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Back when I was interested in theoretical physics (>15-20 years ago), String theory was the Hot Thing.

Imagine my surprise when, in a random browsing, I stumbled upon a science-themed blog "Not Even Wrong" written by Columbia University-associated Math professor Peter Woit where one of the comments by blog's owner stated (emphasis mine):

Many people thought the initial 1984 models for string theory unification were elegant, hardly anyone thinks that about the complicated mess you get out of a conjectural anthropic string theory multiverse.

“Enormous explanatory power” doesn’t really go with “can’t predict a single f—ing thing”….

Given that forming falsifiable predictions is the cornerstone of scientific method, the above quote sounded pretty damning to me.

QUESTION: Is it true that since 1980s, string theory - or at least parts of it associated with Anthropic principle have not made any (or any non-disproven) falsifiable predictions? Or was that comment somewhat hyperbolic?

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user5341
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  • If the mods feel that this belongs more on Physics SE, please feel free to vote to close. – user5341 Apr 23 '11 at 22:04
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    I think it's a good question. I should research this, because at this particular time, I feel that the predictive capability of string theory is beyond our current technology. – Larian LeQuella Apr 23 '11 at 22:08
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    @Larian - Thanks! That would be my assumption based on what I read about String theory back in high school, but I've been out of touch with theoretical physics for waaaaay too long since then to have a proper enough clue. – user5341 Apr 23 '11 at 22:10
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    It has been already asked on physics actually :-) Let's see if we get good answers here (it's a *hotly* debated topic in physics). – Sklivvz Apr 23 '11 at 22:21
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    The underlying problem with string theory for the foreseeable future is that it is not one theory: it's a huge family of theories. If we knew which was the right one, you could use it to predict things, but we can't know until we can run tests that are very much beyond our current technology. So, there are pretty good odds that a string theory is a good description of the universe but this fact does us almost no good at all. – dmckee --- ex-moderator kitten Apr 23 '11 at 22:40
  • the first thing that comes to my mind is "Supersymmetry" – Oliver_C Apr 23 '11 at 22:55
  • I'm confused as to why the anthropic principle is mentioned in the question. It's a philosophical idea, string theory is a mathematical hypotheses attempting to unite quantum mechanics and Special Relativity. – erikthebassist Apr 23 '11 at 23:39
  • Woit's comment (and I read his blog faithfully), in this context are referring to the philosophical ramifications of living in a multi-verse. To actual string theorists, it's a scientific question, not a philosophical one. I suspect much of Woit's disdain for the theory stems from his incredulity over the consequences, not whether the theory is actually true or not. But Woit is right, there are few reasonable testable predictions, and the one's that do exist also fit competing theories. – erikthebassist Apr 23 '11 at 23:50
  • @erikthebassist - (1) competing as in LQG? (2) It sounded to me like (from other comments) he pretty much equates the consequences of anthropic stuff with faith... I could be wrong. – user5341 Apr 23 '11 at 23:59
  • @DVK, (1) as one, also the Holographic Principle... (2) but you won't hear String Theorists talking about the philosophical implications, they stick to the math and the theory. That's it's not testable at the moment doesn't seem to bother most of them. They are quite confident that it will be. – erikthebassist Apr 24 '11 at 00:13
  • @Erik - (2): Paul Davies being just one random example I remember :) – user5341 Apr 24 '11 at 00:21
  • @DVK well he's out a limb on a lot stuff. – erikthebassist Apr 24 '11 at 01:04
  • Does "no predicts can be done at this time" necessarily make something woo? – Andrew Grimm Apr 24 '11 at 02:11
  • @Andrew: Depends on how much you hype it, maybe. – dmckee --- ex-moderator kitten Apr 24 '11 at 03:30
  • I had a professor in college who called it "Quantum Theology" – Zachary K Apr 24 '11 at 07:13
  • **Related:** http://physics.stackexchange.com/questions/15/what-experiment-would-disprove-string-theory – Sklivvz Apr 24 '11 at 14:35
  • **Related:** http://physics.stackexchange.com/questions/2532/what-evidence-exists-for-string-theory-viability – Sklivvz Apr 24 '11 at 14:35
  • @erikthebassist it was my understanding that the inclusion of the anthropic principal was mostly due to the way in which it is described by Hawking in relation to the M Theory because it imposes a limit on the number of observable universes to those capable of sustaining life/consciousness which is capable of observation. I think... – Monkey Tuesday Apr 25 '11 at 05:18
  • @monkey That's assuming that a universe requires an observer to exist, which has not been established to be true by any stretch of the imagination. – erikthebassist Apr 25 '11 at 12:36
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    yeah I don't think we're going to get better answers here than what was already provided oh the physics SE that Sklivvs linked. I'm prepared to be surprised but they pretty much covered the gamut over there. – erikthebassist Apr 25 '11 at 12:43
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    @erikthebassist It's not that the universe requires a conscious observer to exist, but that the mathematical model by which we understand that universe requires conscious observers. It's why the anthropic principle usually crops up when people discuss model-dependent realism, to clarify that there may be a difference between the model and what it represents. While the anthropic principle is not a mathematical concept, it becomes relevent when explaining the logic of using mathematical models to describe the universe. But it's possible I have that all wrong. – Monkey Tuesday Apr 25 '11 at 22:10

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I just read an article in Scientific American: "The Strangest Numbers in String Theory" by John C. Baez and John Huerta, where they state:

At this point we should emphasize that string theory and M-theory have as yet made no experimentally testable predictions. They are beautiful dreams - but so far only dreams. The universe we live in does not look 10- or 11- dimensional, and have not seen any symmetry between matter and force particles. David Gross, one of the world's leading experts on string theory, currently puts the odds of seeing some evidence for supersymmetry at CERN's Large hadron Collider at 50 percent. Skeptics say they are much less. Only time will tell.

So I think our initial thoughts are in line with major names in the field. And as the last four words say, only time will tell.

Larian LeQuella
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    Predictions must come prior to experiments. If it doesn't make experimentally testable predictions, what is there a 50% chance we'll find? Is there a verifiable prediction that Gross guesses might be confirmed? If it's not confirmed, is there a chance it can falsified? That sentence reeks of bad science writing. –  Apr 26 '11 at 12:22
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    Supersymmetry is the prediction. Although I must admit that I don't know exactly what that prediction looks like experimentally. Seeing a force particle along with an elementary particle is the gist of supersymmetry as I recall. – Larian LeQuella Apr 26 '11 at 13:42
  • What I mean is, the paragraph contradicts itself. If string theory and M-theory have as yet made no experimentally testable predictions, what evidence has a 50% chance of showing up? –  Apr 26 '11 at 15:41
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    I have used this answer once before, but... Monty hall has the answer behind one door, and behind the other doors, goats.... – Monkey Tuesday Apr 26 '11 at 22:26
  • @JoeWreschnig The parameters that can be used to configure string theory include values whose predictions diverge from the standard model at conditions only slightly beyond current experimental results and values whose divergences occur at levels far beyond current experimental capabilities. – Dan Is Fiddling By Firelight Feb 16 '12 at 21:01
  • @JoeWreschnig One example of this is creating quantum black holes via ultra high energy cosmic rays or in the LHC. The extra dimensions are only accessible by gravity, which we've only measured down to a scale of ~0.1mm. Below the size of the extra dimensions gravity would be significantly stronger than predicted by conventional physics. If they're slightly smaller than this BHs could be created in collisions; if much smaller the energy needed to create them converges to that of conventional quantum mechanics and general relativity. – Dan Is Fiddling By Firelight Feb 16 '12 at 21:02
  • @JoeWreschnig the odds of string theory making a testable prediction via the LHC is roughly equivalent to the fraction of configurations that will diverge from conventional models at some point below the LHCs peak operating power. – Dan Is Fiddling By Firelight Feb 16 '12 at 21:04