, I have put the posts back yesterday. There were several reasons why I removed them in the first place, LM being just one of them. It doesn’t matter. I do have a lot of other concerns.

    Very good post by Sean Carroll and interesting subsequent discussion.

    Best wishes,
    Christine

  • http://quasar9.blogspot.com/ QUASAR9

    Haelfix,
    I though physics was about what can IS hence IS.
    And ‘theoretical’ physics of what maybe IS or IS not.
    Hence you have more than one: maybe IS and IS nots.
    Just like there IS/are more than one (view) of Utopia.
    But I agree with the rest of your premise, that the laws of physics are ‘known’ as ARE, only until someone shows otherwise – by arguing a point or concept, or theory. Q

  • http://eskesthai.blogspot.com/2006/04/what-good-string-theorist-should-know.html Plato

    An Introduction to String Theoryby Steuard Jensen.


    But by and large, string theorists understand that some sort of testable experimental predictions are necessary in the long run for the theory to be fully accepted as good science.

    There have been enough cautionary perspectives offered here to let everyone “believe and know,” the necessary requirements on the issue of string theory?

    It is the mantra of sorts, that resonates through all of science, does it not?

    Why the “backlash,” is one I’m wondering about too?

    Yidun:

    From my humble viewpoint, however, a theoretical physicist who works for his own dream should not be afraid of criticism, public or private, as longs as those criticisms are scientifically rational but not emotional, because they are healthy for our scientific air at all.

    Stuard. Hope you haven’t been scared away from the conversation. I know I needed to hear the position of others as well, as those who have listed their opinions time and time again here.

    Maybe we can hear more of the feelings(there are consequences to the constant reverberations) of those who wonder also about working within the field of strings? What all this has done to your perspectives about continuing to work in this area in the future?

    While John tells Jacque that he had gotten tired of quantum gravity, I wonder, if one can ever leave it?:)

  • http://www.valdostamuseum.org/hamsmith/ Tony Smith

    Torbjorn Larsson said, about my complaint about not having any forum in which to get an evaluation/criticism of my physics model:
    “… The evaluation you ask for lies implicit in the lack of interest you seem to observe. …”.

    No, the evaluation for which I ask is not the silent treatment (plus abuse).
    The evaluation for which I ask is substantive evaluation of my model in some detail.

    Tony Smith
    http://www.valdostamuseum.org/hamsmith/

    I agree that such “lack of interest” is an indication that physicists do not want to evaluate my model ,
    however,
    such

    This situation is a risk for any product, even ideas. It’s not uncommon or wrong. In short, I don’t see why the market of ideas is vacuous and not working generally and specifically for you.

    The evaluation you ask for lies implicit in the lack of interest you seem to observe

  • http://www.valdostamuseum.org/hamsmith/ Tony Smith

    My apologies for the confusing-looking typo-messed-up postscript to my previous post. I failed to delete some material quoted from Torbjorn Larsson’s comment to which I was replying. The intent of my postscript was:

    I agree that such “lack of interest” is an indication that physicists do not want to evaluate my model,
    however, as I said above, it is not the type of evaluation that I “ask for”, nor is it an indication of that the world of physics is now a well-functioning free market of ideas.

    Tony Smith
    http://www.valdostamuseum.org/hamsmith/

  • Eric Weinstein

    There is no ‘String Theory Backlash’. In order to understand why this is the case, let me continue where Lee left off.

    What is being seriously discussed is how to properly evaluate and diversify imbalances in the portfolio of approaches to advancing fundamental physics beyond the Standard Model and General Relativity.

    That’s it. Since I discuss these matters with both Peter and Lee frequently, I believe I can say that I know them both to be focused on constructively answering the question above. Obviously, neither of them thinks that the allocation to String Theory should be taken to anything approaching zero. What earns them spirited criticism is that they are bold enough to ask whether it should be farther away from one.

    How exactly for some that got to be a crime against science is an issue I have yet to wrap my head around. But since basic research is very much a ‘public good’, the string theory supporters would do well to realize that this is not merely an analogy to a portfolio. The federally and state supported portion of theoretical physics is not only a portfolio but one held by the public rather and advised by the expert community.

    Where this story gets peculiar is that a dangerous economic fantasy appears to have developed within the community of String Theorists. In the most absurd version of this fantasy, only those who are currently funded to work on String related projects are competent to decide the percentage allocation of resources to the String program within fundamental physics.

    It is hard to know what to make of this in the ‘marketplace’ of ideas as this has no analog in finance. A portfolio manager is an expert agent who is expected to deliver on the terms in which she or he has attracted (less knowledgeable) investors. That is the basis of what constitutes a fiduciary duty under the law and a ‘principal-agent problem’ in economics. As such responsible fund managers neither request nor expect allocations without:

    A) External auditing by outsiders with strictly inferior knowledge of the investments.
    B) Complementary allocations to other (preferably uncorrelated) speculative investments.
    C) Timely progress reports based on the terms of the investment.

    The String enterprise has attracted critics precisely because it has been rather timid when it comes to self-criticism. Imagine what Jaques or Lubos could do to best Peter if they really put their minds to it. What a vote of confidence that would be in the string enterprise, to reassure those without expert knowledge that string theorists were their own harshest critics.

    So let me challenge the String Theorists to help those investors with deep concern about their investment in fundamental physics:

    A) Which independent experts who are not working on string related work are competent to review your percentage allocation and suggest whether it should be higher or lower? How can you help us get around the problem of String theorists commenting positively on themselves and negatively on those who are less informed?
    B) What allocations would you suggest for the other programs? LQG? For new programs by younger and less-established physicists and mathematicians? For non quantum-gravity, non-SUSY, extensions of the Standard Model?
    C) Can you review the original terms under which the current allocations were made and give us a progress report highlighting any situation in which expectations and performance were significantly mismatched?

    In summary, the so-called backlash is actually limited to a nonsensical view of resource allocation which keeps the marketplace of ideas from being fully efficient. That is an economic backlash, not a physical one.

    If string theorists wish to keep or even boost their percentage allocation, there is likely no better way than to start aggressive self-critiquing and stop talking about what ‘smart people’ believe when what you mean is ‘string people’.

    It’s been 20+ years since the cancellation result which is plenty of time in even the most difficult of subjects for outsiders to observe a speculative program’s performance and benchmark it against expectations.

    Hopefully,

    Eric

  • Nigel

    Torbjorn Larsson said, about my complaint about not having any forum in which to get an evaluation/criticism of my physics model:
    “… The evaluation you ask for lies implicit in the lack of interest you seem to observe. …”.

    No, the evaluation for which I ask is not the silent treatment (plus abuse).
    The evaluation for which I ask is substantive evaluation of my model in some detail.

    Tony Smith
    http://www.valdostamuseum.org/hamsmith/

    Tony, this is the problem caused by mainstream speculation: the groupthink which asserts one speculative system without any empirical evidence for it, is the same groupthink which is not interested in alternatives.

    The reason speculative M-theory based stuff – instead of your 26 dimensional string theory work – is taken seriously is because of the doctrine “might is right”. It doesn’t make one dot of difference whether you predict things and M-theory doesn’t.

    The people following M-theory are doing so because they believe so many people can’t be all wrong. It’s religion.

  • Lee Smolin

    Hi,

    Thanks to Sean and everyone for this discussion. Eric said most things better than I could so let me just comment where necessary:

    To Moveon: “And hype as well – wasn’t there even an embarrassing press conference called by Lee Smolin a while ago, with the claim that certain observational data would support his theories?”

    I have never in my life called a press conference or sent out a press release. I’d be grateful to know where you got this piece of mis-information.

    What I have done is tried to communicate, in technical papers as well as public talks and essays work by phenomenologists that shows that results of Auger, GLAST and other planned experiments may be able to distinguish Lorentz invariance, lorentz symmetry breaking and deformations of Poincare invariance from each other at Planck scales. I have also written one paper that argued on heuristic and semi-classical grounds that LQG should predict the third option, but I have been clear that there is rigorous support for this only in results on 2+1 gravity.

    To Sean, “Get an exciting physics result that persuades people who are now working on string theory that they should switch to something else.”

    Of course I agree and spend most of my time doing this. But there is a rather high barrier of communication to cross because it remains the case that many string theorists simply are ignorant about other approaches. A very prominent string theorists recently said to me, “Oh, is there a path integral approach to loop quantum gravity?” showing that this very good scientist has missed the main results and directions of the field the last ten years. At his renowned institution, as in several others I visited recently I gave the only talk they have had about non-string approaches to quantum gravity for at least the last 5-10 years. This is compounded by the fact that, once again, there are no talks about alternative approaches at the major annual string meeting. (In contrast to the fact that at LQG meetings we always invite people to report on alternatives, including string theory.)

    So I insist, there are exciting, substantial results in non-string approaches to quantum gravity that, with a few exceptions, many string theorists and high energy theorists remain ignorant about. But why not try an experiment? Invite some of the leading people to give talks next year-I’d be happy to give you a list. I am willing to bet that at least some of your colleagues will be surprised, impressed and interested.

    As to what to do, some proposals are very simple and I discussed them already in my Physics Today Essay. For example, develop an ethic and expectation that if a department or agency invests heavily on one of several rival research programs aimed at resolving a key issue, it also invests in the others. Aim to create groups composed of people working on rival approaches rather than all on the same approach, because this leads to better work and faster progress by everyone. Alternatively, aim to hire the best person working on a particular problem, without regard to research program, and weigh originality and intellectual independence heavily in the evaluation of quality.

    Thanks,

    Lee

  • Thomas Larsson

    Haelfix #82:
    Just to chime in. Jacques Distlers series of posts are in my opinion the only plausible and reasonable starting point for a sensible discussion of the merits of different approaches to QG.

    The problem is that when somebody comes up with a solid scientific argument, string theorists suddenly lose interest. I once pointed out to Lee Smolin here, an infinite-dimensional constraint algebra generically acquires anomalies. Lubos evidently appreciated this observation, since he used the literal quote here (Lubos was of course unaware who the original source was, otherwise he would have repeated his usual “gauge symmetries are a redundacy of the description, you idiot” rant). Some string theorists have independently made essentially the same claim, e.g. Urs Schreiber and the authors of hep-th/0501114, in section 6.1.

    However, my point with this statement was that in any putative theory of 4D quantum gravity, the constraint algebra (the 4-diffeomorphism algebra or the physically equivalent Dirac algebra) must exhibit anomalies, except perhaps for exceptional values like D=26. Whereas string theorists generally seem to agree with me as long as the argument can be used to discredit LQG, they completely lose interest when I point out that string theory does not allow for diff anomalies neither (nor does field theory proper btw).

    For a discussion of why, and which kind of, gauge symmetries must admit anomalies, and a sketch how observer-dependent anomalies arise, see math-ph/0603024.

  • Thomas Larsson

    theory does not allow for diff anomalies neither

    in 4D.

  • D R Lunsford

    The many things in physics that are demonstrably correct all have in common that, in the end, they just “feel” right. This is the aesthetic judgment that makes a good physicist, just as a good ear makes for a good composer, an eye for line and color a good painter, etc. Nothing that is true in physics ever “feels” wrong.

    String theory is wrong first of all because it is monstrously ugly. Nothing with such a form could possibly have anything to do with the real world. Its hideous form originates in the arbitrary substitution of one type of source term (point particles) by another. Clearly point particles don’t work – in fact the entire structure of field equations with source terms is what needs to be fixed. The ugliness of string theory comes from the instant realization that one has not only failed to introduce anything really new, one has taken the old flaws and covered them with cheap makeup.

    I don’t know why this judgment is so lacking in current researchers. It has nothing to do with being smart – we’re all technically smart enough to do whatever is required to make progress. What is missing is what people like Dirac and Feynman had, a “fine seinse for physical realities” (Pauli) that leads to the right question. Pauli said of Dirac “he finished his argument before it was started” (prediction of antimatter).

    The thing that is missing in science is physical intuition. Until that is restored to a prominent role, no progress is possible. I think the stringers chase their chimera so vigorously because to admit defeat means admitting they lack the one thing you can’t do without, and can’t be taught – good intuition.

    -drl

  • http://eskesthai.blogspot.com/2006/04/what-good-string-theorist-should-know.html Plato

    I have always appreciate the synoptic evaluations Three Roads had offered the public, as a state of the nation address, to which it served to get everyone up to date with what was happening in research on quantum gravity.

    There have been enough cautionary perspectives offered here to let everyone “believe and know,” the necessary requirements on the issue of string theory?

    It seems that what can happen in one place(alienation, no acquiesence to model evaluation) is not likely to happen in another?

    While one is being careful to direct society, and speak about the public interest, then it can in a sense become the “same operation,” while defending what one thought a persecution in one area, a “resulting action” in another?

    So you look for signs of this? Just to be “careful” this is not the case. If this is “directing away” from the issues, then what went wrong with how “we defend our positions” in a public way?

    I like leaders of science who debate, and who shall these be? If the arguments are not persuasive, then has the status changed?

    Porfolio distributions, I had always thought are based on percentages of returns and the risk? So you assign monies accordingly to the amount of risk you want to take?

    Such “evalutions in the industry” are common from what have seen from scientists like JoAnne or John Ellis when it comes time to asssess the direction scientists are going? Assign “money” from the public’s interest?

    Is this assessment not correct? That “a body” can control where the public interest are not upheld?

    I alway appreciated Perimeters “basis of developement,” and the careful attention this institution has for inviting all to share diverse perspectives. I believe all universites are respective of this way as well?

    John Baez-Week 222:

    The second most exciting thing at Loops ’05, in my biased opinion, was the work of John Barrett, Laurent Freidel, Karim Noui and others on “matter without matter” in 3d quantum gravity. Simply by carving a Feynman-diagram-shaped hole in 3d spacetime and doing quantum gravity on the spacetime that’s left over, you get a good theory of quantum gravity coupled to matter! You can even take the limit as Newton’s gravitational constant goes to zero and get ordinary quantum field theory on flat spacetime!

    John Barrett of course, may have another way to assess quantum gravity?:) I am sure people are not ignornant of these “ways” as long as they are brought out there to the blogosphere for perspective?

  • http://eskesthai.blogspot.com/2006/04/what-good-string-theorist-should-know.html Plato
  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Eric and Lee, thanks for your comments. Very briefly now, as I have to rush off–

    1. I think it would be great if string theorists had a few talks on alternative approaches at their meetings. In fact, I’d be happy to see physicists in general be more open to listening to work slightly outside their specific fields of research. As a member of the scientific organizing committee for the last couple of triennial GR meetings, I’ve done my best to convince people that it would be good to have (for example) talks on both cosmology and string theory. With some success, although against considerable resistance.

    2. The world where string theorists get to decide how much money string theory gets sounds like a bad idea, but doesn’t sound at all like the world we live in. If I look at the department chairs of big universities, a vanishingly small percentage of them are string theorists. Likewise for program officers at NSF and DOE. Where are all these string theory mandarins controlling their own purse strings?

    3. Which leads me to reiterate once again my point: people are not “string theorists” (or whatever) by nature, but by choice. Departments don’t invite speakers, and funding agencies don’t allocate grants, and universities don’t hire faculty, on the basis of advice from a cabal of powerful string theorists. You can affect all of these processes by getting results that actually do excite people — you can even get people who have been working on string theory to switch to doing something else. That’s what happened with string theory itself, and that’s what will have to happen for any particular alternative to become popular.

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    Eric Weinstein wrote:

    So let me challenge the String Theorists to help those investors with deep concern about their investment in fundamental physics…

    Do the measures you suggest apply to other research activities, or just to string theory?

    Do you see a broad flaw in the existing review process used by the NSF, the DOE and other funding agencies? Or is string theory somehow a special case of a funding anomaly that needs to be dealt with on an ad-hoc basis?

    Second, why do you think that “non quantum-gravity, non-SUSY, extensions of the Standard Model” are being under-funded at the moment? (Relatively! In absolute terms, everyone is under-funded these days.) Seems to me that’s an area that is receiving — perfectly appropriately — a lot of attention and support these days.

    Thomas Larsson wrote:

    Whereas string theorists generally seem to agree with me as long as the argument can be used to discredit LQG, they completely lose interest when I point out that string theory does not allow for diff anomalies neither (nor does field theory proper btw).

    Considering the amount of time of time I’ve spent discussing your ideas with you in various fora over the years, “lose interest” is not an accurate characterization. “Think you’re wrong (and given arguments why I think that)” would be more accurate.

    But, since there’s already a long list of people in this comment thread complaining “My great idea is being ignored/suppressed by the String Theory Cabal!” you’ll understand if I decline to pursue that particular discussion further here.

  • http://www.anthropic-principle.ORG island

    Danny Lundsford said:
    The thing that is missing in science is physical intuition. Until that is restored to a prominent role, no progress is possible.

    That ended the day that uncertainty became a eh, “mechanism” for causality. Then space began expanding faster than light, and now people don’t even know what intuitive physics looks like when they see it!

    Feel the collective hmmmmmm… er, duh… *scratch head*:

    http://www.lns.cornell.edu/spr/2006-03/msg0073465.html
    http://www.lns.cornell.edu/spr/2005-06/msg0069755.html
    http://www.lns.cornell.edu/spr/2006-02/msg0073320.html

    Maybe people will finally start to wake up after the great quantum gravity crash of 2016?

    And don’t even get me started on willful ignorance…

  • http://electrogravity.blogspot.com/ Science

    Island,

    Neither the equations of quantum mechanics nor Alain Aspects experiments disprove causality proper or prove Copenhagen philosophy/politics/religion. So please don’t throw that around here.

    Dr Thomas Love has proved that the entanglement philosophy is just a statement of the mathematical discontinuity between the time-dependent and time-independent Schroedinger wave equations when a measurement is taken. There’s no evidence for metaphysical wave function collapse in either the authority of Niels Bohr, the Solvay Congress of 1927, or Alain Aspect’s determination that the polarization of photons emitted in opposite directions by an electron correlate when measured metres apart.

    Accept that Copenhagen quantum mechanics is speculative. Don’t build it up as a pet religion. The uncertainty principle in the Dirac sea has a perfectly causal explanation: on small distance scales, particles get randomly accelerated/decelerated/deflected by the virtual particles of the spacetime vacuum. This is like Brownian motion. On large scales, the interactions cancel out. If so, then photon polarizations correlate not because of metaphysical “wavefunction entanglement” but because the uncertainty principle doesn’t apply to measurements on light speed bosons, and only to massive fermions which are still there after you actually detect them.

  • Thomas Larsson

    Jacques Distler:

    AFAIK, you have never claimed that one could exploit the fact that the free string is 2D gravity to learn something about 4D QG. Others have. It is undeniable that Lubos used my literal argument to punch Lee.

    The detailed argument can be found in my paper, which is quite able to stand on its own.

  • http://www.anthropic-principle.ORG island

    Thanks Science, and I understand the application of the Schroedinger wave equations the same way that you’ve graciously explained it, but I was referring to stuff like, Hartle-Hawking, in context with these kinds of widely accepted assumptions that aren’t *really* open to review, even when given new physics…

    I apologize for any disrespect that may have come from anything that I may have failed to properly convey.

    My reference to the Dirac Sea is about a whole nother way of doing QG, that doesn’t look too much like the current “attempts”… but it doesn’t conflict with relativity and it does appear to be renormalizable if you don’t mind “Large Numbers”.

  • http://theory.uchicago.edu/~sjensen/research/StringIntro/ Steuard

    Dear Yidun,

    You said:

    Yes, you may not need those public science books that are against string theory. However, the whole society needs them, the society needs different voices.

    I absolutely agree that society needs to hear from the full range of scientific thought. I don’t find anything at all uncomfortable about popular books about alternatives to string theory. It’s just the notion of popular books that seem to be (in large part) about string theory but against it that seems weird to me somehow.

    If popularizations of string theory often misrepresented the status of the theory by saying “These ideas are definitely true” then I’d be more sympathetic. But my experience has been that string theorists almost always use the standard tentative language of science when presenting their work to the public. Their sin (and mine, I’ll freely admit) seems to be simply that while saying “we don’t know if this is true”, we’re still smiling and have an eager, excited light in our eyes. Maybe we should be even more forceful about the lack of experimental evidence, but we’re certainly not distorting our own level of hope and enthusiasm.

    For those who want to counter string theory’s “hype”, I feel like the best bet would be to dilute it, not to fight it head on. Get the public excited about other approaches to quantum gravity directly! Why spend lots of time arguing that string theory isn’t the right approach when you could spend that time explaining why something else is?

    From my humble viewpoint, however, a theoretical physicist who works for his own dream should not be afraid of criticism, public or private, as longs as those criticisms are scientifically rational but not emotional, because they are healthy for our scientific air at all.

    Agreed. I think that I and string theorists in general welcome that criticism. So if anyone out there has a no-go theorem for string theory or new arguments about why it isn’t worth spending time on, I hope that they get them peer reviewed and published as soon as possible. Thus far, though, it seems like most string theorists (from old experts to young folks like me) haven’t been scientifically convinced to give up on the field yet.

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    Steuard,

    The problem with string theory isn’t the lack of experimental evidence, it’s the lack of any predictions about any experiments, and, worse than that, the lack of any plausible idea of how one is ever going to get such a prediction, despite more than 20 years of trying. In my experience, string theorists very rarely publicly acknowledge this situation, or explain what the source of these problems is.

    ” the notion of popular books that seem to be (in large part) about string theory but against it that seems weird to me somehow”

    Given that there are serious problems with making string theory unification work that are well-known to the experts whose existence is being ignored by those hyping string theory to the public, what should one do about this? A referee would properly reject a submitted technical paper about this on the grounds that these problems are known to the experts, so such a paper would not be a scientific criticism. But non-experts with an interest in the subject deserve an explanation of the problems. What should one do in this circumstance? Perhaps write a detailed serious book in which a couple chapters out of 19 would be devoted to laying these things out clearly?

    I strongly disagree with your idea that the answer to overhyping string theory is to overhype other ideas. The respect that the public has for science is based on the fact that scientists have been able to sort out what is true about the world and what isn’t. If we decide that upholding standard scientific norms about this is less important than generating enthusiasm for what we do, we will ultimately destroy our credibility and turn science into science fiction, a subject which lots of people are enthusiastic about, but is very different indeed.

  • http://theory.uchicago.edu/~sjensen/research/StringIntro/ Steuard

    Dear Santo D’Agostino,

    I asked what string detractors felt string theorists should do differently, and you replied:

    Bend over backwards to let the public know that this is a theory in development , and that there is no experimental support yet, so that it is extremely tentative. Emphasize that the foundations of the theory are not well-established, but that we are groping around in the dark, trying to find fruitful ideas. Let the public know about some of the most difficult unsolved problems that are currently occupying researchers, don’t just try to impress them with higher-dimensional razzle-dazzle.

    The thing is, I feel like we already do all that, at least within reason. As I indicated before, you can’t expect us to have a disclaimer on every single slide of our talks. And a talk about the painstaking process of science simply won’t capture the public imagination the way that a talk about a single cool idea can. The challenge is to find a way of talking about cool ideas while still giving an accurate picture of the status of the science along the way. (Reel them in with exciting ideas, and slip in as much training in the scientific method as you can.) It’s not that hard: the search for fruitful ideas can be pretty cool itself. But not, in my opinion, cool enough to carry a whole public lecture.

    But that’s a challenge for all scientists, not just string theorists, and I’m not convinced that string theorists are particularly worse at conveying their understanding of the tentativeness of their ideas than the others. The main difference that I see between string theory and other fields in this respect is that there is a notable community of other physicists who seem to think that the string theorists’ judgement of the status of their own work is incorrect.

    Unfortunately, I have no clear idea how that disparity arose, or what to do about it. But I am not willing to believe that it’s the result of greedy string theorists trying to pump up their funding by misrepresenting the progress of their field: that is entirely inconsistent with my experience. And I’m awfully hesitant to believe that it’s because string theorists are engaging in groupthink (or that they fear unemployment if they speak out against the field). As others have said, there are plenty of other cool subjects in physics available for anyone who thinks string theory is off base (some of which would be quite easy to shift to gradually). It’s hard for me to believe that a substantial number of people feel “trapped” into supporting string theory.

  • http://electrogravity.blogspot.com/ Science

    Steuard,

    Everyone is trapped into supporting string theory if they want to get published, or even on arxiv. If you get suppressed for having an “alternative to currently accepted [string] theory” (Stanley Brown, PRL editor, in email to me), that’s equivalent to be trapped into supporting string theory.

    When you point out that there isn’t a proper theory there at all unlike your work, they give you an abusive rant about their personal problems in life or whatever, and when you point out they are just bitter, you just get get them saying the same thing back to you. They just act like kids and hurl abuse. You can’t answer back, or they say you are being censored for being rude.

  • http://wanyidun.com/blog_r2u Yidun

    Dear Steuard,

    Thanks for your reply!
    The fact is that I haven’t really seen any physicist or mathematician who is totally against string theory, I mean the theory per se, or against anyone who does the theory. They are just trying their best to criticize objectively the shortcomings of the theory based on their understanding, though they might not be completely right. None of them is persuading people from doing the theory. Physicists outside the field and the general public need both positive and negative views on the theory before it is shown precisely to be correct. Moreover, almost no string theorist would like to do so, we thus need other people to do it.
    I am doing loop quantum gravity, I would not feel any uncomfortable on any rational criticism on LQG. And I think that there have been many such criticisms already. However, in contrast to those who criticize string theory, there exist at least several string theorists who extremely dislike any other alternative to quantum gravity; not only in their minds but also in their writing to the public, ST is the only way (Do you really think this is physically right at the moment?)and all others are definitely wrong that are worth no concern. I don’t want to come back to this point anymore, since I don’t really care.
    I do think people doing either ST or LQG, or any other approach should work hard to improve their own work and advertise their own work. At least in my case, I will try my best. You should have seen that apart from arguing the necesity of criticism I didn’t say anything against ST or any other. I’ve taken string courses, attended string summer schools and read interesting string papers , because I think keeping my mind open will never be bad. My supervisor is also happy with this, since he is such a prominent open-minded physicist.
    By the way, I have read your nice website and is fascinated by your intriguing introductory lecture to ST. I am actually inspired by it to make one for LQG and put it on my blog in the near future.

    Thanks,
    Y.

  • http://theory.uchicago.edu/~sjensen/research/StringIntro/ Steuard

    Dear Peter,

    I asked, “Why do we need popular science books dedicated (or half-dedicated) not to sharing some exciting new idea but rather to cutting one down?” You replied:

    String theory is not an “exciting new idea”, it’s one that has been around for nearly 40 years, and for the last 22 years has completely dominated particle theory…

    Rather than spending time defending my use of the word “new”, I’ll go ahead and retract it. But the central point of my question still stands: What is the goal of a popular science book (half-)dedicated to debunking a theory (rather than simply building excitement for alternate ideas as well)? Is the fear simply that broad public interest in string theory is “corrupting the youth” (so the next generation of physicists will only want to do strings)?

    It’s long past time for an honest evaluation of what results have been achieved by all this work, and what the prospects are for future progress.

    Perhaps so; periodic evaluation of scientific programs is a good thing. But that sounds like the sort of thing to discuss in a review article, or at a major scientific conference, or in NSF policy forums. It’s not entirely clear to me how a book aimed at the general public is the best place for it.

    I do understand your point that there should be some sort of correction if the public has mistakenly gotten the impression that string theory is established scientific “fact” or that there are no major outstanding problems with it. But do they actually have that impression? Or do they just think that string theory is a nifty idea if it turns out to be true?

    “Has anyone written a popular science book that’s mostly about why, say, technicolor is wrong? Or about why the resonant valence bond model of high Tc superconductivity is wrong? What makes string theory such a unique target for this sort of broad public criticism?”

    The other ideas you mention haven’t been overhyped for twenty-two years, and been the subject of an endless and ongoing flood of popular books, radio and TV programs while getting ever farther and farther away from any success or contact with the real world.

    Could you be a little more clear about what you mean by “overhyped”? How would you distinguish “overhyping” from “standard public outreach”? Who (specifically) is doing the overhyping? It sounds like you feel that string theorists should be doing something differently, but I don’t see that you’ve addressed the questions about that from my original post. Like any good scientists, we’re going to share our excitement about our work with the public, and I have yet to see a popular presentation of string theory that doesn’t acknowledge that it has no immediate path to make contact with experiment.

    What I’d really like are some specifics. What do you want me as a string theorist to do differently? I already tell people that we have no idea how to test string theory (yet), and that we might be a little nuts for even attempting this sort of unification today. I tell them in no uncertain terms that the theory could easily still fall flat on its face. But I (like most string theorists) remain cautiously optimistic about its long-term chances, and I make no secret of that (nor of my excitement for the field). Given that I have not (yet) accepted your scientific criticisms of the theory as spelling doom for the field, how would you like to see my approach change?

    I look forward to discussions about it with any string theorists willing to actually read what I have to say, rather than to just complain about the fact that I’ve chosen to say something they don’t want to hear.

    That’s a bit below the belt, isn’t it?

    I strongly disagree with your idea that the answer to overhyping string theory is to overhype other ideas.

    Perhaps related to my previously stated confusion about your term “overhype”, it sounds like you and I have a fundamental difference of opinion as to the proper way for scientists to communicate with the general public. My own hope is that by encouraging a broader public interest in science, public understanding of science (both its potential and its limitations) will increase as well. To make that happen, I feel that we must replace the broad perception that “science is hard and boring” with something closer to “science is exciting (and maybe even risky)”.

    On the other hand, my impression is that you would argue that the public perception of science will suffer if scientists publicize too many ideas that are still tentative. As you said,

    The respect that the public has for science is based on the fact that scientists have been able to sort out what is true about the world and what isn’t.

    I conclude that you would say that scientists should limit their public statements to what we’re pretty sure is “truth” to avoid eroding public confidence in our work entirely.

    If that is an accurate understanding of your point, then I should start by saying that I do sympathize with your concern. There’s already been erosion of public confidence of this sort in areas like nutrition. (“Oh, so this week science says eggs are good for you? I don’t buy it: they’ll just flip flop again next month.”) But I don’t think that we can avoid the problem by tightening our standards on public statements indefinitely: the more our reputation rests on “we make no mistakes”, the harder we’ll fall when we inevitably fail to meet that standard.

    Better, to my mind, is doing our best to help the public understand how science actually works and to teach them to be discerning consumers of scientific information. I don’t see how to do that if we focus our outreach primarily on firmly established results. The only approach that I can see being effective is to discuss the full range of ideas, from well-established core principles through tentatively established theories and all the way out to speculative new proposals. And that has the side benefit of allowing us to talk at least a bit about the things that we find most exciting.

  • http://countiblis.blogspot.com Count Iblis

    Alejandro#61:

    Does anybody worry about the belief that any field theory is an effective theory (in the sense of being a non-fundamental approximation)? Perhaps this was the real argument driving these snart people to embrace strings. They believed in the non-fundamentality of quantum field theory (a dogma postulated already at undergraduate level) and then they were forced to reject the only theory that actually makes contact with the experiments.

    Assuming that QFT is not fundamental, you can also argue that many of the arguments for string theory are not valid arguments at all. If you think of QFT as the low energy remnant of some fundamental theory then you naturally end up with some renormalizable theory. Renormalizability is linked to various symmetries. So, we cannot use our intuitions gained from experience in dealing with QFT and extrapolate that to write down the fundamental theory.

    The lesson from history is that it is best to focus on things that are problematic for the known physics. But extrapolating familiar concepts to ”fix” these problems often leads to the wrong solutions, like e.g. the Aether in the 19-th century.

  • http://www.DensityMatrix.com Carl Brannen

    Doug (not the Doug above) writes:

    For instance, we might start with a new look at imaginary numbers! Ha! Imagine the audacity of such a suggestion in this day of sophisticated string theory?

    This comment cuts to the heart of quantum mechanics, the assumption of splitting to a Hilbert space. I think that the way to address it is with Schwinger’s measurement algebra. See, for example, LP Horwitz, 1997 hep-th/9702080

    Another way of putting this is to note that it is possible to define QM completely from a formalism based on density matrices. One can make all the calculations one could need by using density matrices only, with no references to spinors. But one can then produce the spinors by pretending a special density matrix exists, call it |0> == |a>

  • http://www.pieterkok.com/index.html PK

    Science: “entanglement philosophy”, as you call it, has provable macroscopic consequences such as mathematically secure cryptography and the existence of an efficient factorization algorithm. In your comment, you seem to want to deny the objective existence of entanglement (you call it “metaphysical”), but the fact that it is a well-defined and in some cases (i.e., two-qubit entanglement) quantifyable concept with unique observable (computational) consequences refutes this perspective.

    Second, you seem to think that entanglement implies a violation of causality. However, if by causality you mean signalling faster than the speed of light this is not the case. Entanglement cannot be used to signal faster than light because of the no-cloning theorem: an unknown quantum state cannot be copied perfectly. In fact, non-relativistic quantum theory fits very tightly with a maximum signalling speed, due to its probabilistic nature.

    Third, when you talk about the Dirac sea, you seem to think that the uncertainty arises due to imperfect knowledge of the system (Brownian motion is a classical phenomenon). This is called a hidden variable theory, and was explicitly ruled out by Bell’s formulation of his famous inequaliies.

    Finally, the uncertainty principle is a statement about the fundamental accuracy with which two non-commuting observables can be measured. The two observables corresponding to linear and circular polarization do not commute, and therefore define an uncertainty relation. Your argument that this does not apply to photons because they do not exist after detection is not correct: In principle there exist so-called Quantum Non-Demolition measurements that do not destroy the photon (sorry, no Wikipedia link available). Using such QND detectors, the statistics of the uncertainty relation constructed above can be retrieved. A QND measurement of a microwave photon was demonstrated experimentally by Haroche’s group in Paris in 1990. My point is that the uncertainty principle is part of the Hilbert space structure of quantum mechanics, and applies to everything.

  • http://www.pieterkok.com/index.html PK

    For some reason the link to hidden variable theories and Bell inequalities was broken in my previous comment.

  • Part Time Quantum Gravity Theorist

    Quantum gravity is a hard problem. All of the approaches to it at the moment are speculative. At the same time, bright young physicists are told that their purpose in life is to solve the problem of quantum gravity; that’s where the glory is. So a large number of young physicists want to try to work on quantum gravity when they get to the graduate level. The university system requires that a graduate student be able to make concrete progress on a well-defined problem which can be verified by the faculty and outside reviewers.

    String theory is so vast that, for the foreseeable future, there will be areas where small amounts of progress – suitable for a PhD thesis – will be possible. I have no doubt that a large part of string theory’s success in achieving dominance is due to its compatibility with the university system. It may be that progress in some other area – for example, the foundations of quantum mechanics – is what will be needed to have a breakthrough in quantum gravity, but you can’t advise graduate students to work on that, because they will think very hard for five years and have nothing to show for it at the end, except perhaps a religious dedication to their favorite interpretation of quantum mechanics.

    Sean makes the point that those who allocate funding and jobs are intelligent people, capable of making their own decisions based on their understanding of how promising each research area is. This is largely true, and it would obviously be a mistake to impose anything like “affirmative action” for alternative research projects. However, there is still a legitimate question of whether the people allocating resources or jobs are vulnerable to groupthink. No doubt the knee-jerk reaction of many physicists will be to insist that physicists are immune to groupthink, due to their perfect minds. But recall that a person who is completely rational will give some weight to the consensus of the group, and will sometimes go along with the group’s perception rather than his own. This means that groupthink can cause even perfectly rational individuals to collectively make a mistake which none of them would have made on their own.

    The question is whether groupthink is in any way responsible for the current situation. Look specifically at the statement that string theory is, by far, the best hope for a theory of quantum gravity. Obviously, deciding which approach is the best hope is a judgment call, and we will usually defer to the experts on this. The question is *not* whether the statement “string theory is the approach most likely to succeed in producing a usable theory of quantum gravity” is true. The question is whether the perception of its truth is influenced by acquiescence to the better judgment of the group. String theory can be completely true, and it may still be the case that its dominance is helped by groupthink.

    Another question is whether there is a community of string theorists at all, with a common interest in furthering “the cause” of string theory. Furthering the cause may mean promoting public perception of string theory, trying to influence political decision-makers, or trying explicitly to ensure that jobs preferentially go to those who are supportive of the string theory cause, and to deny jobs, credibility or attention to those who criticize the theory. Furthering the cause does not mean researching string theory, but rather trying to improve the support that string theory receives from universities, the public and the government. I think it is unnecessary for me to point to specific individuals or actions to make the case that there is a string theory community in precisely this sense.

    Given that there is such a community, then there is a conflict of interest whenever a member of the string theory community is asked to allocate resources on behalf of their physics department. They have two loyalties – to the physics department and to the string theory cause. Now, it will be insisted that this conflict of interest causes no problems – that string theorists are perfectly capable of putting aside their dedication to the cause when it comes to departmental business. The astute individual will observe that everybody who has a conflict of interest says the same thing.

    A more sober objection would be that astronomers, condensed-matter physicists and so on are in exactly the same situation, and that it is unfair to single out string theorists in this regard. However, there is a difference. String theory is different because it is a conjecture. Condensed matter physicists may work on particular conjectures, but different ones will work on different conjectures. String theorists, on the other hand, all work on the same conjecture (or pretty much – you might count braneworld as a different conjecture, but it isn’t really so different). What binds them together as a community is that they all devote their time and effort to considering the consequences of the string conjecture being true. This is a situation ripe for fostering groupthink. (Recall that even individuals who behave completely rationally will fall prey to groupthink; being clever does not make you immune.) If you wanted to make groupthink more likely, you would get the string theorists to talk mostly to each other, and to consider themselves more intelligent than non-string theorists. This is already the case – string theorists only talk to other string theorists, and they consider themselves more intelligent than non-string theorists (like you, Sean).

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    At the same time, bright young physicists are told that their purpose in life is to solve the problem of quantum gravity; that’s where the glory is.

    Is that what they’re told nowadays?

    Back when I was in graduate school (as related in the post Sean linked to above), I was told, quite firmly, that thinking about quantum gravity was an utter waste of time.

    string theorists only talk to other string theorists, and they consider themselves more intelligent than non-string theorists (like you, Sean).

    The string theorists I know talk seriously to a broad range of people, from nuclear physicists to number theorists (see the posts I linked to above).

    As to whether they think themselves smarter than their interlocutors, that’s the prerogative of youth, isn’t it? Not to worry, even if they do, that misapprehension will quickly fade.

  • Eric Weinstein

    Jaques Distler Wrote:

    Do the measures you suggest apply to other research activities, or just to string theory?

    Hi Jaques. Of course they apply broadly to investments in general well beyond research. I’m surprised and sorry that didn’t come through more clearly.

    I suppose if you don’t see String theorists as behaving markedly differently from other researchers, it doesn’t make sense why String theory would be singled out. Is it possible that the community doesn’t see itself as behaving unusually for a scientific discipline? I guess I never even considered the idea that the community sees itself as open and welcoming to outsiders, critics and new ideas from outside. If that is the case, we could clear up a lot of confusion because the (false?)impression many outsiders have is that leaders in the string community generally believe only the community can evaluate the community.

    Having recently spent part of a week at Perimeter as an outsider outsider, I simply didn’t think of admonishing other research groups like LQG to be more self-critical or open to outside judgment. At least in my case, they really reached out in terms of self-critique and seemed to have the hang of the research diversification issue down cold. In fact, my input was solicited much more than I had something informed to contribute as I was invited there to lecture on Economics and Gauge theory. If I ever run across a single String research group out there which is comparably adventurous and open to outsiders with new ideas, I can assure you I will hold them up as a model.

    Eric

  • Thomas Larsson

    Steuard #102:

    If popularizations of string theory often misrepresented the status of the theory by saying “These ideas are definitely true” then I’d be more sympathetic. But my experience has been that string theorists almost always use the standard tentative language of science when presenting their work to the public. Their sin (and mine, I’ll freely admit) seems to be simply that while saying “we don’t know if this is true”, we’re still smiling and have an eager, excited light in our eyes.

    While you don’t hear much string theory hype from serious people these days, the string theory bandwagon was largely created by Witten’s massive marketing between the two string revolutions (“Theory of everything”. “Magic and mystery”. “21st century mathematics which by chance landed in the 20th century”. “Every advanced civilation discovers QM, GR, SUSY, and eventually string theory”. “Good wrong ideas are very scarce, and no idea as magnificent as string theory has ever been wrong”.) Just look in John Horgan’s book, where EW implies that not believing in string theory is like thinking that the sky has pink polka dots on it. Positively Lubosian.

    Witten’s hype seemed to stop around 1998, though. By coincidence, this is also the year that the CC was found to be positive, something that EW described as the most disturbing fact he had ever learned. I think that the problem is not so much the 120 or 63 orders of magnitude, but rather the sign – it is difficult to use holographic ideas since de Sitter space lacks the right kind of asymptopia to put holographic data on. Perhaps most revealing was his comment from the floor during Strings 2005, where he said something like QM was murky in dS space.

    Also, after 20 years Witten now seems to have stopped claiming that string theory makes one prediction, SUSY (and one postdiction, gravity), perhaps because the Tevatron should have seen something weird in their dataset by now, had SUSY been there in the first place.

  • Part-time Quantum Gravity Theorist

    At the same time, bright young physicists are told that their purpose in life is to solve the problem of quantum gravity; that’s where the glory is.

    Is that what they’re told nowadays?

    Back when I was in graduate school (as related in the post Sean linked to above), I was told, quite firmly, that thinking about quantum gravity was an utter waste of time.

    Part of the effect of string theory’s success has been to change people’s minds about that to some extent. It’s now possible to have a career studying quantum gravity, as we can all see from the many examples of string theorists with tenure and on tenure-tracks. If it wasn’t for strings, perhaps those alternatives would have even less support than they do now; maybe they should be thanking you.

    string theorists only talk to other string theorists, and they consider themselves more intelligent than non-string theorists (like you, Sean).

    The string theorists I know talk seriously to a broad range of people, from nuclear physicists to number theorists (see the posts I linked to above).

    That’s a good start. Perhaps if they can convince their colleagues to do the same then the other physicists in the physics departments will stop commenting to each other about how arrogant and narcissistic the string theorists are. I believe there have been blog entries here at cosmicvariance.com on the subject; I’m quite sure that this isn’t a figment of my imagination.

    As to whether they think themselves smarter than their interlocutors, that’s the prerogative of youth, isn’t it? Not to worry, even if they do, that misapprehension will quickly fade.

    They think they are smarter than the people who *aren’t* their interlocutors. Of course, they will discover by experience that they are no smarter, on average, than the people in the physics department who they talk to. But these are kids who have been doing well in exams their whole life, always top of the class. Their self-respect is derived, to a large extent, from their perception of themselves as intelligent, because this is what has set them apart from their peers and brought them success in life. Now they are members of a group, a group of people famed for being intelligent. But they are no longer the smartest person around. Suddenly their intelligence is average. Self-respect is no longer based on how much more intelligent they are than their peers; it is based on how much more intelligent their group is compared to everybody else.

    By the way, I hear you’re a string theorist. “You must be very intelligent.” Even the nuclear physicists will say it. Probably not the number theorists, though. They’re not impressed by that.

  • krishna

    Prof Carroll,

    “But I think both of you are overestimating the “stickiness” of one’s research specialty. String theorists are not created in specially-designed pods in the basement laboratories of other string theorists. They are just physicists who look at what is going on and decide that string theory is the most interesting thing to work on. (So it is not really like a monopoly — try as you might, you won’t convince the Microsoft corporation to switch to selling Apple software.) If you don’t agree, convince them otherwise! Get an exciting physics result that persuades people who are now working on string theory that they should switch to something else. That is the only way to ultimately make progress.”

    This would be true if students are hired without regard or bias to their possible, likely choice of research areas. In my experience, students are not hired in such fashion. A department where high energy physics is dominated by string theorists (e.g Princeton in the 90′s) will hire grad students who may already be inclined to study string theory, and most of these hired students will eventually study string theory if only because the string theorists can pay them. Ultimately, the funding allocations determine the number of people graduating in a field. So I think the concern about allocation of resources is justified even in relation to individual departmental hiring. If a critical mass of people are trained in a discipline and invest years of effort into research, it is reasonable to believe that they would be subject to groupthink, if only because they are human, and would be unwilling to be particularly objective about their area of work. It is a myth that physicists (or any type of scientists) make objective judgements independent of their personal investments of time and labor.

    Steuard,
    I am not a high energy physicist, and I tend to agree with some that String theory is more visible in the lay media than most other fields of physics, at least judging from the number of articles in the NYT. I think that this may be of concern to the string community itself in the intermediate run. The public is a fickle beast which can turn hostile if not kept fed regularly. Personally, from what little I have studied of string theory, I can understand its attraction to a theorist.

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    Steuart,

    No, I don’t think that pointing out that you’re publicly attacking a book you haven’t read, seemingly just because you’ve heard it contains sections critical of a research program you support is “below the belt”.

    If you want specific examples of hype I’m talking about, go to my blog, type “hype” in the search engine.

    I’m all in favor of people writing books for children or adults who know nothing about science designed to try and get them interested in the subject, but that’s just not the kind of book I wrote, and it’s not the only kind of “popular” science book. Personally, when I want to learn more about some area of science I’m not expert in, the last thing I want to spend my time reading is some breathless, hype-filled promotional piece full of wishful thinking about how exciting and wonderful the author’s research program is. I’d much rather read an intellectually serious book, full of accurate information carefully explained. The people who read expository “popular” books about science are not largely uninformed people who need to be convinced that science is interesting and worth doing. They’re often highly scientifically literate, and trying to learn more about a topic they’re already interested in. When I was writing I was trying to write something I would actually want to read if I knew less about the subject in question. After I was done, my main worry was that I had written something that was so arcane no one would want to read it. I’ve been very gratified to see that that doesn’t seem to be a problem.

    Recall that this book was originally slated to be published by a university press, before two string theorists exerted their influence to put a stop to that. I’ve never heard of these “NSF policy forums” where the state of string theory research is evaluated, but would be glad to speak at one. I’d also be glad to speak at Strings 200X about the problems of string theory, but this doesn’t seem to be topic the organizers of that conference series are looking for people to speak about.

    What should string theorists do? First, there’s a list of things they should stop doing: hyping ideas that haven’t worked, attacking anyone who criticizes them as a crackpot, censoring criticism, engaging in anthropic pseudo-science. More positively, instead of trying to suppress serious discussion of the problems facing the field, they should be encouraging it, and trying to understand exactly what the obstructions to progress on the string theory unification program are, and why attempts to get around them have all so far failed.

  • http://www.pieterkok.com/index.html PK

    Science: Bell showed that in local hidden variable theories we can derive Bell inequalities (which are violated in experiment). Bohmian mechanics assumes nonlocal hidden variables, and it is not ruled out by Bell’s theorem: You cannot (correctly) derive a Bell inequality in Bohmian mechanics.

    If you want to promote entanglement, may I suggest you find a UFO blog to do it on?

    I am disappointed that you do not respond to my arguments concerning the “reality” of quantum entanglement in a scientific manner.

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    Eric wrote:

    If I ever run across a single String research group out there which is comparably adventurous and open to outsiders with new ideas, I can assure you I will hold them up as a model.

    Did you … umh … talk to the string theorists at Perimeter?

    Were they unadventurous and hostile to outsiders with new ideas?

    How about the string theorists at other places you’ve visited?

    “Part Time” wrote:

    Back when I was in graduate school (as related in the post Sean linked to above), I was told, quite firmly, that thinking about quantum gravity was an utter waste of time.

    Part of the effect of string theory’s success has been to change people’s minds about that to some extent. It’s now possible to have a career studying quantum gravity, … . If it wasn’t for strings, perhaps those alternatives would have even less support than they do now; maybe they should be thanking you.

    I see.

    Yet another pernicious effect of string theory.

  • amused

    Hi Prof. Distler,

    For what it’s worth, I think it’s great that you are prepared to engage in discussion on this topic; it will help to dispel a certain perception of string theorists in some quarters.

    A few questions. (1) For a young person whose general interests lean toward formal particle theory, one consideration when choosing a research topic could be the following: There are already lots of people working on string theory/branes, some of them very smart. So the chances for a new person entering that field to make an impact and come up with something genuinely significant might not be that great. On the other hand, with all the attention on string theory, perhaps there are other topics which have not been getting the attention they deserve, and where there is good potential for making interesting and worthwhile progress. What would be your advice to someone who was thinking of working on a non-string topic after making considerations along these lines? (This might depend on your view of the particular topic. Presumably there’s no need to try to convince you of the existence of other interesting formal theory topics besides string theory, since you have already studied one such topic yourself in hep-th/9305026. For the sake of argument, let’s assume that the non-string topic the person was considering working on was equally interesting to the topic you studied there.)

    (2) How do you think such a person would fare in later job applications to formal particle theory groups? It looks like most of such groups are focussing on string theory, branes etc. Would they be at all interested in applications from people working on other formal theory topics? (In case the progress that the person in question had made on their chosen topic is relevant here, let’s assume for the sake of argument that their results were enough for them to easily win a prestigeous postdoc fellowship in open competition, e.g. a Marie Curie fellowship from the EU.)

  • amused

    sorry, hep-th/9305026 should have been hep-lat/9305026 in the preceding comment.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    As anticipated by some of the off-topic commenters, I deleted some of the off-topic comments (although perhaps not as many as I should have). Yeah, I know, censorship of non-mainstream ideas, Einstein never would have been recognized today, etc.

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    Well, first of all, let’s be realistic and acknowledge that, in coming years, the emphasis in hiring is going to be heavily tipped towards phenomenology and cosmology. People doing formal stuff (string-related or not) are going to have a harder time getting jobs.

    My advice to all graduate students is try to work on a variety of different topics. When you’re a postdoc (and have to start applying for new jobs within 15 months of arriving at your current one), it’s a lot harder to “retool” in a significant way. If you cultivated a diverse background as a graduate student, you’ll have a much easier time.

    Mike Peskin went further and used to (?) require that all his students who wanted to work on string theory publish a phenomenology paper first.

    The second thing I’d say is that shying away from a subject because it happens to be popular is not necessarily a good strategy. The whole thrust of Sean’s post is that high energy theorists tend to be a restless lot, descending on a “hot” topic, where progress can be made quickly, and then abandoning it for the next “hot” topic when progress slows.

    As a graduate student, just starting out, you’re probably a little slower to gear up, so I’d stay away from the really high-traffic lanes. But any topic worth thinking about (stringy or not) already has (or has had) smart people thinking about it. There’s no way to avoid competition, unless you want to spend your time thinking about topics so obscure or intractable that they probably aren’t worth thinking about.

    Besides, if you want your results to be noticed, it would probably help if there are some other people interested in the topic.

    Thinking about QCD at finite temperatures and densities is a very interesting (and, because of RHIC, relevant) subject. On my blog, I’ve emphasized the AdS/CFT approaches, but there is a lot of interesting other work that would appeal to someone formally-inclined.

    There’s a host of topics on the interface between mathematics and quantum field theory (too many to list, really), only some of which are stringy in nature.

    And there’s a bunch of really interesting formal work in Lattice Gauge Theory (though, I gather, some of those people have a hard time getting jobs).

    This is all off the top of my head. And, as free advice proferred over the internet, worth every penny you paid for it.

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    amused,

    I think Jacques is giving you the same, honest answer to your question

    ” It looks like most of such groups are focussing on string theory, branes etc. Would they be at all interested in applications from people working on other formal theory topics?”

    that you would get from just about any faculty member in any such group:

    No way.

    A couple years ago I tried to quantify the dominance of string theorists in US particle theory groups at elite universities. Going through the list of faculty at the highest-ranked half dozen US universities (according to US News and World Report: Berkeley, Caltech, Harvard, MIT, Princeton (including IAS) and Stanford) I found 22 particle theorists with tenure who had post-1981 Ph.Ds. Of these 18 were string theorists, 2 did brane-worlds (and don’t seem to object to being identified in the media as string theorists), one was an MSSM phenomenologist, and one did high-temperature QCD. Not a non-phenomenologist non-string theorist in the bunch. Zero. I’d be curious if anyone has more up to date data, or a wider sample size. Lee Smolin has analogous data for how often US universities have been willing to hire non-string theorist people in quantum gravity.

  • http://theory.uchicago.edu/~sjensen/research/StringIntro/ Steuard

    Dear Peter,

    You wrote:

    No, I don’t think that pointing out that you’re publicly attacking a book you haven’t read, seemingly just because you’ve heard it contains sections critical of a research program you support is “below the belt”.

    My “below the belt” comment was in reference to your assertion that I was merely “complain[ing] about the fact that [you]‘ve chosen to say something [I] don’t want to hear.” As I read that, you were essentially accusing me of sticking my head in the sand about challenges to my research field, which is a pretty nasty insult to a scientist (and, of course, untrue).

    I have been open about the fact that I haven’t read your book, and I recognize that without having done so I am very limited in the sort of comments I can reasonably make about it. If you look back at what I’ve written, you will see that I have said nothing about the detailed content of your book (or Prof. Smolin’s, for that matter). My concerns have been entirely about the general notion of a popular science book that puts a substantial fraction of its focus on debunking (or attempting to debunk) a current research area. The fact that you happen to have written such a book and that its target happens to be my own field is almost beside the point in discussing the general issue (though they were clearly involved in drawing my attention to it).

    If that is not an accurate description of your book on a very general level, then I do apologize for leaping to conclusions. But the title (Not Even Wrong, your usual take on string theory as science) and half of the subtitle (“The Failure of String Theory”) certainly give the impression that one major focus of the book is problems with string theory. And the description of the book on Amazon.com only describes it as a criticism of string theory: if that topic does not comprise a substantial fraction of the text, you might want to ask them modify their summary.

    I do appreciate your comments on the actual audience for your book: you make a good point that such an audience is looking to learn more details, not to be talked into enjoying science in the first place. I’m still not convinced that a public anti-string-theory campaign is the ideal approach (if nothing else, it feels like you’re still allowing the string theorists to define the debate), but you’ve explained why you couldn’t see any better option from your point of view, and I can respect that.

    I’d like to think that I personally have been innocent of all of the things that you say you’d like to see string theorists stop doing. From where I sit inside the field, it’s hard to imagine any string theorists that I know being truly guilty of any of them (most of the folks I work with are skeptical of anthropic arguments as well), but I am willing to believe you that there are some people out there who have done so, and I can see how frustrating that would be. I hope you’ll be careful not to lump all of us together as collectively guilty for the misbehavior of a few.

    Thanks again for taking the time to answer my questions!

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    Steuart,

    Thanks for your response, sorry if I misinterpreted your “below the belt” comment.

    I just finished arguing with the US publisher about the jacket copy on the US edition. They want it to be a forceful statement of a single idea designed to get people’s attention and stir up controversy. I’d rather it explain the much wider range of topics in the book. Unfortunately, there’s a limit to what you can do with a couple short paragraphs designed for marketing purposes, and I concentrated my efforts on just making sure that the controversial statements being made were ones I was willing to stand behind (yes, as an idea about unification, I do think string theory has failed). So, I urge people to not judge this book by its cover.

    I’ll also point out to any string theorists who want to complain about how this book is marketed that the only reason it isn’t being published by a university press, where it would likely be marketed differently, is that they stopped this from happening two years ago.

  • Lee Smolin

    Dear Amused and Jacques,

    For what its worth, anyone in the world of non-string quantum gravity would answer your questions differently from Jacques.

    “The whole thrust of Sean’s post is that high energy theorists tend to be a restless lot, descending on a “hot” topic, where progress can be made quickly, and then abandoning it for the next “hot” topic when progress slows.” (This and the quotes below from Jacques’s last post.)

    In our judgment this is why string theorists have not made more progress when faced with the major foundational issues such as the nature of space and time away from the semi-classical regime, and it is also why there are many open conjectures in string theory such as perturbative finiteness, S-duality, etc. Few think about these questions long and hard enough to get anywhere before the next “hot topic” takes everyone’s attention away.

    This was a very productive style of research when high energy theory was driven by many new experimental results but it has clearly failed over the last 30 years to go beyond the standard model.

    It is exactly for this reason that in our world we look for and reward young people who do substantial sustained work on hard problems, based on their own ideas.

    ” But any topic worth thinking about (stringy or not) already has (or has had) smart people thinking about it. There’s no way to avoid competition, unless you want to spend your time thinking about topics so obscure or intractable that they probably aren’t worth thinking about.”

    In our world there is little sense of competition because the best people young and old work on ideas and research programs of their own devising. One trades the challenges of competing to solve well defined problems in already established frameworks with the very different challenge of coming up with possible new solutions to persistently hard problems.

    “Besides, if you want your results to be noticed, it would probably help if there are some other people interested in the topic.” This is true in a community where people have little interest in original ideas. In our community the people we notice are those who surprise us with new ideas. And every year there are at least a couple of new people who get noticed for their new ideas.

    Unfortunately, as you imply, in the US the community of people who think about research in this old fashioned way is small and controls few positions, compared to those who think the style of research Jacques has described is the best way to do science.

    In science results matter, and I am willing to bet that it will become clear in the next years that the more patient, foundational and focused on fundamentals style of research is better at solving problems like quantum gravity, unification and the origin of the universe than the flashy, superficial, fashion driven style of research which succeeded so well from the 30s up to the mid-70s.

    Thanks,

    Lee

  • Belizean

    The sad thing about Jacque Distler’s career advice, which seems perfectly sound, is that it brings to mind the distinction between advancing one’s career in physics and advancing physics itself.

    Advancing your career requires you to generate papers that other physicists will find useful in generating papers. Advancing physics requires that you to produce theories that better explain observable phenomena. While these objectives overlap, they are by no means identical. Were we as obsessed with advancing physics instead of our careers, we would simply shy away from all physics disconnected from the possibility of experimental refutation. We can’t do that, because we’d starve. We would, moreover, be throwing away any chance of being tenured. [How many times have you had to suppress your gut instincts, because you knew that the potential rewards of the research direction favored by your instincts were outweighed by the risks?]

    This goes a long way toward explaining the string bubble. Irrespective of its merits, strings generated a tremendous amount of employment for physicists. External observers, mistakenly believing that physics consists of what physicists do, overestimated strings’ status a physical theory. Unwarranted hyping didn’t help matters. And the sociological phenomena well described above by Part-Time Quantum Gravity Theorist also took their toll.

    The bottom line, it seems to me, is the presence of these huge built-in incentives to careerist behavior. Until this is corrected, theoretical physics will go from bubble to bubble. And the sort of steady (data-guided) progress of the first 85 years of the 20th century will never recur. I have no idea how to fix this short of somehow making anyone with the slightest interest in physics financially and socially independent.

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    Lee paints an idyllic picture of a small community of selfless scholars, pursuing deep truths in a spirit of brotherhood and cooperation. It must be nice not to have those deep foundational thoughts sullied by considerations of how scarce resources (jobs, research funds) are to be allocated.

    But I think I’ll leave further investigation of the mores of different research communities to the sociologists (who are better trained to ferret out the true inner workings behind the stories groups tell about themselves).

    Instead, I’ll pick up on two physics points (off-topic for this blog post, but whatever…)

    …string theorists have not made more progress when faced with the major foundational issues such as the nature of space and time away from the semi-classical regime.

    I will cede to no one the deep insights that the string “duality revolution” gave into the intrinsically quantum-mechanical (“emergent”) nature of spacetime. They are far richer and surprising than anything anyone (no matter how clever) could have come up with by thinking deep foundational thoughts alone.

    there are many open conjectures in string theory such as … S-duality

    This is a beautiful example of what is known as a misplaced devotion to rigour. Proving S-duality of N=4 SYM would, first of all, require constructing the corresponding quantum theorie(s). (It is, after all, the statement that two different classical gauge theories lead to isomorphic quantum theories.)

    No one has rigourously constructed the quantum theory of any nonabelian gauge theory. Doing so for even the simplest one (“pure” N=0 YM) will win you a $1 million prize. Nevertheless, we have pretty good circumstantial evident that it exists, has a mass gap, and even have good numerical estimates of the spectrum of low-lying excitations.

    There’s also lots of circumstantial evidence for S-duality (see here for one rather striking check). It would be foolish to treat it as just another “unconfirmed conjecture.”

    It would be equally foolish to expect a young theorist to fritter away her would-be career in a vain frontal assault on proving it. (At least in the case of pure YM, she could retire on the proceeds of the Clay Math Institute prize, if she succeeded.)

    But, then I gather that Lee is working on embedding the Standard Model in the “rigourously constructed” LQG Hilbert space. Since the Hilbert space was rigourously contructed from the ‘git go, the properties of confinement and a mass gap in QCD will emerge as byproducts of his more ambitious programme.

    Lee, I look forward to sharing a good bottle of wine with you, when you collect the Clay Prize.

  • http://dftuz.unizar.es/~rivero/research Alejandro Rivero

    Iblis, in your remark

    So, we cannot use our intuitions gained from experience in dealing with QFT and extrapolate that to write down the fundamental theory.

    You summarize the reasons for the success of string theory, neglecting any input from 4dim QFT and then from experiment. And I say, this is also the cause of the failure.

    It could be that the fundamental theory happens to be a very particular QFT plus a control of the renormalisation process. It makes sense to try to reorder the fields in the Standard Model to check for other ways to look at the Lagrangian, for instance as Connes Lott model did, or more modernly deconstructed models. It even makes sense to look into Bert Schroer suggestion where a Scalar Field is forced upon QFT as a requeriment of consistence. But people looks at all these things as a “-ph” Lego thing, meaning non fundamental, just model building, because all we know, hmm, that the low energy theory is to be always an effective theory no matter how do you alter it.

  • http://www.eric-weinstein.net Eric Weinstein

    Did you … umh … talk to the string theorists at Perimeter?

    Were they unadventurous and hostile to outsiders with new ideas?

    How about the string theorists at other places you’ve visited?

    Huh? Gosh. What I wrote was:

    If I ever run across a single String research group out there which is comparably adventurous and open to outsiders with new ideas, I can assure you I will hold them up as a model.

    Where did you get ‘hostile’ or ‘unadventurous’?

    What would you imagine that I might have said that would make them hostile? I think you are not getting it Jaques.

    What I see is that other groups now acknowledging a period of prolonged failure are using it as a clue as to what needs to change and how to make the next big advance through diversification. Since I don’t hear a comparable sense of failure within Strings, it is hardly surprising that there is not comparable openness to new ways of diversifying our efforts. If it ain’t broke, why fix it after all? The most I am aware of are some pointed remarks by Dan Friedan. Further, because so much of the structure within string theory is based on delicate relationships between exceptional structures, the field has never been particularly open to outsiders who do not first become resident within it.

    This wasn’t supposed to be an insult. It’s a strategy, albeit one in which I have less confidence during every passing year, but it could be the right idea if you guys are finally on the verge of an epiphany.

    As for hostility …. umh … may I ask you to look at your deliberate use of the interjection ‘…umh…’ in your question to me above and your provocative inference from my words.

    Do I need to spell it out? It’s eerily as if you wish to explain what I am talking about in terms of openness to outsiders by offering a specimen of prickliness as an example. And since you focus on hostility to outsiders, was it not you who famously used the phrase ‘net personality’ about a Callan student who teaches at Columbia and fellow blogger when what I think you meant was ‘physicist’. Probably just an oversight of course but one you might wish to clear up before debating this point further.

    As for PI, you are suggesting an experiment which I am reluctant to run as I met nothing but gracious people while there. But if you insist…I’d hate to shrink from an instructive excercise.

    I gave the general colloquium talk of the week on a Wednesday, left on a Friday and met and talked with absolutely everyone who came to my office, invited me to a meal or otherwise showed any interest in my work or my visit. That included what I thought was a fair spectrum of people. Off the top of my head, I remember meeting Baez, Smolin, Markopoulou, Hardy, Yidun Wan, Friedel, (Steven) Weinstein, Mann and some visitors from abroad. At your suggestion, I looked as many of them as I could remember up at the PI website and was not successful in finding one of them who identified as a string theorist. That seems statistically unlikely, so I will check again when I have more time. However, I had a broad smattering of conversations on everything from foundations, to emergent models of Riemannian geometry to spin foam models to markets. I simply didn’t have comparable conversations with String theorists. I hadn’t even thought about it as a test of the hypothesis until you posted so you can infer whatever you like.

    I myself would imagine that the sample size is too small to draw conclusions.

    Since this thread is getting old, let me make a suggestion.

    We don’t know each other, and I come in peace. I enjoy your blog which I use as a resource as I am presently spending some modest portion of my free time trying to figure out ways to increase the possibilities for funding scientists (including string theorists). Why don’t you make a leap of faith and assume that the suggestions and criticisms are well intentioned? I am happy to talk privately if you ever have some constructive suggestions for how outsiders can better appreciate what is going on in Strings these days. I meant what I said about the fact that I think you could do a much better job than Peter in telling us what we should be concerned about and how we outsiders can learn to better judge Strings as a part of our common portfolio of investments in science.

    Think about it. It’s not a trap.

    Best,

    Eric

  • http://electrogravity.blogspot.com/ Science

    PK on Jun 22nd, 2006 at 8:39 am
    Science: Bell showed that in local hidden variable theories we can derive Bell inequalities (which are violated in experiment).

    This is a posting about string theory not Bell’s theory. If you want to know, Yang-Mills exchange radiation is the mechanism. You can discuss on my blog if you want. Must not go off topic of strings here.

  • Moshe Rozali

    Looking quickly above I see the discussion has moved to the familiar “how awful are string theorists, let me count the ways”. I suggest each one of us will get his portrait taken with some kittens and puppies, just to demonstrate how lovable we really are, maybe that will put this tired old topic to rest?

    More to the point, Sean made some excellent points which are simply ignored. The questions is not the correct strategy for “diversifying portfolyos” other vague analogies people may have. The question is whether the decisions are to be made by professional phycisists

  • Moshe Rozali

    (got trunctaed)… or is there a rationale for the usual decision making process to change, and if so precisely in which ways?

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    Moshe,

    This is not about “whether the decisions are to be made by professional physicists”. Right now funding decisions are made by a mix of physicists and other interested parties who control the money (NSF and DOE people, university deans and other administrators, Fred Kavli, Mike Lazaridis, Sir John Templeton, and others). What I, Lee and Eric are suggesting in various ways is not that the roles played by these decision makers should be changed, but that all of them, physicists and non-physicists, string theorists and non string theorists, should be taking into account the failure caused over the last 20 years by a policy of putting most eggs in one basket, a basket that seems to have been poorly chosen.

  • Moshe

    Peter, I have no experience with funding decisions, but personally have no objection for decisions-makers to consider all relevant facts and opinions, they probably do already. I am relieved nobody is suggesting any structural changes…

  • Aaron Bergman

    It seems to me all very easy to talk about “diversification” and the like, but a lot harder to actually implement something in practice. Where are these great other ideas that we should be funding? Finding new ideas in quantum gravity turns out to be rather difficult. Given the choice, wouldn’t a student prefer to work on something that will lend itself towards a portfolio of research to show to prospective employes? Should we instead start anointing graduate students semi-randomly and give them tenure to work on whatever they feel like? I know that Lee would prefer us all to ponder deep philosophical questions, but what happens when someone spends seven years thinking about the nature of time and ends up producing nothing?

    So, how should we allocate the money? What advice should we give to graduate students (besides to go into cosmology or phenomenology)? “Diversify” just isn’t enough of an answer.

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    Moshe,

    I’m finding it a bit difficult to believe that you and your kittens and puppies are that unaware of how resources are allocated in theoretical physics; the fact that one needs a paycheck to feed the kittens and puppies tends to make one pay at least a bit of attention to this.

    I don’t know about Lee and Eric, but my point of view is that at the moment relevant facts and opinions are not being considered by decision-makers, but if they start doing so, they will start making different decisions. One of these different decisions will be to change the incentive structure so that people are encouraged to try and do new things, not to work on an old idea that has clearly failed. Jacques Distler laid out for “amused” exactly what the incentive structure is that has led to the current failure.

  • Part Time Quantum Gravity Theorist

    Yes, Moshe, you are right. The question is whether any part of the decision-making process should change and if so in what ways.

    There are standard ways of preventing groupthink – have a look at the wikipedia entry on groupthink for details. According to the article, the intelligence community is aware of groupthink and has mechanisms in place for dealing with it, but the WMD “presumption was so strong that formalized IC mechanisms established to challenge assumptions and group think were not utilized”.

    Whenever you have people involved in a speculative endeavor (and quantum gravity is definitely one of these), there should be mechanisms in place to prevent groupthink if these are known about. I have no doubt that string theorists would recommend the use of techniques to prevent groupthink for other communities involved in speculation, like the intelligence community. However, are they able to get beyond their belief in the infallibility of their own community? Would they even admit that the string theory community is exactly the type of community where groupthink is likely to occur – since they are bound together by a commitment to a particular speculation?

    I think Sean understands the string theory community well enough to know that they will insist that there is no need to prevent groupthink – their perfect minds will protect them. We might point out that groupthink will occur even when each individual in the group is acting perfectly rationally. That implies that groupthink safeguards are necessary even when such perfectly rational geniuses are involved. The intelligence community understands this (especially now, after they’ve been taught a lesson about it). Perhaps the anthropic string theorists would agree that the “monovacuists” (as Polchinski calls them) are suffering from groupthink and perhaps the monovacuists would agree that the anthropists are suffering from groupthink. But are safeguards needed? Why no; string theorists don’t need anything like that. String theorists can’t possibly behave like a cult. Their perfect minds will protect them.

  • Moshe

    Peter, I know how money is allocated, I have no personal experience with the process. Once again, I’m all for decision makers to be as informed as possible, including reading your book and Lee’s, I was under the impression something different was being discussed.

    I know a bit more about hiring, so I am curious what you and others have in mind when they suggest to “diversify”, and how is that going to be enforced on individual departments?

  • Part Time Quantum Gravity Theorist

    So Peter, would you agree that the best advice to give to a young graduate student today, who wants to have a career studying quantum gravity, is that he should study string theory? Any other advice would be bad for his career.

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    Moshe (and Aaron),

    If the physics community as a whole develops a more realistic view of string theory, hiring committees and the people who approve their decisions are going to change the decisions they make, no one is going to have to “enforce” anything. Unfortunately I suspect that what is most likely to happen is that people won’t admit that the problem isn’t just string theory, it’s the faddish behavior that led to the way string theory was pursued, and committees will just change over to hiring in the latest faddish area of cosmology or phenomenology. What I’d really like to see is some serious analysis of what has happened over the last 20-30 years, and an acknowledgement that, lacking new experimental data, the field is in a tough spot. Ways need to be found to encourage people to try new ideas, ones that probably won’t work out, and having everyone jump on the same highly speculative idea is really no way to make progress. It’s not easy to come up with good ideas about how to do this and successfully implement them, so I’m not especially optimistic, but I strongly believe this is a discussion the field needs to be having.

    PTQGT,

    I’m not a quantum gravity theorist and not about to give advice to people who are sure that is the problem they want to work on, other than to advise them to make sure that they put the time into understanding what string theory and alternatives actually have accomplished or not accomplished, and don’t make decisions based on hype. I have no idea what this subject is going to look like 10 years from now, quite possibly string theory will be much less popular and going into it now will have been a bad career move. Under the circumstances, the thing to do might be to take the radical attitude of just not worrying about one’s career and doing what one loves.

  • Belizean

    It seems to me all very easy to talk about “diversification” and the like, but a lot harder to actually implement something in practice. Where are these great other ideas that we should be funding? Finding new ideas in quantum gravity turns out to be rather difficult. … what happens when someone spends seven years thinking about the nature of time and ends up producing nothing?

    Aaron,

    You’re assuming that research in quantum gravity must be funded at similar rates year after year irrespective of progress, even if there are no fertile ideas. When explorers find themselves at the base of a mile-high stone cliff with a sheer face, they don’t try to chisel their way through it with a teaspoon or inch their way up it with a can opener. They explore elsewhere. In so doing, they invariably find another way around.

    Just as explorers plan their treks on the basis of how much ground they can cover, funding decisions should be based on the apparent potential for better explaining observable phenomena. Had this criterion held sway 22 years ago, it would have been clear even then that funds could have been more profitably invested in other areas of physics or even other sciences.

    With this criterion in place, the case of the young physicist wasting seven years thinking about the nature of time would no longer be an issue. He’d be thinking his deep thoughts at a patent office or other such employment. Unfortunately for him, funding levels in physics would have declined in direct proportion to the decline in ideas judged likely to explain observable phenomena. Just as throwing money at K-12 education doesn’t necessarily improve it (and it can be credibly argued that it harms it), so it is with physics. A harsh and counterintuitive reality, but it does seem to be true.

  • pheno grad student

    Peter:

    I decided to follow up on your comment where you had made a count of string theory faculty a few years ago of the top universities and bring it up to date. I used slightly different criteria, including junior faculty since there really has been an enormous turnover of late(just look at the number of jobs listed on the rumor mill of late). Also since you included IAS with princeton, I thought it was only fair to include LBL with berkeley and SLAC with stanford since there is a high degree of overlap there as with the IAS. I took the top physics grad schools from US News(alphabetically ordered since they are so close to one another for the most part): Berkeley/LBL, Caltech, Chicago, Cornell, Harvard, MIT, Princeton/IAS, Stanford/SLAC, UIUC. (I didn’t go past 9 since I couldn’t find the 10th via free googling and can’t waste my money purchasing the full US news list…) The result I find is that in the high energy theory groups there are 40 active string theory profs, and 37 actve pheno profs(error bars are probably around +/- 5 depending on how often the groups web pages are updated). I find that number to be vastly different than the one you quoted from a few years ago. Granted we could be using slightly different cuts on activity level/definiton of a string theorist/definition of a phenomenologist, but I doubt the numbers would get so skewed as to get percentage wise 18/22 for strings with this counting.

    For my two cents I think this almost 50/50 setup for ph/th is a perfectly healthy distribution in theory groups as the cross fertilization in fields is very healthy, whereas with alternative QG theories there is almost no interaction with high energy pheno people due to the lack of connection they have to particle physics. Granted it is not 50/50 at each institution but the theory community is pretty small so it evens out nicely. Anyways I hope this quick count can be of some use. With all this everyone can feel free to spin these numbers any which way they want (as I am sure people will) but I just felt like putting some numbers out there…

  • Aaron Bergman

    You’re assuming that research in quantum gravity must be funded at similar rates year after year irrespective of progress, even if there are no fertile ideas.

    I am? In fact, I’d guess that right now we are seeing a transition of funding to phenomeonlogy.

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    For my two cents I think this almost 50/50 setup for ph/th is a perfectly healthy distribution in theory groups as the cross fertilization in fields is very healthy, whereas with alternative QG theories there is almost no interaction with high energy pheno people due to the lack of connection they have to particle physics.

    Re: cross-fertilization. Anyone want to count the number of papers jointly-authored between members of your cohort of 37 phenomenologists and your cohort of 40 string theorists (say, in the past 5 years)?

    I bet that number is considerably higher than a corresponding count done 10 or 15 years ago would have been. Of course jointly-authored papers isn’t the only product of cross-fertilization. But it’s certainly indicative of a trend which my subjective impression tells me is very real.

  • Part Time Quantum Gravity Theorist

    Pheno, so you agree with Peter that the number of employed quantum gravity theorists who are not string theorists is exactly zero? But you think that employing “pheno profs” makes up for this.

    Why don’t you count the janitors as well?

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    I’m sure the number of astrologers is also very small.

    Which is not to say that alternatives to string theory are like astrology. It is to bring it back to my original point, namely: whatever (im)balance of effort there may be between string theory and other approaches to quantum gravity and high energy physics, they exist because of people’s best judgments based on the scientific cases before them. And the balance can be changed in a hurry by the appearance on the scene of compelling arguments that some alternatives are actually more promising.

    If one simply wants to make the scientific case to physics departments and funding agencies (and graduate students) that string theory is over-supported and other promising approaches are under-supported, then: all power to you. Make the case, honestly and fairly, and I am suggesting that people will, for the most part, listen and judge honestly and fairly.

    If, on the other hand, one thinks that there is some non-substantive systematic bias that is distorting the balance away from what it would be on the merits, and that alternatives should be supported qua alternatives, because string theorists are narrow-minded and hegemonic and uninterested in dropping by one’s office or inviting one to their conferences, then I think you are deeply misguided.

    String theorists are made, not born, just as are the people who keep on funding them and hiring them (who, I repeat, are largely non-string-theorists). If you want to change their minds, get some good results that convince people you have an interesting alternative. Until that happens, people are going to keep pursuing the avenues they think are most promising.

  • Part Time Quantum Gravity Theorist

    Sean says:

    If one simply wants to make the scientific case to physics departments and funding agencies (and graduate students) that string theory is over-supported and other promising approaches are under-supported, then: all power to you. Make the case, honestly and fairly, and I am suggesting that people will, for the most part, listen and judge honestly and fairly.

    No matter how many times it is pointed out to Sean that even people who are acting completely rationally and honestly are still vulnerable to groupthink, he will always pretend that he is unaware of this. He will therefore always suppose that if alternatives to string theory aren’t being funded then it’s because they shouldn’t be funded.

  • Part Time Quantum Gravity Theorist

    Incidentally, Sean is preaching the infallibility of the group. He’s displaying groupthink for all to see. A textbook case.

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    Pheno, so you agree with Peter that the number of employed quantum gravity theorists who are not string theorists is exactly zero?

    In that sample of 9 high energy theory groups? Yes.

    If you’d looked in 1980 (i.e, pre-string), you would have found the same result.

    It is a recent innovation (and not an obviously healthy one) to think it plausible that any significant number of people would make a career out of attempting to quantize gravity.

    Wheeler, Feynman, and my late colleague de Wit all did many other things, beside their foundational work on quantizing gravity.

    As I said above, were string theory not useful for other things (that is, if it were “just” a theory of quantum gravity), it would be highly dubious for the above institutions to employ 4 string theorists, let alone 40.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Given my status as a famous textbook author, I should hope I would be a textbook case.

    It looks like I might disagree with Jacques, in that I think quantum gravity really is by far the best justification for doing string theory, and the other stuff is nice while not being central. But I don’t want to damage my rep as a groupthinker.

  • Anonymity Preferred

    Here is a reference point on what is happening with four grad students at my school who are interested in particle theory and/or quantum gravity. It is not a representative sample of the theory students; it just illustrates a few ways that the emphasis on string theory affects what grads study.

    The school could probably be characterized as being at the upper end of the second tier — it is a good school, but not “top ten.” The physics department is relatively small and probably more progressive in some ways than most schools, so the observations below may not be very representative. The high energy theory group, probably predictably, is weighted toward string theory, with some phenomenology. There is also good interaction with theoretical cosmology. The theorists are very competent and well known in their fields.

    The first student I don’t know personally very much, but understand he/she is quite talented and is interested in cosmology and quantum gravity. This person finds loop quantum gravity more compelling than string theory, but there is, predictably, no LQG presence at the school. My understanding is that this person has been offered an opportunity to study LQG at a respected institution elsewhere, so I expect to see one fewer talented grad student around…

    The second student is interested in working on both particle theory and quantum gravity, and thinks independently and is willing to consider less conventional approaches if they show promise. This person has seriously considered doing string theory because it is “the only game in town,” but had serious misgivings about it for conceptual reasons. He/she would be interested in looking at LQG more seriously, but as already mentioned that probably won’t happen at this university. More recently he has decided to work in the experimental group on an LHC detector while continuing to spend a fair amount of time on his own ideas; it will be interesting to see whether he ultimately remains in theory.

    The third student is currently doing string theory, and will probably do his thesis on a string topic. He always intended to do high energy theory, either string or phenomenology. He was significantly swayed by his observation that some very smart people were doing string theory, and that they were convinced they were on the right track. “That many very smart people probably aren’t all wrong.”

    The fourth student is myself. I have also wanted to do high energy theory all along, but also find gravitation very interesting. I am also interested in working on unification physics, but don’t find string theory very attractive. A very important reason is that I don’t see string theory having much interaction with experiment, and I feel strongly that physics theories must be experimentally testable; the requirement that theories be put to a practical test is the fundamental advance of science over philosophy, and empirical tests are ultimately the only way that we can have any assurance that what we believe actually corresponds to “reality.” The other main reason I find string theory unattractive is that it introduces a great deal of baggage, e.g., in the form of extra dimensions and extra particles (I have a related objection to all the new parameters introduced by supersymmetry, which is pretty much required by string theory in my understanding). This is contrary to my belief that unification should lead to simpler models with more constraints than are imposed by the theories we already have, not ones with more degrees of freedom. That may be personal taste, but that’s my taste.

    In my view, the best way to proceed toward unification is to understand the standard model better. There are already about 25 parameters to the standard model which are measured experimentally; after that, the standard model is extremely predictive to the point where no known experiments contradict its many, many predictions. Something is obviously very right with it… Still, in the spirit of understanding things better, I, like many other people, think that it should be possible to calculate at least many of those parameters with the help of a better theory. My feeling is that if we had better insight into the origin of those parameters, we would also gain better insight into what issues are important in trying to unify the standard model with gravity. I have some new (and therefore, by definition, unconventional) ideas that I think have the potential to allow calculation of some standard model parameters, and that is where I want to spend at least part of my time. Naturally, this does not mesh well with the research programs at the University… But perhaps surprisingly, the grad committee chair who is a well-known string theorist seems willing to humor me and let me spend half time working on it, at least for a year or so, depending on progress (without RA money, of course, so I’ll still be TA’ing for awhile). My circumstances are not typical in some ways, and this definitely was a factor; additionally, the final details haven’t been worked out yet, so it is not guaranteed to work out that way, although it seems likely.

    Those are a few ways that theory students with different attitudes about string theory deal with the “string is king” environment at my school. I am not trying to imply general discontent with the subject — I haven’t seen general discontent with string theory. I’m just trying to illustrate a variety of situations. One string theorist would have graduated this year, but found that finding post-doc positions for string theorists has gotten more difficult, so he is delaying graduation for a year while he keeps looking. I guess things are never easy, no matter what route one takes…

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    It looks like I might disagree with Jacques, in that I think quantum gravity really is by far the best justification for doing string theory, and the other stuff is nice while not being central.

    I actually don’t disagree. But the motivations for doing string theory are not precisely the same as the motivations for hiring string theorists.

    One of the considerations in hiring (stressed by “pheno” above) is the cross-fertilization with people working in adjoining specialties. For that, the aspects of string theory that you might consider “not central” play an important role. (And, indeed, that was “pheno”‘s point about ‘alternative QG’ theorists.)

  • Belizean

    You’re assuming that research in quantum gravity must be funded at similar rates year after year irrespective of progress, even if there are no fertile ideas.

    I am? In fact, I’d guess that right now we are seeing a transition of funding to phenomeonlogy.

    Aaron,

    The point is that if total funding for theory declines, your “diversity” problem goes away. Instead of funding an alternative, you simply fund less. If you’re funding approaches X, Y, and Z, and you decide that X is overfunded, it doesn’t mean that you must spend the funds that you cut from X on Y, Z or any other alternative.

  • http://jenniferhead.cfa.harvard.edu Jennifer

    Ah, Belizean, someone else who has dealt with NASA. I remember the Save Hubble discussions, and I was thinking that if Hubble died then maybe the Beyond Einstein program (next generation x-ray astronomy) could get its funding, but I was quickly informed that it was Hubble or nothing.

    Sean, loved the post. I think John B. put it clearly – the question is whether string theory is right or wrong. And I hope that when these two books come out there will be smart articulate string theorists discussing them in print – specifically the reasons why they think Lee and Peter’s arguments against the validity of string theory are not well-founded. Clifford wrote that nice well-written D-brane book so I’m nominating him.

    I can see why scientists continue to be excited by string theory, at least right after Maldacena’s paper in 1997 or 1998, even without understanding almost anything about strings, because the connections between the real world and strings are uncanny. It’s like if you can somehow turn an apple into an orange, there has to be some underlying connection or “sameness” between those 2 objects or why would they be able to transmute in this way? So we’ve got to figure out the concept and definition of fruit (continuing the bad simplistic analogy).

    Also I wanted to say that in the talks I’ve heard given by string theorists, Joe Polchinski when he gave a colloquium at MIT recently, Gary Horowitz back when I was at grad school (funded by shadowy billionaires, you can guess which coast), David Gross, and many more, they have been up front and not at all defensive about the state of string theory and quantum gravity. At Joe’s last talk on cosmic strings he made it very clear that connection to experiment was needed and we don’t have that. So sociologically speaking I haven’t met any dastardly creatures defending the fortress – well, that is a lie because I just remembered one, a young professor on the west coast, but he drives the string theorists nuts too so, as one of the commenters said, you shouldn’t hold everyone responsible for a few bad apples.

    I don’t know Peter, but I do know Lee from his talks and since he’s a high energy theorist I’ll definitely be reading his book. I like Peter’s website though, because whenever he mentions a paper or talk that he takes issue with it’s usually something I’m very interested in reading and unlike him I don’t have my ear to the ground, unfortunately.

    Great post and discussion, thanks…

  • Part Time Quantum Gravity Theorist

    JD says:

    One of the considerations in hiring (stressed by “pheno” above) is the cross-fertilization with people working in adjoining specialties. For that, the aspects of string theory that you might consider “not central” play an important role. (And, indeed, that was “pheno”‘s point about ‘alternative QG’ theorists.)

    True; this is another socioeconomic condition which works in string theory’s favor when it comes to establishing itself in universities. And it is a rational strategy for a university to employ since there are guaranteed benefits even if string theory does turn out to be wrong. And these are the reasons why the taxpayer or benefactor who provides the funding might insist that string theory should be funded rather than the alternatives, even if the experimental evidence favors no particular theory.

    But as somebody seems to have raised above, the question really is whether string theory is right or wrong, or even if the statement that string theory is right has any experimental consequences. And I think that I will concur with the consensus of the group Sean declared himself a member of when he said that quantum gravity is the reason why us purists think string theory worth doing.

    In addition, if universities want to encourage cross-fertilization, I think it would be great to bring the sociologists and psychologists into the theoretical physics department to see what a fantastic mental mess they’ve made.

    But anyway, Jacques, pheno, and I would appear to agree that the motivation for hiring string theorists at present isn’t just to find the theory of everything, or even quantum gravity. If it were, perhaps they could pay a few hermits to scribble nonsense in the attic. But they don’t do that; they hire string theorists.

    The answer to Lee’s question about irrational market behavior would then seem to be that the market is behaving perfectly rationally. It’s only irrational behavior if you think the goal is to find the theory of quantum gravity. Resources are being allocated right now in accordance with a set of established priorities, and solving quantum gravity is low on the list of priorities.
    So if Sean thought that string theorists have all the jobs, therefore string theory must be overwhelmingly likely, then he should change his mind. The person hiring the string theorist didn’t base his decision on how likely string theory was to be true. String theorists get hired for other reasons.

    But it’s not that simple either. Sean’s and Lee’s point of view is more idealistic – money *should* be allocated in such a way as to try to solve the problem of quantum gravity. But the point of view is widespread, and when “The Elegant Universe” is broadcast on the television, I think the idealistic view becomes even more widespread. In fact, I subscribe to this view as well – I think there should be some money set aside for quantum gravity, which will not be spent in accordance with how much it helps some other cause. That money should then be allocated in the most efficient way possible to maximise the probability of finding the answer. Perhaps the government doesn’t want to spend money this way, but some philanthropists probably would.

  • http://eskesthai.blogspot.com/2005/05/unity-of-mathematics.html Plato

    Just curious.

    Are “theoretical mathematicians” by terminology linked to the essence of what the “string theorist” is?

    I just found this paper to be helpful in this regard?

  • http://www.math.columbia.edu/~woit/wordpress Peter Woit

    pheno grad student,

    Since the point of gathering those numbers was to look at what has happened in hiring since string theory hit in 1984, I wasn’t including people whose careers got under way long before 1984. For instance, I wasn’t including Steve Adler at the IAS. Do your numbers also include older people (many of whom never did take up string theory?)

    I was also trying to quantify what had happened at the absolute top of the profession, counting those people in the positions of highest influence in the field, thus the restriction to tenured faculty and to the top institutions. Untenured junior faculty at these institutions are a mixed bag, including up and coming young people who will some day get tenure and have a lot of influence, but also often positions where tenure is unlikely, and whose status is closer to that of a senior postdoc.

    And again, one of my main points is that these jobs are divided up between string theorists and phenomenologists, with none of them at all going to people working on formal aspects of quantum field theory not related to string theory.

  • http://www.wanyidun.com Yidun

    A friend of mine who read this thread asked me to post his comment for him, because he tried and simply could not post it successfully. His name is Hongbao and here is his blog. His comment is quoted as below.

    Hongbao says:
    I would like to say more on stringer and looper.
    Here is a vivid example: One of leading Loopers Prof. Carlo Rovelli came to Beijing Normal University, Center of Chinese Gravitational physics. He gave a serie of talks on recent developments on Loop Quantum Gravity and a public lecture: introduction to Loop Quantum Gravity. In his public lecture, he demonstrated his open mind: although string theory is bascially background dependent at present, background independent formulation is under construction. Loop quantum gravity is an alternative approach to quantum gravity like string theory, thus deserves our investigation. This is a typical mind of Loopers. They prefer their own theory and viewpoint, however they still keep an open mind to any other approach to quantum gravity. But stringers seem not.

    In addition, I would like to say something about smartness.
    I do not think what smart people think on nature is always right. This of course also depends on how we define smartness. From my humble point of view, I only think those who have a good understanding of mathematics rather of physics. Accordingly, Einstein is a not a very smart guy. But Einstein gave us a fascinating picture of the reality. On the contrary, I would not believe that any smart guy such as Witten could do so.

  • http://yourdailyllama.blogspot.com wolfgang

    > Einstein is a not a very smart guy.
    I disagree strongly on this one.

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  • http://www.wanyidun.com Yidun

    Dear Wolfgang,

    I think Hongbao actually means that Einstein has great wisdom but not technical smartness. :-) Yet this is not my opinion.

    Best,
    Yidun

  • Aaron Bergman

    They prefer their own theory and viewpoint, however they still keep an open mind to any other approach to quantum gravity. But stringers seem not.

    Any number of string theorists have looked critically at LQG. That they didn’t like what they found is not evidence, in and of itself, of close-mindedness.

  • Xiaofeng

    Dear Lee (to whom this comment is addressed at the first place, but I would be interested to hear anyones thoughts),

    First of all let me thank you for your time outlining your thoughts on the social workings in quantum gravity circles in general and the LQG vs. string theory relation in particular.

    I am slightly puzzled though by this kind of comparison that assumes that from a high energy physics perspective LQG and string theory are on the same footing and hence a reasonable comparison can be made. If I understand your arguments correctly then you present both LQG and string theory as different approaches to quantum gravity and thus they share the same goal and the difference only lies in the employed methods. If it were such I would agree that a comparison could be made and the results obtained in the two fields could be confronted. However I very much believe that the comparison is not just since string theory is not only an attempt at quantum gravity (regardless of its historical roots or the intention of some of its practicioners) but also a source of numerous insights into conventional QFT (susy Yang-Mills, AdS/CFT, even lattice gauge theory). As a result even if the comparison of LQG and string theory results in some form of judgement (for the purpose of this argument it does not matter which field comes out more favourably in this comparison) in the quantum gravity arena, string theory still has a considerable advantage since it contributed to fields other than quantum gravity as well. On the other hand LQG to the best of my knowledge did not contribute substantially to other high energy physics related fields other than its intended scope, namely quantum gravity.

    Thus I am inclined to think that a judgement or comparison of both LQG and string theory can not be complete if it was limited to the field of quantum gravity.

    Best wishes,
    Xiaofeng

  • Lee Smolin

    Dear Xiaofeng,

    You speak of judgment as if the issue were to choose between LQG and string theory and one had to be sure to be fair. But the issue is not to choose between two theories as if this were a contest for a prize, it is to further the scientific understanding of nature. This means that we investigate promising leads and sooner or later abandon leads that do not lead to predictions by which they are confirmed. We have to think like detectives, not like school officials giving a prize. Moreover the basic ideas beyond string theory and LQG could both be true or both could be false, as they appear to characterize different physical regimes. This is why I personally have invested significant effort on both.

    The comparison I did make is between different styles of research carried out by two communities. The two styles existed previously in the difference between high energy theorists and relativists and it is not obvious to me why string theory was embraced by particle physics types and LQG by relativist types-LQG is an outgrowth of ideas and techniques developed to study strongly coupled quantum gauge theories while much of what string theorists actually do is solve the classical Einstein’s equations. My claim is that the relativists’ more foundational and philosophical style is more suited to solving foundational questions and indeed I think string theory would by now have been better understood had this style been adopted by those interested in it.

    No one is disputing that string theory has led to fruitful ideas and results about supersymmetric gauge theories. But this does not by itself ensure that it is a true unification because experiment may lead in other directions or it may nevertheless fail-for example, there could be no real non-perturbative formulation of the theory. (As none has ever been proposed this certainly should be considered a significant possibility.) And the fact that a theory also incorporates a hypothesis about unification means that it is more not less vulnerable to failure-because it must get more right. If such a theory makes no predictions at all by which it could be tested then it indeed fails.

    Certainly were LQG inconsistent with beyond the standard model unification it would be less likely to be true. But LQG easily incorporates most proposals for beyond the standard model unification including supersymmetry. Furthermore, there is now good evidence that a form of unification emerges from LQG and similar models, see hep-th/0603022. And there is some influence of LQG methods in Freidel’s recent work on solving QCD in 3+1: hep-th/0604185. This is not surprising because the roots of LQG are in the original ideas about loop-field duality in QCD of Migdal, Polyakov, Wilson and others. Conversely, looking back longer, the understanding of how to quantize Yang-Mills correctly came from studies of quantum gravity by deWitt, Faddeev-Poppov and others (ie for them Yang-Mills was studied as an example of a theory with some features of GR.)

    Jacques suggests that someone might earn a Clay prize by rigorously constructing quantum Yang-Mills within LQG. It will certainly not be me, but there are people working on exactly that program. The conjecture is that background independent QFTs are more likely to exist rigorously in 3+1 dimensions than Poincare invariant QFTs. After all, there is gravity in the world and, with the exception of the existence and uniqueness theorems in LQG, no one has succeeded in constructing a rigorous QFT in 3+1. Since Jacques is in favor of people jumping into hot topics to make them go faster perhaps he might want to jump into that. We would welcome his contributions.

    Thanks to everyone for the high level of the discussion here.

    Lee

  • http://golem.ph.utexas.edu/~distler/blog/ Jacques Distler

    Ah. What a breath of fresh air! Actual physics content.

    But LQG easily incorporates most proposals for beyond the standard model unification including supersymmetry.

    “Most”, but not all?

    What sorts of quantum field theories can be incorporated, and what sorts cannot?

    Jacques suggests that someone might earn a Clay prize by rigorously constructing quantum Yang-Mills within LQG. It will certainly not be me, but there are people working on exactly that program. The conjecture is that background independent QFTs are more likely to exist rigorously in 3+1 dimensions than Poincare invariant QFTs.

    In the real world, the QCD scale is 19 orders of magnitude smaller than the Planck scale (for theoretical purposes, it might as well be 1000 orders of magnitude smaller). I don’t see how coupling to quantum gravity is supposed to make any of the problems of constructing Yang-Mills theory easier.

    But I wish your colleagues the best of luck …

    with the exception of the existence and uniqueness theorems in LQG, no one has succeeded in constructing a rigorous QFT in 3+1.

    Ah, yes, the “LOST Theorem”. We really ought to have a discussion about that sometime …

  • the one intelligently designed

    Come on Sean, You know very well if a graduate student in high energy theory is working on something new or something non-stringy, she reduces her chances of getting a post-doc by 100 times. Because people who are hiring are all string theorist and are looking for these specialized skills, not general creative ability. (may be just because the technology involved is highly specialized) Such a thing does not exist in say cosmology, where new directions taken by graduate students will be rewarded.

  • http://www.behindthisworld.com/theWheel/ theOwl

    Hello to all,

    Great blog.

    The foregoing (I’ve read a nontrivial chunk, perhaps 20%), though interesting, vindicates my decision 25 years ago NOT to become a professional physicist.

    It appears possible to me that the whole field of physics is barking up the wrong tree – or perhaps simply that the “right tree” is neither cosmically large or infinitesmally small enough to be deemed worthy of a theoretical physicist’s attention.

    Maybe the “right tree” isn’t even physical. Maybe the word “physical” has outlived its usefulness in this context.

    I found myself writing on something tangentially related to this subject just a few weeks ago.

    Listen to the Moon

    Listen to the Moon

    Regards,

    theOwl

  • Xiaofeng

    Dear Lee,

    Thank you very much for your thorough reply, I’ll try to respond to the points you raised.

    You write

    “No one is disputing that string theory has led to fruitful ideas and results about supersymmetric gauge theories. But this does not by itself ensure that it is a true unification because experiment may lead in other directions or it may nevertheless fail-for example, there could be no real non-perturbative formulation of the theory.”

    and I fully agree with that. As long as experimentally relevant predictions, true description of nature is concerned (which are undoubtedly very ambitious and important goals) a theory can be right or wrong and consequently both string theory and LQG can be right or wrong on the end of the day. These ambitious experimentally relevant issues include quantum gravity, unification, physics beyond the standard model.

    However if we can afford to be less ambitious — and why should not we for a moment when we are facing difficult problems — then we may label a theory ‘good’, useful, insightful or by other generally positive adjectives along these lines based on slightly less ambitious goals, namely if it provides insight and results in other high energy physics fields. You may ask how one can quantify these results and insights if not by experimentally relevant predictions and falsifyability. To that I would respond that these results and insights are in the conceptual framework of toy models which are not directly relevant for experiment but nevertheless further our understanding of nature. As an example, very few of us would agree that the work invested in the study of 2 dimensional exactly solvable and integrable systems constitute a ‘failure’ or are useless in general just because they do not directly describe physical phenomena and produce testable predictions. They are not promoted to be experimentally relevant physical theories but they are still useful and insightful; classic examples of toy models.

    Thus I am inclined to 100% agree with you that at the moment string theory provides zero experimentally relevant predictions and thus does not stand the test of a true physical theory describing nature, however the amount of insight string theory provided for conventional QFT (of the type that can be considered toy models of the real world) already justifies the claim that string theory is ‘good’, useful and insightful and definitely not a failure. These results are a consequence of the working style, habit, attitute, etc. of the string community (including you and others of course who are not string-only but nevertheless contributed to the subject) thus this working style, habit, attitute must be credited for what it achieved. It did not produce a physical, experimatenally relevant, testable theory, true, nothing to hide there, but it did achieve important insight nevertheless which should not be overlooked.

    LQG also provided insight into other high energy physics fields some of which you mentioned in your post but these insights are also in the arena of toy models, that is LQG also failed to make testable, experimentally relevant predictions so far.

    I also understand that over-ambitious claims of some string theory practicioners can be troublesome (“theory of everything”, “unification of all forces”, “unique description of nature”), however these claims carry no weight in a scientific discussion, only the results themselves. Clearly these claims are not justified from the point of view of the actual results since string theory did not achieve anything along these ambitious lines, but the balanced response should not be a total rejection, but only a lowering of the expectations, especially if the lowered expectations are still very high. Not as high as it could idealy be, but still good enough to justify research in this direction. In this perspective I fully agree with David Gross saying “string theory can not be wrong”, since the contrary would be analogous to saying “toy models are wrong”.

    In my opinion one should resist the temptation to be cynical about this lowering of expectations and resist saying “haha, they thought they can do everything and they can do only a small portion of that” especially if that small portion is quite substantial.

    Since you say that the current question is not about a mutually exclusive choice between string theory and LQG I will not attempt to compare the toy model related results of LQG and string theory but limit myself to a conclusion keeping in mind your main argument, namely the style of research, whether a “more foundational” or some other style is desirable. The “string theory style” already showed its strength in studying toy models so I do not see a reason to abandon this style, especially if the competing style, the “more foundational style” can claim victory neither for experimentally relevant predictions nor for toy models.

    Best wishes,
    Xiaofeng

  • anon

    Jacques suggests that someone might earn a Clay prize by rigorously constructing quantum Yang-Mills within LQG. It will certainly not be me, but there are people working on exactly that program.

    – Lee Smolin

    Well mathematical rigor and physical predictions can be two different things. (Rather that someone wins a Nobel Prize for physics than a Clay Prize for math.)

    I would like to see a clear physical description of the LQG spinfoam vacuum, one that can compete with string theory in popular understanding. In a LQG for a Yang-Mills theory, the loop consists (presumably) of the cycle of gravity causing gauge boson radiation from the Higgs field giving one mass to that of another mass, and back again to the first mass? Is gauge boson radiation redshifted by cosmic expansion? Would that weaken long-range gravity without requiring a repulsive dark energy in the Lambda-CDM model? Is this a checkable prediction?

  • S

    theOwl:

    Your entire life is a gift from these physicists that seem like “barking up the wrong tree” to you.

    Try saying this to a medical physicist when you go for an MRI, an X-ray etc.

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  • http://www.anthropic-principle.ORG island

    Owl, with all due respect to John Wheeler, (which is a lot!), you’d have to be independently wealthy to think that we are here to “observe” the universe into being.

    He must’ve missed the guy working the jackhammer…

  • anonymous

    Lee writes:

    LQG is an outgrowth of ideas and techniques developed to study strongly coupled quantum gauge theories

    Funny, in studying strongly coupled quantum gauge theories, usually the first thing one would like to check is that the continuum limit exists. In other words, there should be a fixed point (perhaps Gaussian) with finitely many relevant perturbations. As I understand it, LQG has not yet demonstrated something like this for gravity.

    This is not surprising because the roots of LQG are in the original ideas about loop-field duality in QCD of Migdal, Polyakov, Wilson and others.

    Most of us would say that this loop-field duality has been fully realized, in a very deep way, by string theory. The AdS/CFT correspondence, and its generalizations, are a beautiful example of how the gauge theory can be described in terms of Wilson loops. These Wilson loops have finite thickness, which translates into a the necessit for the holographic dimension. The holographic dimension also encodes renormalization group flow. It’s a beautiful, unifying description of various ways to look at gauge theories, and it came from string theory.

    String theory also has a deep, organic connection to strongly-coupled gauge theory, whereas you seem to suggest that it is merely concerned with the perturbative realm.

  • anonymous

    Err, forgive the typos. Anyway, one might also note that Migdal was thinking about dual string theories for Yang-Mills as early as the mid-80s, if not before, and I don’t mean just the loop equations, but actual worldsheet actions. Similarly Polyakov was something of a prophetic voice in this field. It seems a bit disingenuous to claim them as the root of LQG as if this lends weight to LQG as opposed to string theory.

  • http://arunsmusings.blogspot.com Arun

    With reference to the comment that it is better to get a Nobel in physics than the Clay prize:

    It took some 2000 years to get from Euclidean geometry to non-Euclidean geometry – this following the rigorous mathematical route. But without rigor, could we have conceived of non-Euclidean geometry? It took probably a similar 2000 years or more to get from the operational daily use of real numbers to the rigorous definition by Dedekind, et al. Did we gain any insight from rigor? From intuitive practice?

    We might like to think that our mathematical imagination is fully liberated – but is it really? If this branch of physics (HEP) is indeed to be mathematical rather than experimental, can we afford to be purely rigorous? Can we afford to be purely pragmatic? The truth is that we are blind men, groping.

  • Lee Smolin

    Dear anonymous,

    The point is that while string theory is the natural realization of the gauge field-extended object duality in a background dependent context, LQG is its natural realization in a background independent context. I believe that the LOST uniqueness theorem, math-ph/0407006, gr-qc/0504147, is a precise statement of this. It says that if you want a diffeomorphism invariant quantization of a gauge theory on a manifold with no metric, in which the algebra of Wilson loops and electric flux is realized, there is a unique hilbert space to work in for each gauge group and manifold. It is the one we use in LQG.

    I really wish people would stop seeing this as an either-or competition. There are two regimes, QFT on a spacetime with a fixed metric and diffeo invariant QFT on a manifold with no metric. Shouldn’t the same powerful idea have an expression in both contexts? I am also not being disingenuous, just reporting that the work of Polyakov and Migdal, which I learned from their talks while a grad student, was a major influence on our work in LQG.

  • Cynthia

    If I am understanding Professor Smolin correctly, then I am detecting a subtle idea emerging from his comment #178 in regards to this issue of string theory backlash. More specifically, Smolin appears to be suggesting that a cozy symbiosis could possibly form between string theory and loop quantum gravity. Therefore – instead of declaring war – Smolin is proposing peace between these two opposing factions within theoretical physics. Cool idea!?!? :-)

    Best,

  • anon

    To Cynthia:

    Writing a book entitled “The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next” seems an odd sort of peace proposal…

  • Cynthia

    Aron,

    Overall, I echo your sentiment. On the surface – someone like Smolin – might be sending “black and white” messages which tend to be harsh in nature. However, on a deeper level, he might be revealing “mixed-gray” messages – as conveyed in comment#178 – which tend to soften this harsh nature.

  • http://www.behindthisworld.com/theWheel/ theOwl

    “S” says “Your entire life is a gift from these physicists that seem like “barking up the wrong tree” to you.

    Try saying this to a medical physicist when you go for an MRI, an X-ray etc.”

    S,

    Do I understand you correctly? Surely you’re not comparing X-Rays and Magnetic Resonance Imaging to String Theory? The whole point of the doctor having X-Rays and MRI is that these wonderful technologies facilitate repeatable medical observations, testable by experiment (how many ball bearings did little Howie swallow?).

  • Lee Smolin

    Dear Cynthia and anon,

    I have been making such a “peace proposal” for 20 years. Indeed, LQG developed directly out of work Louis Crane and I did in 84 & 85 to make a background independent formulation of string theory. I followed that up with so far around 18 papers exploring ways to do just that. The most recent of these is “A quantization of topological M theory”, hep-th/0503140, Nucl.Phys. B739 (2006) 169-185. My first book was devoted to the crisis of the landscape-just 6 years too early. My second book explicitly proposed that LQG and string theory were to be unified and that was what I was working on then (2001). Indeed, I never did see them as separate and have always been puzzled how anyone with a serious interest in solving quantum gravity could ignore either one.

    The response of string theorists: roughly speaking, no interest. I got one invtation to give a talk at a conference in Japan, that was essentially it. I was surprised because many leading string theorist were saying all this time that the main problem was to find a background independent formulation of string of M theory. I am not claiming to have solved this problem but I do think I have made a sustained effort to solve it and have discovered a number of useful things that might lead to its solution-if it has one. Instead of interest, the most I got from leading string theorists was lectures explaining why it was permature to attack this problem.

    My forthcoming book is not at all harsh. It is written with respect and affection towards all those working on all the different approaches. It attempts to contribute constructively to science. If someone takes my saying something positive about one approach as an attack on another, or gets emotional in response to an honest acounting of successes and failures, that is not my responsibility, it is a sign that a lot is happening here which is neither rational nor in the best interest of science.

    Thanks,

    lee

  • http://www.behindthisworld.com/theWheel/ theOwl

    Island,

    I’m unsure of whether I understand your comment. My apologies if I totally miss the point here. I suppose this comment is, in reality, respectfully directed to the larger community of physicists here at Cosmic Variance.

    I’m the guy working the jackhammer. Somebody else needed someone to work the jackhammer. They didn’t create me, but they had something to do with the causes and conditions that put this jackhammer in my hands…

    I need someone to get real about the consequences of small armies of smart physicists chasing pretty little imaginary strings at a time when the world needs practical concepts and innovative technologies to pull our collective butts out of the fire.

    Again with all due respect to John Archibald Wheeler, (“delayed choice experiment”, starting on page 334 of Wheeler’s Geons, Black Holes & Quantum Foam), I will take a chance and speculate that one might have to be a physics professor to fail to see that “Singularity” and “SuperString” are sometimes just fancy ways of avoiding saying “God”. Or perhaps of avoiding introducing conciousness into a worldview and field of intuition.

    I am obviously not a physicist. I am not an “Intelligent Design” Creationist either. But I will not take a world view represented to me as Science on Faith any sooner than I will let a Religionist impose Faith upon me from a pulpit.

    From the point of view of an intelligent lay person with some degree of physical intuition, I see physicists pointing to an opaque “Singularity” in one direction and a suspiciosly obtuse and thornily difficult “String Theory” in another direction.

    Guys and girls, it’s just not good enough.

    I’m a musician. Some composers write thornily complex scores that look expremely impressive on paper. In many instances, I do not believe they even particularly care what they sound like in performance, any more than I care what a score of mine looks like.

    Are there physicists like this?

    Again, Listen to the Moon.

  • http://www.anthropic-principle.ORG island

    Owl, I was talking about the blog post that you referenced, which is essentially Wheeler’s interpretation of the anthropic physics that perplexes everyone on all sides:

    Why do I think the discs of the Sun and the Moon appear to be the same size as seen from Earth?
    I think we create them that way. It is always now. Consciousness is the Prime Dimension. Consciousness orients itself up and down. “Down” needs a planet. We create the earth and the sky.
    We need energy and illumination. We create the sun.
    We need a water cycle. We create lots of water and a Moon to balance the Sun’s tidal pull and stabilize the oceans.
    We need an inverse square rule to govern gravitational relationships. Got it. Simplicity itself.
    How big will the Moon appear when we look at it? Physically, it doesn’t matter, so long as it functions tidally.
    Occam’s razor. We keep it as simple as possible. Collectively dreaming, we accidentally create the Sun and the Moon in such a way that their discs appear from Earth to be the same size.
    Symetrical. Pretty.
    “Listen to the Moon”

    My statement was meant to show that it is extremely arrogant to assume that we are enabled by the forces to our benefit, rather than to its benefit.

    We are here to work, not watch.

    What predominant characteristic does a flat yet expanding universe and humans have in common?

    We both have the tendency to increase entropy… *EFFICIENTLY*

    This is a conservation law.

  • anon

    Dear Lee,

    Thanks for your reply. You will not be offended if I observe that someone so identified with loop methods might be felt not to be an entirely disinterested judge of string theory. I am sure your book will be an honest accounting; my worry is whether it will be an accurate accounting. The Bushes and the Clintons can give honest accounts of each other; they may not agree though.

    More interestingly, can I ask you why you think loop methods, or more generally methods aiming to achieve manifest diffeomorphism invariance, should be useful for providing a non-perturbative definition of string theory? I am not an expert on LQG but understand its inspiration to be the manifestly covariant nature of GR.

    Diffeomorphism invariance is a classical geometric property. One of the things I like about string theory is the way it is more than just geometry: for example, the nice description of spacetime topology change through extremal transitions. The degrees of freedom that allow this to happen (branes wrapped on vanishing cycles) are not simple `modes of the metric’. Another example is that of dualities: very different backgrounds are the *same state*. There is no fundamental distinction between winding modes and KK modes; but the latter is the only obvious geometric one.

    So I don’t know what the `background-independent’ formulation of string theory is, but the background we are independent of seems to be far richer than just diffeomorphism invariance – it has at least to include different space-time topologies, be sensitive to non-geometric information and to know about all the dualities. I don’t know what this group should be, but it has to be a lot bigger than that of diffeomorphisms.

    So, why should LQG methods work? Manifest diffeomorphism invariance seems too limited if we want to describe string theory. Diffeomorphisms don’t see dualities and don’t see topology change: why are they a useful starting point for a background-independent formulation?

    Regards
    anon

  • S

    theOwl:

    “Physics” is NOT equal to String Theory. MRI DID come out of a very fancy theory of its time (and one that crackpots STILL love to trash), Quantum Mechanics.

  • Lee Smolin

    Dear Anon,

    Thanks for your question about how loop related methods might be the basis for a background independent formulation of string theory.
    As I explain carefully in my essay about background independence, diffeo invariance on a fixed differential structure is a very restricted notion of background independence. Indeed, much of spin foam models work in a more general setting, which is background independent in the sense that you mention.

    One way to see this is that quantum theory without a background reduces to the study of algebras and their representations. The systematics of this are captured by the theory of modular tensor categories. Other examples of such categories are given by manifolds and cobordisms and also categories of surfaces of various dimensions, embedded in manifolds and their cobordisms. The basis of topological quantum field theories and spin foam models are in functors that relate these cobordism categories to categories of representations of quantum groups.

    It seems natural to use the same set of mathematical ideas to capture background independent formulations of string theory and M theory. The inclusion of branes of various dimensions is straightforward. There have been ideas about how to incorporate the dualities (for example as generalized T-dualities). There are beautiful extensions in the higher category theories to study. The close relation between topological quantum field theories and gravitational theories that is revealed by this point of view seems also to extend to string and M theory.

    As to how disinterested I may or may not be, can I emphasize again that I have spent myself all together many years of work on string theory. I am very interested in it and at times I have believed deeply in it. I actually think that I have a more objective and more correct and detailed understanding of exactly what has and has not been shown in string theory than many “string theorists”-because I had myself a number of times to think carefully through which program was worth the next few years of investment of time. And I have published such assessments before- hep-th/0303185. Let me know if I have anything there factually wrong. But just to make sure I did a great deal of consulting and fact checking with the present book.

    Thanks,

    Lee

  • http://behindthisworld.com theOwl

    S.

    Y’all were able to come up with some pretty good experiments to test quantum mechanics, weren’t you?

  • http://valatan.blogspot.com bittergradstudent

    Owl:

    Yes, QM is quite well tested. General relativity is quite well tested. Don’t you find their logical inconsistency with each other a teeeeeny problem? Wouldn’t it be nice to have a logically self-consistent fundamental framework from which to see the world? One that would get rid of the singularities that you seem to not like all that much?

  • Thomas Larsson

    Since the discussion again seem to gravitate towards background independence and diffeomorphisms, let me make some trivial observations (and Jacques Distler does not need to listen).

    4-diffeos are important for GR for the same reason that conformal transformations are important in perturbative string theory: it is the correct constraint algebra (in covariant formulations, a foliation gives you the Dirac algebra). In quantum theory, we always want representations of lowest-energy type; LQG looks weird precisely because this condition is not fulfilled. The lesson from CFT is that infinite-dimensional constraint algebras generically pick up extensions – the Virasoro algebra. It was because I wanted to do the same thing for 4-diffeos and GR that I discovered the multi-dimensional generalization of the Virasoro algebra and its representation theory.

    From this POV it is obvious which ingredient both string theory and LQG are lacking: the correct quantum form of the correct constraint algebra of GR.

  • http://www.canonicalscience.com Juan R.

    Jacques Distler wrote

    Back when I was in graduate school (as related in the post Sean linked to above), I was told, quite firmly, that thinking about quantum gravity was an utter waste of time.

    Last years, young students were pursued to research in string theory. I know students doing a PhD in string theory because other research fields were -in practice- very limited to funding. I have received mails from people explaining me how abandoned physics because they were forced to do research in string theory and considering it a waste of time.

    That string theory has been sistematically overhyped in both academia and media.

    The string theorists I know talk seriously to a broad range of people, from nuclear physicists to number theorists (see the posts I linked to above).

    In what part of landscape? In real word (here) most of string theorists are just a kind of minimalist cult. Other physicists (experimental, Loop, QM, …) reported this many ways and in many sites.

    “There is today a disconnect in the world of physics. Let me put it bluntly. There are physicists, and there are string theorists. Of course the string theorists are physicists, but the string theorists in general will not attend lectures on experimental physics. They will not be terribly concerned about the results of experiments. They will talk to one another.”

    and “[...] they don’t listen to us.”

    Glashow (The Nobel).

    Juan R.

    Center for CANONICAL |SCIENCE)

  • http://eskesthai.blogspot.com/2006/06/continuing-with-foundation.html Plato

    While a lot of like to think in “frames of reference,” it is hard to let go and explore other potentials within the issues of quantum gravity?

    Lee’s positon has been “exemplitary” by bringing together perspectives on quantum gravity. I can understand his frustration, is a little different, then wanting to hear my proposal? :)

    Yet in these string theoretics “mathematical assumptions” are correct?:)Qui! Non?

    So the “foundational” ground work has been “laid out” regardless ,of what some people think about string theory?:)

  • anonymous

    Last years, young students were pursued to research in string theory. I know students doing a PhD in string theory because other research fields were -in practice- very limited to funding.

    Most physics grad schools are full of grad students who go in thinking they want to do string theory and end up doing anything from condensed matter experiment to astrophysics to particle theory to biophysics. The thought of anyone being forced into string theory is laughable. There are neither enough advisors nor enough funding for everyone who would like to work in the field, and most of them aren’t talented enough in the first place.

  • Part Time Quantum Gravity Theorist

    Nobody cares about the students with no talent. The question is whether the talented ones have the opportunity to work on other approaches to quantum gravity if they recognize the behavior of string theorists as religious.

  • anonymous

    The actually talented ones are able to appreciate that string theory is by far the most promising approach to quantum gravity. None yet has been talented enough to find anything else that is more promising.

  • Thomas Larsson

    When it comes to quantizing gravity, string theory is no alternative to understanding the correct constraint algebra of GR on the quantum level.

  • Lee Smolin

    You can’t make this stuff up department:

    Q: The question is whether the talented ones have the opportunity to work on other approaches to quantum gravity if they recognize the behavior of string theorists as religious.

    A: The actually talented ones are able to appreciate that string theory is by far the most promising approach to quantum gravity. None yet has been talented enough to find anything else that is more promising.

    This is a textbook example of group think, when a group of people become convinced that agreement with them is a test of talent and intelligence. If anyone remembers the point of this thread, it was that some of us believe that Sean’s “market forces” don’t work because of such group think, leading to an inability to make objective scientific judgements of the relative risks and achievements of different approaches.

    Should we then presume you think that the following people who work on approaches to quantum gravity other than string theory do so because they are lacking intelligence or talent: Ashtekar, Bjorken, Connes, Laughlin, Loll, Penrose, Rovelli, Sorkin, ‘t Hooft, Thiemann, Wen.

    Sorry if this seems harsh, but you said it, not I.

  • Bob

    I am just an amateur astronomer with the following observation.

    From just reviewing Thorne’s “Black Holes and Time Warps” and,
    in particular, chapter 11,’What is Reality’ in which “spacetime is viewed as curved on Sundays and flat on Mondays, and horizons are made from vacuum on Sundays and charge on Mondays, but Sunday’s experiments and Monday’s experiments agree in all details”, I can be a touch confused by this exchange. Are string theory and QLG all that far off in their predictions? And if they are, then won’t science run into some wall in the future if the wrong road is being taken just as it did with Rutherford’s solar system model of the atom?

    Even with that last case,Rutherford’s model, wrong as it is to an astrophysicist or particle physicist, still serves a function to introductory chemistry and biology to this day, does it not?

    I recall a similar period mentioned by Clifford Will in his “Was Einstein Right?” in which scientists were describing themselves as Brans-Dicke theorists three days a week and general relativists on the other three work days. Many of Dicke’s criticisms wound up being experiments that NASA took up and received quite a few funds for as I recollect. Dicke may have lost his battle, but regarding his view was a plus for science.

    I also got the impression from Thorne that while Zel’dovich’s biggest fear was losing time when doing experiments, Wheeler’s biggest fear was overlooking any new idea. Wheeler was more deliberate. It seems that the different methodologies of Zel’dovich and Wheeler are still very much alive, the tortoise and the hare. Yet, my impression was that Zel’dovich, Wheeler, Hawking,Thorne and Landau all mixed well and respected each other.

    I would like to think that such an atmosphere still can prevail?

  • Elliot

    the bonsai master
    prunes for the sake of the tree
    not his reflection

  • anonymous

    “Ashtekar, Bjorken, Connes, Laughlin, Loll, Penrose, Rovelli, Sorkin, ‘t Hooft, Thiemann, Wen.”

    What a skillful interpolation of the unquestionably brilliant and of Lee’s own colleagues! Note how it entices the reader to consider, say, Thiemann as in the same class as ‘t Hooft. Also note how when Bjorken or ‘t Hooft talk about quantum gravity, they manage to sound speculative, modest, and curious about the ideas and insights of others. On the other hand, Penrose exhibits the same sort of closed-minded refusal to appreciate well-understood issues, and general lack of any clue about quantum field theory, that certain others exhibit. His undeniable brilliance and his past contributions don’t excuse his current arrogance and dismissiveness of the insights of others.

  • http://eskesthai.blogspot.com/2006/01/kk-tower.html Plato

    Likewise, if the very fabric of the Universe is in a quantum-critical state, then the “stuff” that underlies reality is totally irrelevant-it could be anything,

    says Laughlin. :)

    So in terms of microseconds, where do strings exist mathematically in the expression of “the arrow of time?”

    Do not “reductionistic processes” allow us to think in this way?

    Approaches to the Quantum Theory of Gravity by the PI Institute


    Two methods evolved in the theory of elementary particles to describe such quantized flux tubes. The one, called the loop method, studies them using the basic laws of electricity and magnetism, combined with quantum theory. The second, called string theory, postulates that the quantized flux tubes may be treated as fundamental in their own right, and the laws of electricity and magnetism derived from them.

    Many theorists believe that these two points of view are actually equivalent—just different ways of studying the same thing from different points of view. The idea that they are the same is called duality, which here, as in other areas, signals that the same object is being studied with different ideas and methods.

    Ah, group think by the benefits of Lazardis, Ummm…Qui Non? :) What would you do with 40 billions dollars? :)

  • a different perspective

    I don’t like string theory and I don’t really much like QFT either. My objection is though is not that the theory cannot make any predictions (since QFT can make predictions). Instead my view is very simply: What is the bottom line benefit of the theory i.e. What is the cost/benefit ratio. As far as I understand QFT is extremely complicated, very difficult to make predictions with and very difficult to compute anything with. So it has a very high cost and very few benefits. String theory has precisely 0 benefits and an even higher cost.

    In my view a perfectly correct theory that you cannot compute anything with is perfectly useless. Also a correct theory that makes only 1 or 2 successful experimental predictions is also pretty useless. What is wrong with my view?

    Science has always had a bottomline benefit since most theories did give us bottomline benefits. We could predict things with them and we could use our predictions to make machines. Areas like optics, statistical mechanics, chemistry, electromagnetics, etc are computable and they provided fairly immediate benefits. On other hand modern physics has only really given us Quantum Physics (to be honest I don’t really like GR either (although I do acknowledge that it does have the benefit of allowing us to tell some good bedtime stories)).

  • Bob

    a different view,

    So GR is akin to some bedtime story?

    “Without GR and SR being taken into account, our GPS systems would not be so accurate in locating satellites. Time at different altitudes and different speeds run at different rates and any failure to take that into account results in GPS measurments being off by close to a mile in one day’s time.

    GPS reception is built into cell phones to provide 911 emergency location information and provide position information for emergency vehicles. Hand-held GPS receivers provide position information for hikers, boaters, cars and soldiers lost in battle on the ground.
    All those signals must travel up to the 4 satellites necessary that correct for clock errors and then back to Earth where receivers are. They take GR and SR into account.
    GPS sytems are landing faster jets in shorter time than the navigators of the past who took up dangerous valuable time taking several fixes with their sextants.

    Differential GPS systems guide our farm tractors along the ground to keep them going in very precise patterned lines to the accuracy of one inch, producing a more abundance of crop from our soils while reducing fuel consumption and time.

    They are used by geologists to monitor the flow of glaciers and the growth of mountains. Oceanographers measure the scattering of GPS signals off the ocean surface and use the result to calculate wind speeds at the ocean surface. Engineers monitor deformation in such structures as dams and bridges using differential GPS to provide inch-level accuracy. Wildlifwe biologists place GPS collars in large mammals to study herd migration and ranging behavior”..(Wolfson-Physics in Your Life,lecture 31)

    It can warn humans on the ground of potential weather disaster:

    http://www.universetoday.com/2006/06/28/gps-can-predict-tsunamis/

    QFT and string theory deal with gravity. We have already found out from experiments conducted on Columbia that plants in a free fall have their molecular structures affected. Moss forms into a spiral Fibinacci pattern in weaker spacetime structure that fails to do on the ground. Those plants that have those structures on Earth lost them in outer space. Understanding the interrelations between gravity and biological structures may reveal that certain viruses could one day in the future be withdrawn from a sick human and sent into orbit and be rearranged in a way to aid in a vaccine. Quantum gravity might be manipulated one day that may be able to isolate and withdraw leaking poisonous gases into containers..

    If you want a better bottom line, try this: Forget about sending humans to a dead planet that robots and satellites are already accumulating enough data for our needs.

  • a chinese student

    Lee,

    as (for example) Sean hopes to be a textbook case as he wrote in his comment 152 and maybe others also, I am afraid that some physicists in the thread have not quite understood the point of the discussion. I am sorry if I am wrong.

    As Sean says, once someone presents a successful theory in its complete form (or at least close to it), then everybody does get convinced and the theory becomes the mainstream. Yes, this is how science makes progress. The question is about the period when no one has yet shown a successful theory in its (almost) complete form. Does the free market of ideas in a science community maximize its productivity? Or is it actually not the best way to invest on ideas?

    For example, when Sean says in his comment 148,

    “If, on the other hand, one thinks that there is some non-substantive systematic bias that is distorting the balance away from what it would be on the merits, and that alternatives should be supported qua alternatives, because string theorists are narrow-minded and hegemonic and uninterested in dropping by one’s office or inviting one to their conferences, then I think you are deeply misguided.”

    I think that he has not quite understood the point of the discussion. It is not that string theorists are particularly narrow-minded. It is that people in general, and a community in general *might* have a tendency of “group think” (as you and some of the above people call it) that *might* not maximize the efficiency of the community toward progress. In other words, people in general might not be so open-minded as to maximize their productivity, and that some system might be needed to encourage them to listen to different ideas. Listening to different ideas from that which one advocates might stimulate her productivity more than otherwise.

    I used a lot of “might” in the above sentence because this is an open question that I think no one is able to convince everybody of a single answer, especially because this is not a physics question.

    In the end, although the “free market of ideas” might not be as efficient as we hope, it might still be the best system of doing science. Perhaps?

  • http://www.canonicalscience.com Juan R.

    anonymous wrote:

    Most physics grad schools are full of grad students who go in thinking they want to do string theory and end up doing anything from condensed matter experiment to astrophysics to particle theory to biophysics. The thought of anyone being forced into string theory is laughable. There are neither enough advisors nor enough funding for everyone who would like to work in the field, and most of them aren’t talented enough in the first place.

    I do not remember myself saying “anyone”. But i know many of them being forced to follow the string-brane way.

    Your last “most of them aren’t talented enough in the first place” is just part of the stringy hype. String theory is difficult, yes, but no more than any other field.

    Juan R.

    Center for CANONICAL |SCIENCE)

  • Torbjörn Larsson

    The midsummer holiday was long and eventful, apparently so was this thread.

    Arun said:
    “The refinements to evolution came from increasing accumulation of the working of organisms, including how inheritance works.”

    It was my impression that the fossil record, that I believe is the best evidence that evolution exists, wasn’t too impressive at Darwin’s time. He started out with scarcely little facts, but saw the power in his theory to explain much. Just as string theory currently.

    island says:
    “I believe that Lynn Margulis and others would tell you that they still don’t have it right.”

    Perhaps – not all evolutionary theories are verified and new ones crop up daily. what I mean’t though was that Darwin’s correct ideas ideas was eventually validated.

    Tony says:
    “however, as I said above, it is not the type of evaluation that I “ask for”, nor is it an indication of that the world of physics is now a well-functioning free market of ideas.”

    If the market of ideas is a real market, some products will be refused on packaging and/or content without any real inspection of the use and quality of the products. I agree that in the case of scientific ideas a more substantial inspection and/or refusal process could be asked for, but it’s the market buyers and ultimately consumers that rules that side of the process. Producers can only make as good as or better products than the competition to be ‘bought’.

    Nigel says:
    “Tony, this is the problem caused by mainstream speculation: the groupthink which asserts one speculative system without any empirical evidence for it, is the same groupthink which is not interested in alternatives.”

    Not necessarily if the market analog is useful, see above.

  • damtp_dweller

    I’ve read this thread with interest, observing some gems among the inevitable deluge of crud. However, something which really got my goat was the following:

    Most physics grad schools are full of grad students who go in thinking they want to do string theory and end up doing anything from condensed matter experiment to astrophysics to particle theory to biophysics. The thought of anyone being forced into string theory is laughable. There are neither enough advisors nor enough funding for everyone who would like to work in the field, and most of them aren’t talented enough in the first place.

    Firstly, the arrogance displayed in this quote is quite simply breathtaking (and not a little nauseating). Secondly, as a current grad student in this area let me say that it is not at all representative of the mood within the field, at least among grad students. String theory is of course a difficult subject, but no more so than any other discipline. In fact, were I to be pushed on this, I can think of several problems in more traditional areas which are *far* more difficult than any I know of in string theory (a full proof of the Penrose inequality in GR, an acceptable definition of quasilocal mass, and a rigorous statement and proof of cosmic censorship are just three examples which spring to mind). Unfortunately, cretinous views like those quoted above do seem to be on the increase, particularly among those who have swallowed the string theory hype hook, line, and sinker (and let’s be honest, it *is* over-hyped: anyone who says otherwise is simply not living in the real world). It’s a damn shame that things are the way they are.

  • http://www.canonicalscience.com Juan R.

    damtp_dweller wrote:

    Firstly, the arrogance displayed in this quote is quite simply breathtaking (and not a little nauseating). Secondly, as a current grad student in this area let me say that it is not at all representative of the mood within the field, at least among grad students. String theory is of course a difficult subject, but no more so than any other discipline. In fact, were I to be pushed on this, I can think of several problems in more traditional areas which are *far* more difficult than any I know of in string theory (a full proof of the Penrose inequality in GR, an acceptable definition of quasilocal mass, and a rigorous statement and proof of cosmic censorship are just three examples which spring to mind). Unfortunately, cretinous views like those quoted above do seem to be on the increase, particularly among those who have swallowed the string theory hype hook, line, and sinker (and let’s be honest, it *is* over-hyped: anyone who says otherwise is simply not living in the real world). It’s a damn shame that things are the way they are.

    Still poor than that! String theorists, including the so-called smart ones, are pulling the subject in a completely incorrect and outdated way. It is very amazing to read an article on the topic or hearing some talk where presented completely crackpot stuff from some string theorist. People working in other fields simply receive the talk or the paper (or preprint) as the “joke of the day”. The problem is when undergrads, young impresionable students and the rest are the target. Then audience is seriously misinformed and that is not good for science.

    It would be really difficult to summarize the crackpotism received from string theory authors during last decades (of course, this is not a criticism to any string theorist). But more difficult would be to select one single example. There are many known examples: Lagrangian theory, thermal properties, foundations of quantum formalism, unitarity, all the crackpotism about Landscape and CC, epiroktic scenarios, etc.

    I think that my favourites are:

    1) The completely outdated TFD Dp-brane theory, presented like “exciting” when reusing ideas implemented decades ago by other people (of course all string theory before TFD version was still more boring and oudated).

    2) The claim that string theory is a TOE when does not verify the basic M2I equation of complex systems (equation working in macromolecular chemistry for instance).

    3) The completely outdated ideas on recent version of non-critical string theory, copying stuff from the early 80s and copying incorrectly the equations! (e.g. equation (37) of arXiv:hep-th/9406016 v1 is both outdated and incorrect).

    4) The insanity around Landscape and CC.

    In last Quantum Future (1998), Claus Kiefer and Erich Joos wrote:

    This is even true for tentative frameworks such as GUT theories or superstring theory. Although the latter may seem “exotic” in some of its aspects (containing D-branes, many spacetime dimensions, etc.), it is very traditional in the sense of the quantum theoretical formalism employed.

    But what could one wait from researchers as Brian Greene?

    He rejects without any serious discussion [...]

    Freeman J. Dyson (May 2004)

    Juan R.

    Center for CANONICAL |SCIENCE)

  • http://www.canonicalscience.com Juan R.

    Sorry a typo!

    As explained by Jean Marie Lehn (Nobel also)

    Complexity = MI2

    P.S: I checked that Nanopoulos preprint (and other works) is copying incorrectly equations, with one of the members of the group developing the equation in the 80s.

    Juan R.

    Center for CANONICAL |SCIENCE)

  • http://www.anthropic-principle.ORG island

    island says:
    “I believe that Lynn Margulis and others would tell you that they still don’t have it right.”

    Torbjörn Larsson answered:
    Perhaps – not all evolutionary theories are verified and new ones crop up daily. what I mean’t though was that Darwin’s correct ideas ideas was eventually validated.

    I actually figured as much, but I took the fact that it didn’t read that way to make the point that Lynn… “and others” would also tell you that there is a predispositioning among “neo” darwinists to willfully deny any and all forms evidence that carry implications that creationists might abuse.

    She’s right about that, and I most definitely can give plenty of evidence that this non-scientific mentality isn’t limited to evobiologists.

    My consistently expressed point is that this extreme “anticentrist dogma” is killing science, while obscuring our vision from the true road to the ToE, via the self-evident prediction that falls when it is noted that it is extremely probable that a truly special anthropic connection to the forces of the universe will also necessitate a reciprocal link to the human evolutionary process.

    So the prediction that naturally falls from this is that there exists a mechanism which enables a universe with volume to “leap” to higher orders of the same basic structure… as inflationary theory and about a dozen other projected assumptions bite the dust to empricism.

    Does such a mechanism exist?

    Yes, and I’ve already defined it in this thread.

    http://blogs.discovermagazine.com/cosmicvariance/2006/06/19/the-string-theory-backlash/#comment-35150

    Now if we only had an honest scientist that wasn’t afraid of purpose in nature… like Einstein.

  • Elliot

    I would like to register a critique of the “marketplace” analogy. I think that ultimately scientific theories are about what is correct and what is incorrect from an explanatory as well as predictive mode. It is not Beta vs. VHS. (a side note here… Beta was in fact the better video format from a quality perspective but lost the marketplace battle). My concern is that if you start to consider “market value” of scientific approaches as measured by the number of people who are attracted to work on that approach or how much funding it can attract, it will encourage inertia in that people who have already invested and received support for “Brand X” will be inclined to continue along that path lest they explain to the funding source that they are switching to “Brand Z” which may include an implicit admission that the work on “Brand X” was not fruitful.

    Please note nothing in this comment should be meant to implictly or explicitly be critical of any of String/Brane, QFT, LQG, Info-theoretic models, or any other alternative theory. I am simply worried about the use of a marketplace analogy when the marketplace is by its very nature, inherently bound up in establishing and defending “brand identity” and therefore encourages continuity vs. reexamination.

    Elliot

  • Cynthia

    Elliot,

    I would like to expound upon your insights into the concept of a market-based approach to pure-science research…

    I will initially point out that society has become overly obsessed with the notion that unadulterated, unabated Capitalism is compatible with all sectors of our economy. Furthermore, I will take note that there are some extremely valuable products/services within our economy which are simply not amenable to a market-driven economy. Unquestionably, research in pure-science falls under the distinct category of products/services which should be regarded as lying outside the range of free-market economics.

    Because the “pure-science” sector of our economy is negatively correlated with direct and immmediate profitability, this particular sector should be granted exemption from having to adhere to marketplace economics. More importantly, we – as a society – intuitively comprehend that our financial vitality and societal well-being is positively correlated with progress made in the realm of fundamental science. Simply put, a society’s long-term profitability hinges upon having a viable infrastructure for pure-science research. Moreover, because the free market is generally not receptive to funding such venture-capital projects, society must look beyond Capitalism in order to support fundamental science.

    Perhaps laissez-faire works remarkably well within the marketplace of PC’s versus MAC’s. By contrast, laissez-faire fails to deliver when it comes to unveiling Nature and/or uncovering the origins of the universe.

  • a chinese student

    Cynthia,

    I do not think that the “market place” analogy discussed in the thread is about “market value” of scientific research. I think it was what some people called “an analogy to a portfolio”: the comparison between investment on financial goods and investment on developing ideas in sciences.

    Eric’s post 87 is I think a good summery of a motivation for the “market place” analogy, and let me paste a part of it:

    “What is being seriously discussed is how to properly evaluate and diversify imbalances in the portfolio of approaches to advancing fundamental physics beyond the Standard Model and General Relativity.”

    So, protecting fundamental science from evaluating potential “free market value” of research and investment according to the evaluations is not the topic discussed here. The question that has been raised is: “what if an alternative approach (of a topic in sciences in general), not the most popular approach, was on the right track and we would have noticed it a lot earlier had we invested on ideas more cleverly.” The question is about the method of investment on scientific research purely for the sake of the progress of the science itself, not for the sake of Capitalism.

  • Elliot

    Cynthia/A Chinese Student,

    You are both correct. However to clarify my point is that when you use the marketplace analogy, (with or without financial payoff), you inevitably get dragged into establishing and maintaining brand identity. “Strings” in marketplace terminology is a brand name for a theory of everything. As a “brand” it has certain positive and negative attributes. But the notion that this is the correct way to look at pure science is troublesome and may bear on the process of making “investment” decisions on one approach or another even given the fact that the payoff is not financial.

    My point is cautionary in that when you begin to use analogies such as these, there are some consequences that come along that may not be intended and may be counterproductive.

    Elliot

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  • Ian

    Sean,
    Regarding your article ‘The String Theory Backlash’, you state that you have not read either ‘The Trouble with Physics’ or ‘Not Even
    Wrong’ and yet you go on to say the that you disagree with what the books are saying! Is that
    not stretching your credibility to a rather pointless singularity of meaninglessness.
    And unfortunately it seems to reflect too well
    the string theorists disregard for any requirement for experimental prediction or evidence. The Emperor truly has no clothes…

    Best regards

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Well, I did read the titles of the books, complete with subtitles, which was really all I needed to know there was a disagreement. And I made the reasonable-seeming assumption that the content of the books would be compatible with the public statements made by their authors in multiple venues over a series of years. And now that I have read them, that assumption was correct.

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Cosmic Variance

Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] cosmicvariance.com .

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