Farewell to Reality

Jim Baggott has written a very good new book called Farewell to Reality that will soon come out here in the US. It is already out in the UK, where it is stirring up some debate, and perhaps the US will soon see something similar.

In the preface, Baggott explains that he was motivated to write the book by the experience of watching this BBC program, which featured a combination of serious science with revelations about how we’re all part of a cosmic hologram, there’s an infinity of parallel worlds, and various other examples of what he refers to as “fairy-tale” physics. In the last decade or so there have been a large number of such mass media efforts promoting highly dubious ideas about fundamental physics, and Baggott decided that in his next book he’d try and do something to counter this. I think he’s succeeded admirably: the BBC and other such organizations should atone for their sins by sending copies of the book to their viewers.

The book is divided into roughly two halves, with the first half a well-executed overview of the current state of our theories about fundamental physics, from quantum theory through the standard model and cosmology. It ends with a description of the outstanding problems left unsolved by our best theories, and a good summary of the current situation:

Several centuries of enormously successful physical science have given us a version of reality unsurpassed in the entire history of intellectual endeavour. With a very few exceptions, it explains every observation we have ever made and every experiment we have ever devised.

But the few exceptions happen to be very big ones. And there’s enough puzzle and mystery and more than enough of a sense of work in progress for us to be confident that this is not yet the final answer.

I think that’s extremely exciting…

… but there is no flashing illuminated sign saying “this way to the answer to all the puzzles”. And there is no single observation, no one experimental result, that help to point the way. We are virtually clueless.

With this background he turns to a detailed examination of the speculative ideas that have not worked out, but have dominated the field for the past 30-40 years (SUSY, GUTS, Superstring/M-theory, the multiverse). This is difficult material to do justice to, but Baggott does a good job of giving an explanation of these ideas that includes some understanding of the problems with them. He ends the book with this advice to the reader:

Next time you pick up the latest best-selling popular science book, or tune into the latest science documentary on the radio or television, keep an open mind and try to maintain a healthy scepticism… What is the nature of the evidence in support of this theory? Does the theory make predictions of quantity or number, of matter of fact and existence? Do the theory’s predictions have the capability – even in principle – of being subject to observational or experimental test?

Come to your own conclusions.

The thorniest problems that come up in this sort of discussion are essentially ones about the philosophy of science. What counts as evidence for a scientific theory? At what point does pursuit of speculative ideas that are going nowhere stop being legitimate science? One quickly realizes that naive ideas about the scientific method don’t capture how good science really works. Baggott devotes the first chapter of the book to an overview of his take on what the scientific method really is. In the end, this may be the most important issue here: will books and TV programs promoting the views of a narrow part of the scientific community that doesn’t want to admit failure end up discrediting the scientific endeavour? Some are all too willing to exploit the subtleties of good science to find a way to defend the indefensible, with the multiverse mania pointing to the all too real dangerous endpoint this can lead to.

For some reviews from the UK of the book see here, here and here.

For a BBC Radio program featuring discussion between Baggott, Jon Butterworth and others, see here. Butterworth has written more today here.

Also today in the Guardian, there’s a debate between Baggott and Mike Duff. Duff characterizes the experimental situation of string theory as follows:

Definitive experimental tests will require that the theory also incorporate and improve upon the standard models of particle physics and cosmology. An impressive body of evidence in favour of this has accumulated, but it is still work in progress.

without giving an example of any sort of conceivable such experimental test. I think Duff is being highly misleading here, since the story of the last thirty years is not one of evidence for string theory unification accumulating, but the opposite: the more we learn about string theory, the less likely it seems that it can predict anything. One can argue that string theorists just need more time (Duff points to the idea of atoms arising back in 400BC, taking more than two millennia to come to fruition), but the problem with string theory is not that progress is slow but that it is negative.

On the question of TV programs like the one that motivated Baggott to write the book, even Duff won’t defend them, but blames the situation on journalists:

As for misrepresentation in the media, there will always be sensationalists and attention-seekers in any field, but in my (admittedly biased) opinion, the worst culprits are the journalists.

This is quite amusing coming from someone who (see here) had his university put out a press release claiming that he had made the first discovery of a way to test string theory. He advertises string theory as having found application in quantum information theory, a claim that I doubt is believed by any other string theorist or quantum information theorist. No, the worst culprits here are not journalists, whose mistake is often just that of taking seriously press releases from people like Mike Duff.

Duff invokes the same criticism made back in 2006 that “Sadly, many critics of string theory, having lost their case in the court of science, try to win it in the court of popular opinion.” He’s well aware though that string theorists are losing badly in the court of science (with US physics departments now hiring virtually no string theorists). String theory unification is an idea now discredited in the scientific community, but getting propped up by TV programs and prizes from Russian billionaires. I hope when Baggott’s book comes out in the US, we’ll see a more serious discussion of the issues that it raises.

Update: Duff is unhappy about Butterworth’s mild criticism of string theory, so has responded with a comment at the Guardian site that begins

Dear John

”The concern arises if everyone makes the same wild guess, and the experiments to confirm or deny it are out of reach”.

is more-or-less what people said when theorists predicted the Higgs boson in 1964.

According to Duff, I guess, back in 1964 the situation was just like that of string theory, with the field experiencing what people were calling an unhealthy domination by the likes of Peter Higgs and others working on the Higgs mechanism. That’s a very odd take on the history, given that the work of Higgs and others was virtually ignored at the time.

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84 Responses to Farewell to Reality

  1. H says:

    Can you elaborate the following?

    “String theory unification is an idea now discredited in the scientific community”.

    I am not sure what “the scientific community” includes in this context. String theorist will of course disagree, and people outside of HEP will generally not count as experts. So I guess you are referring to the non-string HEP community? Do you know what their general opinion on string theory unification is?

  2. Peter Woit says:


    I actually know many people who work on string theory who have given up on the idea of getting the Standard Model out of it. The most common attitude I hear among string theorists is that the ways people used to hope to connect it to the SM have failed. They say they work on string theory now not because it’s a viable idea about unification, but because of things like AdS/CFT.

    For some data points, look at the data on what kind of HEP theorists US physics departments are hiring here
    One meaning of “scientific community” here is the faculty of US research university physics departments, who now typically want nothing to do with string theory.

  3. Professor Anon says:

    Well … I suspect that string theory is not discredited among all the faculty of US research physics departments, but the consensus view of the hiring committees does seem to have soured on string theory.

  4. Peter Woit says:

    As another source of data, take a look at the titles of the talks at Strings 2013, here


    Of the 40 speakers, exactly one (Mirjam Cvetic) is speaking on a topic that has something to do with efforts to do string theory unification (i.e. get the SM out of string theory).

    The other things string theorists are working on are more promising, but the string theory hype and unacknowledged failure of the unification idea have definitely soured their colleagues on doing more string theory hiring of any kind.

  5. Peter Woit says:

    By the way, there’s an interesting discussion of the current state of things by Mirjam Cvetic here
    which includes the following:

    “If the simplest supersymmetric extension of standard particle physics is valid, the LHC would have found those particles by now. So I think that, as theoretical physicists working on particle-physics models with supersymmetry expected, that supersymmetry would be discovered at the LHC, and it would certainly be disappointing if supersymmetry is not found after the LHC has run for an extended period. In other words, if supersymmetry is pushed to very high energies because we can’t find supersymmetric particles at the LHC, it’s not going be a very happy situation for us and our theories.

    SW: Should this happen, and nothing beyond the standard model shows up, how do you think theoretical physicists will typically respond?

    I think a typical reaction would be that we can still deal with that, and we just need to adjust the theories. But we have to admit at some point that if our ideas are not being experimentally confirmed, maybe we’re just not on the right track. We need experimental feedback, and without it, theoretical research becomes isolated.”

  6. Bob Jones says:

    “he was motivated to write the book by the experience of watching this BBC program, which featured a combination of serious science with revelations about how we’re all part of a cosmic hologram”

    I haven’t seen the program, but this Baggott guy needs to wake up if he thinks the holographic principle is some sort of wild speculation. The holographic principle is just about the only thing that is well established about quantum gravity…

    “Of the 40 speakers, exactly one (Mirjam Cvetic) is speaking on a topic that has something to do with efforts to do string theory unification (i.e. get the SM out of string theory).”

    That’s why this criticism of string theory is so irrelevant. Hardly anyone is even working on the stuff that you complain about.

  7. Peter Woit says:

    Bob Jones,

    If “we’re all part of a cosmic hologram” is settled science, what’s the experimental evidence for it?

    I’ll stop complaining about string theorists refusing to acknowledge failure when they start publicly acknowledging it. Mike Duff certainly isn’t there yet…

  8. Bob Jones says:

    “If ‘we’re all part of a cosmic hologram’ is settled science, what’s the experimental evidence for it?”

    I don’t care for the language being used here, but holography is, whether you like it or not, a well established property of gravity. You can take ordinary general relativity (no strings, supersymmetry, or extra dimensions) and show that the theory has a dual description in terms of a field theory in a lower number of dimensions. There is by now a ton of extremely nontrivial evidence that this correspondence is true on a mathematical level, including experimental evidence.

    “I’ll stop complaining about string theorists refusing to acknowledge failure when they start publicly acknowledging it.”

    I agree with you that string theory has not convincingly reproduced the standard model, but I’m not sure I would characterize that as failure. The reason is that I’m not sure reproducing the standard model was ever the exclusive goal for string theory. From the very beginning, string theory was related lots of other problems in physics and mathematics, and it led to many important developments in those areas.

  9. Peter Shor says:

    Bob Jones:

    Mathematical evidence based on an analogous theory or experimental evidence? Or have string theorists stopped distinguishing between the two?

  10. Bob Jones says:

    Peter Shor,

    You would certainly agree that general relativity is a well tested theory, wouldn’t you? What I’m claiming is that general relativity (and its generalizations, such as string theory) is mathematically equivalent to a field theory in a lower number of dimensions. This mathematical equivalence is supported by a lot of evidence, including experiments in nuclear and condensed matter physics.

  11. Peter Woit says:

    Bob Jones,

    So, there’s experimental evidence for 4d quantum gravity effects, seen in terms of a 3d conventional qft? Who did that experiment?

  12. Bob Jones says:

    I didn’t say anything about quantum gravity. I’m saying you can take ordinary classical gravity, which is extremely well tested, and by making various field redefinitions, you can show that it’s equivalent to a field theory on the conformal boundary of spacetime, in cases where this boundary is defined.

  13. Peter Woit says:

    Bob Jones,

    If you’re referring to 4d gravity, which is what we have experimental data about, and you’re trying to invoke AdS/CFT, one problem is that we don’t live in AdS4

  14. Bob Jones says:

    “one problem is that we don’t live in AdS4”

    No, that’s really not a problem. The AdS condition is an asymptotic condition, and the gravitational field is free to do whatever it wants in the bulk spacetime. There are also versions of the correspondence that don’t require AdS space at all, for example



    The second of these papers describes black holes with no strings, no extra dimensions, no supersymmetry, no extremality assumption, and no anti-de Sitter space! Is that realistic enough for you?

  15. Mitchell Porter says:

    “Of the 40 speakers, exactly one … is speaking on a topic that has something to do with efforts to … get the SM out of string theory”

    They talk about that next month, in Germany: http://stringpheno2013.desy.de/

  16. Roger says:

    I don’t see any testable hypotheses in those holographic duality papers. Is there anything that Popper would consider science? If so what, and why would it be science?

  17. Bob Jones says:

    “I don’t see any testable hypotheses in those holographic duality papers.”


  18. Peter Woit says:

    Bob Jones,

    You’re invoking several completely different conjectural ideas about mathematical physics, none of which have been experimentally tested or correspond to evidence that we’re part of a “cosmic hologram”.

  19. chris says:

    Bob Jones,

    it might be necessary to remind you, that neither temperature nor entropy of a black hole has ever been measured. Also, there is no experiment about Unruh temperature or just about any quantum effect on a horizon. This is simply due to the fact, that no horizon has ever been observed.

    The closest we have is radio and infrared observations of stellar dynamics around Sgr A*. And that’s quite a stretch from there to any horizon dynamics you claim to be experimentally backed.

  20. EDBM says:

    You say, “… the problem with string theory is not that progress is slow but that it is negative.”, which is a claim whose strength rather surprises me – I would have thought that the worst that could be said was that the field has stagnated since it has not produced any theory which could give any predictions, testable or not. Could you elaborate on your point, and maybe provide some references?

  21. Peter Woit says:


    This topic has often been discussed here. The point is that progress in better understanding string theory models has just led to more and more different classes of them. Early on, there was hope that there were a limited number of possibilities, so you had some sort of predictions possible. At this point, it looks like you can get just about anything out of these constructions, so the idea is pretty much empty in terms of any predictive power.

    One place I’ve written in detail about this is here

  22. Peter Woit says:

    Mitchell Porter,

    The Strings 2013 conference is the one that is supposed to not specialize, but survey the whole field, and it’s the one with the most illustrious and influential advisory committee that chooses the speakers. I think one talk out of forty pretty accurately reflects how much interest leading string theorists have in “string phenomenology” these days.

  23. Bob Jones says:


    Yes, I’m talking about more than one thing here. The points I’m making are the following:

    1. It is reasonable to say that the holography is an established feature of gravity because the holographic principle is implicit in the mathematics of general relativity. It doesn’t depend at all on the validity of string theory or supersymmetry or the existence of extra spatial dimensions. Since this is a statement about the mathematics of an already well tested theory, there’s nothing that needs to be tested experimentally.

    2. If you insist on having experimental evidence for the mathematical validity of the AdS/CFT correspondence, you can have that too. AdS/CFT has been used to make successful predictions about nuclear and condensed matter physics.

  24. cormac says:

    As it happens, I chanced upon the Guardian article yesterday. I have to say I thought Professor Duff offered a calm and reasoned pont-by-point defence to Jim Baggot’s criticisms. It seemed to me that Jim made several comments that were rather broadbrush and he conflated distinct issues more than once, as Mike pointed out in his responses.

    I was surprised Jim didn’t think to make Peter’s usual criticism, that misgivings about ST are not solely about problems such as compactification, or connecting to experiment, but the sociological problem that a great many researchers have been directed towards a research area with these drawbacks, at the expense of other areas, and whether this is healthy etc. Criticism of the theory itself is more easily deflected since defenders can appeal to the history of science, from the atomic theory to general relativity, just as Mike did.

    Overall, I thought Professor Duff a clear winner in that particular debate. I also agree with most of the points he made. It seems to me that a great many ST critics ignore the little word ‘yet’, i.e, do not trouble to acknowledge that problems such as compactification and connection with experiment may, for all we know, one day be resolved (yes, even after 4-5 decades). It always seems a bit one-sided to me to leave this possibilty unsaid….Regards, Cormac

  25. Peter Woit says:

    Bob Jones,

    You’re conflating several completely different things, and engaging in hype about all of them. As for 1., I just don’t see how you get from the conjectures that you link to about a 2d CFT saying something about the horizons of Kerr black holes to the claim that the holographic principle is part of classical GR, other than through an abuse of language.
    As for 2, you’re just repeating hype, about something completely different than 1.

  26. Peter Woit says:


    The problem with Duff’s argument is that it applies to any speculative idea that doesn’t work out. Anyone whose favorite idea about physics goes nowhere can make the case that it just needs more work, and someday they will be vindicated (and pretty much every crank in the world does make exactly this claim). If you allow people to make this case and give them time-scales longer than their professional careers, no one ever has to admit failure. Everyone can happily come up with a bad idea early in their career (or sign on to someone else’s), then get paid for the rest of their careers to work on it, no matter how unpromising it becomes. String theory unification really is an idea that hasn’t worked out. Given the lack of other good ideas, you can argue that some people should keep working on it, but I don’t think you can argue that most of the people who started on it should keep going. I also don’t think you can argue that it’s all right not to admit how bad the problems with the idea are. Finally, it’s really not at all all right to issue press releases and go on TV promoting your idea that isn’t working. It’s this last issue that Baggott makes clear is what he sees as the big problem here, and Duff has no answer for that, other than to blame journalists for repeating the hype he and others put out.

  27. Bob Jones says:


    In the first paper I cited on the Kerr/CFT correspondence, the authors consider the Kerr solution of classical general relativity, and by analyzing the symmetries of the solution, they conclude that there should be a dual description in two-dimensional conformal field theory.

    For an even clearer demonstration of the holographic properties of general relativity, see the paper


    Here the authors study general relativity in 2+1 dimensions and show that the Einstein-Hilbert action is equivalent to the action for Liouville theory on the conformal boundary of spacetime. Of course, the assumption of 2+1 dimensions is a drastic and unphysical simplifying assumption, but it’s still interesting because (2+1)-dimensional gravity is one of the few contexts in which we can treat gravity as a quantum field theory.

    I don’t know what it means to say we’re part of a “cosmic hologram”, but I would say that the papers cited above give pretty convincing evidence that general relativity has at least some holographic properties.

  28. Peter Woit says:

    Bob Jones,

    Now you’re introducing yet a different notion of holography, in a different set of (unphysical) dimensions.

    Actually, I’m a big fan of the paper you link to, which is part of the amazing story of how 3d Chern-Simons QFT is related to 2d CFT. It’s fantastic mathematics and I’m very willing to believe that it has something to do with fundamental 3+1 d physics. Unfortunately I don’t know quite what this is, nor do I think does anyone else….

  29. lun says:

    Bob Jones,
    AdS/CFT has been used to make successful predictions about nuclear and condensed matter physics.
    Can you give me an example of a “successful prediction”? I define predictions in a Popperian way “if system X has a gravity dual, we get experimental result Y, if it does not, system X is for sure not described by a gravity dual”.

    I will make an experimental prediction, “there not a single paper in the AdS/CFT literature that meets the above criteria.” I would be very interested in a falsification of this prediction 🙂
    Otherwise, String/Gauge is still very very interesting, but claiming it leads to “experimental predictions” is misleading.

  30. Bob Jones says:


    See the paper


    The authors show that if a fluid is described by a gravity dual, then the ratio of shear viscosity to volume density of entropy is equal to a universal constant. If the ratio does not equal this universal value, then the system does not have a gravity dual.

  31. Anonyrat says:

    Duff said, in his conversation with Baggott: “Similarly, string theorists did not assume supersymmetry, extra dimensions, the dualities of M-theory or the myriad possible universes; they discovered them to be consequences of a theory that subsumes empirically well-established features such as general relativity, gauge field theory and chiral quarks and leptons.”

    While there is a limit to the analogy, the mechanical models of the aether incorporated all the relevant known physics, had counter-intuitive features, and similarly ought to have worked per the best of knowledge that existed at the time.

  32. lun says:

    Bob Jones, see

    With a “classical gravity dual” your statement might have been a bit more precise, but then the assumptions involved (Nc—>infinity) are a bit too naive to really compare to experiment.

  33. GMBH says:

    Bob Jones: I actually work the shear viscosity of strongly correlated fluids. The paper you refer to, 0405231, does not make any experimental prediction whatsoever. It contains a CONJECTURE for a lower bound on the shear viscosity. The conjecture is based on a calculation for a very specific model which is not realized in nature, I.e not in a quark gluon plasma nor in cold atomic gases. If you want to make accurate predictions for the shear viscosity, you have to work much harder using realistic models and not just elevate a result for a very specific model to magically be true universally. The lower bound conjecture can actually be derived from mere dimensional analysis. If this is one of the main examples of an experimentally testable prediction of string theory, then that field is in real trouble.

  34. george ellis says:

    Bob Jones:

    “For an even clearer demonstration of the holographic properties of general relativity, see the paper http://arxiv.org/abs/gr-qc/9506019

    This paper relies on a negative cosmological constant. The experimental data is that the cosmological constant is positive. The paper does not apply to the real world.

  35. Bob Jones says:


    I’m mostly interested in the applications of AdS/CFT to gravity, so I don’t understand the technicalities of these applications to the quark gluon plasma. I have not heard this claim that the lower bound conjecture can be derived from dimensional analysis. Could you elaborate on that?

  36. Bob Jones says:

    george ellis,

    There is a much more obvious reason why that paper does not apply to the real world. I addressed all these issues in my comments to Peter.

  37. imho says:

    I knew this day would come and I fear it’s only the beginning. I hope I’m wrong.

    Science has flourished over several centuries, not because of our talents for persuasion or our political connections or our eloquence in explaining our points of view. Science has flourished because we produce tangible concrete results that improve the world. Even fundamental Physics research has been able to justify it’s existence by claiming some yet unknown future benefit(s). The public trusts us to deliver, because in the past, that’s exactly what we’ve done. This is our bread and butter and it’s the fundamental reason the power structure tolerates us instead of taking our lunch money. What do you think happens when we remove Physics from the testable real world and start pontificating about untestable apparitional fairy-tails?… I’ll tell you what happens. We lose the public debate to Pat Robinson and Joel Osteen… I promise they are infinitely more persuasive then any of us. Jim Baggot will only the begining.

    I know, I know, inside the ivory tower it’s pretty easy to become completely convinced that that rest of the world is as thoroughly interested and impressed with our intellect as we are. But trust me… they are not. We exist because we create bombs and magic black boxes. We’re funded Billions because we claim that’s what is needed to create more bombs and magic boxes. This is the difference between Physics funding and Philosophy funding. Anyone who seriously believes the powers the be will continue to heavily fund a few thousand people to engage in intellectual masterbation is confused about this world and how things work.

  38. Chris W. says:

    From Bob Jones:

    “This mathematical equivalence is supported by a lot of evidence, including experiments in nuclear and condensed matter physics.”

    “If you insist on having experimental evidence for the mathematical validity of the AdS/CFT correspondence, you can have that too. AdS/CFT has been used to make successful predictions about nuclear and condensed matter physics.”

    These statements strike me as profoundly muddle-headed at the outset. “Mathematical equivalence” or “mathematical validity” must be established by mathematical arguments, not experimental evidence, by definition. By extension, it is not at all clear what “is supported by” is supposed to mean in this context.

    Note that by experimental evidence I mean observations on real physical systems, not computational experiments. Regrettably the two are sometimes confused.

  39. Bob Jones says:

    Chris W.,

    I actually agree with what you say. Unfortunately, a lot of people don’t understand this point, and so we often see demands on this blog for “experimental tests” of AdS/CFT.

  40. Peter Woit says:

    Bob Jones,

    This has long ago stopped making sense, and it’s not even really relevant to the topic. Enough.

  41. lun says:

    Bob Jones, have a look at
    A bound of ~1/12 is “derived” from the uncertainity principle.
    I say “derived” because the assumptions used are of course unrealistic (using the Boltzmann equation for a strongly coupled system) ,but then again N=4 Nc=infinity in the UV is also an unrealistic assumption.
    I agree that the number coincidence is intriguing.

    For the reaction of the heavy ion community to the claims of string theorists, look at the theory summary of the “Quark Matter” conference, the leading conference in the field
    which if I remember correctly was covered on this blog too.
    The talk was provocative, and there are people in the field with a more conciliatory attitude, but it does represent a wide-spread feeling,especially by experimentalists.

  42. amused says:

    Quotes from Duff in the debate:

    “Finally, you offer no credible alternative. If you don’t like string theory the answer is simple: come up with a better one.”

    Alternative to what? To a Theory of Quantum Gravity? To a Theory of Everything? Note the sophism here; the implication that these grandiose topics are the only ones worth pursuing in fundamental theoretical physics.

    “The battle for the correct theory will not be won on Amazon or on the blogosphere, however. It will be won in the pages of scholarly scientific journals.”

    What a disgusting lie. If it was true, and if interesting and important physics progress was being made in string theory, then the pages of PRL would be full of string theory papers. Instead there are almost none… In their frustration at having hardly any important progress to report to their physics colleagues in PRL, string theorists of Duff’s ilk resort to duping the general public with hype, published, e.g., in that illustrious scientific journal the Op-Ed section of the NY Times.

    I wish the public would know how much contempt Duff and string theorists of his ilk (hopefully not all of them) have for the scientific journal system in reality. Scientific output on non-string topics in fundamental theoretical physics is considered to be worthless by them, regardless of which or how many journals it is published in. E.g., when assessing job candidates, single-author PRL publications on a non-string topic by some young person count for flat zero when weighed against string theory publications by another young person in a lesser journal where he/she is joint author with a bunch of senior and illustrious people.

    IMHO the problem is not with string theory, which is interesting and worth pursuing as a theoretical model of quantum gravity even if it turns out not to have direct relevance for Nature. (Toy models which exhibit interesting theoretical properties are often studied in theoretical physics, and lessons learned from them are often valuable for “real physics” later.) Instead, the problem is with how string theory has been pursued. In particular the hype to the general public and the sociological insistence that it is the only legitimate topic to work on in fundamental theoretical physics.

  43. Lowell says:

    So why is 2+1 general relativity gravity? I has no gravitons.

  44. GMBH says:

    Bob Jones,

    Here is what I meant with my comment on the lower bound and dimensional analysis: Dimensional analysis gives you, that for a strongly correlated system the ratio of the shear viscosity to the entropy density must be some number B times Planck’s constant divided by Boltzmann’s constant. Now, the hard bit is to calculate B. A proper test for a theory is to predict a value for B which is then experimentally confirmed. What the paper 0405231 does is to show that B=1/4pi for a specific class of systems with a gravity dual. This class of systems is not found in nature. The authors then simply conjecture, that all systems in nature must have B>1/4pi. This is not a proper quantitative prediction – it is simply a postulate.

  45. RF says:

    Nice post. Any chance you could provide a page number for the quotation above which starts “Several centuries…” and ends “… virtually clueless”. I wasn’t able to retrieve the passage online. Much appreciated!

  46. Jim says:

    Thanks to Peter for his kind review and to all who have troubled themselves to make comments. I thought I might respond to one or two of these.

    Bob Jones – please keep going. I think you’re helping to prove nearly all my points. I’m afraid parts of the theoretical physics community have developed a misleading interpretation of ‘evidence’. In ‘Farewell to Reality’ I devote some time to talk about the difference between ‘coherence truth’ and ‘correspondence truth’. Coherence truth can be established in terms of mathematical relationships, when something has been shown to be equal or equivalent to something else. These somethings might involve physical concepts, and to establish true relationships between these is obviously a good thing to do. But I argue that the notion of scientific truth is based on a ‘correspondence truth’ established between theoretical ideas and empirical facts. Something is scientifically true if, and only if, it corresponds to established facts about the real world.

    Now, I don’t deny the power of imaginative and speculative thinking, and I accept that it can take a very long time to establish the truth of a theory, but it seems to me that some contemporary theorists have retreated into their own, self-referential world, content to ‘discover’ coherence truths in the math but abandoning entirely any sense of obligation to seek scientific truth. Peter Shor – this is the point I think you were making. Actually, I’m really fine with all this – just don’t call it science.

    cormac – I’m obviously disappointed that I wasn’t more convincing in my debate with Mike Duff. I’m very well aware of the sociological issues but other commentators (such as Lee Smolin and Peter, in his book and on this blog) have made these arguments very well in the past and I suspect there’s little more to be said. In writing ‘Farewell’ I wanted simply to point out how very tenuous this structure is – from my perspective it really does look like a theoretical house of cards – yet this hasn’t prevented some well-known theorists from publishing popular science books and making radio and TV documentaries which collectively give the rather misleading impression – intended or not – that this is all accepted science. And their efforts to change the way we interpret what science means really scares me. My ambition was to provide something of an antidote to this. Perhaps you could suspend judgement until you’ve read the book?

    imho – I knew that ‘Farewell’ might be misinterpreted as an attack on science. It’s not. I trained as a scientist, taught science at university in the UK and ran my own (experimental) research group for many years. I have even published theoretical papers. I’m not trying to influence science policy or inform debates about funding. I do worry that the rush to string theory has meant that other – possibly equally fertile ideas – have been neglected (which is the point that amused has made). I don’t offer any solutions in ‘Farewell’ – a valid criticism. I just wanted to foster the debate.

  47. nemo says:

    imho, I can see what you mean but, as a physicist and a teacher, I slightly disagree. Sadly, bombs and black boxes do play a role. Prestige plays a role too. However, hard sciences, e.g. physics, and mathematics, e.g. operational research, have shown that the various methods they follow have been and are very effective to build solutions to solve problems. That is, also, why funding of physics is much larger than funding of philosophy. Physics, mathematics and engineering have led to much better problem solving than philosophy. That plays a role, too.

  48. Professor Anon says:


    You say

    “when assessing job candidates, single-author PRL publications on a non-string topic by some young person count for flat zero when weighed against string theory publications by another young person in a lesser journal where he/she is joint author with a bunch of senior and illustrious people.”

    Do you have any evidence for this? Hiring meetings typically contain both non-string-theorists and string theorists. I can’t imagine any string theorists being that openly disrespectful of their colleagues.

  49. imho says:

    AMUSED Says:
    “the problem is not with string theory, which is interesting and worth pursuing as a theoretical model of quantum gravity … Instead, the problem is with how string theory has been pursued. In particular the hype to the general public and the sociological insistence that it is the only legitimate topic to work on in fundamental theoretical physics.”

    IMHO responds:
    Yep! Exactly!… and I’ve stated on other comments, there is nothing wrong with fundamental research at the appropriate scale. The problem is the hype and the massive diversion of funds away from magic boxes. We are signing our own death warrant if we choose to stop playing the game(s) we are good at and enter the debate stage with Huckabee and Gingrich. Only inside the walls of Stanford is it absolutely obvious that those charlatans aren’t even worthy to share the same stage with people of our formidable intellect. Outside the walls, Palin is a prophet and we are overly-pampered out-of-touch nerds in an Ivory tower. This will not end well.

    to NEMO: So prestige will fund the next collider… it must be an interesting world you’ve created for yourself?

  50. Anonyrat says:

    Thanks for that link to the theory summary of the Quark Matter conference.

    There is the stern admonition:

    “AdsCFT MUST be accountable to the same scientific standards as are other computations, or else it is not science”.


    ” Issues must be scientific:
    Controlled approximation
    A result must be falsifiable.”

    Other than with the cold fusion fiasco, I’ve not seen such a strong scolding made in public like this. This is really eye-opening – even though I follow Peter Woit’s blog quite regularly.

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