Talk:String theory/Archive 3

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Unreferenced speculation

"Brane-world scenario

This section does not cite any references or sources. <etc...> (November 2008) Another possibility is that we are "stuck" in a 3+1 dimensional (i.e. three spatial dimensions plus the time dimension) subspace of the full universe. This subspace is supposed to be a D-brane, hence this is known as a braneworld theory. Some believe that some combination of the two ideas — compactification and branes — will ultimately yield the most realistic theory.[citation needed]"

Looks like some rogue physicist has tried adding some wisdom to this article :p 121.219.54.76 (talk) 04:36, 9 April 2009 (UTC)

lack of quantitative data

This article is rather disappointing to me in that it seems more of a qualitative summary of the status of string theory. In fact it reads more or less like some of the popular science children's books, where one has protons, neutrons, quarks etc next to a big shiny sign saying "what is stuff made of?" Of course there is nothing wrong with such treatments, but it does not seem appropriate to the audience that actually wants to know the driving equations behind a result ie such as advanced university undergraduate level. Not really terribly satisfying to a trained scientist. It would be helpful if there was more discussion of the precise abstract structures used, their applications, field equations from actions etc. Even if this was down in watered down language like matrix multiplication etc that would be ok - the Feynmann lectures in physics are a good example of the sort of standard that I would like to see. Perhaps an expert in the field can address this glaring inadequency. RogueTeddy (talk) 09:31, 28 February 2009 (UTC)

The reason that you don't do that is because it is a wrong way of thinking. This article could describe the particular choice of mathematical objects which were useful in the early days for describing string theory, but that would leave out the physical motivation. The physical reasoning makes it clear why it had to be that way (in hindsight).

String theory is completely different from field theory: you don't give it a local space-time description. There is no action principle, or a field equation, at least not in the usual sense. There's the RG fixed point equation, which reproduces the classical field equations, but that's a classical background equation, it's not supposed to generalize into a quantum dynamical law. The action for strings is the action for a path-integral on all string paths, which is just like a Feynman diagram in Feynman's original formulation, it is a way of calculating a unitary S-matrix. It separates out positive and negative frequencies and produces no space-time description in the usual sense of the word. Using it, you can't really say "I have a description now, what's a description of the future". You have to do it by S-matrix, which means "I have a bunch of incoming free particles, what will come out once they scatter?", or else you have to say "I have an AdS space, and some state on the boundary, how does it evolve in boundary-time". Either way, the holography gets in the way of a straightforward action principle in what you would think of as the usual space-time.

The string action on the string worldsheet should not be thought of as a space-time description, but as a summary of the particle content on the worldsheet (or as a description of the dynamics in a specially chosen AdS3 space). You can give a field theoretic Lagrangian description for the low-energy field theory approximation, and work with that, but that's just supergravity, it's not strings. If you want to do strings, you have to give up on a microscopically detailed picture of space-time.

The only real dynamical descriptions are those which are reasonable from a holographic point of view. A light-front or an AdS asymptotic space, or some other near-extremal black hole asymptotics. In those situations, you are given a special type of space-time, and the description method is not the obvious one: you don't make space-like slices of equal time and describe a state on a slice. Since the pedagogically best description of the theory is not at all clear, it is hard to know where to start with a mathematical description. It is probably best do it in historical order. But history begins with a lot of Regge theory.Likebox (talk) 17:32, 3 March 2009 (UTC)

I am not an expert in the field.Likebox (talk) 17:34, 3 March 2009 (UTC)

Thanks for your explanation Likebox, it certainly makes things a bit clearer to me. For instance I had not heard of the S-matrix before, and its role in scattering etc. I guess my particular bias, which is not necessarily right, is that for progress in physics one must really develop one's abstraction (mathematics) and physical intuition in lockstep, rather than letting one outpace the other. Nonetheless you make some very interesting comments and I appreciate your response. Best wishes, RogueTeddy (talk) 20:28, 7 March 2009 (UTC)

I agree that the mathematical development needs to follow the physical intuition closely. But in this case, I don't know the best path through the historical strata of formalism. The problem is that the mathematically clearest and most elegant formalism is the worldsheet CFT, and then there are certain things that are hard to explain properly:

1. Physical Masses: The excitation content of the string theory is a bunch of particles whose masses are given by the conformal scaling dimensions of the 2D fields. Why is that? In the modern way of thinking, it's a manifestation of holography. But it was discovered before holography historically, and it is difficult to motivate directly from the worldsheet expansion. Historically, it came from the assumption of Regge behavior and straight line trajectories, because the Regge assumption tells you the masses in terms of the angular momentum, and the angular momentum turns into a scaling dimension on the world sheet by conformal invariance. But that's so opaque physically. I am constantly amazed that those seventies people figure all that out from such miserable input.
2. Scattering Amplitudes: to get the actual scattering amplitudes from the worldsheet correlation functions you have to do some sums over channels. Historically, this came first, with Veneziano, so this wasn't mysterious. But if you start with the worldsheet description, it's hard to justify. The worldsheet amplitude needs to be "pasted on" to the boundary conditions. Since the string expansion is not derived from a Hamiltonian, the pasting needs to be laboriously justified by unitarity. In modern textbooks, since you don't need to match to experiment, the calculation of the scattering probability is usually not carried out all the way.
3. Unitarity: The string perturbation expansion is unitary, but it isn't constructed from a field Hamiltonian, so there's no fundamental reason for it to come out unitary. In AdS/CFT, in a holographic interpretation, worldvolume unitarity follows from unitarity on AdS space. But the unitarity of the string genus expansion is hard to understand. To prove it, I think you need to use non-covariant space-time 1/L0 propagators, and use the very out of date "sewing" rules. It isn't obvious. This point is glossed over in modern textbooks, which end up just assuming unitarity.
4. No Ghosts: But the textbooks make a point of proving the no-ghost theorem. The problem is, the no-ghost theorem is not hard or illuminating on the worldsheet. But historically, no-ghosts plus sewing loops guaranteed perturbative unitarity for the string perturbation expansion.

There's probably a really good way of explaining all the points that I can't see.Likebox (talk) 16:51, 9 March 2009 (UTC)

Just to make the previous comment clearer: a description of string theory starting with an action principle, like NG action, and then deriving energy momentum etc for the particle spectrum is not satisfactory for a first-principles explanation. The reason is that this way of doing things does not make unitarity obvious, nor the interactions, except if you already know all about dual models, sewing, and Regge theory. It makes more sense holographically, but ignoring that, the action principle is just a physically suggestive mnemonic to derive the string spectrum. It is useless if your goal is to compute scattering amplitudes from first principles.

For example, suppose you try to explain the theory to a martian:

You: Earthlings have discovered a theory of quantum gravity!

Martian: Thank you Earthling! We on Mars understand field theory very well, but not quantum gravity. How does it go?

You: just replace points by strings in the sum-over paths formulation of field theory!

Martian: (thinking) Ok. But what is the world-sheet action?

You: Isn't it obvious? It's area! (write NG action)

Martian: Why not include the extrinsic curvature?

You: Um... you just don't.

Martian: Why not include nongeometric worldsheet fields?

You: Um... you just don't.

Martian: Why can you use space time embedding coordinates as if they are flat, when the geometry is fluctuating?

You: That's because, as you'll see, the theory describes strings much longer than the Planck length!

Martian: So how can you call it a theory of quantum gravity?

You: (irritated) look, just calculate the spectrum.

Martian: Ok, Ok. It's the area. (Calculating) I get some masses and angular momenta. Ok. How do you describe the forces?

You: Isn't it obvious? It's by genus expansion!

Martian: Why can't I add interactions whenever the strings intersect?

You: Um... you just don't.

Martian: How do you know it's unitary?

You: Um... it just is.

There's also a grizzled old S-matrix physicist who's been overhearing the conversation:

S-matrix friend: Mr. Martian, ignore this young person. I can explain everything to your satisfaction. This theory is designed to give a theory of particle exchange, just like Feynman diagrams. The particles which are exchanged have to be present in the spectrum. The spectrum consists of linear Regge trajectories.

Martian: So what is this area action?

S-matrix friend: That's just a way of summarizing the spectrum. Once you know the spectrum, you derive the interactions by enforcing unitarity when the particles exchanged in the t-channel are those in the spectrum, the amplitudes have no point-like behavior, no power-laws, they fall off as expected from Regge theory. That's why you can't add extra stuff like interactions at the point of intersection. Also, notice that the sum over channels has this nifty world-sheet duality, let me show you (scribbles duality diagrams).

Martian: I see! So how come it's all derived from this world-sheet action?

S-matrix friend: The miracle is, that the amplitudes you get by this procedure, when you remove all the ghosts, end up being a sum over different genus surfaces of a world sheet action that is conformally invariant. I don't know why that works.

Martian: (calculating) You're right! why is that?

S-matrix friend: Stop asking why. Notice there's a tachyon. You need supersymmetry to get rid of that.

Martian: (calculating) You're right! It's a miracle.

S-matrix friend: ok. Note the graviton in the spectrum.

Martian: Another miracle. (folds tentacles) But that's not real quantum gravity--- you're just doing perturbations around flat space! Where's the fluctuating geometry?

S-matrix friend: (folds arms) You ungrateful alien! I show you a finite perturbation expansion for gravity, and you complain!

The S-matrix person and the alien are about to come to blows, but then a holography person chimes in:

Holographist: I can explain everything! It's really because the physics of the sum is revealing a property of the classical black hole limit of these strings. There's a corresponding holographic description for many different types of black hole in the theory.

Martian: Is that how come it's unitary both on the worldsheet and in space-time?

Holographist: Yes, that's because the conformal theory is really describing the dynamics of an AdS space. It's a near horizon dynamics.

Martian: Ah! I think I'm starting to understand all these miracles. Thank you Earthlings. We on Mars have been stumped by quantum gravity for two millenia. We are amazed by your wisdom and foresight. (flying saucer takes off)

The point is that if you want to explain the mathematical formulation of string theory in a logical, rather than historical, way, you need to explain unitarity and S-matrix. Otherwise, how can you justify the world sheet action and genus expansion? They really don't make any sense at all outside of S-matrix theory. Modern books just gloss over this, although it was a big deal in the seventies.Likebox (talk) 18:21, 9 March 2009 (UTC)

To restore balance, I want to add that the above discussion is really overselling the S-matrix point of view, and shortchanging the modern one, which is superior in nearly all aspects. The above is just a list of annoyances for learning string theory, which I think can be made clearer with some historical development.

Reading the above, a lot of the suggestions are just plain wrong. In particular, it is not too hard to give a modern presentation which treats all the points above, with very little S-matrix theory:

1. The NG action is natural, it's lowest order Lorentz invariant term, so you can't just modify it by higher order terms without fine-tuning the area coefficient to zero. In principle, you could do the fine tuning, but that question is the same as "how many consistent string actions are there?"
2. To justify the scale-dimension mass correspondence, all you need is conformal invariance--- translation on the a long worldsheet tube gives the mass, and it's the same as a scale transformation on the worldsheet after you map the tube into a punctured plane. That's the 1980s presentation for the mass/dimension correspondence. I personally didn't internalize it until I understood that historically, this is the Regge trajectory hypothesis, except reworked to talk about operators and CFT's instead of the spectrum directly. This type of discussion is fine if you accept that the worldsheet theory must be a CFT, but it doesn't motivate why it should be a CFT. Linear trajectories plus sewing motivates this.
3. To justify unitarity, it is enough to show that a genus expansion cut up along a tube keeping the external momenta fixed is equivalent to the sum over all operator insertions, giving a Feynman propagator for each particle in the known spectrum. This can be easily shown in the modern point of view. When a string is cut, you can do the sum over the endpoint by letting the tube shrink to a point, splitting the point in two, and including all the operators you can put at that point in the sum. This reproduces the unitarity condition.
4. I left out factorization, but that's OPE. Also natural. The only difference is that the seventies point of view constructs a consistent OPE from the spectrum assumption and soft scattering, which might motivate things better but takes more steps. The 1980s point of view is just as good for this, but is perhaps somewhat less motivated.
5. To get the actual S-matrix elements from the amplitude is easy to understand by analogy with field theory. So that's not really a big deal.

In short, like everybody says, it's really no problem to reproduce every old fasioned result from the 1980s formalism. But I still think (perhaps for no good reason) that the historical stuff is better for motivation. So maybe there's a good way to write the mathematical development after all (along the lines of Green Schwarz Witten):

1. Discuss the Regge theory semi-quantitatively, giving the explicit amplitudes as examples.
2. Discuss the transformation to the conformal world sheet point of view, and how to replace trajectories with towers of operator dimensions. I think it is best to introducing the L operators in the Regge point of view, and then changing to a CFT interpretation.
3. quickly introduce NG and Polyakov actions, because that's easy. It's never the rate limiting step.
4. Then show unitarity etc in the CFT point of view, but relating it back to S-matrix stuff.
5. Then textbook stuff.

Perhaps this should be the plan for the article. Sorry for rambling. I had no idea how to write this clearly before, perhaps because I didn't understand it well enough.Likebox (talk) 22:09, 9 March 2009 (UTC)

conceptual inconsistency

Inconsistency of string theory follows from assumption of Lorentz invariance and hidden dimensions concept, because the existence of hidden dimensions should manifest itself just by Lorentz invariance violation in analogy to wave spreading at 2D water surface (the reference frame of underwater is just a result of surface wave dispersion into third dimension). This leads into landscape of infinitelly many solution and lost of testability (http://aetherwavetheory.blogspot.com/2009/02/consistence-problem-of-string-theory.html) —Preceding unsigned comment added by 194.213.42.170 (talk) 16:29, 3 March 2009 (UTC)

History Section

Normally, I would be totally fine with splitting the history off. But in this case, look at all those red links. Each of those links represents a person who got too little credit for their work. This work was just too hard for nearly all physicists in the 70s to follow, because it relied on S-matrix theory and Regge theory, which were high falutin inventions. In the eighties, it was revived, but in the path-integral form due to Polyakov. Again, the S-matrix people who actually developed the theory were left out.

Because this is the great lasting contribution of S-matrix theory, and because S-matrix was laughed at by most physicists (even string theorists!) for the last 40 years, I think it's only fair to leave the history here, because many of the neglected people are mostly still alive and deserve a little recognition for founding this field.Likebox (talk) 03:29, 12 April 2009 (UTC)

String Theory Makes No Predictions

String theory is known to make predictions only at an energy scale which is likely to be too high to be directly probed by experiments. This is not contested by knowledgable critics, but there are people who say "string theory makes no predictions", leaving it ambiguous whether they mean in principle or in practice. The statement "string theory makes no predictions in principle" is wrong. The statement "string theory currently makes no predictions in practice" is sort of right. The purpose of the section is to make the distinction clear.Likebox (talk) 17:01, 15 April 2009 (UTC)

GA Reassessment

This discussion is transcluded from Talk:String theory/GA1. The edit link for this section can be used to add comments to the reassessment.

GA Sweeps: Delisted

As part of the WikiProject Good Articles, we're doing sweeps to go over all of the current GAs and see if they still meet the GA criteria. I believe the article currently has multiple issues that need to be addressed, and as a result, I have delisted the article. Although several references are listed, there are no inline citations for a large portion of the article's content which is required under the criteria. Add additional citations from a variety of sources to provide a balanced representation of the information present. Perhaps sources can be pulled from the main articles linked to within the article. Look to books, magazines, newspaper articles, other websites, etc. The lead also needs to be reduced to four paragraphs (look to merge the paragraphs and take out some of the information) to better summarize the article. See WP:LEAD for guidelines. There are also multiple grammar issues throughout the article as well as a popular culture section that needs to be converted to prose (and cut out the non-notable occurrences). Although the article has been delisted, the article can be return to GA status by addressing the above points. Once sources are added and cleanup is done, I recommend renominating the article at WP:GAN or you can contact me on my talk page and I'll review it for you so you can bypass the month-long backlog. If you need assistance with any of these issues, please contact me on my talk page and I'll do my best to help you out. --Happy editing! Nehrams2020 (talk • contrib) 06:51, 9 June 2009 (UTC)

String theory is BS

Regarding Mintrick's request for more "string theory is BS" opinions, "Problems and Controversy" used to start out with this:

Following the appearance of two books claiming string theory has failed, a hot media debate evolved in 2007.

"For more than a generation, physicists have been chasing a will-o’-the-wisp called string theory. The beginning of this chase marked the end of what had been three-quarters of a century of progress. Dozens of string-theory conferences have been held, hundreds of new Ph.D.s have been minted, and thousands of papers have been written. Yet, for all this activity, not a single new testable prediction has been made, not a single theoretical puzzle has been solved. In fact, there is no theory so far—just a set of hunches and calculations suggesting that a theory might exist. And, even if it does, this theory will come in such a bewildering number of versions that it will be of no practical use: a Theory of Nothing." -- Jim Holt.

And then went on to say more or less what it says now: the substantive criticisms. This was deleted, I think because the quote was somewhat polemical and devoid of scientific content. But the opinion is definitely out there in the public mind, and probably should be represented somehow.

Keep in mind, though, that the mathematics and physics of string theory is both extremely beautiful, very subtle, and the product of many brilliant underrecognized physicists, some of whom lost their jobs in the 1970s in a great purge. This tragic history makes string theorists touchy about criticism. But I think the section can be balanced to your liking by reintroducing the quote.Likebox (talk) 21:25, 23 June 2009 (UTC)

I think that as long as we establish that the debate is not a scientific one, we should be OK. We can take heavy guidance from global warming and related articles. Mintrick (talk) 03:45, 24 June 2009 (UTC)

There's a differece from global warming, though. The consensus is that string theory is possible, meaning that it makes sense, not that it is true of our universe. Whether it is true for our universe, there's no consensus. I tend to believe it is, others tend to believe it isn't. The consensus for global warming, however, is that not only is it possible, but it is also happening. So that's a difference.

I reinserted the discussion. Thanks for bringing that up. It did bother me when all the criticisms were deleted (although I don't agree with them, I think they are interesting to preserve).Likebox (talk) 03:53, 24 June 2009 (UTC)

Re: global warming, I was speaking merely in terms of how one can cover the public debate, which is distinct from the scientific consensus. Global warming, as a FA, apparently does a good job of combining the two. Mintrick (talk) 03:59, 24 June 2009 (UTC)

Is string theory falsifiable?

I removed most of the content in this section and re-wrote the rest, because almost none of the previous content had any bearing on the question asked by the section title (instead, it concerned the question of how to differentiate string theory from other theories - NOT whether it's falsifiable).

I think much of that material should go back in as a new section - perhaps entitled "controversy" or "verifiability". I will do so later when I have time, if someone else doesn't first. —Preceding unsigned comment added by Waleswatcher (talk • contribs) 21:01, 20 April 2009 (UTC)

Actually the section right above is incorrect as well. It claims "For a theory to be physics, it must be corroborated empirically, through experiment or observation". However there are thousands of examples of theories, which few would dispute fall under the heading "physics", which have zero empirical support. For example, there are myriad proposals for beyond the standard model particle physics, of which few if any have experimental support (so far). Similarly physicists spend much - probably most - of their time studying various "toy models", ranging from pure QED to percolation models to precisely conformal field theories to crystals with periodic boundary conditions, none of which are considered realistic and certainly do not exist in the real world. Are these theories also not physics? If so, many textbooks will have to be re-classified, and many classes re-named.

I'll edit that later, but first I'll let other wikipedians have their say so as not to change too much too quickly. Waleswatcher (talk) 21:23, 20 April 2009 (UTC)

My major issue with this change is the statement that vacua of string theory are Lorentz invariant, unitary, and contain GR, hence testable (or falsifiable, if you like). String vacua all contain GR, and of course they are unitary or else they wouldn't make sense, but this is not a good falsification/verification criterion. Falsifiability is about the predictions that are unique to the theory. For example, I could say that I believe that there is an invisible shadow moon, and say "my theory is still rotationally invariant, so if you find a violation of rotational invariance you falsified my theory". That's no good. You need a unique prediction.

Lorentz invariance has another problem: string vacua are not necessarily Lorentz invariant. There could be all sorts of vector, spinor, and tensor condensates that break the symmetries. Fundamentally string theory is Lorentz invariant in 11 dimensions, but obviously that's not true of our world.Likebox (talk) 22:35, 20 April 2009 (UTC)

Re: falsifiability - can you back up your statement that falsifiability must be only about "unique" predictions? I've certainly never seen that anywhere, in any discussion of what constitutes science. In fact I don't see how any such criterion even makes sense: suppose you have two theories that differ only in something that hasn't yet been tested. Which one is the "unique" one with regards to the existing evidence? I hope you don't think it's the one proposed earlier, since that obviously can't determine what is scientific and what isn't. So I don't agree, and unless you can back that up with citations (say from Popper's writings) I don't think that can stand - you're not allowed to just make up your own criteria for this (and frankly, that's what the whole article reads like as it is).

As for Lorentz invariance, you're right - but that actually is related to a deeper problem with this article. There are really many string theories; it's not really one theory. So it's impossible to make completely generic statements about it, and requiring that it be predictive or falsifiable is actually problematic from the very beginning. It's like asking whether quantum field theory is falsifiable. It is, but only because of some really basic aspects (like the ones I mentioned for string theory). But in any of the string solutions which might describe the world, there is 4D Lorentz invariance, GR, etc., as I said. Note that loop quantum gravity does not predict those things, at least according to some experts - for example, it's claimed to predict Lorentz violating dispersion relations (and not the kind you can get from a background of string theory).

As for unitarity - many physicists would disagree when you say it must be unitary to be consistent. For example, string theory is supposed to describe gravity, and therefore cosmology. No one understands how unitarity works in cosmological spacetimes. I actually share your prejudice anyway, but it's just a prejudice - and therefore a non-trivial prediction as well.Waleswatcher (talk) 01:07, 21 April 2009 (UTC)

Yes. Fundamentally, for a hypothesis to be useful, it must make a NEW prediction; if it only replicates predictions of other theories, then it has no inherent predictive value because it doesn't actually say anything at all. I can say that invisible pink unicorns cause gravity, and obviously, disproving that gravity exists would falsify my hypothesis, but without any unique predictions, you cannot differentiate between my pink unicorn theory and Einstien's theory of relativity. It has no added predictive power, and ergo is worthless. This doesn't mean it isn't falsifiable, but it isn't useful in any real sense. Titanium Dragon (talk) 02:02, 4 June 2009 (UTC)

The removal of the quote and the context of the debate is OK by me, I don't think the critics are very serious and their criticism is not very substantive. But the unique predictions of string theory are the recurrence spectrum of particles (resonances), and the eventual equality of the spectrum with black hole spectrum. That's what gravity has to say. More specific models make more specific predictions, but since we don't have a model which matches the world, that's all we can say.Likebox (talk) 22:44, 20 April 2009 (UTC)

Again, unless you can back up this "unique" criterion, it's not going to work as an argument. I'll leave the article alone for now - I have no interest in an edit war. Looking forward to hearing your view, in fact. Cheers, Waleswatcher (talk) 01:07, 21 April 2009 (UTC)

Well, I've read through the wiki on Popperian falsifiability linked to in this article, as well as another resource on Popper I have, and I can't find any mention of the "uniqueness" criterion proposed by Likebox. On the contrary, Popper was very clear: a theory is scientific if it is falsifiable by some possible set of empirical data. That certainly applies to string theory in its guise as a theory of everything. So I'm going to go ahead and change the article back, with some additional clarifications to address some of Likebox's points (many of which were valid). Likebox, if you don't agree, please discuss it here before reverting the changes. I'm sure we can come to a compromise that will improve the article. Waleswatcher (talk) 13:04, 21 April 2009 (UTC)

Added some of the old discussion back in under a new subsection heading. Probably could benefit from some additional editing and re-arranging, but I think it's much more accurate now than it was. See what you think Waleswatcher (talk) 13:24, 21 April 2009 (UTC)

I agree that Popper had a certain point of view, but I don't think that his point of view should be thought of as definitive, or final. I could make up a theory that says "AIDS is caused by bad drinking water" and then say that this would be falsified by a measurement of the gravitational field of the sun. If the prediction is not unique to the theory, it's just not a good criterion. I don't think Popper said this, because it is an implicit assumption of his.

The right way to say it is that if you have two different theories A and B, then the falsifiable predictions are those made by B which are not shared by A. This is a little tricky to apply in string theory, because it is getting clearer that string theory pretty much is the only way to build a theory of quantum gravity which is fully consistent with the holographic principle.

By the way, I only reverted so that the discussion on the recurrence of particles, the string spectrum, would be reinserted. I will reinsert that by hand from now on. I agree that differences of opinion are healthy, and it is always good to hear a new point of view, so please make more changes.Likebox (talk) 15:04, 21 April 2009 (UTC)

I agree that Popper's falsifiability criterion isn't gospel. But I do think it's a commonly accepted standard one can apply relatively easily, and I'd like the article to reflect that since it's brought up there. The critics of string theory make many valid points (in my opinion), but they're not about falsifiability in the Popperian sense - they're about verifiability, or whether string theory is worth spending time pursuing.

I'm not sure I understand your A, B thing. Suppose the theories are perfectly identical. Then B has no falsifiable predictions according to your proposal (and neither does A, presumably, since nothing distinguishes them). But obviously B can be scientific - it can be anything. Now modify B slightly, so it differs from A - it should still be scientific if it was before. So I don't think your criterion works, and in fact I really don't think it's possible to establish any criterion that relies on "uniqueness" in that way. You're looking for something beyond falsifiability - you're trying to establish when a new theory is interesting, or worthwhile. But I think that's a separate debate and should be clearly delineated. Anyway as you say string theory is pretty much the only option, so its predictions are automatically unique when it comes to quantum gravity.

I'll try to improve the article a little later when I have more time. I don't think the referencing is satisfactory as I have it - it would be nice to have specific references for each of the characteristics I've claimed make string theory falsifiable. I can find some, but it will take a little time.Waleswatcher (talk) 15:46, 21 April 2009 (UTC)

No, I am talking about falsifiability. Let me give you a realistic example: suppose I tell you that I have a new theory that modifies Special Relativity as follows: it adds a "soul", and it says that the "soul" instantaneously moves from point to point, faster than the speed of light.

To falsify this theory, you only need to falsify special relativity. But the new thing, the "soul" would be immune from falsification.

In the same way, string theory adds "strings" to quantum mechanics and GR, so to say you have a falsification of the theory, you need a falsification of the new thing, the string, not the old thing.Likebox (talk) 16:19, 21 April 2009 (UTC)

Sorry, that wasn't a great example. There's a better example: Bohmian quantum mechanics. It adds a real state to the quantum mechanical wavefunction, and gives you an equation of motion for the real state. Assuming that the real state starts out in thermal equilibrium, the predictions of Bohmian mechanics are identical with ordinary quantum mechanics. So in physics, people usually equate the two theories, and call Bohm's theory an interpretation of QM, not a new theory.

Don't worry about the referencing for the falsifiability--- I wasn't planning on challenging it--- I think your view is very much in line with Popper's. But the critics of string theory are more exacting--- they want actual falsifiability in real world terms in our lifetime. I mean, who wouldn't like that? It's especially maddening because previous "unfalsifiable" assumptions about neutrinos and black holes have both already been rigorously tested.Likebox (talk) 16:47, 21 April 2009 (UTC)

But Bohmian quantum mechanics is certainly a scientific theory by Popper's criterion, because it is falsifiable. Even if its predictions were absolutely identical to (say) the Copenhagen interpretation (they're not, but that's another topic), that would still be true. If not, it would mean QM is not a scientific theory, which is plainly absurd. So again - I think this criterion of uniqueness is misguided at least in regards to Popperian falsifiability, and since that's probably the most universally known standard for what constitutes science, that's what should be applied and discussed in this article (our personal and idiosyncratic views shouldn't be in there).

As for falsifying string theory in our lifetime, that is very easily possible - for example, by finding that GR is not the correct theory of gravity at long distances, or that photons from distant sources travel at speeds that depend on their frequency, etc. This point (falsifiability) is central to the issue and needs to be made clearly in the article, so I've re-instated it. Other than that I like the way you've arranged things, and have only tweaked things a little. It looks like we're converging, and I think the discussion is now much more accurate than it was.Waleswatcher (talk) 18:09, 21 April 2009 (UTC)

I think the current version is pretty good, and I am sure that we will converge. All I am trying to do is put text that explains what it means to say "string theory is not falsifiable" in a way that is charitable to the critics who say it, and also reasonable for the people who oppose this position. Since I think string theory is falsifiable, it's hard for me to be objective.

Fair enough. It seems to me the current version does a pretty good job of that, but I'm certainly open to making it better.Waleswatcher (talk) 21:31, 21 April 2009 (UTC)

When discussing falsifiability, we must remember that it is a real-world thing--- theories are tested (and falsified) all the time. This is why your examples of falsifying strings are not so satisfying, because they are not falsifying string theory per se, but the low energy limit. It's like saying "Relativity could be falsified tomorrow if we find that Newton's laws don't work at low velocities". That's true, but it doesn't really have much bearing on the accuracy of relativity theory itself. It's like the old saw about verifying that all swans are white by noting that a non-white basketball is not a swan. It's an observation, but it doesn't act to shift your prior confidence in the hypothesis very much at all, because there are a ton of non-black things that are not swans, but only so many swans. Likewise, there are a ton of different theories that reduce to Newton's laws at low velocities, which are not relativity. On the other hand, when you see a white swan, your confidence in the hypothesis is increased by a lot. Similarly, if you experimentally confirm a quantitative prediction that relativity makes, but Newtonian dynamics does not make, then your confidence in the theory increases.

Hang on - you shifted ground in the middle of that paragraph! You went from saying (correctly) that one can falsify relativity with a simple observation, to discussing how to verify a statement about swans. But it's the difference between falsifiability and verifiability is precisely what I'm trying to clear up with these edits - those are not the same thing (in fact it's precisely the asymmetry between them that lies at the heart of Popper's philosophy). To verify something one must check every possible counterexample (in your swan example, one would have to check every non-white object in the universe and make sure none are swans). But to falsify it, one need only find a single black swan. In the case of string theory, one can falsify it with a single one of an infinity of possible observations, because it is actually an extremely constrained theory. But to verify it, one would have to confirm all its predictions (which is impossible for any theory, actually), and the trouble for string theory is that all or nearly all of its accessible predictions are shared with lots of other theories. But I repeat, it is falsifiable, and therefore - according to Popper - scientific.

(one shouldn't intersperse comments like this, because it makes the discussion hard to follow for others, but I'll follow suit). You are right that I did shift, but that's because I don't think that the critics of string theory are talking about nitpicky points of Popper's philosophy. They are talking about string theory. That means that they conflate the notions of "falsifiable" and "verifiable" a little bit.Likebox (talk) 23:30, 21 April 2009 (UTC)

I'm happy with most of the edits you just made, with one exception - the thing about testing with particle accelerators. The point is that one might be able to use observations of the early universe (where the energy scales were extraordinarily high, much, much higher than at the LHC) to test that (for example, cosmic microwave background temperature fluctuations). Perhaps there should be a subsection discussion that, but for the moment I'd rather leave that caveat in place. Waleswatcher (talk) 21:31, 21 April 2009 (UTC)

Yes, you are right about cosmology. But it's a tough sell to say that it will probe string harmonics. The standard inflation scale is many many orders of magnitude lower than the standard string scale. It's probably going to give us the leading order corrections to gravity, at best, and nothing more.Likebox (talk) 23:30, 21 April 2009 (UTC)

Your argument about string theory is better than this analogy would suggest, because General Relativity and quantum mechanics are so hostile that string theory might be the only possible combination. Straining the analogy, verifying that a randomly chosen non-black aquatic bird is not a swan actually does give you some confidence that swans are white, because there are not that many more aquatic birds than swans. But, again, it would be better to see a swan. Similarly, verifying that our world obeys GR and QM gives you confidence in strings, because strings reduce to GR and QM and not a lot of other theories do (maybe none), but it would be better to test a unique prediction.Likebox (talk) 21:01, 21 April 2009 (UTC)

Sorry - I'll respond down here. You may regard the difference between "falsifiable" and "verifiable" (which by the way is impossible for any scientific theory) as "nitpicky", but I don't share that view, neither do any philosophers of science, and neither should any scientist that's thought carefully about these questions. Anyway, enough - I think the article is fine as it is now.

About cosmology - the natural value for the inflation scale is about 10^15 GeV. The natural value for the string scale is about 10^16 GeV (the unification scale). So I'm not sure what you mean by "many many orders of magnitude". Maybe I'll add a section on that topic.Waleswatcher (talk) 00:09, 22 April 2009 (UTC)

I agree with you on everything now, with some minor quibbles, which, as you say, are irrelevant to the article, so good enough.

About inflation: the natural scale is the radius of the observable universe in Planck units at the end of inflation, which is something like 10^4-10^6 Planck units (I think this is more or less precisely known), or something like 10^13 to 10^14 GeV (I might be off here, I am relying on folklore, not personal experience with models). That's a few orders of magnitude lower than the string scale, which is a few orders of magnitude smaller again than the Planck scale, but how much exactly depends on the precise vacuum. There's some freedom there, but there is definitely going to be suppression by a factor of between 10 and 1000 for each higher order term in the gravitational effective action, so given the reality of cosmological data taking, there's no way you're going to probe the fine structure of higher string harmonics. At best we'll get the one loop coefficient of corrections to gravity. That's a data point, but would be easily reproduced in any quantum theory of gravity, even the stupidest ones with a lattice Planck scale cutoff. But you might have more up-to-date information about this stuff than I do.Likebox (talk) 03:53, 22 April 2009 (UTC)

I'm glad we all agree. Unfortunately, that's all WP:OR. Particularly the bit that concludes falsifying GR would falsify string theory. I've tagged it. 210.9.143.27 (talk) 18:45, 7 July 2009 (UTC)

Sparticles and Superpartners

If it's true that the search for sparticles and superpartners would be a test of string theory and that the required energies are likely to be achieved in our lifetimes; then, should this be mentioned in this article? Of course if either of these two conditions are not the case (either their existence would not be a good test of the theory or the needed energies are not going to be available any time soon) I can understand leaving out any mention of them. Jg og 2 (talk) 11:52, 27 June 2009 (UTC)

My understanding is that the existence of superpartners is a result of assuming certain symmetries when extending the standard model, and so is not a test of string theory itself. All it'd demonstrate is that an accurate mathematical description of reality must include supersymmetry. The simplest model that does so is the Minimal Supersymmetric Standard Model, which does not require string theory. --Christopher Thomas (talk) 19:22, 27 June 2009 (UTC)

an interesting article

String Theory, Quantum Phase Transitions, and the Emergent Fermi Liquid. See also: Physical reality of string theory demonstrated
--JWSchmidt (talk) 15:42, 7 July 2009 (UTC)

Popular culture section

I've removed this section. It does absolutely nothing to inform about popular perception of string theory in a way appropriate to Wikipedia. Simply listing a number of primary sources is not appropriate to building an understanding of cultural perception, as it is essentially original research. While the individual subjects mentioning string theory may be notable, that does not make their references to it important enough to be mentioned here. 21:45, 19 June 2009 (UTC)

But in other articles, pop culture stuff is OK. It brings together a bunch of references each of which is only interesting to a small number of Buffy fans, or Pokemon buffs, but it does no harm to the more serious content. If each reference is notable and sourced, then the references give you an idea of the degree to which the subject is on the popular mind, so to speak.Likebox (talk) 21:59, 19 June 2009 (UTC)

Also, when deleting the work of a bunch of editors without a really great reason, it is not very respectful of their efforts.Likebox (talk) 22:01, 19 June 2009 (UTC)

It's not OK anywhere. And no, these lists do not "give you an idea of the degree to which the subject is on the popular mind, so to speak." They show you how obsessive a web-base each of those things has. What you are suggesting is that we can present a variety of primary source appearances, and out of that gain information. That is essentially original research. Wikipedia is built on verifying information from secondary sources, not building new information from primary ones. It doesn't matter how many people "worked" on a section; it only matters that it's encyclopedic. Their mis-perception is regrettable, but by correcting it here, we can avoid other users making such mistakes in the future by imitation. Mintrick (talk) 22:05, 19 June 2009 (UTC)

Also, I remind you not to violate WP:3RR. Mintrick (talk) 22:06, 19 June 2009 (UTC)

I'll try again--- you are totally wrong. "Encyclopedic" by Wikipedia standards includes any information that is

1. Notable
2. Sourcable

That's it. That's the only criterion. Stop vandalizing.Likebox (talk) 23:30, 19 June 2009 (UTC)

I'm afraid you're mistaken on every matter of policy you've mentioned (and you've violated a few rules in the process). I dare you to cite anything that supports your position. Encyclopedic is hardly a matter of settled debate. And you'll notice that vandalism requires bad faith, which you should not assume in this case.

That aside, I can assure you that these random references do nothing to establish significance. The idea of "do no harm" does not hold water. By that token, what's the harm of any vacuous, irrelevant information in any article? What harm does "My cat's breath smells like catfood" do if it's applied to the bottom of a page? These references are of similar relevance. Mintrick (talk) 23:34, 19 June 2009 (UTC)

You think I can't cite policy? Wikipedia is not a paper encyclopedia (I hate citing policy--- you would think everyone has already read everything). There are no paper costs, and there is no size limit. There are similar collections of references all over Wikipedia, and they are extremely valuable for a person trying to find a perticular fact about the particular pop culture item that is being described.

If I search for "star trek" and "string theory" on google, and if the information is here, I would find out which episode it was that mentioned string theory. It is unlikely that anyone would search your cat's breath. That's what "notable" means.Likebox (talk) 23:42, 19 June 2009 (UTC)

"Not paper" is a red herring. What about that supports your definition of encyclopedic? Indeed, it specifically says that it's not a free pass for inclusion, and that there are other things that an article must do in order to be included. You'll notice that WP:NOT also says that "merely being true, or even verifiable, does not automatically make something suitable for inclusion in the encyclopedia" (which directly contradicts what you said before). And no, that's not what notability means. Notability is about substantial coverage in independent sources; that's all. You are again, deeply mistaken about the letter and spirit of the policies you mention. Mintrick (talk) 23:50, 19 June 2009 (UTC)

I am not mistaken. The whole point is that Wikipedia can have a page on every single Pokemon character, and that's OK. The criteria for inclusion are notable, verifiable (and on topic) which all these things are.

If your idea of contributing to an encyclopedia is deleting information which has been patiently gathered by many others. Then go away. Seriously. Do something else. Your contribution is unnecessary.Likebox (talk) 15:36, 20 June 2009 (UTC)

Yet again, you are flagrantly mistaken. Wikipedia doesn't have a page on every Pokemon character; it was decided that was most definitely not OK. Your assertion that "The criteria for inclusion are notable, verifiable" is directly contradicted by policy. Did you read what I quoted from WP:NOT? It states, up front, that what you asserted is incorrect. You need to stop being incivil.

Further, "patiently gathered" information is a mistaken impression of how this material appears. If that were teh case, you might see something valuable like a cited description of how this aspect of physics was perceived by the general public. Instead, you get a dozen people who remember "Hey, didn't some TV show/book/comic mention string theory? In it goes!". Information is precisely the wrong term to use for this stuff; it does not inform. At best, it triggers the happy human "I get the reference!" instinct. Mintrick (talk) 15:50, 20 June 2009 (UTC)

The stuff about "Wikipedia can have an article on every single pokemon character" is lifted from some policy page or other. Your interpretation of Wikipedia policy is not the standard one. Wikipedia is a comprehensive summary of all human knowledge, not only that knowledge deemed "important" by snobby people. This means that "I get the reference!" references are useful too. Now I can find out which cartoons mention string theory. Why should this information be censored?Likebox (talk) 15:58, 20 June 2009 (UTC)

Uh huh, "Some policy page or another". Care to cite that? Or your assertion that my interpretation is nonstandard? Heck, what is my interpretation as you see it? This information is not being censored any more than information about my hypothetical cat's breath is. It's just that neither one is important enough to be mentioned in an encyclopedia. If you're looking for random pseudo-information about any subject conceivable, check Google; that's what it's for. One of the aspects of information is the isolation of the significant facts. Since this encyclopedia must contain information, certain unimportant facts should be omitted where not relevant (as a bunch of insignificant references are here).

You consistently refuse to answer my arguments, instead preferring to cite nonexistent policies and rules that magically support your viewpoint, which has no basis in the rules, all the while accusing mine of being nonstandard. That is not acceptable; please respond to my points with actual references to real policy.Mintrick (talk) 16:07, 20 June 2009 (UTC)

I will respond to your comments by asking you to stop vandalizing and go away.Likebox (talk) 23:23, 20 June 2009 (UTC)

(deindent) Ok, maybe you have a point. Sorry for being hostile. These sections can become full of tedious cruft. I think that the solution is to make a list of casual references that have just enough information for the interested reader to look up the reference for themselves. I tried to do that. Is that ok?Likebox (talk) 20:43, 23 June 2009 (UTC)

I appreciate your efforts, and thank you for moving forward. However, I feel that the new form really highlights what it is that I was talking about. What I think would be a great section is something based on secondary sources that tells us what people in general really think about string theory (e.g. that it's B.S.). I don't think that the current form approximates that, nor do I think it's even a first step. You don't start with primary sources that manifest perception to make general claims; that's original research. The problem is, I'm just not sure that any secondary sources exist that work towards what I'm talking about. Mintrick (talk) 20:50, 23 June 2009 (UTC)

Ok! Now I understand. For the "string theory is BS" point of view, that's adressed in "problems and controversy". The main authors are Smolin and Woit. This might be augmented by quotes from notable critics, like Sheldon Glashow or Philip Anderson.

The pop-culture section is really just meant to be a list of cross-references, not much more than the "see also" section. A "popular reactions" section might be appropriate.

I have to admit, the point of view that string theory is BS is underrepresented. The edits from a scientific point of view generally reflect the accepted (and incredible, but nearly certainly true) belief that string theory is actually a consistent theory of quantum gravity. I write from this point of view, because I actually believe string theory is correct. If you feel that the "string theory is BS" faction is underrepresented, maybe you can try adding more criticisms to the "controversy" section.

The problem is that there is little new to say there. What exactly is the BS part? String theorists admit they have a problem connecting with reality, and it is hard to know whether there is an acceptable alternate theory which is consistent. But my POV makes it hard to be objective.Likebox (talk) 21:09, 23 June 2009 (UTC)

I removed the section because it had again descended into arbitrary trivia that afforded no extra insight to the article (I moved one with particular significance to the "see also" section), and no hint at the relevance, importance or notability of these references. In what way will any reader of this article benefit from the knowledge that a fictional character from Sliders was a graduate who specialised in string theory? (Please also refer to WP:IPC#List content.)

It has just been reverted without an edit summary, so I'm hoping an explanation will be forthcoming soon! Oli Filth^{(talk|contribs)} 18:13, 31 August 2009 (UTC)

The explanation is: I don't like deleting stuff. Someone wrote it, it's information that is accurate and sourced, and who knows if it's useful. This type of "contribution" to the encyclopedia is cheap--- anyone can do it--- and therefore seductive. It is much easier than writing new material. This means that there are thousands of people whose idea of a contribution is to delete material.

I don't like the deletion/creation imbalance that this can produce. So I reverted your deletion. Plus I like the section.Likebox (talk) 19:46, 31 August 2009 (UTC)

None of those is a valid argument for retaining the section. In particular:

• "Accurate and sourced" are not sufficient; notable, significant and relevant are other requirements.
• "Who know if it's useful" - well, hopefully the person who added the material, otherwise what's the point of it? If the introduction of material can't be justified, then it serves no purpose. I'm hardly the first person to point out that these trivia sections are usually just pointless article clutter.
• The fact that deleting is a common form of copyediting does not make it an incorrect one.
• "I like it" is not a compelling reason!

I'm afraid you'll have to do better than that... Oli Filth^{(talk|contribs)} 19:55, 31 August 2009 (UTC)

Ok--- the contributions are obviously notable, significant for people who find TV shows significant, and relevant to people who are interested in what non-experts think of the theory.

But I agree that they can clutter the article, so I try to keep them short. But what's the point of deleting them? Sorry. If you look above you can see that this is a recurring subject, and there are good arguments on the "keep" side. I am not going to repeat them.Likebox (talk) 19:59, 31 August 2009 (UTC)

It has been explained previously in this discussion thread what is meant by "notable", etc. in this case. Why is it notable that (for instance), the character from Sliders was a physics graduate in string theory? Where are the secondary sources that reference and discuss this as in some way relevant or pertinent to the subject of this article?

Incidentally, the only discussion I can see (including in the archives) is this thread. With respect, there weren't any good argument for "keep"; as far as I can see, your previous arguments (all of which were correctly dismissed by Mintrick) have been:

• It does no harm.
• Being reliably sourced is a sufficient condition for inclusion.
• WP:NOT#PAPER as a free pass for inclusion.
• Deletion is bad.

If I've missed something, then I apologise, and if so, perhaps you could point it out? Oli Filth^{(talk|contribs)} 20:16, 31 August 2009 (UTC)

I'd say the IPC section speaks to the notariety of string theory: it's now so well-known it's found its way into popular culture. And aside from the Sliders bullet, the entries are all reasonably nontrivial. --Cybercobra (talk) 20:03, 31 August 2009 (UTC)

Quoting for WP:IPC (I know it's just a guideline, but it's a good one): "passing mentions in books, television or film dialogue or song lyrics should be included only when that mention's significance is itself demonstrated with secondary sources". The song lyric is plainly just a passing mention. I'd argue that the mentions in Big Bang Theory are equivalently fleeting. I accept that the Elegant Universe is significant, so that's why I moved it to the "see also" section.

As it happens, the ability to uncontroversially place an item in the "see also" section is my personal rule of thumb for the threshold of what's acceptable in a "popular culture" section. It demonstrates that it's plainly significant and relevant. Oli Filth^{(talk|contribs)} 20:27, 31 August 2009 (UTC)

(1) WP:IPC is an essay, not a guideline. (2) Though each mention in Big Bang Theory might be passing, the regularity and frequency of them makes it significant enough, in my mind, to merit mention. (3) The fact that lowbrow entertainment such as rap is even mentioning something as sophisticated as string theory seems, to me, remarkable. (4) Notability is a requirement for article topics, not article content. --Cybercobra (talk) 20:49, 31 August 2009 (UTC)

Sorry, I meant to say "essay"! Whilst I accept your 4th point about notability, note also that I referred to significance and relevance. It's not up to us to bestow these qualities, it's up to the existence of appropriate secondary sourcing (which is the gist of what WP:IPC is getting at).

If any of these items are discussed elsewhere in the context of string theory, then I would be happy to see them prosaically discussed here in this article. Oli Filth^{(talk|contribs)} 21:03, 31 August 2009 (UTC)

There are most likely easy to find secondary source mentions of string theory's notability for all the items. For example, you might read a Lupe Fiasco album review that says "One of the songs, Hurt my soul, mentions string theory". You might read a review of Big Bang Theory that says that Sheldon is a string theorist. So the notability and sourcability of most of the items is probably without question. On the other hand, does it merit inclusion? I think it does no harm, and might do good.Likebox (talk) 20:52, 31 August 2009 (UTC)

Well, finding such sources would be a good start! But the need to demonstrate the veracity of the cultural references is hardly the crux of my argument. Neither of your hypothetical examples would address the significance of such throwaway references. Oli Filth^{(talk|contribs)} 21:03, 31 August 2009 (UTC)

History section again

The history section is waaay too long. In fact, it seems to be just as large (if not bigger) than the actual History of string theory article ! Also, I don't think that the history section should be left alone because many of the neglected people are mostly still alive and deserve a little recognition for founding this field (see above History section discussion). Recognition should be given (in the right place and the right article) and as noble as this aim is, it does not help the article; most readers won't wade through the section and instead will go straight to the history article, especially if they know it's shorter than the section in the string theory article ! The history section should outline the main features of the history of string theory while the details should be in the history article. I would strongly recommend that the history section be reduced drastically and the removed material be transferred to the history article. : ) MP ^{(talk•contribs)} 20:23, 8 July 2009 (UTC)

Just had a wild idea. Why not transfer (the nicely summarised version of) the content from History of string theory to this article, and move the stuff in the History section in this article over there ? What we need in the history section is a much reduced version of what is presently there and the history article needs more details. A wee bit like duality ... :) It seems like the perfect solution. Thoughts ? MP ^{(talk•contribs)} 20:23, 8 July 2009 (UTC)

What you are missing is that this history is already very short. It is barely fair, and could be made much better by mentioning more people and papers. Each major development only gives a few names, and takes up one paragraph. It really should be left as it is. The article called "History of String Theory" is a mess, and it is only partially written.

There are still major things missing: one is the construction of nonstandard string theories in the 1980s, which was considered unpopular back then (after heterotic strings were discovered, everything else was an embarassment of riches) but are now important as part of the landscape catalog. This includes weird string models too. The other major thing that is missing is post AdS/CFT developments, in particular AdS/QCD, Landscape backgrounds, and the Chern-Simons membrane action.Likebox (talk) 21:50, 8 July 2009 (UTC)

The historical content of the section may be very short (from some people's viewpoint), but the section is just too long. Which is precisely why the History article is there. I reiterate: readers are unlikely to wade through the massive section; if they want details, they can be found in the history article. The section needs to be condensed down to a handful of paragraphs, outlining the main features and aspects of the development of string theory, leaving the history article to flesh out the details. Otherwise, why have the history article ? It clearly serves as a useful branch from the string theory article. MP ^{(talk•contribs)} 11:02, 9 July 2009 (UTC)

Perhaps we should take a leaf out of the General relativity article (a featured article). GR has been around a lot longer than string theory. Maybe we can take a few pointers from there. MP ^{(talk•contribs)} 11:29, 9 July 2009 (UTC)

There is no difficulty in reading the section, as far as I can see. It isn't that long compared to other histories.

String theory was developed by a community of physicists in many stages, and each stage in the history is very notable. The history is a compactly written sketch covering these developments in extremely rudimentary outline.

String theory, in terms of content, is much bigger than General Relativity. If you make a unit of "1 Einstein" to describe the mathematical content of Special Relativity, or of Planck's harmonic oscillators, then General Relativity is about 3-4 Einsteins worth of technical work. It's history is extremely simple, because it was developed by one person working alone, over about eight years, with some contribution at the end from David Hilbert. So the history is: Einstein thought about it for a long time, made some mistakes, then figured it all out after some competitive prodding.

String Theory is much more complicated: it's about 15 Einsteins of technical work. There are about 3 Einstein's of work in the 1960's and 1970's, with Regge theory and S-matrix theory. Another 3 Einsteins of work in Veneziano strings and Dual Models, another 3 Einsteins of work in the superstrings, GSO projection, and simple backgrounds, another 4-5 Einsteins in the conformal field theory, heterotic backgrounds and orbifolded strings and path-integral perturbation theory from the 80s, another 4 Einsteins with branes and AdS/CFT, and a couple more Einsteins of work since then. Thats a whole lot of Einsteins, and each individual only contributes a couple of Einsteins, and there's a lot of overlap.

When you have this sort of team effort, you need to be careful. If you write a primitive sketch, you end up writing falsehoods.Likebox (talk) 16:18, 9 July 2009 (UTC)

I didn't say that it's difficult to read the section. You also say, It isn't that long compared to other histories - could you please provide examples of these other histories, as I'm not sure exactly what you're referring to, thanks. Written properly, the main features of string theory can be summarised in a much shorter way than is presently the case in the article, without compromising the veracity of the history. Also, the history of GR consists of more than just Einstein's formulation of it; what about the solutions (and development of mathematical terchniques to find them), subsequent formulations of the theory, astronomical and cosmological testing, not to mention gravitational waves ? Yes the theories are different in scope and simpicity, but they can both be summarised concisely. I reiterate: the current history section is too long and the history of string theory article should include most of the historical details. Please comment on this latter issue, as you haven't done this yet. MP ^{(talk•contribs)} 16:03, 10 July 2009 (UTC)

The examplen of a page with a long history section is mass-energy equivalence, which includes all the 19th century missteps and false starts. I think this is one of the best histories you'll find (most of it is due to User:D.H.)

The essential difference between GR and strings is that the formulation of GR was complete more or less once Einstein's equations were written down. Aside from some work on the initial value problem and work on black holes in the 1960s, the laws of motion were understood.

String theory, on the other hand, is not perfectly formulated even today. The stages in development are discovering different windows of calculations, and each one is just as fundamental. The physical insights about the formulation of the theory which were gained at each stage are really comparable. So there's no way to say "ok, this period is more fundamental, that period is less fundamental". Historically work from before 1984 was marginalized.Likebox (talk) 20:45, 10 July 2009 (UTC)

Note that mass-energy equivalence is still only a B-class article. You still have not responded to the presentation issue and why we have the history of string theory article. Presentation should not be compromised for content. MP ^{(talk•contribs)} 20:13, 11 July 2009 (UTC)

What can I say about presentation? I like it this way. You might not. I don't know exactly why. Can you be specific about what you don't like?

By the way, mathematics and physics articles that are good tend to stay B-class because mathematical folk knowledge is hard to source. You can cite the original papers, but it is very helpful to modernize the notation and clarify the arguments.Likebox (talk) 01:22, 12 July 2009 (UTC)

I don't think we are getting anywhere in this discussion :). It would be helpful if others could contribute to this discussion. Anyway, I feel there are too many technicalities and details in the current history section. So, what I intend to do is work on 2 sandbox articles, User:Mpatel/sandbox/String theory and User:Mpatel/sandbox/History of string theory - perhaps this would be a better approach, and then we can reach consensus (hopefully with more people) on what is best for both articles. MP ^{(talk•contribs)} 12:56, 12 July 2009 (UTC)

What technicalities and details?Likebox (talk) 13:13, 12 July 2009 (UTC)

Mathematics of String theory

Being a highly mathematical theory, perhaps there is scope for creation of a Mathematics of string theory article ? Or maybe it should be called Mathematical formulation of string theory; in a similar spirit to Mathematical formulation of quantum mechanics or Mathematics of general relativity. MP ^{(talk•contribs)} 20:18, 8 July 2009 (UTC)

Related to this, there should be a section in the string theory article regarding the (mathematical) formulation of the theory, given that it is heavily maths-laden. See also Quantum mechanics#Mathematical formulation and General relativity#Definition and basic properties. MP ^{(talk•contribs)} 13:02, 12 July 2009 (UTC)

Something to consider ...

On the illustration ... Shouldn't the Atomic level be listed as -- protons, electrons and neutrons And it follows that the SubAtomic level should be quarks And then on to strings ....

-- steve Srlevine1 (talk) —Preceding undated comment added 23:52, 12 August 2009 (UTC).

Is string theory predictive?

I restored some of the language in that section (which by the way was hammered over many edits nearly a year ago as a compromise). Some of the recent edits due to Afteread were simply wrong. The following comments refer to those edits.

It makes no sense to say that string theory "depends" on other theories like quantum mechanics. It just IS quantum mechanical, that's a property of the theory, not another theory it "depends" on. Saying it "depends on QM" is like saying it "depends on arithmetic". Same goes for Lorentz invariance. As for general relativity, it contains it as a limit. It doesn't depend on it, GR is literally a special case of string theory.

There's no such thing as "legitimately falsifiable". A theory is either falsifiable or not; either Popper's criterion is satisfied or it isn't. String theory is very easy to falsify.

This unreferenced sentence "The difference is that string theory makes few new predictions beyond those of the three other theories." is false. String theory makes an enormous number of predictions that are unique to it. The problem isn't that, it's the energy scale at which those predictions become easy to test, which is probably out of reach of humanity for the near future. So string theory is falisifiable and hence scientific according to Popper, but hard to verify as distinct from other putative theories of quantum gravity that share its low-energy properties like Lorentz invariance etc. (if there were any others that is - there aren't). Waleswatcher (talk) 15:13, 16 December 2009 (UTC)

Is everything (that's been changed) that is cited actually from the cited works? Dougweller (talk) 15:33, 16 December 2009 (UTC)

Which changes are you referring to? The "changes" I made returned the section to more or less its old form. As for the refs, Polchinski says that string theory is QM, unitary, Lorentz invariant, etc. The other ref has a whole list of falsifiable predictions of string theory, some are mentioned here. Waleswatcher (talk) 04:00, 17 December 2009 (UTC)

String theory, M-brane, whatever

A 134th dimension also solves this. Not that this is the actual solution. —Preceding unsigned comment added by 68.200.98.166 (talk) 02:03, 28 January 2010 (UTC)

I can see a 10,213 dimension too... 68.200.98.166 (talk) 02:09, 28 January 2010 (UTC)

How Would You Find Strings?

Yes, I am a high school freshman, but I put interest in this subject.

In my math classes, I learned that graphing one-dimensional means you are graphing on a number line. Also, lines have no thickness. So if strings are one-dimensional, you could not ever see them even with an incredibly powerful microscope. There must be other ways to prove this theory... —Preceding unsigned comment added by 68.102.246.97 (talk) 23:43, 4 September 2009 (UTC)

Yeah, you rather confirm the theory by its predictions, like masses, cross sections, ect.

Your argument of the problem of direct observtion of the builing block "string" would be even more true for point particles. 212.186.99.222 (talk) 18:03, 3 December 2009 (UTC)

Because of quantum mechanics, both point particles and strings get "smeared out" so that they aren't really 0 or 1 dimensional. Two other relevant comments are that string theory also contains objects (branes) that with more dimensions, and that according to string theory your microscope would "see" strings with other strings, not with particles (because light is composed of photons and photons are a string mode). Waleswatcher (talk) 14:33, 15 December 2009 (UTC)

I would just like to put forward the view that the use of the word 'math' could be considered offensive to those who value the English language and so the use of such a colloquial term I feel is not appropriate on a public site.(Redface1 (talk)) —Preceding undated comment added 00:58, 13 February 2010 (UTC).

Tags

I reverted some tags anonymously. If you don't know string theory, why are you mucking with the intro? If you do know string theory, how can you be confused by the statement "strings and branes are little charged black holes"? Or do you want to go back in time to the eighties?Likebox (talk) 07:03, 5 March 2010 (UTC)

Likebox stop being an offensive twit, it will only get your ass banned. Learn to WP:AGF. Also do not make unbased assumptions about what other do or do not know, it makes it sound like it is you how is uncertain about his qualifications.

About the tags themselves. I find especially the second statement dubious, since it is not like string theory would fall if the holographic principle turned out to be false. That sort of precludes it from being the overarching physical insight. The first statement is less dubious, but it is also not apparent to me that any string (or brane) can be interpreted as a vibrating black hole.

Of course, I may be wrong about either of these statements, but in that case it should not be too hard to provide references showing that these statements are supported by the string community.TimothyRias (talk) 08:01, 5 March 2010 (UTC)

I have no qualifications and I am not asking for any--- I am asking you to learn string theory before making dubious modifications. I don't give a flying fuck about getting banned, the political situation here is intolerable already. I know you were acting in good faith, you are just ignorant.

All of string theory is based on the holographic principle, which was largely distilled from the world-sheet expansion. Nothing in string theory makes sense outside of holography--- it's like evolution for biology. Biology was around before evolution too.

To say "string theory wouldn't fail if the holographic principle were false" is just as ridiculous as saying "General relativity wouldn't fail if the equivalence principle were false". This is not OR, but it might be too good content for this encyclopedia, so I will try to remove it, although I wrote everything starting from this point, so I find it hard to remove.Likebox (talk) 16:41, 5 March 2010 (UTC)

The only way I could see to remove it was to excise most of the content written by me. I hope that this is Ok. I believe that it is best if others write about string theory on Wikipedia from now on, to avoid giving impressionable people the idea that those who know the field are also active here.Likebox (talk) 17:02, 5 March 2010 (UTC)

A few of the sentences here were written by others, and out of respect for them I should preserve the text here. The issue of course is that the text is modern, treating holography as an integral part of string theory. This is only happening in semi-popular literature now, although the relevant technical work dates from 1989-1999.Likebox (talk) 23:45, 5 March 2010 (UTC)

If you have no qualifications, then why do you insist on calling others ignorant idiots every time they make comments hinting that the current versions of articles are less than perfect? I also agree with Tim, if these are obvious statements, then it should be trivially easy to find sources backing these statements. Headbomb {talk / contribs / physics / books} 19:46, 6 March 2010 (UTC)

My only qualification is learning the theory, and the only thing I ask is that you do the same. It is not difficult to find sources for all the material, but they say the same thing in words that are more technical.Likebox (talk) 21:04, 6 March 2010 (UTC)

WP:V trumps personal enlightenment I'm afraid. So if it's not difficult to find sources, it should be just as easy to place them in the article. Headbomb {talk / contribs / physics / books} 21:37, 6 March 2010 (UTC)

Please follow the discussion. Nobody asked for sources, the material was labelled "dubious". This demonstrates lack of understanding of 90s string theory, since indeed these statements would have been considered "dubious" in the 80s. If you want the thing sourced, it will be easy to do. On the other hand, I would rather remove it, because I think it gives the impression that Wikipedia has knowledgable string people around.Likebox (talk) 21:42, 6 March 2010 (UTC)

Tim marked them as dubious, aka doubts this is true/has concerns that the statements do not accurately reflect the status of string theory. The way to alleviate these concerns is to give a solid source which discusses this. So yes someone asked for sources, and you've reverted that request several times now. So if you are able to source things, please do and everyone will be able to verify that the concerns are unwarranted (assuming that the source indeed supports the claims it is purported to support, of course). And if you don't want to source them because of who knows why, then live with the dubious tags, or with the possibility that the section is eventually removed. Your call. Headbomb {talk / contribs / physics / books} 21:54, 6 March 2010 (UTC)

I removed the section and placed it below.Likebox (talk) 22:50, 6 March 2010 (UTC)

Likebox, I don't doubt that you think you "learned the theory", but I somehow doubt that you actually "learned the theory". I contrast to what you think I did actual "learn the theory", enough so to know that you little presentation deviates significantly from the standard presentation. At best it is a non-standard POV (which makes it problematic enough for wikipedia by itself). Moreover, I have very good reason to think that at the very least there is something wrong with the wording of the sentences I marked dubious, because as they stand they are contradictory to some of the results of AdS/CFT. TimothyRias (talk) 00:01, 7 March 2010 (UTC)

The "nonstandard presentation" I give below is now the standard presentation. I don't like to cite anything that postdates it. Most presentations outside the professional literature pretended that the subject stopped developing in 1988, and did not adress the advances in black hole understanding of the 90s.

I am asking you to learn string theory so that you don't say ridiculous things like the above. "AdS/CFT" is exactly the identification of black hole and string states for near-horizon geometry of branes, and nothing that I said contradicts it, the exact opposite. The identification of branes/strings with black holes by Polchinski (and by Witten and by Vafa/Strominger) is the very basis of AdS/CFT, and is how you count black hole microstates. The fact that you challenge it is disturbing, because it is hard to find a specific cite for things that are this elementary.Likebox (talk) 06:35, 7 March 2010 (UTC)

Since you are ok with string theory, I am looking for cites for modern presentations, but be aware that the presentation on Wikipedia was the first attempt at a popular-level presentation of modern string theory. Susskind wrote a popular book which came out about a year later.

I will try to be less thin-skinned. You were just asked for clarification. The statements you are tagging say the following:

"Holography demands that the low-dimensional theory which describes the oscillations of the black hole must also describe the spacetime around it" I chose this wording carefully, both because this is the original statement of 'tHooft around 1986, and the one supported by his toy model of a Schwartschild black hole, but also this is a more or less precise statement of AdS/CFT--- the oscillations of the black hole are the scalar fields in the CFT side, and loosely speaking, the gauge field too, which can be thought of as "identity shaking", the branes switching identity. The positions of the branes, the oscillations of the black hole, are matrices, but they reduce to numbers at large separations, and their interpretation at large separation is the separation of the branes from one another, just as you would expect from shaking. They also Higgs the gauge fields on the branes, so that you lose the identity of the branes at large separations.

"The Branes and strings are quantum mechanical vibrating extended charged black holes." The qualitative statement was made by Witten first (I think), but Polchinski made it precise in 1995 with a direct identification of D-branes with RR-charged "p-branes" (extended extremal charged black hole solutions in Supergravity). The dualities of Fundamental and D-strings in type IIB theory makes it clear that the fundamental string is no different, and there are CFTs which describe F-string oscillations in certain limits. This statement was also too modern to be included in popular level works, so you are right to question it.Likebox (talk) 06:55, 7 March 2010 (UTC)

The issue I have with the second statement is that, I'm not convinced that all black holes and branes may be interpreted as extended charged BHs.

Something else to keep in mind is that it has never been proven that holgraphy is an integral part of string theory. The best evidence comes from work on the AdS/CFT conjecture, but that is still a conjecture that has only been checked in specific cases. TimothyRias (talk) 08:28, 7 March 2010 (UTC)

(deindent) Holography is not just AdS/CFT--- it is also plane old string perturbation theory--- when it is done the Mandlestam/1980s CFT way. There are a bunch of surprises in 1980s string perturbation theory that, in hindsight, are just 1d holography. The first is the UV/IR connection--- the divergences at short distances are long distance related! This was a shock, but it's just holography. The second is the perturbative CFT on the world sheet itself--- you must remember that the CFT description of world sheet dynamics came as a total surprise in the 70s, so for example, the mass-squared is the L_0 operator. Then there is the strange exponential growth in density of states which reproduces black hole entropy (more or less, in a hand-wavy way due to Susskind). A fourth example is the equations of motion/world-sheet RG duality. Yet another is the unexplained relation between world-sheet and space-time supersymmetry. I repeat: all the strange mysteries of 1980s string perturbation theory were revearled to be obvious consequences of the holographic principle in the 90s (I am not sure that all of these are related to holography in the literature).

Next There is Matrix theory, which predated modern AdS/CFT and was foreshadowed in 1989 work. This was also important in that it is holographic principle explicity and most obviously, because it's just quantum mechanics not field theory so there's no "C" in "CFT", it's just "QM", but its still holography. The principle itself is why you expect 2d-CFT to have anything to do with gravity--- CFT is the degrees of freedom near any black hole. This has recently been extended to Kerr-CFT, where the extreme black hole is neutral, but spinning fast enough to be extremal. There is no doubt about these statements in the modern literature, but they needed to be explained clearly so that people would understand that string theory actually makes sense--- it's not a big academic fraud like other things I won't name.Likebox (talk) 08:47, 7 March 2010 (UTC)

I finally understood what you are saying (despite the blooper)--- you meant "I am not sure that all strings and branes can be interpreted as charged black holes", well I am sure. All the matter content of string theory (D-branes, F-strings, NS-branes) is exactly identical to the extremal black hole spectrum of the related low-energy supergravity theory. Not only that, but you can even interpret certain orbifolds as these types of objects put together. I agree that the statement conveys useful non-trivial information, which is why I made it.Likebox (talk) 08:51, 7 March 2010 (UTC)

Removed intro material

String theory is a theory of gravity, an extension of General Relativity, and the classical interpretation of strings and branes is that they are quantum mechanical vibrating, extended charged black holes. The overarching physical insight behind string theory is the holographic principle, which states that the description of the oscillations of the surface of a black hole must also describe the spacetime around it. Holography demands that a low-dimensional theory describing the fluctuations of a horizon will end up describing everything that can fall through, which can be anything at all. So a theory of a black hole horizon is a theory of everything.

Finding even one consistent holographic description, a priori, seems like a long shot, because it would be a disembodied nonlocal description of quantum gravity. In string theory, not only is there one such description, there are several different ones, each describing fluctuations of horizons with different charges and dimensions, and all of them logically fit together. So the same physical objects and interactions can be described by the fluctuations of one-dimensional black hole horizons, or by three-dimensional horizons, or by zero-dimensional horizons. The fact that these different descriptions describe the same physics is evidence that string theory is consistent.

An ordinary astronomical black hole does not have a convenient holographic description, because it has a Hawking temperature. String theories are formulated on cold black holes, which are those which have as much charge as possible. The first holographic theory described the scattering of one-dimensional strings, tiny loops of vibrating horizon charged with a two-form vector potential which makes a charged black hole a one-dimensional line. Fluctuations of this line horizon describe all matter, so every elementary particle can be described by a mode of oscillation of a very small segment or loop of string. The string-length is approximately the Planck length, but can be significantly bigger when the strings are weakly interacting.

All string theories predict the existence of degrees of freedom which are usually described as extra dimensions. Without fermions, bosonic strings can vibrate in a flat but unstable 26-dimensional space time. In a superstring theory with fermions, the weak-coupling (no-interaction) limit describes a flat stable 10-dimensional space time. Interacting superstring theories are best thought of as configurations of an 11 dimensional supergravity theory called M-theory where one or more of the dimensions are curled up so that the line-extended charged black holes become long and light.

Long, light strings can vibrate at different resonant frequencies, each such frequency describing a different elementary particle. So in string limits, any elementary particle should be thought of as a tiny vibrating line, rather than as a point. The string can vibrate in different modes just as a guitar string can produce different notes, and every mode appears as a different particle: electron, photon, gluon, etc.

The only way in which strings can interact is by splitting and combining in a smooth way. It is impossible to introduce arbitrary extra matter, like point particles which interact with strings by collisions, because the particles can fall into the black hole, so holography demands that it must show up as a mode of oscillation. The only way to introduce new matter is to find gravitational backgrounds where strings can scatter consistently, or to add boundary conditions, endpoints for the strings. Some of the backgrounds are called NS-branes, which are extreme-charged black hole sheets of different dimensions. Other charged black-sheet backgrounds are the D-branes, which have an alternate description as planes where strings can end and slide. When the strings are long and light, the branes are classical and heavy. In other limits where the strings become heavy, some of the branes can become light.

Theory, or Hypothesis?

Why is this stuff considered a theory, rather than a hypothesis? —Preceding unsigned comment added by PhiDeck (talk • contribs) 19:18, 18 March 2010 (UTC)

Many physicists strongly oppose the idea that string theory is not falsifiable, among them Sylvester James Gates: "So, the next time someone tells you that string theory is not testable, remind them of the AdS/CFT connection ..."

--Dc987 (talk) 08:18, 31 March 2010 (UTC)

Who are these "many physicists" Dc987? Seems like weasel words to me (no offense given by this statement). The various forms of string theory cannot be quantified, and can only be explained through mathematical formulas. (This is my first real edit, and I do not claim to be an expert, but I have tried and am continuing to try to enlighten myself on the topic, so please go easy on me! :-) Also I totally agree with the statement made below. Could this page be simplified a bit? It is hard to wrap my head around. I am not asking for the topic to be dumbed down like much of the pop-science shows you see on television that insult a person's intelligence. All I am asking is maybe explaining some of the science jargon used, and whatnot. Thanks!24.18.0.136 (talk) 04:16, 23 May 2010 (UTC)

NO THEORY

The composite mass of the structure of matter is in fact the relevant dimensions of an endless string made up of honeycomb or hexagonal shaped strings that progress in movement and consist of the conformation of gas particals pixels and matter on a large scale structure. The dimensions of these endless strings made up in form of the honeycomb pattern combines into a spider web type pattern and is structually sound through combination movements. —Preceding unsigned comment added by 58.172.178.137 (talk) 17:28, 4 May 2010 (UTC)

Speedybrown6 (talk) 02:50, 28 March 2010 (UTC)Speedybrown6

Er... See: String_theory#History and History of string theory. --Dc987 (talk) 05:42, 31 March 2010 (UTC)

I don't really get how strings work.

Anything that is infinitely thin like a string and has mass seems strange, because the smaller the volume of it that you look at, the more dense it appears. The smallest point of it would be so dense its escape speed would exceed the speed of light and it would become a black hole, losing its material properties since black holes only have gravity and rotation. 154.20.194.233 (talk) 06:19, 15 June 2010 (UTC) ...

It is possible on subatomal levels to go faster than speed of light. Mass is the string property which depends of the wave level.

Basecaly, string is a fast moving source (which can even be in more than one place at the same time) which is a source of the wave-particle field. All the properties of the coresponding particle depend on the oscilations on that source string.Čeha (razgovor) 09:01, 6 July 2010 (UTC)

I don´t like the first picture

It puts me off reading. I would remove the picture or change it with another one. —Preceding unsigned comment added by 190.188.3.11 (talk) 01:24, 14 July 2010 (UTC)

What's new ?

Anything new in string theory in the last 10 years? —Preceding unsigned comment added by Alphachapmtl (talk • contribs) 20:31, 5 August 2010 (UTC)

Critical dimension and consistency

The article currently states that the critical dimension of string theory is not fixed by any consistency condition. This is pretty much orthogonal to what I know about string theory. My understanding is that the critical dimension follows from the requirement that the conformal anomaly present in string theory is absent, and that this only happens if there are 26 (or 10 for superstrings) spacetime dimensions. Of course, my info on this may be dated, but my gut feeling is that the work on super-/subcritical string theories is getting WP:UNDUE weight.TimothyRias (talk) 15:35, 6 September 2010 (UTC)

What?

This needs to be simplified greatly. I'm an university student who is used to tackling complex academic texts (granted, mostly humanities related), but this makes no sense to me. Layman's terms simplified explanation would be useful. The way I see it encyclopedia is aimed at general public, it is not reference tool for theoretical physicists. 203.206.49.48 (talk) 15:50, 22 March 2010 (UTC)

only amenable to a mathematical explanation. --Dc987 (talk) 05:46, 31 March 2010 (UTC)

I agree with the OP, its not like its impossible to explain string theory in "layman's terms"; there's plenty of sources where such explanations can be found. We shouldn't force users to research the theory off-site to understand it. What's the point of putting an article in language that only a person who already knows about the subject can understand? Deliberately phrasing the description of a theory to make it seem complicated and advanced should violate some Wikipedia standards about giving undue weight. You don't see the evolution or gravity theory pages expressed in such complicated terms, at least not within their respective headers. --IronMaidenRocks (talk) 03:39, 15 May 2010 (UTC)

I agree as well. I can read msot of it fine, but it sometimes requires me to re-read sentences. I think that has to do with the terrible word placements rather than "difficult words." 64.234.0.101 (talk) 17:49, 31 July 2010 (UTC)

Definition of 'science' - theoretical physicists have to realise that experiment is not the criterion for science. In geohysicsa, astronomy and in many fields of human sciences (history, political sciences) events occur only once and cannot be repeated: you cannot experiment of various possible leads of Sarajevo shots that started the WW I. You cannot experiment with Tungusta impact. You cannot experiment with WTC attack. You can only observe them. That's why I modified the end of the first chapter. —Preceding unsigned comment added by Martti Muukkonen (talk • contribs) 19:58, 30 October 2010 (UTC) ÷

Testable does not mean just laboratory experiments, it includes observations of events such as astronomical ones and historical ones. So if someone came up with a new theory of comets, which could be confirmed by examining past impact records including the Tungusta impact. The text you added seemed to confuse this somewhat: yes, repeatable laboratory experiments are better from the point of view of proving something, but that's not always possible. Often science has to be done after the event, for a whole number of reasons. Nor is this a particular property of physics, it's a property of all science.

The weakness of string theory is it makes no predictions at all, or at least none that are different from existing theories such as QM and relativity at energies we can measure. But this well understood b←y all scientists, and as this article is intended for quite an advanced readership I don't think it needs elaborating further. It is explained further down at some length, as it's an important aspect of the theory, but much of that is too advanced for the introduction.--JohnBlackburne^words_deeds 20:31, 30 October 2010 (UTC)

there is no reference to other sources that can help the reader clarify the concepts, linear algebra works with multiple dimensions, but it is not even mentioned as a starting point for clarification. —Preceding unsigned comment added by 130.76.64.117 (talk) 02:01, 19 November 2010 (UTC)

Cutting the lead

While the lead was clear and very nice in wording, it was way too long, so I cut it so it has max. 4 paragraphs and should fit in 1 screen. It can be still shrinked a bit, however I don't think simply removing more content from the lead would be any good. In my opinion the better approach would be to put more work into enlarging "Overview" section, so some informations just won't be needed in the lead anymore. So if someone is inclined to make a longer general introduction, please do it in this section. I will happily make further compactification of the lead. -- kocio (talk) 14:54, 6 September 2010 (UTC)

One thing to be aware of is that WP:LEAD also requires that the lead reflects the content of the article.TimothyRias (talk) 15:37, 6 September 2010 (UTC)

For me "how long is the lead?" and "is it a good summary?" are two somehow orthogonal questions. The {{Lead too short}} template currently includes the summary problem, however in my opinion "may not adequately summarize its contents" doesn't always mean "expanding the lead to provide an accessible overview of the article's key points". It's rather a problem of consistency with the rest of the article, not the length of the lead, even if it's related most of the time. In case of such a big and non-obvious article someone really should overlook the whole article and make a new lead out of it to satisfy both rules, which is unfortunately far beyond my skills. kocio (talk) 10:48, 8 September 2010 (UTC)

History

What has happend since late 1990s? I don't see any more in the history section. Is it still thought of as a viable theory? —Preceding unsigned comment added by 74.180.160.27 (talk) 14:18, 20 November 2010 (UTC)