What Scientific Idea is Ready for Retirement?

Every year John Brockman’s Edge web-site hosts responses to a different question. This year the question was What scientific idea is ready for retirement?. It shouldn’t be too hard to guess what I chose to write about, with results available here.

Every year Brockman manages to attract more responses, so this is now getting to be a statistically significant sampling drawn from the population of people who write about science for the general public. Before trying to divine some general trends among the physics responses, I’ll first mention a few of them that stand out as unusual.

First, there’s one from Paul Steinhardt that I very much agree with. He’s had it with the multiverse and thinks it needs to go. I’m very glad to see someone else making many of the points that I endless repeat on this blog in a tiresome way. So, go read what he has to say, which ends with this challenge to the theoretical physics community:


It would be great to see someone other than him and David Gross start publicly speaking out.

A second outlier is Gordon Kane, who uses this as an opportunity to claim that he had predicted the Higgs mass using string theory. I don’t know of anyone other than him who takes this seriously. He doesn’t mention his other string theory based predictions, which include the prediction that the LHC should already have seen gluinos.

Another odd one is from Max Tegmark, who argues that we have to get rid of equations in physics that aren’t just based on finite and discrete quantities. The only positive argument I can see from him for this is that it would help get rid of the “measure problem” of the multiverse, but listening to Steinhardt and dumping the multiverse itself seems to me a much better idea. Tegmark has a new book out, I’ll write more about this here in a few days.

Maria Spiropulu is with me on the need to retire naturalness, also wants space-time to go. Getting rid of space-time has multiple proponents, including also Steve Giddings and Carlo Rovelli.

Another theme is people starting to sound like John Horgan, announcing we’re reaching the limits of science. Martin Rees thinks that some scientific problems may never yield to our understanding: “The human intellect may hit the buffers”. Ed Regis thinks the cost of a next generation collider is just not worth it for what it is likely to tell us.

A variant of this is the argument that we’ve reached the end of the road for unification and simplicity in our basic physical laws. Here the argument often seems to be that since SUSY/GUTs/string theory were such beautiful elegant ideas, their failure means the whole elegance thing is misguided. Another point of view (which I think someone wrote a book about) would be that these always were heavily oversold as “elegant”, since if you looked into them they were rather complicated and didn’t explain much. Writing in the anti-elegance vein are experimentalist Sarah Demers:


along with Marcelo Gleiser and Gregory Benford. At this particular time in intellectual history, it seems that hardly anyone has anything good to say about mathematical elegance as a powerful principle behind deep ideas about physics.

Finally, the biggest contingent are the multiverse maniacs. There’s Andrei Linde, who deals with the problem of evidence for his ideas by:

A pessimist would argue that since we do not see other parts of the universe, we cannot prove that this picture is correct. An optimist, on the other hand, may counter that we can never disprove this picture either, because its main assumption is that other “universes” are far away from us.

He’s joined by Sean Carroll, who wants to do away with the Popperazi and their inconvenient demands for falsifiable predictions. Also writing in support of the idea of a multiverse of different physical laws, implying we’ll have to give up on the idea of understanding more about the ones we see are Lawrence Krauss and Seth Lloyd.

Update: A couple more late additions that I missed. Eric Weinstein is with me in going after “string theory is the only game in town” as something that should have been retired long ago. Alan Guth uses this venue to promote some recent speculative work on the arrow of time with Sean Carroll (no paper yet, so hard to tell what it really is).

Update: Sean Carroll has a blog posting up about his argument for getting rid of falsifiability. He seems to not be getting a lot of support, either in his comment section (see for instance here), or places like here. I don’t think the skeptic community is ready to disarm itself intellectually in arguments against religious believers by ditching the conventional scientific method.

Update: Scott Aaronson writes here about the falsifiability issue, pointing out about string theory/multiverse research that


Sean Carroll responds that the problem here is

somber pronouncements about non-falsifiability from fuddy-duddies.

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70 Responses to What Scientific Idea is Ready for Retirement?

  1. tulpoeid says:

    Half of the answers you cover make me wish that the public will one day demand to end public funding of theoretical physics. It’ll definitely be more beneficial to science compared to the present state.
    If the public can achieve the end of private funding as well we’re even more on the correct path. And while we’re there, can the public also make it quick? :p

  2. Tim Howells says:

    I’m puzzled by Prof. Steinhardt. See this video from April 2011:
    In this talk he describes string theory (starts at 44:40 mark) as a very elegant theory that unifies many observations and has great explanatory power, and which is the only game in town anyway etc etc. He cautiously criticizes cosmic inflationary theory but only because he wants to propose a new theory in which “Brane-Worlds” existing in 11 dimensional space bounce off each other eternally, with each bounce creating an effect that is almost indistinguishable from the big-bang, but possibly with different settings for the natural laws etc etc.

    By contrast his Edge paper sounds very coherent and sensible, and quite inconsistent with the talk at least in terms of string theory.

    Disclaimer: I am not a physicist or a mathematician! I would be interested in comments on this by more knowledgeable people.

  3. imho says:

    First a general statement, from a cond matt theorist perspective. It seems to me that you guys are 1.5 good papers away from deriving gravity from the thermodynamics of entanglement, yet I keep hearing about the multiverse and string theory… I guess old habits die hard? Thank god for the faction of the new generation that seems to have a wonderful ability to completely ignore the old guard and chart their own path. I will enjoy watching this all play out.


    Don’t worry, other scientists (even Physicists) have already started the process of “redirected” funding. No one thinks it’s a good idea to end public funding, but it’s probably a good idea to reduce the number of young people in certain fields.

  4. Shantanu says:

    Peter: one more thing which Maria has mentioned is possible death of particle dark matter
    which I too would have pointed out if I had a chance.
    PS: I presume the deadline for writing something is over?

  5. Peter Woit says:

    Tim Howells,
    Steinhardt’s objections aren’t really to string theory itself, but to the “string landscape” idea and its version of inflationary cosmology. For more about his objections to this, see his Scientific American article, available here

  6. Peter Woit says:

    The way this works is that Brockman sends out invitations asking people to write something in December, deadline to send something to him was a week or so ago. He then does some minor editing. Those writing can see the responses as they are posted, with the order I guess inverse chronological in terms of time received.

  7. I agree that string theory has not made any predictions, but isn’t it a little extreme to ask that we completely “retire” the whole framework? If nothing else, isn’t there some useful mathematics that has come out of it?

  8. Jesper says:

    I find the contribution from Sean Carroll quite weird/extreme/confused/self-contradictory. He wants to get rid of falsifiability, and yet he ends with “… but nature is the ultimate guide.” To me that doesn’t make any sense – I guess my point of view is quite mainstream and much repeated here…

  9. Jesper says:

    Just one more sentence on Sean Carroll. If ‘Nature’ has zero way of saying “you are wrong” – which is falsifiability – then how can it be the ultimate guide? To me it sounds more like having a Teddybear to hold your hand …

  10. Peter Woit says:

    Curious Wavefunction,
    What I wrote was specifically about string theory unification, the idea of getting a unified TOE using strings in 10d (or M-theory in 11d). These days “string theory” often is used to refer to all sorts of things that have little or nothing to do with this, and little or nothing to do with quantized strings. One can’t sensibly argue against all of “string theory” in this larger sense, partly because it does include valuable ideas, partly because it’s unclear exactly what one would be arguing against…

    I certainly agree. One of things I find most incomprehensible about Sean Carroll (as well as Max Tegmark and some others) is the way he simultaneously devotes his life to going to war with religion, taking up the banner of the scientific method, while at the same time announcing that his research shows that the conventional scientific method has to go. Of course he’s right that the scientific method is more complicated than sometimes portrayed, with much more to it than “falsifiability”. But the kind of theoretical work he favors (e.g. his multiverse explanation of the arrow of time) come with no convincing ideas about how to test it, with or without “falsifiability”. The “nature is the ultimate guide” sloganeering does then seem very empty.

  11. Pawl says:

    If you search the abstracts from December’s Texas Symposium on Relativistic Astrophysics, you will find no mention of “multiverse” and only two (in contributed talks) for string theory. Much of the Symposium was about cosmology, although admittedly much of that was given over to observation.

  12. Low Math, Meekly Interacting says:

    I sometimes think a blog post devoted to an updated view of on how one could even hope to define “(Super)String Theory/M Theory” would be a valuable endeavor, if it’s not a huge inconvenience. I’m vaguely aware of the complexity from an outsider standpoint, and I think Matt Strassler, to give one example, has done a phenomenal job of helping to clarify some of these exceedingly complex issues. As a biologist I’m used to sloppy nomenclature, but in the field of HEP, “String Theory” seems to almost anything you want it to be, and different, quite well-informed HEP theorists might not even agree that what a particular investigator is doing amounts to “string theory” research. It’s appears to be quite hard to even define basic criteria like “success” and “failure”. Sure, maybe the ST landscape is without predictive power and many now seem to agree that this represents a failure of sorts. At least, it’s a major disappointment when juxtaposed with the late-20th-century enthusiasm for the idea of a vacuum selection principle falling out of “M Theory” that would yield the Standard Model and GR as a low-energy limit. That whole notion appears to be as dead as dead can be, and has apparently been pining for the fjords for well over a decade.

    But what of the rest? Lots and lots of legitimate debate about that, I think. A tool for learning more about quantum field theories? Seems like there’s at least a case to be made. Its role in this new amplitude business (along with twistors and all kinds of other things I could barely comprehend)? Does anyone even aspire to know with any level of certainty? Insights into strongly-coupled condensed matter systems? Much more debatable, perhaps, but maybe not as hopeless as the anthropic principle.

    I’m truly not attempting to do anything like advocate, just hoping to gain some additional clarity about it all in the public discourse, if such a thing is attainable.


  13. Peter Woit says:

    The complexity of some of these issues is one of the main reasons I wrote a book, and I think what’s in the book holds up very well, with not that much changed in the past ten years since the book was written. For some of the more recent topics that have gotten a lot of attention as advances in “string theory”, typically again there’s a very complex story, which would require a book-length treatment to do justice to (but I’m not going to write that one…). For example, there are now probably close to 10,000 papers referencing the original AdS/CFT paper, and I’m not going to do justice to what they cover in one, or many blog posts. Strassler’s series of several blog posts does try to do this a bit, although he ends up writing a sizable chunk of a book, just to get at one small piece of that story.

    The other problem here is that I don’t have the expertise to evaluate the significance of some heavily promoted supposed applications of string theory. For applications of AdS/CFT to heavy ion physics, you need a heavy ion physicist, although Sabine Hossenfelder has had some good blog entries about this. For AdS/CMT, you need a good condensed matter theorist, not me. The story about amplitudes and twistors is an incredibly complex one, I’ve tried to say something here about the parts I understand, link elsewhere for what appear to be the best sources of info about things I don’t understand. To be honest though, I find this often a discouraging business, with sometimes a lot of people more interested in muddying the waters and making dubious claims (“string theory explains high temperature superconductivity”) than in really explaining what is going on. I certainly encourage anyone who understands these issues to write clear and honest explanations of them, and I link to such things when I see them, but my willingness to devote lots of time to that thankless task is pretty limited.

  14. CFT says:

    I actually liked Max Tegmark’s paper. He has a logically valid point, Infinity is not measureable, and thus putting anything into any kind of measureable (finite) ratio with it is ridiculous, and not logically sound. I understand the concepts of big and little just fine, and how they are relational, and how things can be measured and compared in a ratio of known sizes. I reject the premise you can put anything into a logical relationship that is truly infinite, unless you are using the term euphemistically. If you don’t know how big (or small) something truly is, ‘infinite’ is not the correct answer. Just say, ” I have no idea how big it is, or how far it goes, I have no way to measure it…my data has limits and I admit it” and you are on the road to making rational arguments that are scientifically accurate and honest about the limitations of your data. Infinity is an abstract concept. Concepts or ideas can be infinite, because they are a product of your imagination, not limited to measureable data, and not bound by physical limitations or time. Reality is by comparison, far more stringent logically, and utterly bound by the limitations of measurable (finite) data, time, and space.
    As for Sean Carroll,
    I ditched his blog a long time ago when I realized he talks out of both sides of his mouth about the scientific method, treats the definitions of words like taffy when it is convenient. Sean has openly shown contempt for anyone who does not share his political views and has great difficulty discerning science from open political advocacy. I do understand his methodology however, if you eliminate falsifiability from the criteria of logical scientific reasoning, you can make any fanciful claim whatsoever and never be wrong or ‘not even wrong’ since you can always claim it is true somewhere else or ‘in another universe’. IMHO: Sean would not seem to have internalized the burden of proof or evidence in THIS universe.

  15. hopffiber says:

    Low Math, Meekly Interacting,
    there is a lot of work indeed that on the surface only seems vaguely related to string theory, like the whole amplitude business, integrability, entanglement entropy and so on. These are interesting on their own, and I hope that (even) Woit will agree that they contain many valuable ideas. However, most of these ideas comes from string theory in one way or another, mostly through AdS/CFT. And as AdS/CFT shows us, a string theory can be precisely equivalent to a quantum field theory, so the two things are really closely related, even if it might seem distant at a glance. One can do a lot of quantum field theory using string and M-theory.

    And I think that talking about the landscape, sure it is disappointing and the hope of a unique theory of everything seems far gone, but really, it’s the same as in quantum field theory. In QFT, we have an infinite landscape of possible models, and there is no selection mechanism at all, so one could state that QFT is very non-predictive and indicative of a multiverse. We need experimental data to select a specific QFT model, namely the standard model, and then this model in turn is highly predictive and can be tested against new experiments. This is the same that we seem to have in string theory, it’s just that the we don’t understand the string theory vacua as well as we understand different QFT models, and that the experimental data is a lot harder to get (since the energy scale of quantum gravity is very high). But once you select a specific string vacua, the model is in principle just as predictive as say the standard model.

  16. Peter Woit says:

    What you write is pretty much pure hype, exactly the sort of thing that makes attempts to have a serious discussion about complicated issues pointless and unrewarding. For the last part of it, see

    Sorry, but if it’s not directly about the material in this posting, I’m deleting it as off-topic.

    “Infinity” is a perfectly well defined concept (not finite), as well as an extremely useful one. I don’t see what the value is in abandoning it, other than requiring much more complicated ways of saying true things. There are some very specific cases in physics where it appears in an abuse of language, with multiverse maniacs the main offenders. But I don’t see what conclusion can be drawn from this other than that they shouldn’t do it.
    As for political views of bloggers and others, I’m not going to allow debate about that here. However dumb such expressions can be, the arguments about them in comment sections are even stupider.

  17. Anonyrat says:

    The best line in Sean Carroll’s piece is “Fortunately, science marches on, largely heedless of amateur philosophizing.” Indeed!

  18. Anonyrat says:

    Even if we accept Sean Carroll’s criteria of good scientific theories — they are definite and they are empirical — in place of Popper’s falsifiability, his two examples are no good.

    * Particles as strings is definite, but not empirical.

    * The multiverse may be empirical (if you accept Carroll’s reasoning) but it is not definite.

  19. Neil says:

    The Edge website might need to be retired. I’ve been trying to get on it all day without any luck.

    It seems to me, though, that the very question suggests that something is wrong with physics today. It used to be that a scientific idea was retired because it was inconsistent with observation, such as the plum pudding model of the atom or the steady state theory of the universe. Now it seems to be a matter of fashion and exhaustion.

  20. Justin says:

    Woit, would you be optimistic if the top theorists began working on new ideas? I have this bad feeling that even if the greatest theorists were working on non-string related ideas, that they still would go nowhere. My feeling is that there’s nothing left for a physics student to dream about.

  21. Low Math, Meekly Interacting says:

    Hi, Peter,

    Oh well. I still think an “updated skeptic’s survey” would be a wonderful read, but I thank you for the attention you gave my thoughts anyhow.

  22. Peter Woit says:

    It’s not really a matter of “new” vs. “old” ideas. It’s entirely possible that progress could be made by re-examining old ideas. And, while people are trying to market the multiverse as a “new” idea, it’s one that has been around forever and is now past its sell-by date.
    The problem with the whole multiverse business is that it’s a desperate attempt by some people to avoid admitting that certain ideas have failed. If their ideas haven’t worked out, they could go do something else with their lives, or try different ideas. Instead they go on a campaign to convince people that no one can ever understand the things they’ve failed to understand, not exactly inspirational to physics students everywhere.

    Quantum field theory is an example of a topic we still understand very poorly. Anyone who studies it will find a lifetime’s worth of things to ponder. Just ignore the multiverse maniacs, wait for them to retire, and for journalists to lose interest as it becomes clear how old and tired their ideas are. Physics and math are full of fascinating, poorly understood things to think about.

  23. harryb says:


    I am most of the way through Max Tegmark’s new book you refrence – (Our Mathematical Universe). Its a strange brew. The first five chapters, as he admits, are mainstream, and seem perfectly lucid standard model material. Then comes the Multiverse in its various Levels.
    It is interesting to see this up close – the detail of the earlier chapters and quite interesting perspectives on particle physics suddenly dissolves to leave personal statements and increasing use of exclamation marks. As his own biography unfolds in the book, you see a personality prone to hype and headlines gradually grab the Multiverse as the next great misunderstood Relativity Theory.
    Tegmark’s switch mid-book from lucid guide to particle physics, to wild-eyed evangelist of outre science, particularly the Multiverse, is very sobering. The two “books” sit uncomfortably – one grounded in deep theory, the other a very personal journey into extreme beliefs, which he associates with Newton, Einstein and, to Tegmark, Everett.
    Physics succumbs to attribution error, and availability heuristics.
    Many many wild theories were also shown wrong Mark!, one shouts at the book, but those are conveniently overlooked.

  24. Peter Woit says:

    Thanks. There’s a lot to say about this, both about Tegmark as scientist and about the scientific claims of the book. I’ll write a lot more in a separate posting in a few days, hope to have an interesting discussion on this topic then.

  25. Patrick says:

    Neil: I think it’s a lot easier to ditch a theory when there’s a clearly better one on hand; and that’s not really the case in BSM physics. Hence the cliched defence that string theory is “the only game in town.” And in any case, I think it’s unfair to characterise “physics” on the behaviour of this sub-field’s practitioners.

  26. Chris W. says:

    Edward Fredkin and Stephen Wolfram should sue Tegmark for copyright infringement. Fredkin gets first dibs on the award. 🙂

  27. MR says:

    What is surprising to me is the idea of withdrawing the notion/concept of space and time. Even the quantic human observer is deeply attached to its own space and time, which is a mixture of the macro and micro realms. If the goal is to reduce space to the quantum space and time to the quantic time, ¿what do we mean by quantic space-time? We know little of black holes, superluminal effects, dark matter and dark energy, very little indeed to say that space-time should be deleted, seems like a bizarre idea.

  28. JR says:

    The more common proposal is not that space-time should be “deleted”, just that space-time is emergent from something else. We have encountered numerous emergent phenomena in other areas of physics. See http://vimeo.com/65880636 for examples.

  29. Neil says:

    Patrick: We do not disagree. Now that I’ve finally accessed the Edge website, I see that most of the entries are about assumptions, organizing principles or world views that should be retired, rather than precise theories or models.

  30. Hack says:

    Physicists are too polite, people like Sean Carroll should be laughed right out of physics and science. In fact it is a shame Edge published his response. I will refrain from name calling, but this is utter foolishness and the sooner physicists put an end to this nonsense the better. Many years ago I thought physics was one of the last bastions of ‘truth’ well that is obviously no longer the case.

    And yes, I know the argument, but so and so is brilliant and has made valuable contributions in others fields. Well if brilliant so and so is leading the charge into the wilderness and foolishness, maybe he’s not as brilliant as everyone thinks.

  31. Peter Woit says:

    Sean Carroll’s point of view is unfortunately not an unusual one, but a relatively mainstream one these days. If you want to kick him out of science, you’d have to do the same thing for a bunch of prominent physicists, including various $3 million prize winners (did you read Andrei Linde’s piece?). Carroll I think sees himself as Mr. Science, a voice of the physics establishment. The problem is what is going on with the physics establishment, not him (and this is the point Steinhardt was making).

  32. Jeff says:

    The link for Sarah Demers’s statement is pointing to Ed Regis’s.

  33. Peter Woit says:

    Thanks, fixed.

  34. ScentOfViolets says:

    I think you’re letting Sean off too easy, Peter. The problem is that he is determined to present his opinions to the public as the voice of mainstream science on this particular subject when the reality is that he represents a minority viewpoint, in fact, I would say an extreme minority. I’ve seen him become quite irritated more than once when this misrepresentation is pointed out to him and he needs a public smack down by his peers on this one. Let me emphasize that I have no problems with him presenting his ideas in a book to the lay public despite the fact they are (imho) wrong-headed at best. I just have problems with him misrepresenting those views to the lay public as mainstream thinking. That sort of thing has got to stop – and won’t until there is some sort of visible policing by his fellows.

  35. Kavanna says:

    Hail Mary pass, indeed. Is it the fourth quarter, last down?

    To get back to basics: naturalness, elegance, and unification are sound approaches to modern physics. They have more than proven their worth. However, the technical avenues that we have now for implementing these ideas have been, for the moment, exhausted. And anyone who knows this history — starting with Maxwell’s unification of electricity, magnetism, and light, and his prediction of the displacement current — knows that this program has worked only when it remained close to experiment and stimulated the technology needed to expand what could be tested, when adequate technology was not previously available.

    These days, if you want to expand our fundamental understanding of the universe, you need to be doing astrophysics and cosmology. High-precision laboratory experiments are also worthwhile. Accelerator-based fundamental physics is dead.

    Carroll is a fine popularizer of science. But his arguments about falsifiability are incoherent nonsense. It’s amazing that these same people object to, say, creationism or astrology as being anti-science or non-science. The truth is that they’re poseurs, riding on the historical prestige of science to perpetrate something that clearly isn’t science. It may only seem so to the layperson, and even lay people, these days, are getting wise to this hoax. Steinhardt’s statement about “unfair competition” is right: it’s Gresham’s Law applied to science: bad ideas driving out even the possibility of good ones.

    Reduction of funding for theoretical physics is an idea whose time was already here a decade ago. (I mean string theory-like mania, not astrophysics or cosmology, or whatever’s rooted in experimental and laboratory science.) The problem is that the people administering such reductions are almost certainly going to be the same “string/multiverse” maniacs.

  36. Bernhard says:

    I just read Sean Carrol’s response. I don’t feel like reading anything he has to say ever again. It is a barely crackpot point of view defended with academic eloquence. HEP, once feared and admired, is becoming the laughing stock of science because of these guys.

  37. Peter Woit says:

    I still think that Sean Carroll is not the problem. If you know anything about academia, you know that the people with significant influence are those holding tenured full professorships at the major physics research departments. Sean is not in this category (he’s an astronomy Ph.D. who didn’t get tenure and is now a research associate, not even on a tenure-track line). The problem is people like Linde, Susskind, Polchinski and all too many others like them. They are the ones in leadership positions of the field, the ones claiming multiverse mania as mainstream physics, and they are the ones responsible for the problem. The day they abandon this or get a public smackdown from their peers and lose credibility will be the day Sean changes his tune. He’s a symptom of the problem, not its source.

  38. emile says:

    Kavanna and Bernhard,

    I think we probably agree on the definition of science but you two have to be careful…

    Kavanna: “accelerator-based fundamental physics is dead”. Really? We just found a new particle in 2012. In 2013, it was called “a” Higgs boson by CERN based on the results of the 2012 run. That’s pretty fresh… Now, do you disagree with Sarah Demers who says that we should “measure the hell” out of that particle? Do you already know the answer? The LHC is re-starting at higher energy. Do you already know what will be found or not found? Should the thousands of physicists bother looking at the data at all? Nobody knows what will be found. We need to experimentally check that there is nothing else at those energies. If after running at higher energy the LHC finds nothing and the Higgs that was found looks even more Standard Model-like, then we can talk about what the future of accelerators should be. It may be a likely scenario for you and me but as scientists, we absolutely have to check.

    Bernhard: you write “HEP, once feared and admired, is becoming the laughing stock of science…”. First of all, for every Linde, there are a dozen theorists (phenomenologists), doing calculations that make predictions that can be tested and are tested by the 6000 LHC experimentalists. This is normal science and it is doing great. The problem comes from a minority (though high-profile) people who want to redefine science. Hundreds of -scientific- papers are coming out of the LHC , comparing predictions made by theoretical physicists with observations made by experimentalists. So the results show that the SM explains everything up to now. This still needs to be demonstrated experimentally. If that is Nature’s choice, then so be it. Don’t denigrate all this *scientific* work.

    In general, I get annoyed with the notion that “physics is in trouble”. Physics is doing just fine. I am part of a big physics dept. and the research done by my colleagues in various fields, both experimentalists and theorists, is very interesting and exciting. I wish I could live longer and work in other branches of physics. Even in HEP, science is getting done by 98% of the HEP physicists… We need to fight back when high profile physicists want to redefine the meaning of science but we should not say that physics is in trouble. We should say that these guys are not doing physics.

  39. george ellis says:

    What emile says is exactly right. The entire group that Peter complains about are not what most present day physics is about, see for example http://iopscience.iop.org/1367-2630/page/Focus%20on%20series. They are a very small albeit very vocal group on the fringe of mainstream physics. And they are in fact advocating, implicitly or sometimes explicitly (as in the case of Susskind and Carroll), abandoning the core feature of testability that has led to the rise of modern science. If you abandon that core, astrology is Ok too. But they do not represent mainstream physics nor even mainstream high energy physics. And in terms of philosophy, they are real amateurs.

    As to Tegmark’s comments on infinity: I think he’s absolutely right. David Hilbert said the same thing: infinity is needed in mathematics but it never occurs in real physics. If you claim it does, then give me an experiment that will demonstrate that any physical entity whatever is infinite (number of galaxies in the universe, number of *physical* points between my fingers when I hold them 10cm apart, anything you like where it is claimed that a physical infinity of something exists). You can’t. There is no such experiment. You should rather refer to the large but finite number that is relevant to physical observations and testability. Nothing is continuous on a small enough scale if spacetime is quantised, as seems to be very plausible. It just looks continuous when coarse-grained to experimentally relevant levels.

  40. Anonyrat says:

    Which scientific idea is ready for retirement?

    It seems some of the ideas of some of theoretical physics’ most elite researchers are overdue for retirement.

    We know that in America, the elite retire only with golden parachutes. It seems to me the Milner prizes could serve that purpose. The elite, having received their golden parachutes, can retire along with their prize-winning ideas, keeping their dignity intact. Perhaps one (secret) condition of the prize should be that the recipient should not publish in a scientific journal again.

  41. imho says:

    Hi Peter,
    Regarding your comments about who is influential and who isn’t… I couldn’t disagree more. It’s not like scientific culture exists in some impregnable bubble, completely immune to the normal rules of human interaction. Of course those with the biggest microphones get heard, of course they have influence. The specific detail of their official title, while important, is not the only significant term. I would argue that young up and coming graduate students are just as interested in Sean, Peter, and Lubos as they are Linde, Susskind, and Polchinski. I would also argue that funding agencies are just as exposed to former as the latter. Your own experience is a glaring confirmation of this. The only thing special about Sean is that the ideas he’s been selling for the past decade are pretty widely agreed upon to be nonsense.

  42. Peter Woit says:

    George Ellis,
    Yes, you can formulate physics questions in ways that avoid using “infinity”, but what I object to are claims that this actually solves your problem (which is what Tegmark is claiming). An example would be the “infinities” of quantum field theory, where, yes, it is often a good idea to think about the problem in terms of a finite cut-off theory. In non-renormalizable theories though, this doesn’t do away with your problem, it just makes it clear that the problem is that you don’t understand what is happening at the cut-off scale, and this matters when you try and calculate some physical quantities.

    Similarly, the “measure problem” of multiverse theories is not one that can be removed by announcing that everything is finite. The problem isn’t infinity, but that you don’t really have a theory: “anything goes” is going to be an empty statement, whether things are finite or infinite.

  43. Peter Woit says:

    I’m sure blogs do have an influence, with for instance Lubos doing a great job of convincing graduate students to avoid string theory, and physics departments not to hire string theorists (if he starts arguing for the multiverse, that will be very helpful…). In the long term though, it’s the tenured people at certain institutions who train the next generations of theorists and either succeed or don’t at helping them make careers in the subject (as well as convincing their colleagues who to hire to ultimately replace them). The subtext of a lot of this debate is a battle over whether major research institutions will hire those doing multiverse research, and whether the NSF/DOE will fund grants to them. Susskind and allies often behave as if they have won this battle, but I think it’s still on-going (Steinhardt’s piece is an important salvo). When the whole business started more than ten years ago I thought it was so ridiculous that it would go nowhere, but I was very wrong about that, and have no prediction now for where things will end up.

  44. notagain001 says:

    Peter what do you think of Ed Witten’s argument for string theory?
    He’s a true believer

    ed witten’s take on string theory

    You claim that string theory is the only theory that incorporates quantum gravity. Some physicists make the same claim about a different theory: loop quantum gravity, which unlike string theory does not require any extra dimensions. This has generated some controversy in the literature. What is your take about this?

    Instead of taking your question literally and giving a negative answer, I’d prefer to answer another question. One really can only expect string theory to be related to areas of mathematics and physics that have real substance. And indeed, it has fascinating links with numerous areas of science. A list would be too long to offer here, but would have to include the theory of strongly interacting gauge theories, heavy ion physics, the theory of quantum critical points, topological field theory, topological insulators, noncommutative geometry, twistor theory, and on and on.

  45. Peter Woit says:

    This really is off-topic, and discussed ad nauseam on this blog. The best answer to the question of where I disagree with Witten about string theory is that I wrote a whole book about this ten years ago, and I don’t think much has changed since then (except for SUSY not appearing as Witten and other string theorists had hoped…)

  46. Bernhard says:


    I used “HEP” without much care. I agree with you first paragraph, after all I am myself part of the effort. I used HEP because people talking about this sort of baloney (and I also agree we should not even say this guys are doing physics) are in majority connect to HEP. Considering they are very outspoken and powerful this tend to affect people doing real HEP.

    About physics being in trouble, well that is certainly not my feeling working with it and also not the feeling I have when I go to conferences. But it is definitely my feeling when I read a lot of current outreach material, which is read by everybody (hence my laughing stock comment).

    Perhaps after these guys are gone people will just forget about all this multiverse business. What worries me is that people defending this crap are very influential and how much they will infect the youngsters is still to be seen.

  47. Hack says:

    emile and george ellis,

    What you say may be true, physics is not in trouble, it’s just a few over hyped physicists. The problem than is that these over hyped physicists are the face of physics, supposedly the best and the brightest! I teach a conceptual physics course, what do the vast majority of my students ask me about? String theory. Because of these over hyped physicists, many students have asked about and believe that string theory is correct and is a valid old fashioned scientific theory. In fact I have a had a hard time convincing them to just look at it as an unproven, untestable theory. Meanwhile, very few students know about things such as dark matter, dark energy, super conduction etc. Now we can blame educators or publishers or journalists. But in the end this ‘policing’ resides with the physics community, they are the only ones that can put a stop to this nonsense (or if some how funding dried up). If the statement ‘physics is in trouble’ bothers you I understand, a lot real testable physics research is being done. But than it seems to me you need to get rid of the people who hype their foolish theories or at least get them to shut up. As I said before, physicists are too polite. Oh, which reminds me, students also ask me a lot about the multiverse, lucky me.

  48. srp says:

    Hack, dark matter and dark energy get tons of media play. Admittedly, much of this is redundant or badly explained, but as mysterious “we don’t know what’s going on” stuff they are naturally appealing to lay audiences.

    It’s an interesting fact that lay audiences are usually a lot more curious about what is unknown than in what is pretty well known–a naive view would suggest that people would want to get “the good stuff,” high-quality tested and articulated knowledge. But I think the notion of a mystery, a story whose ending is unknown, is intriguing, while something worked out is more threatening and mentally confining to the lay audience.

  49. george ellis says:

    I agree more needs to be done on the public relations side for solid physics. Here are a few of the books that do so:

    1. Stuff Matters by Mark Miodownik

    2. The first half of Jim Baggotts’ book Farewell to Reality, see


    3. The Theory of Almost Everything: The Standard Model, the Unsung Triumph of Modern Physics by Robert Oerter


    4. The Wave Watcher’s Companion: Ocean Waves, Stadium Waves, and All the Rest of Life’s Undulations Gavin Pretor-Pinney


    and of course

    5. QED: The strange theory of light and matter by Richard Feynman


    and a host of astronomy books such ss

    6. Gravity’s Fatal Attraction: Black Holes in the Universe by Mitchell Begelman and Martin Rees


    Why do they not make as much impact as the far out stuff? Maybe because they are not written in such a polemical way. And we are not served well by theoretical physicists who look down on other branches of physics as inferior and say so publicly. Nor for that matter by physicists who look down on other branches of science like chemistry and biology.

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