Of Particular Significance

Am I Misleading You About String Theory?

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 09/19/2013

You’re making it quite clear that you’re devoted to doing exactly what I find problematic: misleading and confusing people about the status of string unification by refusing to distinguish between two completely different technical issues.

So I stand accused by Peter Woit, in his latest comments on Tuesday’s post.

Dear readers, you are now the jury, and I stand by your opinion.  I do not want to mislead you — indeed, the purpose of this website is to be a reliable, trustworthy source of information about high-energy physics for the public —  and if I have misled you, I will correct the error.

If you look at Tuesday’s post, you will notice that at the start I stated (abridged here, but you can look back at the full text)


String theory has several applications, and you need to keep them straight. Let me mention two.

  1. Application number 1: this is the one you’ve heard about. String theory is a candidate (and only a candidate) for a “theory of everything” — …[which] really means is “a theory of all of nature’s particles, forces and space-time”.
  2. Application number 2: String theory can serve as a tool. You can use its mathematics, and/or the physical insights that you can gain by thinking about and calculating how strings behave, to solve or partially solve problems in other subjects. (Here’s an example.)


I carefully distinguished these two things, because the first is highly controversial, and the second — well, it should be much less controversial.   And also because I don’t work on the first, and I work occasionally on the second, when it proves helpful to the physics I’m interested in.  String theory sits in my toolbox, ready for use if needed.

Then I went on to mention that if string theory in its vanilla form were true in Application Number 1, then you would be able to make predictions for how particles would scatter that are characteristic of their being strings — although no one in the next century or maybe millenium is likely to be able to carry out such experiments.  Now, I thought this was also non-controversial, and made it as an off-hand comment; but Woit complains that this is highly misleading, and also that I’m misleading you on purpose.

He’s wrong that I’m misleading you on purpose, but he’s right that there is a risk of being misled and that the situation is indeed complicated.  So I added a note at the end of the post emphasizing the importance of the qualifier “in its vanilla form”, and that there’s no guarantee at all that string theory, even if it were true, wouldn’t be in ginger passionfruit soybean flavor, in which case the predictions would be different.  Apparently this wasn’t enough for Woit; I am still accused.

Personally, I have never thought string theory was likely to predict the particles and forces of nature in a unique way.  I am not surprised there’s a huge landscape of possibilities; I’m only surprised it seems so… conventional.  In my opinion, any sufficiently complicated quantum field theory or quantum gravity theory will likely have a landscape.    And so, in this sense, string theory is very unlikely to ever make predictions for exactly what particles and fields we will find in nature… these details will likely depend on the early history of the universe and on accidents of history that we are not going to learn about from the theory itself.  On this point, most high-energy physicists seem to be agreed right now.

Question for readers: Do you feel misled, by what I wrote Tuesday, into thinking that I believe that string theory currently makes, or is likely to make, unique and specific predictions about nature? 

If you do, then I screwed up, and I’ll correct the error.

Now I’d like to ask you another question.

In his comments to Tuesday’s post, Woit said that his “short-hand claim `string theory makes no predictions‘ is obviously a simplification of a very complicated situation, one that has been exploited for decades by string theorists making bogus claims for predictions.” [boldface mine]

Question: When Woit says “string theory makes no predictions“, and “string theorists making bogus claims for predictions“, do you think he means only Application Number 1, which is what he called “string unification”?

Or do you think he means Application Number 2 as well?  Am I, because I have string theory in my toolbox and I use it occasionally, accused by Woit of being a “string theorist making bogus claims for predictions”?  Or am I not, in fact, accused?

In particular, let me requote the accusation he levels at me:

“…misleading and confusing people about the status of string unification by refusing to distinguish between two completely different technical issues.

Question: Is Woit, in your opinion, “misleading and confusing people about the status of string theory as a whole by failing to distinguish between two completely different applications of the theory“?

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135 Responses

  1. Terrific work! This is the type of information that are meant
    to be shared around the web. Disgrace on the seek engines for not positioning this publish
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  2. All that being said, I wish you hadn’t made the occasional snarky remark about Woit’s publication record etc in your debate last week.

    Its one of Woit’s favourite tactics in debate:

    – He will keep making remarks about how his opponent is muddying the waters, misunderstanding basic issues, setting up straw men etc etc until the opponent is provoked into making a personal attack.

    – Then he will immediately play the victim, claim that the entire argument is politically/personally motivated and hence he has no further interest.

    Anyway, I at least learned a lot from the arguments you were making.
    Thanks for that !

  3. Dear Prof Strassler, I’m coming very late to the party, but for whatever its worth:

    Q1: Regarding you being misleading – Not at all. The distinction was very apparent. In fact, your comparison of string theory vacua to initial conditions in Newtonian gravity was a revelation and put a lot of things into perspective for me.

    Q2: Regarding Woit – I’ve followed his blog for quite a while.
    He is focused mainly on criticizing string theory unification – in particular, the fact that ST currently makes no useful predictions about particle physics.
    He also spends a lot of time critiquing the “Multiverse and Landscape” combo, and IMO, rightly so.
    The claim that “String theory predicts a Multiverse with many different laws of physics” is incorrect and simply dishonest.
    I’m not sure whether string theorists or the media are responsible for this hype – to me it looks like Woit blames string theorists.

    Q3: However, I HAVE seen Woit make stronger claims that string theory is not even consistent, and that applications in other areas are not useful either. See for instance, here:

    Reading his blog, I got the distinct impression that String Theory is a set of vaguely defined calculations and approximations without any clear underlying principles or even a self consistent framework.

    If, as you say, (in your most recent posts), you DO have a consistent framework and equations, and the main obstacle to Application 1 is a near-infinite choice of initial conditions, then this certainly is very misleading.

    Looking forward to your sequence on QFT and string theory.

  4. I actually found an answer to my question about why we cannot find a candidate vacua in the string landscape by a process of classification and falsification of alternative vacua .This paper ,http://arxiv.org/pdf/hep-th/0602072v2.pdf , concluded that this problem is at least NP hard and therefore not computationally tractable.

  5. I think that the view that ST is not experimentally verifiable, confuses many. It may be that we will never reach the energies needed to directly confirm but I remind that no one a century ago would have thought it possible to image an atom or explain it’s chemistry through QM.
    Even if ST fails in its goal, we need it researched. Like most mazes one can only find the way through these by testing different paths. Some of those require much leading through the explored maze just so one can see what points in the right direction.
    Thanks to both you and Professor Woit. In the days before the Internet and before the standard model, before Bell ran into Aspect and before dark matter – when I was still in grade school Dirac had already laid out some math and ideas that foreshadowed and in some part laid some foundation for ST. Professor Woit reviewed the book The Strangest Man about Dirac at http://www.math.columbia.edu/~woit/wordpress/?p=1904
    I think his criticism of the last pages of that book by Farmelo reflect that he has a different expectation of beauty and simplicity than did Dirac, but anyway leave that to others.

  6. Dear Prof,

    I am frequenting your site because you are one of the (extremely) few who are trying to “.. serve the public, including those with no background knowledge of physics”. Being one of them who have no great knowledge of high energy physics your website fills my expectations exceptionally well.

    And as far as I am concerned, questions like “Am I Misleading You ..?” should not be posed here. I assume with reason that you ask this question to yourself often enough. You also get it answered by the kind of questions that arise in the comments section.

    Your readers perhaps are well aware that there are differences between experts about a lot of theories, like about string theory. For my needs they should be discussed elsewhere, as I cannot take part in them anyway. Suffice if you mention them or give a link.

    So, please continue teaching the way you started. Few experts can do what you are doing, which in this case is sharing their knowledge without cheating.

    (Also, just having read the comment from Bob (September 22, 2013 at 9:56 AM) I fully agree with him except his last sentence.

  7. I don’t see the point of this post at all. There are hundreds of smart, thoughtful people that come to this blog that leave comments, sometimes critical. They are mostly ignored or briefly responded to in the comments by Matt. And that’s the end of it.

    But when Peter Woit, the failed physicist, turned crackpot conspiricist, criticizes Matt, well then, its time for an entire post dedicated to Woit’s claims.

    It’s actually pretty insulting to the rest of us for Matt to address Woit so much and rarely respond like this to the rest of us. Well Woit is a professor, so I guess this is what Matt cares about, rather than the content of their argument.

    Matt, you only misled us when you gave Woit so much airtime, as though he were really at the cutting edge of physics,

    I will be much less likely to come to this blog again.

    1. I also think it’s inappropriate to dedicate so much space and time to the man and to overlook so many readers who would deserve a much better treatment and much more energy. Moreover, the man is not a professor. He is a “senior lecturer” which is a politically correct phrase for an “superannuated teaching assistant”.

  8. “Unpredictive string unification vacua”.
    Is the universe transparent or opaque? This is a consequence of the massless nature of the photon (conformal invariance of Maxwell’s equations). This assumption enables one to calculate absorptive processes in Minkowski space with an appropriate redshift factor. The galaxies, which we shall assume have a geometric cross section which tends
    to a finite limit (maybe in the form of black holes) as t -+ CO, will eventually bum them- selves out, after which the total photon number per unit comoving volume can only decrease.

    The value of the electron charge would become a defined number, not measured, making magnectic constant μ0 a measured quantity. Consequently, electric constant e0 also would not be exact. This measurement error can be related to that in the fine structure constant α !
    Here relative permittivity e/e0 is misleading in general relativity ? – The imaginary portion of the permittivity.

    It is like the difference between “rest mass” and “relative mass” ?

    /Math is a body of knowledge that can go on its own and does not need evidence from other fields of knowledge to work fine./

    The exponential functions and quadratic functions are stastical – The opposite of polynomial Factoring – the probability density
    — to “bridge” the metric or matrix domains (electromagnetic or realm of photons).
    Relativity make them more “natural”. But whether it is a physical reality or a result of experimental measurement is an issue.

  9. I do not feel misled by either blogger. Instead, I know each has a point of view. What I would like to see, is a friendly rivalry between these two fine gentlemen explaining basics such as Lie Algebras, including math. I would like to see discussion going from Dynkin diagrams to structure constants.

  10. Matt
    Your blog is terrific and there was nothing misleading in your string theory post.
    Now i have a question. I realize that going through 10 ^ 500 potential vacua by hand to see if any bear any resemblance to reality is pretty daunting (although it looks like we might have quite a bit of time available).
    On the other hand, i assume many of these vacua share at least some attributes in common, such that they make the same predictions about at least one element of reality. I also assume that a major effort in string theory is to categorize vacua in such a way based on this commonality of at least one prediction and then exclude the classes of vacua where the common prediction is false and then iterate the process.
    I’m sure it would be extremely interesting to your readers to explain if such a program is possible and potentially tractable and ,if so, where it stands?
    I suppose Woit would argue that such a process is akin to writing Shakespeare with infinite monkeys banging on typewriters, but it is not quite that bad if you accept that 10^500 is not infinity and you start by eliminating monkeys whose typewriters don’t have a working letter ‘e’, etc.
    I am also concerned that this might be an NP complete problem and therefor not tractable at all, although i believe the question of whether a quantum computer could solve a NP complete problem in polynomial time is still an open question.

    1. JWL, your question is very important but might not be able to answer it directly. Yet, it can be answered from a different angle. When the mystery of dark energy is resolved, all those zillions vacua are no longer an issue. While the dark mass and the dark energy are still mysteries in the mainstream physics, it can actually be discussed. I often use an Apple boy/G-grandmother dialog to discuss a very complex problem, as it can address an issue from many different angles. But, it will definitely get to lengthy. Under this comment length constrain, I can only answer your question by showing a backbone framework without any detailed elaboration.

      Dark energy issue can be discussed by asking a few *correct* questions.
      A. The dark energy survey is now investigating the galaxies and supernovae up to 8 billion light years always, as it is the current event horizon for us. Of course, we know that there are something beyond that horizon, as the universe is now about 16 billion years old. Thus, the first question is, “Where is the edge (boundary) of this universe?”
      Answer: *Here*, (why? Omitted). The coffee cup on your desk is the *edge* of this universe.
      B. As far as we know today, the dark energy is the cause for the cosmic expansion acceleration. The second question will be, “What is the outside of the edge for this universe expanding into?”
      Answer: *Next*, (why? Omitted). The universe does not expanding into the *outside* but into the *Next*. That is, your coffee cup (not moving in your eyes) was moved from *Here (now)* to *Next (Here)*. And, this expansion can be written as,
      {[Here (now), Now], [Here (next), Next]} = {Delta S, Delta T} = (Delta S x Delta T)

      C. What is the *cause* to cause this movement?
      Answer: * ħ (Planck constant)”, (why, omitted).
      Thus, ħ = {delta S, delta T} = (delta S x delta T), this is a *cause – effect* equation and the dimensions need not match, as they will be adjusted later on.
      So, ħ/(delta S x delta T) = I

      D. What is *I*? *I* is 1. But there are many *1*s. The 1 cent is dramatically different from the 1 trillion dollars. *1* can carry dimensions. There is a very special *1* = kF. What is k or F? It does not matter at this point. Thus,
      ħ/(delta S x delta T) = kF or F = K ħ/(delta S x delta T)
      By working out the dimensions, the F turns out to be a *force*, and the above is the *Super Unified force equation*.

      Originally, this *Super Unified force equation* was derived from a different pathway, from the fiber structure of the space-time-sheet. Of course, it will be too lengthy for here. Thus, I have used a conceptual pathway here. There are a few very clear concepts here.
      1. The edge of the universe is *Here*.
      2. The outside of that edge is *Next*.
      3. The force moves your coffee cup from *here (now)* to *Next (here)* is the super unified force which is the emergent of the dark energy.

      Now, it is very clear that the dark energy consists of three parts [Space, Time and Mass (coffee cup)], and they three form an *iceberg model* which gives the precise *prediction* about the Planck data (dark energy = 69.2; dark matter = 25.8; and visible matter = 4.82). The detailed calculation for *predicting* the Planck data is available at http://prebabel.blogspot.com/2013/03/planck-data-last-straw-on-higgs-back.html

      With the dark energy mystery resolved, those zillion vacua are no longer an issue.

  11. In my previous comments, I have said that I was not misled by Professor Matt Strassler. As his post is very fair and balanced, I do not think that it can mislead anyone although there are a few commenters saying otherwise. The whole issue is about the M- /F-string theories and SUSY (with s-particles) have misled the entire mainstream physics for the past 40 years. As it should be, the central debating point is about *predictive-ness*. But, it again got into the nitty-gritty, becoming meaningless. I am quite sure that many laymen can agree with me on one point about this predictive-ness issue.

    a. Any prediction in or about the Alice Wonderland is nonsense. Any theory beyond the Standard Model must *predict* the known physics (that is, making contact to it). In this case, it must reproduce the particle zoo of the Standard Model. Both M-/F-string theories failed on this simple criterion after 40 years of trying. That is, they are trashes in terms of *physics* regardless of whether they are made of pure gold or not.

    Woit’s arguments against M-/F-string theories, SUSY (with s-particles) and multiverse are quite weak as he does not have the *correct* answers in his hand to replace those *wrongs*. But, his courage of fighting against a super powerful institution (formed by many big names of M-/F-string theorists and SUSY devotees) single handed made him a great hero in the physics history. I personally do not like his abrasive personality but still must give him my salute for his courage and the great deed done to physics.

    This debate can only be resolved by having the *correct* answers for the mysteries of the universe. As Professor Matt Strassler said, “You need to unify at least hypercharge and weak isospin with gravity if you want to play that game.” Yet, without knowing what the gravity is, any next step becomes meaningless. Today, we are kind of knowing that gravity consists of three parts (visible mass, dark mass and dark energy). Fortunately, we now have the Planck data (dark energy = 69.2; dark matter = 25.8; visible matter = 4.82). Thus, any theory which *predicts* those simple numbers will be a viable theory for these mysteries. In my view that the dark energy issue can be easily resolved by answering two conceptual questions.
    1. Where is the edge (boundary) of this universe?
    2. What is the outside of that edge (boundary)?

    Knowing the answers of these two conceptual questions, they can then be translated into equations. Then, this debate will reach a conclusion.

    1. Woit is neither the first nor the most courageous to fight against the String Theory “Establishment”.

      If I have to name somebody that did put his money where his mouth is (regarding the fight against the ST “Establishment”), is Dr Sheldon L. Glashow.

      We all know that in Science in general, and in Physics in particular, there are no authorities, but only experts, and, in this case, so far the jury is still out.

      Kind regards, GEN

  12. I cannot answer whether you have misled anyone because I do not believe that question has a clear, objective answer at this time (I understand I could be wrong even in this). But I do have a few comments:

    I was surprised to see Woit’s initial objection. I believed you were making a deliberate attempt to distinguish between hype and reality. I would have expected Woit to appreciate the effort. I can only surmise that he believes you are substituting one type of hype for another, but I am in no position to dermine the truth (or truthiness) of such a claim.

    Second, there are clearly very strong emotions in the HEP community. Consequently, it seems many of criticisms of Woit have no basis in reality. I am amazed at the constant barrage of straw men he has to deflect. Whether this is a cause, effect, or both, of his tone I do not know.

    I quite enjoy both of your blogs. They serve very different, but equally fascinating purposes. Keep up the great work, both of you.

  13. I side with Prof Matt’s science approach,
    I understand… the issue is, unpredictive string unification vacua – not “the string unification is BAD” !

    /Math is a body of knowledge that can go on its own and does not need evidence from other fields of knowledge to work fine.
    Differential Geometry, as well as Tensor Analysis have a life of their own without any help from General Relativity (the contrary may not apply as well)./

  14. Matt, everybody knows that string “theory” makes no predictions that are experimentally accessible. The predictions you cite are fantasies that have no chance of being tested. So what? Forget it. Do not care.

    There is no way to avoid, in life, to hurt somebody unwillingly. The desire to avoid such situations, the desire to be innocent, brings a lot of harm on one’s environment. Just check around you: all violent people feel innocent, whereas really friendly people often feel guilty.

    So yes, you unwillingly misled your readers. So what? Forget the incident an continue on you path.

  15. Quest for simplicity?

    According to Lubos Motl, http://motls.blogspot.com/2013/03/tyson-vs-greene-lesson-in-demagogy.html, “you really need something like 1,000 pages for an introduction to the subject [string theory]”. On the simplicity criterion, the string theory of today fails. That does not mean it can’t be substantially simplified – or maybe it can really be a theory of everything. Or maybe the God is a lawyer rather than a mathematician.

    Keep up the good work, all of you, Strassler. Woit, Motl.

    1. It’s a different, more important type of simplicity than a small number of pages one needs to learn it. It’s a simplicity one sees once he masters the subject – a small number of independent rules and laws that control the theory.

      Physics hasn’t been easy-to-learn since Isaac Newton established it. His writings were very long, by the way, and one needed to learn the calculus and other new math tools. These requirements of course grew as physics was getting deeper

      Just like one needs hundreds of pages to learn or teach quantum field theory, the same is true for string theory. In the usual aspects of abstractness and sophistication, string theory is more complex. When it comes to the unified character of the rules and basic concepts, string theory is simpler than quantum field theory in the same sense in which quantum field theory is simpler than previous approximate theories in physics.

      1. the string theory has foundation of the spacetime,that has the noncommutative geometry as base.then the time is splitted-time with 2dimensions- curving the space in infinite 4-dimensional spacetime continuos.then there the string theory appear

  16. Strassler,

    First. To establish some context, I am a well established researcher in math phys and in applied physics.
    To the basic question, “Are you misleading me?,” the answer is no. But this is only because I have read a multitute of sources, thought about the science/math, and find that your position is incorrect. Your writings are an attempt to mislead, but it is not clear that you realise that. It is clear that when someone has a significant fraction of their career, that is, has invested a big part of themselves, on a position in public, it is easy, even necessary, to fool one’s self and believe. It is almost religion. Most scientists deny this, especially in themselves, because they have a view that psychology plays no role in their thought processes; all is pure logic. Even the above question is a manuever to rally support and thus strengthen your own resolve.
    High energy physics is not unique in this behavior nor even the first. The behavior is driven by money, a desire for fifteen minutes of fame, fear of failure, a seeking of security. Another field of physics that suffers horribly from self delusion is magnetic/inertial fusion, especially as relates to power production. In the recent Physics Today there is a piece on mounting an interstellar mission. Another is the space elevatorr. Physics is not alone and the pressure even drives some to fraud.
    A statement on the usefulness of string theory as a tool. Yes, it is, but the degree to which it is usefuI is very overhyped.
    As to whether Woit distinguishes between the use of string theory as a tool and as a particle theory, I can say that he does, at least for the two or so years that I have followed these several blogs. His stance has always been clear to me.
    There is no need to respond to me because I am not arguing, I am just stating my position. I have read the arguments more than enough, but probably will continue to observe, as it is somewhat entertaining and I am interested in seeing how the story plays out. I have no desire to participate
    in the almost endless round and round.

    Take care

    1. “Your writings are an attempt to mislead, but it is not clear that you realise that.”

      You really can’t have it both ways, jd.

      “Even the above question is a manuever to rally support and thus strengthen your own resolve. It is clear that when someone has a significant fraction of their career, that is, has invested a big part of themselves, on a position in public, it is easy, even necessary, to fool one’s self and believe. It is almost religion. Most scientists deny this, especially in themselves, because they have a view that psychology plays no role in their thought processes; all is pure logic. The behavior is driven by money, a desire for fifteen minutes of fame, fear of failure, a seeking of security.”

      How fortunate for the rest of us that YOU’VE shown up to offer your assessment of Matt’s psychology.

      “There is no need to respond to me because I am not arguing, I am just stating my position. … I have no desire to participate in the almost endless round and round.”

      Well, you just “participated,” and you did so in an incredibly condescending and dishonest way.

      Obvious troll is obvious.

  17. The truth of these two sentences:

    1 String theory needs the tremendous assumption there are more than 4 space-time dimensions and is extremely difficult mathematically.
    2 We can’t actually build a particle accelerator capable of testing these predictions (of string theory); our technology is about a thousand million million times below where it would need to be.

    is probably too much for any “normal” person but let us not discourage the courageous ones.

  18. I want to add something that I feel has been overlooked so far, and that is string theory’s enormous contribution to mathematics.

    I understand that most of the buzz on here is over whether or not string theory is contributing to our understanding of Nature and the Universe. The answer you get no doubt depends on whom you ask. But as long as one person has found the theory beneficial in the usual predictive sense, or even at the level of creating new insights, then the answer should be a resounding “Yes.” And let me emphasize that such benefits should not be limited to application of the theory as a whole, but extended to any and all of its local principles or subcontexts. (Point, set, match to Matt on this one.)

    But it works both ways. When Witten (who started his doctoral program in applied math only to later switch over to physics) decided to let the intrinsic beauty of math govern his way of thinking, it led to a mathematical revolution of sorts (particularly in homological algebra, algebraic topology, and differential geometry). An entire community of mathematicians rallied in response to Witten’s program, and it led to many meaningful discoveries.

    Now here’s the thing. These mathematical discoveries depend NOT ONE WHIT on the future fate of string theory. They are absolute truths. And such truths have a habit of resurfacing, be it in a similar theory or a dissimilar one. That’s just how mathematics works.

    I realize that my comments may be a bit oblique to the main line of discussion here, but if I met a string theorist on the street I’d buy him a caramel macchiato.

  19. “String theory can serve as a tool. You can use its mathematics”
    Perfect, I love maths 🙂
    “Here’s an example”.
    Ok, I immediately go there, even if I’m reading from my droid…
    I can’t find the maths. Well, it’s my fault, I have to switch on my laptop with a bigger screen 😉
    I’m in a hurry, I skip sentences and periods, yet I don’t find a single formula, theorem, equation…
    till I see
    “BlackHat is the computer program that Kosower and his friends have written to…”
    I’m a programmer, I love this, so I’m already opening the pdf…
    but it’s just full of external references … I try to search on my own, finally I find
    http://arxiv.org/pdf/1111.5759v3.pdf “An Introduction to On-shell Recursion Relations”
    “A picture from string theory, where gravitons are described by closed strings, provides a very good hint. The celebrated Kawai-Lewellen-Tye relations, which express on-shell graviton amplitudes as “squares” of on-shell color-ordered gluon amplitudes, were derived by taking the field theory limit of string theory, based on relations between open and closed strings.
    Although “squares” like KLT relations are natural in string theory, they are totally obscure in field theory. The Hilbert-Einstein Lagrangian and the non-Abelian Yang-Mills Lagrangian are very different.
    It is very desirable to have an understanding purely in field theory. ”

    Let me understand this!!!
    Maybe you should write an article about Weyl spinor, Dirac equation, Lorentz group, Gauge theory, Lagrangian, Lie group and non-abelian group…


    1. This is an ill-defined question. There are 19 parameters (if I recall correctly) in the Standard Model. Specify the 19, and you can (in principle) predict anything. Of course some calculations are very difficult. But we are lucky: the Standard Model consists of three types of forces, each of which was relatively easy for humans to figure out. Our calculational tools are pretty good and improving all the time.

      Meanwhile, because there are a vast number of vacua in string theory, you have to tell me which vacuum you are in. In some (not very useful or important) sense, string theory has no parameters; there’s only one string/M theory, as far as we know. But that’s not important, because to predict anything in string theory you must pick a vacuum from the insanely large (no one knows HOW large) library of them. Until you do that, string theory predicts virtually nothing — maybe literally nothing, I don’t actually know. (Woit will tell you it is literally nothing even in principle, but I don’t know how he knows that.) You can’t really say how many parameters are required to specify the vacuum, because they aren’t adjustable like dials. You just have a huge pile of 10^100 or 10^500 or 10^2000 choices, and somehow you have to figure out which one you’re in, without tuning any dials to move gradually from one to the next.

      In short, string theory and its vacua are currently a complete mess, as far as Application Number 1. I have no idea how anyone will get it out of that mess, but stranger things have happened in science…

  20. Matt, many of the physics-specific details in this exchange are passing well over my own head (my fault for not following your blog more closely). But I find Steven Ericsson-Zenith’s response above especially intriguing nevertheless. Perhaps a future post on your own epistemological underpinnings would be instructive. I know that I would be very interested in reading something of that sort. In fact I’d be very interested in seeing you address the rest of Steven Ericsson-Zenith’s thoughts directly as well.

    Hoping things are well with you,

  21. I am only a lay observer, but from having read this blog for the past couple of years it is clear to me that Matt Strassler is *not* a cheerleader for the String Theory team.

    Reading David Woit’s comments and criticisms you’d get the opposite impression.

  22. The truth of these three sentences:

    1 String theory does not work in 4 dimensions
    2 String theory and its applications are extremely difficult mathematically
    3 “we can’t actually build a particle accelerator capable of testing these predictions; our technology is about a thousand million million times below where it would need to be”

    should be to much for any “normal” person (“normal” here by definition :-)) but let us not discourage the courages ones.

    1. Matt, thanks for deleting but you deleted the wrong comments. I’m sorry, could you delete this one and the two comments right above this one. Then I will rephrase what I wanted to say because I do think it is at the heart of the matter. Sorry again.

  23. Mislead…Mislead? You Matt, no way! Certainly not intentionally…

    But don’t ask us, your gentle readers to judge, at least don’t ask those of us who do not have a PHD in physics and did not spend the better part of our life’s studying String Theory. How the hell would we know if we were misled? We are going to tell you “no, of course not” – not because we really ‘know’, but simply because we like and respect you and we know by your posts the time and effort you put into the site. Also there is probably not one of us who at one point or another hasn’t said: “Wow, I didn’t know that” reading your posts. So please keep at it…

    As to String Theory, there is a big difference between what I ‘know’ and what I’ve ‘heard’ (but don’t really understand). I know that in String Theory the fundamental particles are not viewed as point particles but as tiny (really tiny) strings on the order of 10^-35m in length. I know that this gets rid of a multitude of nasty infinities that otherwise show up in calculations with point particles. Strings are so small it would take an accelerator the size of the solar system to test this aspect of the theory. That is not the theories fault, that is just the way it is.

    Then there are things I’ve heard, but don’t really understand. I have heard that depending on the String Theory (as there are certain basic variants) there are either 10 or 26 dimensions. And somehow connected to this is the fact that String Theory is a natural candidate for a Theory of Everything (TOE), a theory that unifies the four forces of nature. Somehow the theory identifies a closed loop string with a spin 2 zero mass particle – the graviton, and somehow if you have a theory with gravitons you have Einstein’s General Relativity (though how this works is a great mystery to me).

    Then I have heard that String Theory explains the weakness of gravity by postulating that that closed loop strings – gravitons – are not locked into our four dimensional space-time but travel through all 26 or 10 dimensions thus diluting the force to its observed level. It is my understanding that there is a fairly simple equation (can’t remember it right now) that relates the distance at which gravity becomes much stronger to the number of dimensions …or some such. However all experiments to date indicate Newton’s inverse square still holds down to 10^-6m or so.

    After that I pretty much go blank…except for the image of Lisa Randall on Morgan Freeman’s “Through the Wormhole”, tossing elastic bands with magnets on the ends (open Strings, electrons, quarks, photons, etc.) at a metal board (the Brane) all sticking, while the closed loop strings (gravitons) do not stick…

  24. Two things I can say about Woit who is a smart guy and should know better. One he is arrogant. Two he is emotional. Two things which are detrimental to a truly critical thinking scientist where unemotional skepticism or at least doubting our strong virtues. There is nothing wrong with having preferred beliefs, that is one way theoretical breakthroughs are made, but to outrightly not listen to the opposing view and then accuse them of things is at best unprofessional. However, this is high stakes physics where ego’s trample on peoples feelings. Your not like that, but I admire you for sticking up for yourself. I do like Woit’s blog, but I wouldn’t want him for a thesis advisor or boss.

  25. String Theory is a tool but what is the use of a screwdriver with a head that does not comply with any screw ?
    String Theory is not testable because it is a way of thinking, which of course is not wrong, it is just one of the ways humanity “thinks” it can explain REALITY. In fact it philosophy with a lot of mathematics.

    1. Well, that is not completely correct in a sense.

      Let me give you an example.

      Einstein was completely convinced of the principle of non priviledged observers as being a very strong principle in Special Relativity first, as welll as in GR.

      To make sure that que equations of GR were really consistent from the standpoint of the equivalence of all observers, no matter what reference body any observer would be standing on, he invented all sorts of weird and absurds reference bodies, with all sorts of possible characteristics, so as to be able to test that the equations were form invariant for all these weird systems.

      Even though he thought that many of such systems were not very likely to happen in nature, he also thought that from a conceptual and theoretical standpoint, it was valid to use them.

      I do not see why we could apply a similar idea with ST regarding that some of its concepts many not be very likely to apply to nature but nonetheless it does make sense to use them.

      Kind regards, GEN

    2. That’s not true. String theory is not a “way of thinking”; it is a set of equations, a set that is incomplete and poorly understood, but can nevertheless be used to make certain calculations.

      And string theory does in fact give you a tool to solve problems that are relevant for thought experiments and even real experiments. I now feel compelled to explain this long chain of arguments carefully; I had no plans to do it, but with statements like these, I feel I have no choice.

      1. I think you should use your time more productively Matt. Don’t get bogged down with all this Woit stuff. Take a bit of a steer from this interesting little chat. But otherwise carry on as you were. Now where were we? Bass guitar: Dummmmmmm….. A resonance.

    3. the string theory is a theory purely mathematics ,with just some relations
      with the physical world taken by ours minds.
      the background of the strings theory has spacetime as it supports.

  26. Back before the World Wide Web we used to split the blogs into parallel branches for expository and oratory. All we had was ASCII text, but we were scrappy.

  27. i think that only is possible that the string theory be correct in 4-dimension manifolds with exotic structure as the connection of space and time in spacetime continuos that has the metric of einstein.but no existence of extradimensions

  28. For those of you who contend that String Theory is not a scientific theory because its predictions are not experimentally verifiable, let me say at once, I agree with you. Nonetheless, it is an unshakable mathematical theory (as is any theory that is built from axioms and conforms to certain universally accepted mathematical ideas and principles). The “promotion” of a mathematical theory to a scientific theory depends on how well the former models reality, and this is often a question of great subjectivity. Additionally, some mathematical theories model reality only locally, and this has proved to be of significant scientific value historically.

    I wonder how many who superciliously reject String Theory would be willing to characterize the theory of the Big Bang on similar dialectic grounds. Its predictions are not experimentally verifiable (at least not until we are able to “look” below Planck density, which, according to QM, is never). Yet no one would deny its role in providing certain speculative insights as the human mind strives to perceive its surroundings.

    1. Let’s keep mind the famous quote from Benjamin Peirce: “Mathematics is the science of the necessary conclusions”.

      Following from this principle, we can assert that math is a body of knowledge that can go on its own and does not need evidence from other fields of knowledge to work fine.

      Other fields of knowledge are all the time going to the watershed of Math to get useful stuff to work on.

      Differential Geometry, as well as Tensor Analysis have a life of their own without any help from General Relativity (the contrary may not apply as well).

      Kind regards, GEN

  29. ” String theory is an essential tool in the toolbox of the theoretical physicist, and it’s here to stay — not because it’s necessarily the theory of “everything,” but because it has proven over the decades to be profoundly and broadly useful.” – From String Theory to the Large Hadron Collider http://profmattstrassler.com/2012/08/15/from-string-theory-to-the-large-hadron-collider/

    Pretty straight forward. The creation of insights is an important aspect of applying tools for that creating of insight.

    “Dr. Maldacena and Dr. Polchinski each gave brief lectures related to their work. Both included broad overviews of string theory basics, with Dr. Polchinski noting the importance of “thought experiments” to help physicists make advances in the field. He said that physicists are excited about future experiments using particle accelerators such as the Large Hadron Collider at CERN, where some of these “thought experiments” could be validated.” Noted physicists awarded Dirac Medal- http://prizes.ictp.it/pio/words/news/prizes_news/2009/noted-physicists-awarded-dirac-medal

    So I think it has been pretty clear to me where you stand Prof. Matt Strassler

  30. Having followed his posts for a while, he only has issue with string theory as a comprehensive physical theory of everything. Now, I have other thoughts about his views that I won’t elaborate at the moment

  31. Matt, When I look at the volumes you have now written to make modern physics more accessible to the non specialist – its amazing there have not been more challenges from other physics specialists about some misleading statement or other. I am sure you won’t let the occasional broadside from one or two others stop you and your back is broad enough to shrug off such things. I wonder how many challenges these critics would get if they attempted to produce a similar volume of free, publicly accessible material?

    And another thought. How many of the challenges are coming from those who want to sell you their books instead of giving it all away as you do?

  32. Woit did seem to get very evasive by the end of the discussion, he didnt address the points you specifically laid out and instead has responded with exaggerations about funding issues. (Despite you stating specifically that you dont blame him, and it not being hugely relevant to much of the discussion.) To be fair though you have both been rather quick with each other at times.

    He has also gone on to say that this response is taking him out of context, but I dont see that it has done. You summed up his point in the green text and if thats not what hes saying then hes done a bad job of putting things across.

    I think Woit does seem to make some reasonable remarks despite this. I think the addendum genuinely made things clearer and while Im certainly not qualified to tell for sure I have to suspect that fleshing out those details further could make things clearer still. (Though Im sure there is a limit to this given the complexity of the subject.)

  33. Matt, I don’t think you have intentionally mislead people, but that does not infer you know where you are actually going. There are so many others in the HEP arena trying to fit this universe (data) to theory (ST), and finding it wanting and irrational in their anthropic reasoning landscape, or ‘preposterous’ as Sean Carroll would say, thus allowing themselves to float away from our reality, practically sneering with disdain about our unexceptional (boring) corner of existence in their far grander multiverse.
    Peter has his own blind spots and can make no commitment to how much of the SM will have to be scrapped when it becomes clear that the rot he describes goes considerably deeper than ST, and will shake his entire beloved mathematical comfort zone to it’s very core when he realizes how many of his own oxen we be gored in the house cleaning.
    That being said, Peter is pointing out the obvious truth: ST is a mathematical theory in search of a purpose (and continued funding) now. It has failed in every hyped and portentous purpose rebranding to date. In actuality, Application #2 continues to grow in desperation as Application #1 continues to whither in frustration at an accelerating rate which is evidenced by university hiring trends across the world. Peter is also correct on one other major concern: ST has hurt HEP. Too many exaggerated promises, too much nonsense and outright lies, too many resources, going to one theory at the expense of other avenues of research, and yes, there were other avenues. Think of it as a physics community equivalent to “Too Big to Fail”, which shouldn’t surprise anyone considering what the math quants who ran over to the finance sector (after abandoning ST) did to ‘finance risk assessment’ and the world economy (same nonsense, same exaggerated promises, same implosion, different subject).
    That too having been said:
    I am NOT either one of your sycophants, and I call for a Pox on both your houses.
    Matt, Einstein was at least talking about space and time how they relate to observation in this world, he lived in reality and still liked it, he admitted he made mistakes, claimed he still needed to fix things until the day he died, and he wasn’t diddling around with a slide rule to see if it gave him a magic number he could hang on something and claim it a prediction. Studying more complicated purely mathematical structures of any kind with a ‘tool’ made of math that can’t describe our universe accurately is not in the least bit likely going to lead you closer to ‘physical’ anything. If you want to ‘gain insight’ and better understand your kid, you observe your kid, not your best friends twice removed ex-wife two states over…who died of moose bites years ago. Mind you, moose bites can be very nasty!
    Peter, you are very good at pointing out the foibles of ST. Your criticisms are polished and valid. BUT…You are dreadful at removing the beam from your own eye, as you sit in your glass house with a slingshot in your hand and a smirk on your face. The Standard Model is no more coherent logically than the ‘dippy processes’ that it relies upon to work at all, that still have not been cleaned up or corrected. At least Feynman admitted everything leaked and that his magic ‘trick’ was probably not mathematically valid.
    You are professionally comfortable with the inconsistencies, circular logic, messenger photons that are smarter than golden retrievers, hand waved renormalizations, appearing and disappearing magic void particles , and completely non physical physics that rely on very pushed math and sophomoric debate tricks to skirt explanation. Lets say you get your wish, and ST comes tumbling down. Have you given it any thought? What do you think will happen next, folks are going to say, “Well, everything was fine until that no-good rotten STRING THEORY came along, moved in, stole our lunch money, went crazy and ruined the neighborhood, Whew, now things are going to be great!” What they are going to do, Peter, is start asking questions like: Where did we go not even wrong? Did this just happen all of a sudden? Where did this odious string thingy come from? How long has this kind of stuff been going on? Is what ST evolved from any more valid or less crazy?
    And they are going to find a back trail of BS (not the degreed kind) leading right to your prestigious house of SM. What will you do then? Claim you didn’t know there was a slight foundational problem? Change your blog name to “Not Even Wrong…About The SM Too”?
    If I ruffled either of your egos…good. You both really need it, and you both already have enough adoring fans to cover your whine fest.

      1. I’m not the guy who feels superior to both the fundamentalist and the atheist, Mike. Like Steven Ericsson-Zenith said, this debate is more of a religious discussion than science. I’m more like the atheist here. But not quite. Like I said above, I’m siding with Matt.

        1. Sorry, I should have been clearer—I was replying to Chris.

          I believe that Chris has committed the “false equivalence fallacy” here. Twice, actually:

          #1: Between the precarious position of string-theory-as-a-theory-of-everything and the soundness of the Standard Model (you know, that pesky theory that never gets anything right-oh-wait-it-actually-successfully-predicted-the-Higgs-and-many-other-phenomena).

          #2: Between Matt and Peter more generally as pertains to the context of this thread (please correct and forgive me, Chris, if I’m inferring something here that you didn’t mean to imply). Yes, Matt has responded to Peter with a few low blows, but Peter has accused Matt of being *purposely* misleading on this subject. The middle ground is no high road here.

          1. No probs Mike. But IMHO there are some “issues” with the Higgs. Like Matt said, the mass of the Higgs particle does not entirely come from the Higgs field! The Higgs mechanism is said to be responsible for 1% of the mass of matter. IMHO that’s wrong. It’s 100%. And trust me, the middle ground is the right ground. Ever looked at a lattice? Twang it. You could focus on the squares. That’s QFT. Or you could focus on the lines. That’s string theory. The middle ground is knowing what you’re dealing with. And on balance, Matt occupies it. Hence I’m backing him. You should too.

  34. I can’t answer second question, because I couldn’t fully understand the nuances of it.

    About the first question: What I always thought is that string theory can’t be tested experimentally because the energies required were way out of range. Hence I never viewed it as a scientific theory, as scientific theories need to be falsable claims, which ATM is just not possible, and it is not likely to happen soon.

    I thought too that string theory had a lot of flexibility, you can choose some things to change radically what the theory predicts.

    So in that light, reading this blog (which I have started recently and I enjoy immensely) has not changed my views, either they were correct or not.

    The only point that Matt has brought home with me, is that string theory although not a scientific theory, can be useful. Being a mathematician I know that riemman geometry was developed before it had any usefulness, so for me there is no resistance in accepting that string theory can be useful even if it is not right.

    Sorry for the long answer, but I wanted to be thorough, as this debated is quite heated.

  35. The distinction between application 1 and 2 were crystal clear from the start. Also, the provision that only certain types of string vacua could theoretically be tested in an experiment we can barely imagine building centuries in the future. It was not exactly a rallying cry for application 1! I can only hope you keep up the good work Matt.

  36. What I always feel funny about such warnings “xy misleads about abc” that the warners seem to think people have no mind of their own.

    Mr. Strassler I read you blog and Mr. Woits over the years and it is obvious you discern better and restrain from broad conclusions and I have always liked that about you. Mr. Woit is more on the rethoric side.

    If anything you explained the problem with string theory in more detail, and more understandable. So I honestly dont see why you should care too much. You dont need our opinions to strengthen you, a simple statement lile: “I dont mislead, to the contrary, I explain it in detail” would have been all thats needed.

    The more energy you invest in defending you case the worse. Mr. Woits accusation cannot really hit you, ever.

  37. I think that Dr Woit objects to the idea that ST #1is still taken seriously after moving the goalposts to an energy level we will never be able to test after failing (in his opinion) to find any confirmation in the LHC results. Test after test seems to conform to the SM and yet he still feels that ST dominates the funding and the papers, and undeservingly so.

    Otoh Dr S. Clearly points out that most ST people are not working on any grand unification theories but rather pushing to find some handle on where the next breakthrough will be. And he’s said many times that ST has many flaws that render it less useful as a picture of #1 while still being a useful tool for calculations of a meaningful sort.

    Soooo Dr. W seems overwrought here.

  38. To raise objection to a claim that string theory has been “blown out of the water” is certainly not tantamount to claiming that string theory is a perfectly viable theory. I do not see that Matt has committed any impropriety in this post, or in his (now infamous) initial post. Further, for anyone to insinuate that his (mis)deeds have been “intentional” is unjustified and undignified.

  39. Matt – I am a layperson and I imagine fairly typical of your target audience. I have a real interest in physics, and a little background in the subject but I have never been able to come terms with quantum physics. The maths is too hard, the concepts seem too weird, the popular science books don’t go deep enough, and the professional stuff just goes right over my head. You do a brilliant job of bridging the gap for people like me and you have contributed greatly to my understanding.

    I have certainly never felt misled by your writings, and I really appreciate what you are doing on this blog.

  40. “String theory can serve as a tool.” If string theory is not an indispensable mathematical tool (i.e., other mathematical tools can accomplish the same tasks as string theory), then the “applications of string theory” might be considered a form of hype. I say that this blog has done a good job of clarifying the issues involving string theory (except on the Milgrom issue and the space roar issue). In mathematics, it’s hard to argue with success, and string theory is very successful mathematically. Are quantum incompleteness and quantum indeterminancy the two pillars of quantum gravitational landscapes?

    1. I like your point about being or not “indispensable” and if “other mathematical tools can accomplish the same tasks as string theory”. When I was young, this thinking was a main motivation for me to disregard string theory; after all, it was about sweeping manifolds with a line; usually with a closed line, sometimes with some boundary. But it seemed to me that topology had already, or should develop by itself, the tools to do such kind of scans; and that the geometric aspects of positioning a line inside a manifold with some metric were already perfectly captured by the Riemann tensor. In fact, given some definitions of Riemannian curvature, it was hardly surprising that the idea of using the moves of a world-surface to measure a manifold was producing such tensor and thus “gravity”. So I deemed string theory “not indispensable”, without considering the different pace of development of mathematics and physics.

  41. No, rest assured, you have not misled anyone.You are entitled to your opinion and you have clearly stated that. Moreover you are very knowledgeable, polite and “nice” in answering questions. People should read different blogs anyway and form their opinion, just as in political sphere, people should not just listen to either FOX or MSNBC channels only and expect clear perspectives!!! (Just kidding!) Personally I do not mind these wars! My guess is that when SR, GR and QM were proposed, there were fierce battles. But there was no internet, so they went at a slower pace. Presently, I think ST should be given some more time. Even if it does not have any direct experimental support, at least it unifies GR and SM , which no other framework does at the moment.

  42. Peter looks a little mischievously ornery, just like one of my grandkids. Are you? Good kid but can drive me nuts. Excuse my comment.

  43. The whole thing seems like a lingual problem. If we separate 1) The String Theory of Everything [SToE] from 2) the working toolbox of string-based equations [toolbox] the problem seems clearer.

    Woit’s point is that 1 doesn’t make testable predictions, and that the Brian Greenes of the world have done real damage to science by claiming that a SToE is plausible.

    Strassler’s point is that the string toolbox has been massively successful as a framework (whether strings actually exist or not) and the Woits of the world have done real damage to science by making the term “string theory” synonymous with pseudoscience.

    Seems like the issue is using the same blanket term for different ideas… which is of course what Strassler made special care to avoid doing in the initial posting. Once we get to the comments section it becomes a lot of unintentional talking past each other without realizing it.

  44. Whoa, way too much for my finite mind, when brilliant minds disagree, of course, and every theory has its limitations, even the best to date. Though the worst, whatever those are, have a purpose. Please be courteous. My ears hurt or is my mind?

  45. This stuff is hard. You do a great job. I don’t know enough to know if we are misled (aforementioned hard) but it does not seem like it to me.
    Do physics blogs attract strange, and even demented, followers? Yes.

  46. Perhaps a deeper reason for the current confusion and flame is that eventually some “2nd kind application” could imply the success of a different kind of “1st kind”; so one needs to keep always distinguishing between hype and future, hypothetical, possibilities.

    Suppose for instance, for the sake of discussion, that compactification on some “unknownfold” allows for a oriented open type I superstring -a currently forbidden beast-. Such strings could be used, and this should be an example of the 2nd kind, to study the now trending composite higgses and even for composite models as -to name one- hep-ph/9510342. And if one of such models happens to be unique in some sense, it could be claimed as a final success of string theory of the 1st kind, even if has not been discovered by a process of theorising about string unifications.

  47. Dear Dr. Strassler,

    I always come here to learn something about HEP and I’ve never been disappointed.. You impress me with your careful exposition of complex topics and extraordinary patience in answering comments; a phenomenal teacher.

    Innocent on all counts!

    Redeye’s and Joan Vaquez’s words speak for me as well.

    Many thanks.


  48. Just to point out the obvious: my words are being taken out of context, by someone who it seems blames me personally for ruining his career by poisoning the mind of some wealthy person who was ready to provide millions for a Strassler-led LHC institute. Go read the actual exchange of comments if you care. The whole thing though is so bizarre and with such little relationship to reality or a serious discussion of complex issues that I can’t see why anyone with any sense would bother.

    1. Peter, on other hand, if you add to the context the example
      of Type 2 application of string theory, it is at the same time more understandable and more puzzling: Strassler seems to be implying that your criticism ruined the development of the theory described in that example, which nowadays -from a couple days ago- is known as the theory of the Amplituhedron.

    2. “[B]lames me personally for ruining his career … ”

      Wow, exaggerate much?

      And yes, he did take you somewhat out of context here, but you weren’t exactly specific on the other thread about which “two completely different technical issues” Strassler “refus[es] to distinguish between.” If you weren’t referring to the two applications of string theory that he specifically went out of his way to distinguish between in that post and in this post, then what WERE you referring to? And if you WERE referring to the two applications of string theory that he specifically went out of his way to distinguish between in that post and in this post—well, then you’re just wrong.

      (In other words, there was a lack of clarity on your part in the other thread that undercut your attempt to associate Strassler with the string-theory hype machine that he’s often criticized.)

      1. Mike,
        To quote myself:
        “String “vacua” designed to provide string duals to QCD are just completely different beasts than the ones that have to do with string theory unification.”
        The whole discussion was about predictivity of string vacua, I don’t see how one can read what I wrote and not understand that the “two issues” I was talking about are the one I was complaining about (unpredictive string unification vacua, claimed by Matt to be predictive in his posting), and the one Matt was trying to use to muddy the waters about string unification’s problems, string vacua like the AdS/CFT case, which are something completely different (If you don’t care that your string vacuum looks anything like real world physics, you can do all sorts of interesting things).

        If you honestly read what I wrote, I don’t think that it was unclear this is what I was talking about. These are exactly the same points I’ve been making for years, ad nauseam.

        1. I am not, nor was I then, nor have I ever tried to muddy ANY waters about string unification’s problems. Let me say it explicitly: string unification’s problems are ENORMOUS. That has been my opinion for 25 years… not just the 10 years since all the string theorists came to that conclusion. And that’s why, in my entire career, I have never ONCE worked on string unification.

          Peter, you’re so locked into this one issue — “String Unification is BAD” — “String Unification is BAD” — “String Unification is BAD” — that you’re no longer able to listen. And you paint even people who mostly agree with you with the same brush as people who disagree with you, all the while making indefensible, scientifically unsound statements.

  49. Oh, and when I say “useless”, I do not mean in the “tool” sense, I mean in the “prediction” sense 🙂

  50. Let start out by stating my starting position. I am a physicist, though in an area far removed from particle physics. I am therefore quite a bit more knowledgeable than a typical layperson, but not even remotely as knowledgeable about this particular topic as either Strassler or Woit. I also am a long-time reader of both Woit’s and Strassler’s blogs. I find both enjoyable and informative.

    As to the two aspects of string theory, I don’t see how any serious reader could fail to note that Prof. Strassler’s original post went out of its way to distinguish between them. He even enumerated them, and then referred to each aspect by number in the rest of the post. When I first read the post, I was impressed that he did such a good job of distinguishing these two aspects of String Theory because confusing these two applications is common.

    Regarding whether or not the original post is misleading about the ability of String Theory to make predictions, here I disagree a bit with Prof. Strassler.
    Yes, he says “vanilla string theory”, but the average reader has no idea what that really means. The average reader does not understand that “vanilla” string theory is a tiny speck in a vast ocean of theory. It ignores the fact that a major problem with String Theory is that we DON’T KNOW which version to use! Comparing the landscape of QFT to the landscape of string theory is very misleading, because in QFT, WE DO know which version to use. OK, we don’t know EXACTLY which version to use, but we have a pretty good idea. Going back to the “flavor” analogy, in QFT we know that the dominant ingredient is vanilla. Is it possible that a dash of sugar or a pinch of mint is in there? Sure. But we know it is not going to turn out be pure chocolate. The problem with string theory is that there are 10 to the 500th power flavors, and we have no clue which one is even the main ingredient. In order to say that “String Theory” as a whole makes predictions, you need to have some basis for saying either a)all flavors of String Theory make this prediction or b)you have a good reason to choose your specific flavor over all of the other ones.

    So my verdict is this: On the question of whether or not Prof. Strassler misled concerning the two aspects of String Theory, I say NOT AT ALL. I would question whether or not anyone who says he did even read the post.

    On the question of whether he misled about String Theory making predictions, I would say yes, to an extent. While he did use the qualifier “vanilla”, I think the significance of that qualifier would be lost on the vast majority of readers. Most would take this as “String Theory” in general. Even if they noticed the qualifier, they would not know that there is no reason to prefer “vanilla” predictions over the multitude of other flavors.
    Obviously to the extent that there was misleading, it was not intentional. In his mind, and in a technical sense, what he said was correct, but it was likely to be misinterpreted.

    The only point on which I would say a fully disagree with Prof. Strassler is in comparing the landscape of QFT with that of String Theory. If the landscape of QFT were anywhere near as much of a problem as the landscape of ST, QFT would be just as useless.

    1. On your last point — “The only point on which I would say a fully disagree with Prof. Strassler is in comparing the landscape of QFT with that of String Theory. If the landscape of QFT were anywhere near as much of a problem as the landscape of ST, QFT would be just as useless.” I think you misunderstand me — which is my fault, I wasn’t clear.

      I said: “In a sufficiently complicated theory”, and I meant that. For instance: if I had a field theory with thirty gauge groups, fifty-seven types of fermions and a few hundred scalar fields, how would I ever compute the effective potential and figure out where the vacuum of the theory was? String theory is more complicated than this, and the problem of finding its preferred vacuum, even if there was a unique one, is extraordinarily difficult. But my point is that complicated field theories share this problem.

      On your middle point — I am still struggling with how I should have done this. On the one hand, of course you are right that there are a vast [VAST!] number of very different types of vacua in string theory. On the other hand, it is very common, if you actually look at vacua, to have a set of massless particles (or particles very light compared to the Planck scale) that are weakly-interacting strings, as in a vanilla string theory. Besides that fact, we actually KNOW that we live in a rather weakly-interacting sector of the universe — that’s why the Standard Model is described by a weakly-interacting, calculable quantum field theory at LHC energies. So I don’t think you can claim that my statement about how particles will scatter *if* they are tiny strings is absurdly limited. More to the point: precisely *because* I can predict how strings scatter, I can *check* if they are weakly-interacting, tiny strings. So that, too, is a prediction, even if it turns out to be false! In short — why does a prediction have to be right, experimentally?! The important thing is that it is rigorous, scientifically well-defined, and falsifiable!

      1. Matt, my overall impression from the general tone of your blog is that like Lubos Motl, Peter woit etc, you’re interested in educating the public about the state of physics, and you don’t deliberately mislead people. But like us all, you get rattled when someone in the media, including blogs, expresses a misinformed view of String theory, SUSY etc, and so you have a need to put the record straight.

        I also get the impression that there’s going to be a decline in funding for String theory, more funding for QFT over the coming years because of what the physics community, lead by academics such as Nima Arkani-Hamed, has decided is worth pursuing in the near future.

        1. I’m not sure Arkani-Hamed has that much influence, actually. Frankly I’m not sure who does, right now. There’s arguably a leadership vacuum.

          But public funding and faculty positions for string theory in Application Number 1, and in applications to math, already started shrinking years ago. (String theory as applied to math is now just as likely to be funded by NSF Math Division, I think.) That’s been partly compensated by large donations of private funding, to things like the Simons Center at Stony Brook; Simons is famous for his important mathematical physics work, and went on to make a killing using mathematical finance.

          I don’t think funding for Application Number 2 within physics, at least for people who are doing the highest quality work, has dried up… relatively speaking. I’m not sure because I haven’t been doing this for the past five years

          What’s more worrying is that funding for science as a whole is drying up. So what’s more accurate to say is that everyone is being cut, but particle physics (appropriately, in my view) is suffering less than more formal areas of the field, like pure string theory, with applied string theory somewhere in between. Unfortunately particle physics for the LHC never really reached its potential in the U.S., due to a variety of causes, which a number of us worked hard to counter, but failed.

          1. I mentioned Arkani-Hamed because he’s a well known, charismatic public speaker, but mainly because it looks as if his collaborative research into scattering amplitudes over the past few years might be hinting at the next mini revolution in physics, as you mentioned some time ago on this blog:


            and recently publicized:


            The fact that the LHC is currently running adds to its importance, and its ability to influence the physics community into deciding which topics are hot and exciting in the foreseeable future.

            1. Well — keep in mind that what Arkani-Hamed and his friends are doing, while very impressive, still only applies to very special quantum field theories with no immediate real-world application. They are working mainly on the so-called “maximally supersymmetric field theories”. It’s a long way from there to a theory like QCD. But not SO long. It is by no means unprecedented to use the maximally supersymmetric field theories, and then the minimally supersymmetric field theories, as a stepping stone toward the non-supersymmetric field theories like the Standard Model. This was done for so-called “one-loop” calculations, which are calculations which account for the first effect of quantum fluctuations of fields on the scattering of particles.

              In short, this work seems very promising to me, but the article you linked to is probably over-selling it a bit right now. Let’s give it 2 or 3 years and see where they are… at any one time, there are always promising developments that in the end fall short of one’s hopes. This one is more promising than most, but still… patience.

              One more point to keep in mind, of course: they aren’t directly using string theory, though string theory has had some input, as I described. They’re using broader principles. However, supersymmetry in its maximal form is crucial for keeping the problems simple enough to solve.

  51. Matt:

    Q: Do you feel misled, by what I wrote Tuesday, into thinking that I believe that string theory currently makes, or is likely to make, unique and specific predictions about nature?

    A: No I don’t. But I do feel you that and your colleagues have misled yourselves because you lack vital insights. And that’s why you haven’t yet made those unique and specific predictions about nature. For want of a nail.

    Q: When Woit says “string theory makes no predictions“, and “string theorists making bogus claims for predictions“, do you think he means only Application Number 1, which is what he called “string unification”?

    A: Yes. But it doesn’t really matter. Tools don’t make predictions.

    Q: Is Woit, in your opinion, “misleading and confusing people about the status of string theory as a whole by failing to distinguish between two completely different applications of the theory“?

    A: No. The status of string theory is not good.

    But this “war” isn’t black and white. Woit is a standard-bearer for the standard model, and moreover for himself. He is a propagandist, a polemicist, and he deletes a lot of comments, including all of mine. Yes, you are arguably something of a standard-bearer and propagandist too, but IMHO much less so. IMHO you are more sincere, and you try to explain. So in this battle between Scylla and Charybdis, I will choose Charybdis. I choose you.

  52. I agree with Wyrd Smythe above: you generally go out of your way to provide nuance and to only say true things, which means being very careful, and one has to have tried oneself to be this careful in writing about anything to appreciate the skill it involves. I’m an academic, and by far the biggest flaw in my students’ writing is not being careful enough and ending up appearing to claim much more than they can actually defend–not because of deliberately inflated claims but because of carelessness with language.

    I will not be surprised to see your readers agree with you on your own blog. But this case seems clear-cut enough that I would bet that if Peter Woit asked the same question on his own blog (in an honest way), even his own blog readers, who I assume are sympathetic to him, will have to agree you were exceedingly careful about distinguishing the two issues.

  53. But you’re all forgetting one key point here:


    Kidding aside—assuming that Peter Woit wasn’t referring to some *other* “two completely different technical issues” that you actually *were* conflating, he’s obviously off-base. I found your article characteristically lucid.

    That said, the “you’re wasting your life” stuff was a bit of a low blow. At the risk of coming across as a condescending prick, I’ll confess that I cringe a little every time you let that kind of nastiness slip out—it undermines the otherwise patient and levelheaded persona you’ve established here, which is so crucial to fostering public trust. Your frustration is totally understandable, but in general I think it advisable to hold off on the “Post Comment” button until one has chilled one’s beans. I, for one, prefer your jabs witty and above the belt.

  54. Dear Professor Strassler,

    I am not sure whose comment you are replying to here. I posted a comment on your site quite recently, which left me feeling ashamed afterwards. In short, your site is excellent and I wish other learned people ( e.g. Susskind and Hawking for starters ) would provide the same service. My ‘apparent’ attack is not levied on you or your service, it is the philosophy of modern and classical physics with rankles me.

    Physicists such as aforementioned provide the lead – but I have my doubts as to their wisdom. ( for example: if a black hole is degrading by loss of thermal energy why does it not shimmer even by even a small amount?

    Mathematics is a superb piece of human ingenuity & tool – and upon my rail visit to Paris today via the TGV it behaved perfectly as a result of it. My frustration is that I believe it is good for engineering in a Cosmos full of material and energy etc. But in the philosophical world using maths to describe Nature to predict how it works can only fail. ( at current time & thinking).

    I have read many many tech papers absolutely full of superb mathematics and quite bewildering. The presentation and thought behind it is magnificent – but is has no relevance and quite useless as a tool to aid our insight into how things really tick.

    Please continue and describe research phenomena – you are doing a good job. And if I may say we need more Prof Strasslers’ and less TV based orators although they provide some fascinating presentations.

    We need a new apple genus ( genius )!

    Kindest regards


    1. Regarding “if a black hole is degrading by loss of thermal energy why does it not shimmer”:
      Black holes are believed to emit thermal radiation. It is just that a black hole (especially a large one) seen by an observer who is far away has a very very low temperature, so the radiation has very long wavelengths and it is very dim. In the Wikipedia article on Hawking radiation you can find some example calculations.

  55. I felt misled two or three times while reading your text yesterday, first time when you explicitly told “electrons” instead of, say, fermions, to describe high energy testability of string theory. By doing that, it seemed you were giving some credence to app number 1.

    I was also misled because I did not clicked in your “Here’s an example.” so that further mentions to LHC in the text, that you were surely doing in the context of this example (amplitude calculations, etc), could also be interpreted as support of app number 1 (string unification).

    So surely the second failure is to be blamed upon me, because I did not put attention to click on the references (I was reading from a mobile phone, if it serves as an excuse). But the first kind of failure depends both of the care of the writer and the attitude of the reader. If the reader is somehow prevented against string unification hypes, he can overreact. Being from the 1990 graduates that suffered the virtual disappearing of support to any other approach to unification, I am in this particular state, so I felt in the error of interpretation, and surely other people did.

  56. Personally I don’t agree that there is such distinction between Application 1 and 2 and indeed I find it misleading.

    I’m willing to accept it though if someone could name the UV complete theory of gravity (application 1) in the AdS bulk which is dual to the SYM CFT on the boundary (AdS/CFT Application2) and that name is not String theory.

    String/M theory is the one and only theory of QG unifying all fundamental forces of Nature and its particle content. If this is not true then nothing else is true, everything falls apart.

    PS. Matt can’t you put an RSS feed for the comment section too?

  57. No, i do not feel misled. Although I am also aware that my layman status does not allow me to have a sufficiently informed opinion of the matter, and that although I am in principle sympathetic of Woit’s cause, I don’t have sufficient knowledge of neither the science aspect nor the state of the field.

    I do however very much appreciate your blog, since I am curious and want to learn as much as possible about the edge of our knowledge. If there is any resource on the Internet better than this, I haven’t found it (and would really like to know about it if one does exist). And being a regular reader of both your and Mr. Woit’s blogs, I obviously know about both your and his opinions, so again, no I am not really worried about being misled.

  58. That is really rude , impolite and arrogant to the highest degree , maybe those are the people you know , but in general most people are good , fine , gentle and honest.

  59. What a heck is happening…? Matt, most of the people are ill behaving, narrow minded, bitter, stupid or having from mild to severe mental problems. From that perspective.. why bother? At least, don’t let them go under your skin.

    You can’t beat idiots they have the home advantage 😉

  60. not to quibble about words, but for an awfully long time, theory meant making testable predictions – even if it blows up and needs improvement. At least one is fairly certain it is not just a mathematical fantasy, however consistent internally. Another expectation is to include the prior best theory. (eg Weinberg shows that QED is contained in Electroweak.) Otherwise I tend to call it Speculation. Maybe that comes from reading Popper a long time ago.

  61. Proceed Professor Strassler , your blog is the best in the mission of introducing the public into the wonderful world of physics.
    Thank you Dr.Strassler.

  62. 1. No, I was not misled into that kind of thinking.
    2. I think Woit is in a kind of denial of what you call “Application 2”.
    3. Yes, and Woit cares more about being paid attention to than being objective. I do find him entertaining sometimes, especially when he posts rumors, but his whole crusade against string theory, SUSY, multiverse, etc. can be safely ignored. It speaks more about his failure to contribute anything valuable to science than about the failures or drawbacks of those theories.

  63. Matt: You are always fair and clear on your point. No, I was not misled.

    The *mislead* is a very important issue which has never been discussed before, and it has the dire consequence for the advancement in physics, especially for this *final* step. It was so accidental that I did discuss the *misled* issue in my comments at your last post. There are two types of mislead.
    1. Mislead by wrong information — this has no long time effect.
    2. Mislead by *right* information — this could be very, very harmful with dire consequence, as the bright *right-lights* can blind the view to the next gate.

    In your case, you were not misleading, no misleading of the either types. The whole thing was just a bit too emotional. Woit’s reason of against string theory was a bit too shallow. But, for the public in large, they have given the string (M- or F-) theory 40 years to success, but it has failed to make any contact to Standard Model, the only criterion understood by the lay public. This *single* point is enough to convince the public that M- or F- theory is nonsense although the string theorists still form a very powerful institution. This is why Woit has his market.

    1. Woit put a *bet* on “M- or F-string theory is nonsense in terms of physics” and is confidence that he is going to win for the reason that those are now obviously failed theories. The fact is that he is obviously wining the bet thus far, and the public at large are betting the same thing with him.

      Yet, the string theorists are still forming a very powerful institution, no one dare to shake it. This makes Woit a great hero in the public eyes.

  64. Matt, you have stressed over and over that, even if String Theory turns out to be wrong, it will still be used because it is a very good tool to better grasp some aspects of other theories, and is this a solid argument that Woit is deceptively leaving out of his comments.

    We know that General Relativity is a proper theory to explain gravitation, while Newton’s theory is wrong, but Newtonian physics are still used for dynamics/kinematics with low speeds because it is easier to calculate (than with GR’s formulas) and the numerical predictions will be just as good as with GR.

    We also know that QFT is a proper theory to explain atoms and molecules when compared with Schrodinger’s formulas, but when it comes to do calculations for computational chemistry, it is a derivation of Schrodinger’s formulas that are still used, because it is a proper and easier tool to use for such work.

    Kind regards, GEN

  65. Innocent on all counts. Perhaps you’ve made some errors along the way; I am not able to judge that, but “misleading” implies a specific intent, on your part or on your accuser’s part.

    I fully subscribe to Joan Vazquez’s comment above. Carry on with my thanks.

    sean s.

  66. It’s about 100X easier to be a critic, than to provide clarity for lay-persons on science-frontier topics. Steady as she goes! Sure didn’t leave me misled or confused!

  67. This is a great blog and I really appreciate your efforts to explain everything from a logic perspective, always stating explicitly and differentiating the hypotheses, the experimental results and the conclusions that one can extract.

    There are trolls everywhere, even in theoretical physics, so please don’t be upset due to their unfounded accusations, and don’t gibe them an attention that they don’t deserve.

    Thanks for making physics available to the public and showing that it is, as it used to be, the study of nature through reason and experiment.

  68. First, for the reader, caveat emptor, “let the buyer beware.”

    State your case as you see it, be receptive, but please do not base your opinions upon reader consensus. It sets a bad example. From my POV if you and Woit have a problem it is that neither of you state your epistemology with any clarity … a fault of most physicists today.

    All physics needs to begin with a statement concerning epistemology. It is not something that can be taken for granted in these debates.

    It seems to me that most of these conflicts in contemporary physics are the result of diverse and unacknowledged epistemological differences. The debate becomes more of a religious discussion than science. It’s not even philosophy of science.

    There are numerous clearly stated scientific epistemological and existential positions available to take. They are themselves imperfect, both of you need to pick one, refine it, and make it your own. And start by discussing your differences in this regards. All other discussion is irrelevant until you complete this task.

    1. “please do not base your opinions upon reader consensus.”

      I don’t. I’m looking for the wisest critiques I can find.

      I agree with your point of view, and am setting off to make these situations much clearer, so that this need not happen again.

  69. Actually, you know what? I’ve been reading this site nearly since Matt started it, and if anything, one observation I’ve made about his work is that he goes out of his way to mention nuance and distinction. It almost (almost!) rises to the level of being a distraction when he tangents off to insure we understand the limits and nuance of his point.

    But thanks to that careful attitude and serious attention to detail, I’ve had what amounts to a very good free lesson in theoretical physics, and for that I’m grateful beyond words.

  70. Smolin has a different theory which is perhaps an agenda behind his book. Woit has forceful objections, but has misunderstood your intent. String theory may be useful to play with but after 35 years with no way to really test it, we obviously need a breakthrough we are not seeing. This suggest stringiness is not the way.

    1. I don’t know Dave. I’m generally thought of as antagonistic towards string theory. But “wave harmonics” isn’t all that different, and I’m happy with waves.

      Testing, one two.

  71. Matt,
    Thank you for your incredible tenacity in the difficult quest to be precise yet accessible to those of us who are not particle physicists, but who share the excitement of gaining glimpses into the physical characteristics of our universe. Your work in this regard is exceptional. Please carry on.

  72. I read your article with the express intent of seeing whether there would be any hype associated with it. To the contrary, there was no hype and instead I felt enlightened. I didn’t feel mis-led becasue I do not feel the article attempted to lead me to believe anything, rather to understand two different aspects of string theory. What I do not understand is exactly how string “theory” qualifies as a theory. Perhaps that’s another article. Isn’t it still in the category of a conjecture, especially when compared to QFT or GTR?

    1. Excellent question: the word “theory” means something very specific in particle physics, and I think the best way to say it is this: “a theory is a consistent set of equations that can be used to make predictions about physical phenomena, either in the real world or in a consistent imaginary world.” String theory may only describe an imaginary world, not the real one we live in, but it appears to be a consistent (if still poorly understood) set of equations.

  73. re: your question to readers: Do I, the reader, believe that you believe that string theory currently makes, or is likely to make, unique and specific predictions about nature?
    No I don’t!

  74. I’m not a fan of psychoanalysis, but Woit’s personal crusade against string theory almost forces one to wonder whether he was cuckolded by a string theorist. Work on string theory or not, point out the problems with the theory that you discover or not, I don’t care, but to make one’s life revolve around a silly crusade to criticize at every turn a physical theory and anyone even remotely associated with that theory seems irrational. There, no doubt, has been a lot of hype promoting string theory by certain members of the physics community, certainly a lot of people were excited by the possibility of a unified theory, and the unjustified hype should rightly be criticized, but I would just like to say, “chill out!” Matt, your post on string theory, as is usually the case, was very fair I thought, one cannot not be expected to list every exception to the general principles of a theory one is explaining. You do a go job of listing the most important caveats to what you are claiming without getting bogged down in a post with listing every possible alternative and every possible exception.

  75. I didn’t feel at all mislead, and certainly not intentionally. For me, this post did perhaps bring a few points into the light. I’d never questioned whether I expected ST to provide a single answer, and it’s an interesting point you made about how any theory predicts a landscape. Is there any measure of degree between the landscapes predicted by QT and those by ST? Are the landscapes equally “large”?

  76. Matt, I do not feel myself being misled in any way by your posts in the website, whether it be String Theory or any other subject pertaining to Physics and Science.

    Getting down to the details of Woit’s comments, IMHO I think that this is his reaction to your earlier comments regarding the quality and accuracy of his blog posts, but as I have already said, this is my personal opinion.

    Kind regards, GEN

  77. Matt, fear not! Each reader comes in here with their own biases, strengths and histories of exposure to theoretical physics. How they integrate what they read into what they already know, is out of your control in the majority. At the edge of knowledge, it is very easy to be misunderstood… more so than elsewhere!

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