Susskind Letter to NYT Book Review

This is about the sixth week in a row that the Sunday New York Times Book Review has had something about string theory or the Landscape controversy. It has become the main place in the popular press to follow this. Tomorrow’s issue contains a letter from Susskind responding to the recent review of his book by Corey Powell.

Susskind has two complaints about the review:

1. That he was not engaging in “braggadocio” by writing “as much as I would very much like to balance things by explaining the opposing side, I simply can’t find that other side” since “The comment merely reflects a fact that all parties, on both sides of the controversy, agree upon: as things stand now, there is no explanation of the fine tunings of nature other than the one discussed in my book.”

This isn’t really accurate. For fine tunings other than the CC, there are other widely accepted explanations (e.g. supersymmetry). For the CC, many people don’t believe that the anthropic string theory landscape is really an explanation, at least not a scientific one.

2. He justifiably complains that Powell accuses him of believing that we are about to discover a “final answer” to the problems of fundamental physics. He is quite right that he doesn’t actually make any such claim, and that his point of view and Powell’s don’t differ here.

Update: The Moonie-owned right-wing newspaper The Washington Times has a review of Susskind’s book. It describes the argument of the book and ends:
To religious believers, the idea that the universe is designed by a Creator to allow the existence of human life is fundamental. To Mr. Susskind and those who think like him, that idea is so unacceptable that they are willing to abandon the idea that nature follows one set of laws, the principle upon which modern science was founded.

The reviewer at least has noticed that Susskind is giving up on modern science, although he attributes this to Susskind’s unwillingness to face up to evidence for intelligent design, instead of unwillingness to face up to the failure of his pet theory.

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23 Responses to Susskind Letter to NYT Book Review

  1. Who says:

    “… I simply can’t find that other side” since “The comment merely reflects a fact that all parties, on both sides of the controversy, agree upon: as things stand now, there is no explanation of the fine tunings of nature other than the one discussed in my book.”

    This looks like a remarkable case of forgetfulness (or glossing over the facts). In 2004 Susskind registered the existence of a testable explanation (CNS) by posting attempted rebuttals on the arxiv. One of these was subsequently deleted. He entered into an inconclusive exchange over CNS, which included one or more letters published at Not Even Wrong, if I remember correctly, after Smolin posted hep-th/0407213. Susskind was sufficiently exercised about CNS within the past two years that he ought to be cognizant of it, and acknowledge that he knows of a proposed “explanation of the fine tunings of nature” which is empirically testable.

    The CNS explanation may be wrong, but it makes testable predictions and has not yet been shown to be so. This is normal for scientific theories, which stand until falsified since final confirmation is impossible.

    It is obvious that “all parties, on both sides of the controversy” do NOT agree that no explanation has been proposed and thus that there is no “other side” to be mentioned. Susskind suppresses the fact that he has engaged in heated debate with one of the parties on the other side.

  2. Who says:

    BTW the topic of the thread is not Susskind in general so much as the two points he made in his letter to the NYT. We can ignore his complaint #2 which Peter says is justified—it was probably included only for completeness. His complaint #1, however, can be challenged.

    **”… I simply can’t find that other side” since “The comment merely reflects a fact that all parties, on both sides of the controversy, agree upon: as things stand now, there is no explanation of the fine tunings of nature other than the one discussed in my book.”**

    This assertion was challenged by Peter.

    It can also be refuted by reference to an article by Susskind himself posted on the arxiv

    http://arxiv.org/abs/hep-th/0407266
    Cosmic Natural Selection
    Leonard Susskind

    This article by Susskind deals with a proposed (and so-far not eliminated) “explanation of the fine tunings of nature” other than the one discussed in Susskind’s book. The fact that he wrote the article shows that he is aware of the existence of this alternative explanation. So when he says that he “can’t find” an alternative explanation, or that one does not exist, he is not being forthcoming, and is spreading a misconception.

  3. arnold says:

    was my comment censored? why?

    I am very disappointed…..

  4. woit says:

    arnold,

    I was away from this for over a day, when I came back there were a large number of comments, many of them irrelevant to the topic, so I deleted quite a few, but then realized that I shouldn’t have deleted so many. Unfortunately, once deleted, I have way of retrieving them.

    In particular, someone pointed out that it is not true that “all parties” agree that the Landscape is the only explanation of fine-tuning, that “God said so” is an explanation that has many adherents. This is true, and it’s true that this kind of explanation is just as scientific as Susskind’s.

  5. arnold says:

    Hi Peter,
    thanks for clarifying.

    I was worried that you were adopting the same policy as Lubos: just ban whoever thinks differently!

    In particular I completely agree with you: I wanted to point out again that these two explanations are at the same level. No proof, you have to believe them.

  6. D R Lunsford says:

    arnold – Peter only deletes comments that need to be deleted. As the author of many deleted comments, I can attest to Peter’s editorial skill.

    -drl

  7. woit says:

    Can’t decide, should I delete that last one or not… These editorial decisions are sometimes difficult.

  8. Chris Oakley says:

    Those who complain about deleted comments should remember that this is Peter’s party and he can invite who he likes.

    Personally, I am just grateful that there is anyone at a respectable university prepared to give higher priority to truthfulness than acceptance by the academic community. A lot more of this needs to happen.

  9. ObsessiveMathsFreak says:

    To religious believers, the idea that the universe is designed by a Creator to allow the existence of human life is fundamental. To Mr. Susskind and those who think like him, that idea is so unacceptable that they are willing to abandon the idea that nature follows one set of laws, the principle upon which modern science was founded.

    OK, now I’m lost. This is like an Agatha Christie novel. Can anyone me exactly who believes what now? Is this going to turn out that science was in fact murdered by every other passenger on the train!?

  10. anon says:

    OMF:

    Nearly everyone is out to destroy science for their own ends, so Susskind isn’t alone. Newton had to overcome all kinds of bigotry.

    Newton is the founder of laws of nature. He discovered an inverse square law proof (for circular orbits only) in 1666, but only published his book in 1687. The major delay was doing extra work and finding a framework to avoid three kinds of objectors:

    (1) Religious objections (hence religious style laws of ‘nature’/God)
    (2) Petty colleagues who would ridicule any errors/omissions
    (3) ‘Little smatterers’ (Newton’s term) against innovation (=> Latin)

    It would have been delayed longer if Halley had not funded the printing from his own pocket when he did.

  11. Who says:

    the case for resorting to anthropics always seems to have a step where the speaker throws up hands and says “we have no alternative, it’s forced on us!” (as in the Sussking NYT letter where he pretends he could find no alternative explanation of fine tuning)

    This step in argument involves suppressing or conveniently forgetting about CNS. I hope this will be come progressively more awkward. One thing that may help is a new article to appear in ELSEVIER HANDBOOK IN PHILOSOPHY OF PHYSICS, by G. F.R. Ellis of the University of Cape Town. This was posted on arxiv today.

    see pages 41 and 46 of
    http://arxiv.org/abs/astro-ph/0602280
    Issues in the Philosophy of Cosmology
    George F. R. Ellis
    To appear in the Handbook in Philosophy of Physics, Ed J Butterfield and J Earman (Elsevier, 2006)

    quote from page 41
    ***Option 5: Cosmological Natural Selection. If a process of re-expansion after collapse to a black hole were properly established, it opens the way to the concept not merely of evolution of the Universe in the sense that its structure and contents develop in time, but in the sense that the Darwinian selection of expanding universe regions could take place, as proposed by Smolin [205]. The idea is that there could be collapse to black holes followed by re-expansion, but with an alteration of the constants of physics through each transition, so that each time there is an expansion phase, the action of physics is a bit different. The crucial point then is that some values of the constants will lead to production of more black holes, while some will result in less. This allows for evolutionary selection favouring the expanding universe regions that produce more black holes (because of the favourable values of physical constants operative in those regions), for they will have more “daughter” expanding universe regions. Thus one can envisage natural selection favouring those physical constants that produce the maximum number of black holes. The problem here is twofold. First, the supposed ‘bounce’ mechanism has never been fully explicated. Second, it is not clear — assuming this proposed process can be explicated in detail – that the physics which maximizes black hole production is necessarily also the physics that favours the existence of life. If this argument could be made water-tight, this would become probably the most powerful of the multiverse proposals. ***

    quote from page 46
    ***9.2.8 Physical or biological paradigms—Adaptive Evolution?

    Given that the multiverse idea must in the end be justified philosophically rather than by scientific testing, is there a philosophically preferable version of the idea? One can suggest there is: greater explanatory power is potentially available by introducing the major constructive principle of biology into cosmology, namely adaptive evolution, which is the most powerful process known that can produce ordered structure where none pre-existed. This is realized in principle in Lee Smolin’s idea (Sec.9.1.6) of Darwinian adaptation when collapse to black holes is followed by re-expansion, but with an alteration of the constants of physics each time, so as to allow for evolutionary selection towards those regions that produce the maximum number of black holes. The idea needs development, but is very intriguing:

    Thesis H4: The underlying physics paradigm of cosmology could be extended to include biological insights. The dominant paradigm in cosmology is that of theoretical physics. It may be that it will attain deeper explanatory power by embracing biological insights, and specifically that of Darwinian evolution. The Smolin proposal for evolution of populations of expanding universe domains [205] is an example of this kind of thinking.

    The result is different in important ways from standard cosmological theory precisely because it embodies in one theory three of the major ideas of this century, namely (i) Darwinian evolution of populations through competitive selection, (ii) the evolution of the universe in the sense of major changes in its structure associated with its expansion, and (iii) quantum theory, underlying the only partly explicated mechanism supposed to cause reexpansion out of collapse into a black hole. There is a great contrast with the theoretical physics paradigm of dynamics governed simply by variational principles shaped by symmetry considerations. It seems worth pursuing as a very different route to the understanding of the creation of structure. 37 **

    Footnote 37 is cf Susskind’s book, Chapter 13. I have not seen it. Perhaps someone could say what is in Susskind Chapter 13 that Ellis might be referencing?

    In any case it is only a small gain but having something in an Elsevier handbook will, I guess, make it a tiny bit more difficult for advocates of anthropics to gloss over the existence of this alternative.

  12. woit says:

    Who,

    Thanks for the reference to the Ellis article. I hadn’t seen it since I don’t normally look at astro-ph. But please, that’s the third comment here about Susskind not properly considering CNS. Enough is enough

    CNS is just one of several alternatives to the anthropic explanation of the CC that people have proposed, but that don’t have very wide acceptance. Maybe it’s right, maybe not, but it’s a sociological fact in the physics community that this is not an idea that has a lot of adherents. Susskind is correct in claiming that there are no other ideas about the CC that have wide support among theorists. The problem is that, while his own anthropic ideas do now have fairly wide support, there is an even larger group of theorists that would argue that what he is proposing isn’t actually a testable scientific proposal. Until he comes up with some kind of test of the idea, the “anthropic explanation” of the CC is something that I think most physicists don’t consider an actual explanation.

  13. Aaron Bergman says:

    CNS is just as bad as any other stuff. It’s just a different choice of a measure. You still have to include some sort of anthropic prior if you feel that computing statistical probabilities is a useful or interesting thing to do.

  14. Who says:

    Peter, I’d be interested in hearing discussion of ANY falsifiable hypothesis that addresses the values of fundamental dimensionless constants.

    Susskind calls this “explains fine tuning”—-which puts a kind of anthropic slant on it right at the start.

    I’m not talking about the (narcissistic) question of why the parameters of the standard model are suitable to our kind of life. I mean set the issue of life aside and propose a falsifiable hypothesis that has something to do with why the constants are what they are.

    I think you may agree that one cannot effectively counter Susskind’s “change the rules to save my baby” initiative just by disapproving of it. Or reporting that the majority of physicists disapprove. One has to make the alternatives visible, and discuss them. You mentioned there are several alternative explanations. Does each make some falsifiable assertion?

    Aaron: I believe you are mistaken when you say CNS is “just an different choice of measure”. The basic testable assertion CNS makes is that you Aaron cannot show us a continuous deformation of the parameters—a path in parameter space starting at the observed values—with a monotone increase in BH abundance along that path. If you CAN find a small continuous change in the parameters which steadily increases BH abundance then congratulations, show it to us and I will say you have refuted CNS. It’s that simple.

    To talk Bayesian priors and conditional probability is to unnecessarily force the CNS conjecture into a Bayesian framework, at considerable risk of obfuscation. I have been familiar with Bayesian methods for several decades—a good (statistician, decision theorist, etc.) friend of ours has been a Bayesian at least since the 1960s. The current buzz among physicists does not enthuse me. I think I understand some of the appeal to string theorists in their present plight, and why Bayesian methods look especially good. But I think it is unnecessary complication to put everything into that framework. The initial choice of prior and calculating conditional probabilities are often a bit dubious.

    Your comment about “just a different measure” was so brief, Aaron, that I could not be sure whether you were referring to the current Bayes buzz or something else. If it was something else, please clarify.

  15. Aaron Bergman says:

    The basic testable assertion CNS makes is that you Aaron cannot show us a continuous deformation of the parameters—a path in parameter space starting at the observed values—with a monotone increase in BH abundance along that path

    No, it doesn’t. CNS is just a mechanism saying that there are more universes with black holes than universes without black holes. In other words, the measure is highly peaked around those universes that tend to produce lots of black holes. If you believe in that sort of statistics, then the best you can say is that it is likely that we live near the peak of this distribution. This is exactly the same as people putting other measures on the space of possible vacua/theories. It just so happens that this measure has a peak (assumedly.) One would think that eternal inflation, for example, might produce a similar phenomenon. More so, if you do want to do that sort of statistics, you have to look at the conditional probability based on the fact that we exist. Now, as I understand Smolin’s argument, this probably isn’t a big effect for his assumed distribution, but the principles involved are precisely the same.

  16. Who says:

    The basic testable assertion CNS makes is that you Aaron cannot show us a continuous deformation of the parameters—a path in parameter space starting at the observed values—with a monotone increase in BH abundance along that path

    here I am paraphrasing what Smolin gave as the basic testable assertion of CNS in his most recent paper about it. Please see the italicized statement at the bottom of page 29 of his paper
    http://arxiv.org/hep-th/0407213
    Scientific Alternatives to the Antropic Principle.
    this is the bulleted statement of the CNS hypothesis in section labeled “5.2 Natural Selection”

    If you will pardon me for saying so, Aaron, you seem confused about what is the basic testable assertion of CNS. I would urge you to carefully read section 5.2 of that paper. Don’t rely on what you may have HEARD people say that CNS asserts—read a firsthand source.

    I must be brief, not wanting to overemphasize CNS. Perhaps we could discuss this at Physicsforums where we would not be abusing Peter’s hospitality if we spoke at length.
    ——————————-

    Peter, I stress that ANY directly falsifiable hypothesis bearing on why the dimensionless parameters of the standard model and cosmology are what they are is of interest.
    What I want is something like “Statement S” in section 5.2 of Smolin’s paper in that it is brief and clearly falsifiable, but it doesn’t have to be CNS. It would be great to have several alternative testable explanations.

    Even though I am good friends with a reputable Bayesian probabilist, I must say that the current Bayes buzz in physics strikes me as a sign of sickness. Smokescreen and distraction while they get anthropics and the Landscape in through the back door. Just my opinion.

  17. Aaron Bergman says:

    If you will pardon me for saying so, Aaron, you seem confused about what is the basic testable assertion of CNS

    No, I’m really not. Smolin is precisely saying that the distribution (ie, measure) on the ‘multiverse’ is strongly peaked. That’s all. Look on page 29. It is no more or less testable than any other peaked measure on the space of vacua (or non-peaked — frankly, I find the whole idea of any measure at all being testable rather distasteful.)

  18. Who says:

    thanks for your reply Aaron. I will not say more about our difference of opinion in this thread, out of consideration for Peter.

  19. Aaron Bergman says:

    It might be worthwhile to elaborate how CNS does not obviate anthropic considerations. Imagine a situation, for the sake of arguments, where the number of black holes — or whatever universe creation mechanism you prefer — does not lead to universes particular suited for life. This does not preclude the existence of life, however; even in a fitness landscape such as Smolin imagines, there is percolation away from the peaks. Eventually, there will exist universes in which life is possible. So, in this situation how would one ‘predict’ the probability distribution of various parameters? You would condition your distribution on the existence of life. This is exactly what the anthropic types do. That Smolin has chosen a mechanism to get a highly peaked prior distribution isn’t particularly relevant towards this point in principle, although the particular distribution Smolin argues for may render the anthropic correction minor.

  20. woit says:

    Aaron,

    Please, Who is right, enough about CNS unless there really is something new to be said on the subject. This has been discussed at great length already in other postings as well as in this one.

  21. Aaron Bergman says:

    Actually, given that “Who” posts this stuff on CNS every single time anyone mentions the anthropic principle, I don’t think anyone has said this in his presence. I finally got annoyed enough to post it.

    But I’ll stop now.

  22. Who says:

    on an off topic thing: an essay by Halvorson on Algebraic QFT was just posted
    http://arxiv.org/abs/math-ph/0602036
    Algebraic Quantum Field Theory
    Hans Halvorson, Michael Mueger
    202 pages; to appear in Handbook of the Philosophy of Physics (North Holland)

    “Algebraic quantum field theory provides a general, mathematically precise description of the structure of quantum field theories, and then draws out consequences of this structure by means of various mathematical tools — the theory of operator algebras, category theory, etc.. Given the rigor and generality of AQFT, it is a particularly apt tool for studying the foundations of QFT. This paper is a survey of AQFT, with an orientation towards foundational topics. In addition to covering the basics of the theory, we discuss issues related to nonlocality, the particle concept, the field concept, and inequivalent representations. We also provide a detailed account of the analysis of superselection rules by S. Doplicher, R. Haag, and J. E. Roberts (DHR); and we give an alternative proof of Doplicher and Roberts’ reconstruction of fields and gauge group from the category of physical representations of the observable algebra. The latter is based on unpublished ideas due to Roberts and the abstract duality theorem for symmetric tensor *-categories, a self-contained proof of which is given in the appendix.”

    I expect Peter would in any case find and report this at his convenience, but it seems like happy news so I take the liberty of noting it.
    Halvorson’s essay is a contribution to the same Butterfield and Earman Handbook that Ellis essay is in!

  23. urs says:

    Given the rigor and generality of AQFT

    No doubt about its rigor, but on the generality side something seems to be missing in AQFT. There is as yet not a single physically interesting QFT which would be describeable by AQFT.

    While it is to be expected that sometime in the future QFT will be cast in a mathematical form of the sort envisioned in AQFT, it seems that something crucial is missing.

    (For instance the locality condition in AQFT seems to be too strict, precluding field commutators as they appear in gauge theory.)

    In our math seminars we have AQFT people sitting together with those working on the FRS description of 2D QFT. This is also rigorous, but it does describe physically interesting interacting theories. But amusingly, nobody knows how these two approaches are related.

    and we give an alternative proof of Doplicher and Roberts’ reconstruction

    In case anyone is interested, I had mentioned Michael Müger’s talk on his new proof of Doplicher-Roberts here.

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