What are the experimental predictions of the various string theories?
Have any of those been experimentally verified so far?
Is belief in string theory paying any rent?
Some would say we should have found supersymmetry. (But I haven't looked into this stuff in detail myself yet.)
Yes, results form the LHC have been disappointing, so far. This talk pretty much summarized the official results up to a few months ago, and they're not encouraging. We're pushing the boundaries of the mass region implied by the Higgs mass hierarchy problem. What's confusing is that we would expect to find something in that region, even if it's not SUSY, but up to now nothing popped up.
It is strange that "Forty Years of String Theory: Reflecting on the Foundations" doesn't have any of the bigger names from string theory (particularly, no Ed Witten?), but has pretty much the full list of controversial (some people would say outright currently crackpotish[1]) names like 't Hooft, Verlinde, Smolin and lately also Susskind. I am not picking sides, but this raises all sorts of red flags about it. I bet Motl will be all over this.
I'll have a look at Susskind's paper, particularly if he is railing against reductionism.
[1] 't Hooft's and Susskind's contributions to modern theoretical physics can't be understated, but their general reputation suffered in recent years.
All the people you've mentioned (with the arguable exception of Smolin) are extremely deep theorists, and I don't see how anyone reasonable could label them crackpots. Sure, their recent work has been highly speculative and deviates from the theoretical mainstream in various ways, but I'd hope readers on this website wouldn't consider those sufficient criteria for crackpottery.
I'm sure Motl has called some of them crackpots, but Motl is basically a theoretical physics troll and his judgments about his colleagues are usually laughably unfair and hyperbolic. I'd advise against treating him as a reliable source, even when he's talking about his area of expertise. Sure, he knows his physics, but I've also found him to have a number of very bad epistemic habits, chief among them an abnormal aversion to admitting error.
I agree and tried to be careful saying "some people" (which is not exactly good practice, I know). As I noted below Motl is a fascinating specimen. I certainly don't consider him to be a an authority on who is a crackpot or not, nor do I agree with many of his opinions or methods.
Still I think it is a strange mix of authors for this topic.
Typo alert: not "t'Hooft" but "'t Hooft".
Motl is ... not exactly immune to charges of crackpottery himself.
Gosh, thanks, fixed it... I know I'm not the first to screw this up, but still...
Yes, Motl has to be handled with lot's of care, though usually as far as physics goes I find him alright (unlike say climate change and a bunch of other stuff). His tone can be off-putting, but I see him still as a useful contrarian in some areas and generally an interesting case study of an extremely bright person with some strange opinions and a very... interesting personality (to put it mildly).
If you were to read only one paper, make it the one by Michael Duff.
I have read this paper, and frankly I am a bit annoyed because of the time I wasted. There is basically no scientific content, just the usual physics blogosphere vitriol and gossip, now in a journal article. Where can I read about string theory, as opposed to the politics of string theory?
Sorry about your negative experience. The issue and the paper is about the state of the field, not about the string theory itself. If you want a popular description of the string theory itself, you can try this. For a quality primer, this is a text accessible to upper undergraduates in physics. But be aware of the amount of effort required.
I am SO going to get through all of that.
...
Though, if I do capitulate, i'm going to program games. And torment players with a final puzzle requiring them to understand a "simple" quantum computer program. MWAHAHAHAHA!
Those of us interested in "fundamental physics" may find a few interesting tidbits in the latest issue of Springer's Foundations of Physics. It has contributions from the prominent figures in String Theory and related fields, such as the Nobel laureate Gerard 't Hooft, father of the anthropic landscape Leonard Susskind and one of the founders of the leading alternative to the String Theory, Loop Quantum Gravity, as well as the author of several popular books about fundamental physics Lee Smolin. Eric Verlinde, the author of the controversial Entropic gravity model, also contributed. A couple of philosophers of science added their two cents.
While Springer is not an open-access publisher, this volume is free, as are many others during December 2012.
A few quotes from the introduction, which seem relevant to the issues of truth, realism and rationality:
"He ['t Hooft] compares string theory to other theories and models which are not free of problems but we generally consider to be well-defined: celestial classical mechanics, quantum mechanics, and QCD, and concludes that string theory is not in as good shape as any of these theories."
"Rickles develops a version of the “no-miracles argument” for scientific realism to the case of mathematically fruitful theories, thereby defending the rationality of those who pursue string theory in the absence of better alternatives, rather than making a statement about the truth of the theory."
"Susskind argues that developments in string theory are telling us that a narrow form of reductionism is wrong: “[I]f one listens carefully, string theory is telling us that in a deep way reductionism is wrong, at least beyond some point.” The reason is that various string dualities interchange what is fundamental and what is composite, large and small lengths scales, high-dimensional objects with lower-dimensional objects, and so on. According to Susskind, “In string theory this kind of ambiguity is the rule.” “Personally, I would bet that this kind of anti-reductionist behavior is true in any consistent synthesis of quantum mechanics and gravity.”"
If you were to read only one paper, make it the one by Michael Duff. Here is the abstract:
"Using as a springboard a three-way debate between theoretical physicist Lee Smolin, philosopher of science Nancy Cartwright and myself, I address in layman’s terms the issues of why we need a unified theory of the fundamental interactions and why, in my opinion, string and M-theory currently offer the best hope. The focus will be on responding more generally to the various criticisms. I also describe the diverse application of string/M-theory techniques to other branches of physics and mathematics which render the whole enterprise worthwhile whether or not “a theory of everything” is forthcoming."
