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Bhny, your comment reminds me of those that attacked Galileo's, Newton's, and Einstein's theories. - Brad Watson, Miami [[Special:Contributions/66.229.56.118|66.229.56.118]] ([[User talk:66.229.56.118|talk]]) 14:42, 16 September 2011 (UTC)
== How is the string theory scientific? ==
This article claims that the string theory is a scientific theory even though the string theory does not adhere to the scientific method (has no testable predictions) and is by definition pseudo-scientific.
It's possible for something to be falsifiable and still have no testable predictions. According to this article I can say that anything is scientific if it relies on the truth of General Relativity or Quantum Mechanics even if it has no testable predictions, which is obviously nonsense.
Using this article's reasoning we can conclude that Intelligent Design is scientific.
So why are the authors of this article biased towards making the string theory appear scientific?
--[[Special:Contributions/96.255.71.164|96.255.71.164]] ([[User talk:96.255.71.164|talk]]) 04:42, 4 September 2011 (UTC)
:You're just misinformed. String theory has testable predictions. [[User:Dauto|Dauto]] ([[User talk:Dauto|talk]]) 04:53, 4 September 2011 (UTC)
The article has a lot of criticism and the intro doesn't say that it is a "scientific theory", it says it's a research framework that is a contender for a theory of everything. I think it's safe to call it scientific research. [[User:Bhny|Bhny]] ([[User talk:Bhny|talk]]) 15:20, 4 September 2011 (UTC)
:It would also be safe to call it a scientific theory but the article chooses to be conservative which is fine. [[User:Dauto|Dauto]] ([[User talk:Dauto|talk]]) 15:28, 4 September 2011 (UTC)
::For some reason the Wikipedia editors have blocked out my response, so go read it here http://en.wikipedia.org/wiki/User_talk:96.255.71.164#String_theory_not_scientific
::--[[Special:Contributions/96.255.71.164|96.255.71.164]] ([[User talk:96.255.71.164|talk]]) 05:54, 30 September 2011 (UTC)
:If anything the article leans heavily to the conservative side. String theory is falsifiable which by definition means that it makes experimental predictions. The only question is how novel or significant those predictions are, which is debatable and under active research. So the last sentence of the first paragraph seems to be incorrect. [[User:Isocliff|Isocliff]] ([[User talk:Isocliff|talk]]) 22:23, 4 September 2011 (UTC)
::In what way exactly is the sentence wrong? It says "testable predictions". Obviously string theory makes predictions. Isn't the big problem that the predictions haven't been testable?
::(the weasel words- "some scientists" need to be fixed) [[User:Bhny|Bhny]] ([[User talk:Bhny|talk]]) 02:14, 5 September 2011 (UTC)
:::Well one important example is gravity and general relativity. These can be viewed as "obvious" today or "postdictions", but its still true that every time we test general relativity, as in the recent frame-dragging experiments by Gravity Probe B, we are doing experiments that could falsify string theory if they produced the wrong result. The same can be said of the experiments that have been done in recent years verifying the exactness of the Lorentz symmetry. So one could make a case that the ways to test string theory are so far not yet sufficiently convincing, but its wrong to assert categorically that its untestable, unfalsifiable, unscientific, or anything like that.
:::It would be nice to be able to say it predicts us to observe particle X at exactly Y energy, but there doesn't seem to be any justification for expecting this would be the case. Im not an expert on the phenomenology or anything, but its clear that string theory is compatible with all kinds of particle physics content, but there also exist a lot of very firm rules (such as dictated by dualities, etc) that can be checked in principle. To check them to a significant degree probably requires very high energy collisions, but the fact that these tests are economically inconvenient to humans is not the same thing as being untestable. [[User:Isocliff|Isocliff]] ([[User talk:Isocliff|talk]]) 04:22, 5 September 2011 (UTC)
String theory is scientific by any definition I know of, the best of which is Popper's. To be scientific, theories (according to Popper) only need to be falsifiable. But as is mentioned in the article, this is obviously the case for string theory. For instance string theory is locally Lorentz invariant. Many experiments have been done to check whether this holds for nature or not. If any of those experiments (past or future) show that nature isn't locally Lorentz invariant, string theory is falsified. So it's clearly scientific by that criterion. Obviously string theory is more than just Lorentz invariance, and so to convincingly confirm that it's right we need to do more than just check that nature is Lorentz invariant. There's a discussion of that in there too.
I don't think the fact that string theory is mathematical belongs in that section. Mathematics is too general to be falsified, it's just the logical consequences of various sets of axioms, and axioms cannot be falsified.[[User:Waleswatcher|Waleswatcher]] ([[User talk:Waleswatcher|talk]]) 14:07, 30 November 2011 (UTC)
:Before further changes get made to the testability section, perhaps we should discuss them here. Something close to the language that's there now was extensively discussed and finally agreed on several years ago. There are some basic facts relevant here: string theory is quantum mechanical, all known versions of it reduce to Einstein's general relativity (the full, non-linear theory) in the low energy limit, and all string theories are fundamentally Lorentz invariant. That makes them falsifiable, full stop. Therefore, they are scientific according to Popper. There's no debate I'm aware of on that, because these really are basic facts about the theory. The problem of string theory is that it probably doesn't make predictions that are falsifiable with current technology AND that are "new", meaning not shared by other putative theories that are QM, Lorentz invariant, and reduce to GR (never mind that no other such theory exists....). [[User:Waleswatcher|Waleswatcher]] ([[User talk:Waleswatcher|talk]]) 17:04, 8 December 2011 (UTC)
== Two small points on history ==
Useful article. Comments:
1. The term "bootstrap program" is used but undefined and meaningless to outsiders.
2. Has actually nothing worth noting happened since 1997? Or is the jury still out? Recent controversies would be of interest.
[[User:Burressd|Burressd]] ([[User talk:Burressd|talk]]) 21:14, 30 November 2011 (UTC)
:I added a link to "bootstrap model". I find the wording redundant "...complete the bootstrap program for this model". Could we change it to "complete the bootstrap model"? [[User:Bhny|Bhny]] ([[User talk:Bhny|talk]]) 22:15, 30 November 2011 (UTC)
== widely believed to be consistant? ==
<blockquote>Since string theory is widely believed[who?] to be a consistent theory of quantum gravity, many hope that it correctly describes our universe, making it a theory of everything.</blockquote>
Really? It widely believed to be consistant? Consistant with itself? That means no divergences or infinities? Did somebody prove that? Or it's widely believed that somebody has proved that, even though nobody has actually proven that? I suppose we need a cite that many people believe something that isn't true. [[User:Sbharris|<font color="blue">S</font>]][[User:Sbharris|<font color="orange">B</font>]][[User:Sbharris|H]][[User:Sbharris|arris]] 06:20, 8 December 2011 (UTC)
:The phrase "consistent with itself" is a tautology. These questions are the subject of countless papers that you may read, and yes all conceivable kinds of self-consistency checks have been passed. In practice, establishing consistency means checking in detail that all rigorously derivable conclusions are consistent with one another, its much more difficult to prove that all possible logical inferences that may ever be drawn will all be consistent, but so far there is no consistency problem whatsoever. If you want to be precise, the consistency of quantum field theory isn't a rigorously derivable truth either, but that doesn't mean its inconsistent. In fact there's a huge amount of evidence that it is consistent. So you're "who" tag doesn't make much sense. – [[User:Isocliff|Isocliff]] ([[User talk:Isocliff|talk]]) 06:47, 8 December 2011 (UTC)
::QFT (or more precisely, non-Abelian guage theories without anomalies) are renormalizable and free of infinities. This basically makes the entire standard model (all forces but gravity), renormalizable, as t'Hooft proved in 1971. [http://www.staff.science.uu.nl/~hooft101/lectures/erice00.pdf] No string theory that predicts fermions has been proven finite and free of divergences beyond the 3-loop case. So the idea that string theories that are candidates to be theories of everything are "consistent," is rather like claiming that Fermat's theorum has so far passed all consistancy checks because the integers 3, 4 and 5 have been checked! [http://math.ucr.edu/home/baez/week195.html]. (Yes, I know Fermat's theory was finally proven for all integers, but that's not what has happened to any string theory that has any chance of being a discription of nature). Smolin's paper on these problems, that later was expanded into a popular book ([[The Trouble With Physics]]) is available here: [http://xxx.lanl.gov/abs/hep-th/0303185]. Here's what is says about consistancy, and it quotes from the group that has actually computed terms. <blockquote>(from page 34) "As it does not appear to be widely appreciated that the '''consistency''' of string perturbation theory is still open [26], I quote here from a recent paper by experts in the field, which announced the proof of consistency at the two loop level: (quote follows) '''Despite great advances in superstring theory, multiloop amplitudes are still unavailable, almost twenty years after the derivation of the one-loop amplitudes by Green and Schwarz for Type II strings and by Gross et al. for heterotic strings. The main obstacle is the presence of supermoduli for world-sheets of non-trivial topology. Considerable efforts had been made by many authors in order to overcome this obstacle, and a chaotic situation ensued, with many competing prescriptions proposed in the literature. These prescriptions drew from a variety of fundamental principles such as BRST invariance and the picture-changing formalism, descent equations and Cechco homology, modular invariance, the light-cone gauge, the global geometry of the Teichmueller curve, the unitary gauge, the operator formalism, group theoretic methods, factorization, and algebraic supergeometry. However, the basic problem was that gauge-fixing required a local gauge slice, and the prescriptions ended up depending on the choice of such slices, violating gauge invariance. At the most pessimistic end, this raised the undesirable possibility that superstring amplitudes could be ambiguous, and that it may be necessary to consider other options, such as the Fischler-Susskind mechanism[131].'''</blockquote><p>As Smolin makes clear, the problem with the (infinite number of) string theories is not what they show, but what people THINK they show. No, Mandelstam did NOT show that any string theory is free of all infinities, or even that it is free to the extent of what t'Hooft did for guage theories. Smolin himself believed prior to his review what this colleagues had been telling him, that at least some versions of 3-D string theory that describe actual known particles, or are capable of it, were free of infinities (which means they might possibly be true). So far, none has actually been proven to be so. <p> So, string theory is DIFFERENT from guage theory QFTs describing the 3 non-gravity forces of the standard model. So, in what sense does your sentence make sense? <p> As a second problem, what is this stuff about "theories of everything"? Because all string theories are dependent on a Minkowski SR background which does not change in time, so far there are no quantum gravity theories that are free of infinities for even strong field gravity waves, which are the needed kind to deal with. After all, the flat-space-limit weak-field spin-2 gravity quantum was presented in 1930, and nobody needs strings to describe it-- you can read about weak field "gravitons" in Misner-Thorne-Wheeler. The "gravitons" in all string theories today are this same weak-field gravity quanta, so the fact these particular gravitons have no infinities, is not very interesting, since weak gravity waves are obviously not strong enough to have any contact with a "theory of everything," and certainly are not "quantum gravity" as we need it. Plain old general relativity describes gravitational waves far more powerful than this, but of course by that time, the field is not quantizable. Weak field gravitons never had any infinities before anybody had '''thought''' of string theories, but then, they also never had enough energy to need anything but a linearized GR field description anyway-- so what's the point? In other words, if string theories reduce to [[linearized gravity]] (as they all do), but not [[general relativity]] (which they most certainly by definition do NOT do, as Smolin points out), then what's the point? All that means, is these theories reduce to a field theory that isn't even as accurate as the field theory Einstein came up with, in 1915. Einstein's generalization has passed tests (linear gravity doesn't predict Mercury's precession). String theory (if you can call it a theory) has passed no tests, but if it reduces in the end to linear gravity, as all 10<sup>1500</sup> versions of it do, it can't be a candidate for a theory of everything (TOE), since it isn't even a candidate for describing the orbit of Mercury, let alone more interesting physics. So again, '''which''' people hope '''which''' string theory will be a theory of everything, and which theory is it, that they have hopes for? There are more string theories than particles in the universe by far, but the right one certainly cannot be any of the background dependent-ones. And if Smolin is right, all proposed classes of string theories are background dependent (they live in 4-d asymptotically flat space-time, even if they do have extra dimensions), which means NONE of them can possibly be candidates for TOEs. <p> To put this another way: You see those loops that are supposed to be the "gravitons" in string theories? Do you see them actually bending the space-time through which they move? No? That's right, you don't. And that's a HUGE problem. Since in any "Theory of Everything," they must. [[User:Sbharris|<font color="blue">S</font>]][[User:Sbharris|<font color="orange">B</font>]][[User:Sbharris|H]][[User:Sbharris|arris]] 21:42, 9 December 2011 (UTC)
::: Despite your frequent use of the caps lock, almost every sentence you wrote is wrong. All string theories (or more precisely, all corners of string theory) possess [[general relativity]] as their low energy limits, not linearized gravity. This is a completely unambiguous, quantitative conclusion you can see worked out in detail in any string theory textbook. You should not be using a popular level book as you singular resource in order to dispute the most basic facts about what string theory implies, especially if its a book written by a person whose sole purpose is to reduce the stature of string theory and get more people to work on his own idea. String theories are fully diffeomorphism-invariant, i.e. they possess the same gauge symmetry as general relativity, and frequently this freedom is used to ''gauge fix'' to flat space in order to make calculation easier, but any suggestion that string theory is wedded to flat space is quite far removed from reality. If this was true, string theory would not have anything remotely approaching the interest and activity that it does. (and again its pretty hard not to notice if you step one inch into actually learning the subject)
::: This means that string theory is fully background-independent in any physical sense of the word, because any change in the background is shown to be equivalent to a particular condensation of matter within it. The only case you can really make, and its a legitimate one, is that we should try to find a language that makes the background-independence manifest. As Joe Polchinski (who wrote one of the best textbooks on the subject) has said [http://blogs.discovermagazine.com/cosmicvariance/2006/12/07/guest-blogger-joe-polchinski-on-the-string-debates/] "In string theory it has always been clear that the physics is background-independent even if the language being used is not, and the search for a more suitable language continues."
::: Im not going to debate the merits of string theory with you here, but your statements are demonstrably, factually wrong. If you want to get any kind of informed opinion about string theory then reading some textbooks on the subject would be advisable. Or if you will only read popular level accounts I strong suggest taking Smolin with a grain of salt and get some other books. For example, Hawking's book is mentioned in the introduction of this article. But I would not recommend reading any books that get major facts wrong. Disclaimer: I am not promising to correct all your misimpressions and you seem to have quite a few others remaining. For example, you seem to think that stabilizing moduli is some kind of major unsolved problem. Well its not. – [[User:Isocliff|Isocliff]] ([[User talk:Isocliff|talk]]) 00:49, 10 December 2011 (UTC)
:::: Stabalizing moduli '''is''' a major unsolved problem. And since you quote Polchinski on Smolin, I may as well quote Smolin's answer back [http://www.thetroublewithphysics.com/Response%20to%20Polchinski.html]:
::::'''Regarding background independence, Polchinski claims that, “(as Smolin belatedly notes), Maldacena duality provides a solution to this problem, one that is unexpected and powerful.” This exaggerates and distorts the situation. What is true-and what I acknowledge, is that if the strong form of the AdS/CFT conjecture is shown to be correct, then a very weak, and limited form of background will have been achieved. But for reasons just mentioned, which I explain in detail in the book, this is still a big if.'''
::::'''What has been shown so far relies on the fact that one can use the fact that SUSY N=4 Yang-Mills has the same global super-symmetry as perturbative physics on a background AdS5 X S5 spacetime, to express some physical quantities in the latter in terms of observables of the former. This is great mathematical physics and a great achievement, but the whole point of general relativity and quantum gravity is that the generic solutions are governed by no global symmetries because the geometry of spacetime is completely dynamical. This has two implications. First it makes it very non-trivial to show the strong form of the Maldacena conjecture, because it must extend to solutions of supergravity arbitrarily far from those with global symmetries in the bulk. However, if this is possible at all it will be because the full algebra of global super-symmetries remain on the boundary. The case of asymptotically flat will be much harder because there the asymptotic symmetries of the generic case are very different from the global symmetries of the ground state, and indeed there are no proposals for a gauge-gravity duality in this case. The case of positive cosmological constant-which appears to be the physical case-is harder still. And we have not even yet touched the real meaning of background independence, which is that fixed classical fields or global symmetries play absolutely no role in the formulation of the dynamics or observables of the theory.'''
::::'''The latter is what is meant by background independence in the rest of the classical and quantum gravity world, and so far string theory and the AdS/CFT conjectures do not come close to addressing it. It was in fairness to string theory that I was willing to acknowledge that the strong form of the AdS/CFT conjecture, if true, would provide a very limited and weak form of background independence. One would hope that in fairness to the truth string theorists who make this point would also hasten to acknowledge how far this would be from the real, full meaning of background independence. Brian Greene does acknowledge this when he proposes that the latter idea be distinguished by calling it “manifest background independence.”'''
::::'''Polchinski also acknowledges the difference, when he says, “In string theory it has always been clear that the physics is background-independent even if the language being used is not, and the search for a more suitable language continues.” But this is not the most accurate way to put it. It would be more accurate to say, “Some string theorists believe that the formulations of perturbative string theories and dualities between them that they study concretely are approximations to a deeper, background independent formulation. This missing background independent formulation is not just a different t language for the theory, it is hoped to be the statement of the principles and laws that define the theory, from which everything studied so far would be derived as an approximation. Despite this belief, only a few concrete proposals have been made for the laws and principles of this conjectural background independent formulation of string theory and none has gained wide support.”''' [end of quote]
::::You can read the whole thing on the link. String theory is not wedded to flat space, but neither is it completely free of needing a space to back it. Indeed as you know, the various anti de Sitter spaces in [[AdS/CFT]] become more and more difficult to use in theories when the global universe they are supposed to explain is a manifestly de Sitter universe, with a positive cosmological constant. Something just being discovered by the Hubble Space Telescope as Maldacina made his first conjecture (alas). Which is still a conjecture. At least Ed Witten has admitted that string theories giving rise to de Sitter universes like ours, don't look like anything thought of, so far. [[User:Sbharris|<font color="blue">S</font>]][[User:Sbharris|<font color="orange">B</font>]][[User:Sbharris|H]][[User:Sbharris|arris]] 03:59, 10 December 2011 (UTC)
::::: Again, Im not going to sort through all of your misconceptions and resolve them all for you, but what you say is wrong and ''demonstrably'' so. You can quote Smolin all day long, but these are quantitative questions that have been decided in ''papers'', not in popular-level books. The AdS/CFT is not in any way critical to these arguments and I didn't bring it up. The key point was that string theory possesses the same diffeomorphism symmetry as general relativity, and implies Einstein's equations as a low energy limit. Those are two unambiguous facts that are true of string theory as it exists today, not some dreamed about completion of it. They are pretty important things to know about it, and I cant guarantee I will continue conversing with someone who wont acknowledge these basic characteristics of the topic in question. Again, your wrong statements include your assertion that de Sitter space and moduli are "major unsolved problems". Does the actual literature written on these topics matter at all? I will leave a few recommended selections here. [http://arxiv.org/abs/hep-th/0701034v3] [http://arxiv.org/abs/hep-th/0610102] [http://arxiv.org/abs/hep-th/0503124v2] [http://arxiv.org/abs/hep-th/0505160] – [[User:Isocliff|Isocliff]] ([[User talk:Isocliff|talk]]) 05:06, 11 December 2011 (UTC)
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