There have been so many reviews about Lee Smolin's (The Trouble with Physics) and Peter Woit's book (Not Even Wrong) in the last weeks, that I have kind of lost track who said what about whom and why. Besides the reviews, there are comments on the reviews, comments on the comments, psychoanalytic examinations of the author's intentions, or otherwise people who take the opportunity to comment on whatever they think the problem is, or isn't, or what other peoples problems are, or aren't. And if there is no problem, how boring, let's go make one, preferably for somebody else.
Today for instance, I read George Ellis review in Nature (Nature 443, 482, 5 Oct. 2006) about Lee Smolin's book "Unburdened by proof - String theorists are setting a worrying trend by downplaying the need for experimental evidence."
The review itself is very reasonable in my opinion, the biggest part being a summary of the books content, with only spare judgement ("an excellent presentation of the foundations of fundamental physics", "Smolin crystallizes what many in the physics community feel about these extravagances of string theory"). The last paragraph then adds the opinion of George Ellis (so I presume)
What is crucially needed in developing string theory is a serious attempt to engage with the philosophy of science, developing an approach to theory validation that is adequate where insubstantial evidential support has to be supplemented by other principles of inference. So far, this has not been done.
Though I seriously hope that evidential support for or against string theory will arise soon and it won't be necessary, I do agree that in the absence of any contact to reality, we should think about where to draw the line between theoretical physics and mathematical physics. However, this does not only account for string theory. I should also add that I certainly don't mind mathematics, having started up as a student of maths, but one shouldn't sell the one for the other.
The same issue of Nature also features an editorial titled "Power and particles, String theories dominate for good reason." This is probably meant as kind of an antidote, but is so weak that it does completely fail in its intention, ending with the sentence "Critical-mindedness is integral to all scientific endeavour, but the pursuit of string power deserves undaunted encouragement.", which can be easily read as a support for the accusation about the exclusiveness of the string community.
Also in this same issue is a commentary about Lee's and Peter's book by Geoff Brumfiel, titled "Theorists snap over string pieces- Books spark war of words in physics." which quotes Joe Polchinski:
In recent years the theory has contributed significantly to heavy-ion physics, according to Joe Polchinski, a string theorist at the Kavli Institute for Theoretical Physics in Santa Barbara, California. When the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in Upton, New York, first produced a hot quark gas, it was string theory that correctly predicted, retrospectively, some of the gas's properties. "In many ways, I feel the boundaries with other areas of physics are coming down," Polchinski says.
Though I am not sure whether I would call the application of the AdS/CFT correspondence to heavy ion physics a direct prediction of string theory (?!??), I do agree that I think the boundaries to other areas of physics are coming down, and I see this as a very good development. More importantly, it is one that is already taking place.
And this is the purpose of my writing today. In my perception, it is not even a very recent shift in priorities that many of those working on string theory have realized that a connection to what Lee calls 'the real world out there' should be a prime goal in their research. That is, unlike the exploration of all mathematical features of the allegedly beautiful theory, string phenomenology has grown to be an important field, maybe sparked by the idea of large extra dimensions in '98.
I myself know numerous people working on string phenomenology, and even though I personally don't believe that string theory is the-one-and-only theory of everything, this is not a vacuous project. Of course one can now argue how much of string theory does really go into predictions for colliders or the such, or whether any such connection would be unique and what one can learn from that at all. These are all questions that one has to think about, that one can argue about, and to address them is part of the scientific endeavor. E.g. you might want to check the paper I found on the arxiv today:
LHC String Phenomenology
Authors: Gordon L. Kane, Piyush Kumar, Jing Shao
which addresses the LHC inverse problem, that is: when we see some new physics at the LHC, can we uniquely find out what was its cause? Surprising for me, the authors state that this problem has received little attention until lately. This surprises me because it was my favourite question to ask in whatever talk: if you see these signatures, can you be sure it's what you have predicted and not something else? A question that is widely applicable in almost every talk btw, very handy. And the answer is usually: no.
In the last weeks I have read so many nasty things about 'the string community' that I suddenly feel like I have to state that is a very unbalanced polarization taking place in a public debate. A debate about what theoretical physics means in the 21st century, which in my opinion should not have been lead in public in such an unscientific way. Unfortunately, this has already happened and I can only hope, that it calms down to a level where we can discuss raised concerns without being personal. In my experience, string theorists are not more or less scientifically blinded by their own believes than those working out other believes about how nature fools us. Though I admit that some of them behave kind of strange when they are clustered to groups.
To quote another paragraph from the above mentioned article by Geoff Brumfield:
The books leave string theorists such as Susskind wondering how to approach such strong public criticism. "I don't know if the right thing is to worry about the public image or keep quiet," he says. He fears the argument may "fuel the discrediting of scientific expertise".
This, I'd say depends on whether the arguments are discussed with scientific expertise. Or personal insults.
Note added: Lubos has something to say about the Nature articles as well.