Monday, May 30, 2016

Book Review: “Why String Theory?” by Joseph Conlon

Why String Theory?
By Joseph Conlon
CRC Press (November 24, 2015)

I was sure I’d hate the book. Let me explain.

I often hear people speak about the “marketplace of ideas” as if science was a trade show where researchers sell their work. But science isn’t about manufacturing and selling products, it’s about understanding nature. And the sine qua non for evaluating the promise of an idea is objectivity.

In my mind, therefore, the absolutely last thing that scientists should engage in is marketing. Marketing, advertising, and product promotion are commercial tactics with the very purpose of affecting their targets’ objectivity. These tactics shouldn’t have any place in science.

Consequently, I have mixed feelings about scientists who attempt to convince the public that their research area is promising, with the implicit or explicit goal of securing funding and attracting students. It’s not that I have a problem with scientists who write for the public in general – I have a problem with scientists who pass off their personal opinion as fact, often supporting their conviction by quoting the number of people who share their beliefs.

In the last two decades this procedure has created an absolutely astonishing amount of so-called “science” books about string theory, supersymmetry, the multiverse and other fantasies (note careful chosen placement of commata), with no other purpose than asking the reader to please continue funding fruitless avenues of research by appealing to lofty ideals like elegance and beauty.

And indeed, Conlon starts with dedicating the book to “the taxpayers of the UK without whom this book could never have been written” and then states explicitly that his goal is to win the favor of taxpayers:
“I want to explain, to my wonderful fellow citizens who support scientific research through their taxes, why string theory is so popular, and why, despite the lack of direct empirical support, it has attained the level of prominence it has.”

That’s on page six. The prospect of reading 250 pages filled with a string theorists’ attempt to lick butts of his “wonderful fellow citizens” made me feel somewhat nauseous. I put the book aside and instead read Sean Carroll’s new book. After that I felt slightly better and made a second attempt at Why String Theory?

Once I got past the first chapter, however, the book got markedly better. Conlon keeps the introduction to basic physics (relativity and quantum theory) to an absolute minimum. After this he lays out the history of string theory, with its many twists and turns, and explains how much string theorists’ understanding of the approach has changed within the decades.

He then gets to the reasons why people work on string theory. The first reason he lists is a chapter titled “Direct Experimental Evidence for String Theory” which consists of the single sentence “There is no direct experimental evidence for string theory.” At first, I thought that he might have wanted to point out that string theorists work on it despite the lack of evidence, but that the previous paragraph accidentally made it look as if he, rather cynically, wanted to say that the absence of evidence is the main reason they work on it.

But actually he returns to this point later in the book (in section 10.5), where he addresses “objections made concerning connection to experiment” and points out very clearly that even though these are prevalent, he thinks these deserve little or no sympathy. This makes me think, maybe he indeed wanted to say that he suspects the main reason so many people work on string theory is because there’s no evidence for it. Especially the objection that it is “too early” to seek experimental support for string theory because the theory is not fully understood he responds to with:
“The problem with this objection is that it is a time-invariant statement. It was made thirty years ago, it was made twenty years ago, it was made a decade ago, and it is made now. It is also, by observation, an objection made by those who are uninterested in observation. Muscles that are never used waste away. It is like never commencing a journey because one is always waiting for better modes of transportation, and in the end produces a community of scientists where the language of measurement and experiment is one that may be read but cannot be spoken.”
Conlon writes that he himself isn’t particularly interested in quantum gravity. His own research is finding evidence for moduli fields in cosmology, and he has a chapter about this. He lists the usual arguments in favor of string theory, that it connects well to both general relativity and the standard model, that it’s been helpful in deriving some math theorems, and that now there is the AdS/CFT duality by help of which one might maybe one day be able to describe some aspect of the real world.

He somehow forgets to mention that the AdS/CFT predictions for heavy ion collisions at the LHC turned out to be dramatically wrong, and by now very few people think that the duality is of much use in this area. I actually suspect he just plainly didn’t know this. It’s not something that string theorists like to talk about. This omission is my major point of criticism. The rest of the book seems a quite balanced account, and he restrains from making cheap arguments of the type that the theory must be right because a thousand people with brains can’t be mistaken. Conlon even has a subsection addressing Witten-cult, which is rather scathing, and a hit on Arkani-Hamed gathering 5000 citations and a $3 million price for proposing large extra dimensions (an idea that was quietly buried after the LHC ruled it out).

At the end of the book Conlon has a chapter addressing explicit criticisms – he manages to remain remarkably neutral and polite – and a “fun” chapter in which he lists different styles of doing research. Maybe there’s something wrong with my sense of humor but I didn’t find it much fun. It’s more like he is converting Kuhn’s phases of “normal science” and “revolution” into personal profiles, trying to reassure students that they don’t need to quantize gravity to get tenure.

Leaving aside Conlon’s fondness of mixing up sometimes rather odd metaphors (“quantum mechanics is a jealous theory... it has spread through the population of scientific theories like a successful mutation” – “The anthropic landscape... represents incontinence of speculation joined to constipation of experiment.” – “quantum field theorists became drunk on the new wine of string theory”) and an overuse of unnecessary loanwords (in pectore, pons asinorum, affaire de coer, lebensraum, mirabile dictum, for just to mention a few), the book is reasonably well written. The reference list isn’t too extensive. This is to say in the couple of cases in which I wanted to look up a reference it wasn’t listed, and the one case I wanted to check a quotation it didn’t have an original source.

Altogether, Why String Theory? gives the reader a mostly fair and balanced account of string theory, and a pretty good impression for just how much the field has changed since Brian Greene’s Elegant Universe. I looked up something in Greene’s book the other day, and found him complaining that the standard model is “too flexible.” Oh, yes, things have changed a lot since. I doubt it’s a complaint any string theorist dare raise today.

In the end, I didn’t hate Conlon’s book. Maybe I’m getting older, or maybe I’m getting wiser, or maybe I’m just not capable of hating books.

[Disclaimer: Free review copy.]

Win a copy of Why String Theory by Joseph Conlon!

I had bought the book before I was sent the review copy, and so I have a second copy of the book, entirely new and untouched. You can win the book if you are the first to answer this question correctly: Who was second author on the first paper to point out that some types of neutrino detectors might also be used to directly detect certain candidate particles for dark matter? Submit answer in the comments, do not send an email. The time-stamp of the comment counts. (Please only submit an answer if you are willing to send me a postal address to which the book can be shipped.)

Update: The book is gone!


  1. Nope - not the person I had in mind. But in case I'm wrong, I'm happy to let myself be educated, so if you have a reference please post it. The paper I am referring to is from 1985.

  2. I think it is Edward Witten (together with Mark Goodman)!

  3. Yes, right! It's Ed Witten :)

    The book goes to Joel - Sorry Phillip, he beat you by like 10 seconds or so!

    Joel, can you send a note to hossi[at] and let me know the address you want the book be shipped to?

  4. You need to increase the resolution of the timestamps. :-)

    At least on some blogs, the order in which comments appear does not always reflect the order in which they were received. :-|

    To boost my credibility here is the reference:

    Goodman, Mark W.; Witten, Edward: "Detectability of certain dark-matter candidates", Physical Review D, Volume 31, Issue 12, pp.3059-3063, 15 June 1985

  5. Sabine, this is the paper you are referring to:

    They calculate the cross sections for certain types of dark matter, but the proposal, according to this very paper, is due: Drukier and Stodolsky, citation number 5. Goodman and Witten show that in the 2nd paragraph of their paper.

  6. Daniel,

    They proposed the detector - to detect neutrinos, as it says in there. Goodman and Witten pointed out it could also be used to detect dark matter (certain types thereof).

  7. A good review. It is clear from his metaphors that he either never took college literature or his teachers were asleep at the job. Every good writer needs to have suffered through one or more merciless but correct lit professors who prune them of their bad metaphors and trite phrases.

    Of course things change with time, in 1975 I would have gotten nailed for using the "prune" one here. But it is not so over-used today.

  8. "string theory, supersymmetry, the multiverse and other fantasies " The maths are deep, elegant, and hugely published. No performed experiment validates. Attempt falsification. Geometry is a proper test of spacetime geometry.

    A geometric Eötvös experiment sources physics' chiral quirks (e.g., baryogenesis). Physics excludes it. Chemistry embraces it. Exhaustively validated physics apparatus runs it. Observe single crystal left-handed alpha-quartz versus single crystal right-handed alpha-quartz violating the Equivalence Principle. No prior observation is contradicted. The worst it can do is succeed.

  9. I've almost finished the book and I thought it was fair and objective about the current state of string theory. A nice change from the usual. Perhaps too much detail meant some of the later chapters dragged. I think your review says it all.

  10. And the second prize which goes to Phillip, is two copies!

    Nice review, Sabine. I share your sentiments.

  11. John,

    The other copy is in a poor shape, not only because I ran out of sticky notes and bent over multiple corners, but I also dropped it on the ground and almost ran over it with my car. Also, I'd prefer to keep a copy myself, it might come in handy as a reference for this or that.


  12. "He somehow forgets to mention that the AdS/CFT predictions for heavy ion collisions at the LHC turned out to be dramatically wrong, and by now very few people think that the duality is of much use in this area."

    I know you've talked about the failure of AdS/CFT to correctly predict results when it comes to heavy ion collisions before, but I was wondering what exactly this might mean in relation to the prospects of string theory (which I still consider myself a fan of). Is there something in the calculations we're missing? Does the quark-gluon plasma generated by those collisions behave in a way that wouldn't actually justify using AdS/CFT? Does not being applicable "in this area [high energy particle collisions]" say anything about it's generality?

    I've always wondered how serious a problem this is for the theory, especially considering the fact that several things could be going wrong outside of AdS/CFT actually being wrong in some sense. I'd really appreciate any help clearing all this up!

  13. Hi Sabine; one thing is certain, I won't by this book.

    After 40+ years of quasi-stagnation, maybe SciFi is all that remains to be found...
    On the other hand, I assume you do have a clearly agreed list of what needs to be solved or found. I mean agreed by the community.

    Following the last 40+ years, and considering the integral sum(IQ x time) or the sum sigma(ink + paper) involved on those problems, it is somewhat natural to considering that the manner is not appropriate. String Theory is not better, OK, but at least it seems seductive and there is nice work to do...

    In my opinion, the alternate possibility would be that the list is wrong. If you take that seriously, the question you may need to ask is: what kind of problem do we miss to solve in order to explain some observations which, based on your generation's theoretical background, are not problems at all?


  14. "... the book is reasonably well written."

    Damning with faint praise.

    The wikipedia entry on that idiom should link to this review :-)

  15. Henning,

    I actually meant it. The writing is good, it's easy to follow, it's not dull either, and the sentences are understandable. There are some authors who manage to fabricate sentences I have to read a couple of times to parse, but I had no problems with this book. The oddest thing about the writing in this book is, as I mentioned, that Conlon goes to length to explain all kinds of technical expressions (like strong and weak coupling) but then clutters the text with Latin, French, and German - why? I mean, I learned both Latin and French (and speak German), but still I had too look up some of the lesser used expressions just to figure out what he was trying to say. Did he do this to show off or to annoy the reader? It doesn't make any sense to me. Best,


  16. pete,

    No, it says that the quark gluon plasma probably isn't as strongly coupled as they originally thought it is, which makes the AdS/CFT duality even less useful as they initially thought it is (QCD not being supersymmetric). There might be some aspects for which you can use it, but you'd still have to add some perturbative calculations. And then, once it turned out that the real world is messy, most string theorists seem to have lost interest in the topic.

    Don't get me wrong, I don't blame them - I come from an institute where everybody worked on heavy ion physics and wanted nothing to do with it. Instead I went to the US with the intention to become a string theorist. So I totally understand the sentiment. I also think though this was clear from the very beginning that string theory wouldn't turn out to be a magic wand to solve heavy ion physics. I am mostly annoyed that first they go around and make rather silly big claims and then when they figure it isn't that easy, instead of admitting they might have been a little too naive, simply hurry away and pretend it's never happened. Best,


  17. akidbelle,

    I think you will like my upcoming book...

  18. Hi Sabine,

    you don't take much risk writing this; I like what you write already.
    I am sure you will let us know when it's out...

    By the way, when?


  19. akidbelle,

    My deadline is Dec 2017, and then it might take 9-12 month to publication. But the way it looks presently I might be done earlier. So... I am guessing some time between late 2017 and late 2018. I'll tell you more about this once I know the details better. Best,


  20. Curious about your book Sabine, good luck. My guess is the next 10 years will be pivotal for physics research.

  21. Sabine, I wish I was as luck as you to get free copies of all these books :-)
    Anyhow does the book address/acknowledge the criticisms of string theory by Woit, Smolin,others?
    If so, what does it say?

  22. Shantanu,

    The book has a chapter addressing criticism, but it's not explicitly aimed at any person. I don't have the book with me and can't recall exactly which point it picked up on. Not the ones that I personally find troublesome. One was the question of UV finiteness I think.

    Well, they send me the books because they want me to write a review on them. You should look at it this way: I get a 30$ book for free, and in exchange I have to read 250 pages and write 1000 words. It's not a particularly great deal.

  23. Hi Sabine,

    I would say your main criticism of the failure of holography in heavy ions is unfounded. While many in the field (myself included) remain highly skeptical of it's applicability, it nevertheless has remained a very active non-perturbative technique. For instance the bound for the ratio of shear viscosity to entropy density from holography has held up fairly well with even the most sophisticated relativistic hydrodynamic models. Also, the equation of state from holography is sometimes used in model building (normally as a comparison to a lattice EoS), and it remains one of the only ways to really compute many of the transport coefficients (which the lattice living in Euclidean space has a hard time doing). Holography has been important as a strong coupling comparison to the more canonical non-pertubative but weak coupling approaches for studies of thermalization and also anomalous transport effects. Jet quenching is obviously still a problem (I'm guessing this is where you're criticism is most heavily based on), but holography is still thriving for the time being in HICs.

  24. Mark,

    You're putting words in my mouth I didn't use. I never spoke of a "failure of holography", I spoke of a failure of its applicability to heavy ion collisions at the LHC. And yes, I am referring to jet-quenching. I don't actually disagree with you, I just think we have a different interpretation of "thriving". Either way, to come back to my criticism, don't you think that to give a balanced account the author of the book should have mentioned that AdS/CFT doesn't just allow one to compute what's happening in a heavy ion collision? Because you could have gotten away with that impression. Best,


  25. "astonishing amount of so-called “science” books about string theory, supersymmetry, the multiverse and other fantasies note careful chosen placement of commata) "

    Unfortunately, commas placed there do not have your desired effect. You're still saying it's all fantasy. Maybe it's different in German.

    Something else: One has the distinct impression concepts like 'multiverse' you elsewhere have supported, possibly defended. Likewise String Theory.

    It would add a lot clarity, if you announced major developments of your personal stance. Also it's very interesting to hear what tipped the balance.

    or do I got that wrong?

  26. pien,

    I practice the Oxford comma. And just in case the reader didn't figure that, I even explicitly drew attention to it. If I left you with the impression that I "support" the multiverse, you must have dramatically misread me. I might have said that some variants of the multiverse have some aspects that might possibly one day in the far future be useful for something. That's a far cry from being "supportive".

    As I explained here, the reason we see "multiverses" popping up is that physicists don't want to realize it's logically impossible to construct a theory of nature using mathematical consistency alone. Best,


  27. Another vote for the Oxford comma:
    1) I leave my estate to Tom, Dick, and Harry Each get 1/3.
    2) I leave my estate to Tom, Dick and Harry. Tom gets 1/2; Dick and Harry each get 1/4.

    I'd go for "number" of books rather than amount. However, "amount" could be a subtle insult to the cumulated number of pages absent their partitioning into books and authors. Basic science is a religion searching for the Answer within dogma. Grant funding is a business plan intolerant of risk. It's been done before. It terrifically failed.

    The multiverse is obscene. It demands that failing to validate one string theory vacuum validates all string theory vacua. Not assigning grades in a competition validates the excellence of all competitors? No. Trying real hard is not indistinguishable from doing real well. Labor input does not create value.

  28. Hi Sabine,

    I like the last sentence... a real lot! It reminded me of something I read some time ago:

    In Disturbing the Universe, Freeman Dyson writes, "Dick [Feynman] fought back against my skepticism, arguing that Einstein had failed because he stopped thinking in concrete physical images (as MDT does!) and became a manipulator of equations. I had to admit that was true. The great discoveries of Einstein’s earlier years were all based on direct physical intuition. Einstein’s later unified theories failed because they were only sets of equations without physical meaning. Dick’s sum-over-histories theory was in the spirit of the young Einstein, not of the old Einstein. It was solidly rooted in physical reality."

    What do you think Sabine?


  29. My favourite example of what can go wrong when not using the Oxford comma: "I dedicate this thesis to my parents, God and L. Ron Hubbard".

  30. "I practice the Oxford comma"

    First to say that, what you said when 'explicitly drawing attention' was sufficient that I'm sure everyone reading was clear you wanted your sentence to be read as 'multiverses only' as fantasy.

    So there's no problem, but I am presuming you are interested to known when something isn't right at the level of language.

    The Oxford Comma is a's not something that is declared. You have to actually put the comma in a specific position. In your sentence that would immediately before the 'and' in 'and other fantasies'.

    But whether you put it there, or where you put it, the comma in that situation does not change the intuitive and grammatically correct interpretation that you regard all three as fantasies.

  31. piein,

    You're not making sense. You understood what I meant, you even say that it was clear to everyone reading, so for what I am concerned the grammatical construction I chose did exactly what it was supposed to do. Honestly, I don't really care if you think it's correct, as long as it says what I want it to say.

  32. I don't understand how AdS/CFT can be used, when our universe is dS.


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