Talk:String theory
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It seems likely that observable phenomena will be emergent ones from the complex interactions of strings in any real-world scenario. Presumably string theorists are using chaos theory and computer simulation to deduce these emergent phenomena? I can't imagine that anyone expects to find a nice analytical solution that manifests itself in the observable universe when, at quantum scales, virtually every observable thing is an incredibly complex system.
Has anyone explored the relationship between string theory and the Transactional Interpretation of quantum mechanics? Both involve the representation of particles as standing waves in n-space (although I agree that the TI much simpler). The TI states that it is the interference of advance & retarded waves that creates these standing waves. This seems to elegantly resolve every quantum paradox, while at the same time making use of a previously disregarded solution to Maxwell's equations. Does string theory still disregard waves that propagate backwards in time...?
The article says '..measure distance between two points.. rotate that observer'- are we talking about rotating the observer about its own central axis, or rotating it about some third axis? This is confusing 24.176.6.165 07:23, 29 Dec 2004 (UTC)
The article says that in string theory, spacetime has either 10, 11 or 26 dimensions. But http://superstringtheory.com/basics/basic5a.html says:
That sounds crazy -- because bosonic strings live in 26 dimensions but supersymmetric string theories live in 10 dimensions. But the extra 16 dimensions of the bosonic side of the theory aren't really spacetime dimensions. Heterotic string theories are supersymmetric string theories living in ten spacetime dimensions.
- I believe that the quote you've given comes specifically from a discussion of "heterotic" string theories. They are called "heterotic" because left-moving and right-moving excitations (think of them as waves moving around the closed string) look very different. The left-movers look like excitations of the bosonic string and the right-movers look like excitations of the supersymmetric string. That's the context of the statement you quoted above. (For the record, the comment about 11 dimensions refers to M-theory.) -- Steuard 02:21, 26 Mar 2004 (UTC)
Shouldn't the title be string field theory? Or am I mistaken for something else? -- Taku
- Google would suggest not - 211,000 hits for "string theory" and 5,860 for "string field theory". I've never heard it called string field theory. Angela 20:03, Oct 18, 2003 (UTC)
- String field theory is an alternative formalism for string theory. It's ultimately the same thing. Mporter Jan 29, 2004 (AEST)
I have a question concerning this theory. The idea of 10, 11 or 26 dimensions, or evens strings themselves, doesn't seem very elegant. So, can we say there are no strings or 11 etc. dimensions, but it is our only way to describe the world as it is? (Because the mind is unable to understand it in another way than "string" or "dimension"?) E.g. there are no Calabi-Yau-Spaces, but we can describe the thing that is as if there where Calabi-Yau-Spaces? So: reality stays beautiful, because it is our mind that is not capable enough to think of a real elegant theory. I like this more than saying "there are 11 dimensions". Hhc2 14:19, 21 Oct 2003 (UTC)
- On the one hand, one way of doing physics is not to bother asking wether Nature really behaves the way your model says as long as it gives the right answer to experiments. This is mainly due to Quantum Mechanics where people stopped asking wether particles really travelled along two different paths at the same time as long as the probabilities they got where the good ones. Your position is thus perfectly acceptable form this point of view. But on the other hand you should accept the idea that Nature is not reducible to what our senses tell us. For example can you find an absolute reason why spacetime should be 4 dimensional ? All you can say is that at your (low-energy) scale, Nature seems to be 4 dimensional, right. But you cannot infer the answer, say, just after the Big Bang. There's no reason why the dimensionality of spacetime should be an absolute concept. So you can distinguish between Nature and our different representations of it but Nature still could change considerably with the scale. Stating the contrary would be a bit anthropocentristic :) LeYaYa 8 Feb 2004
- I am glad that - after some months - somebody has answered my question! I would like to point out that my intention was not to reduce nature / the reality to a level that I can understand it. That indeed would be anthropocentric. I wanted to express the regrettable status of my mind, which ist not able to think at the same time in 11 dimensions and call it beautiful or elegant.
- Reading the popular articles on string theory, I have the impression that they talk about strings as existing objects, that the average reader must come to the conclusion that the universe consists of some sort of very small spaghetti, only to small to see them. hhc2 6. march 04
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Fixed article a bit
I don't have the time nor the energy to write a long essay, but I fixed a lot misconceptions and ouright errors in the original page.
A link or quick defininition for the term "perturbative" in this context would be helpful for the layman.
Although the general structure of this article is quite good, I think we should word it more carefully. All the arguments given are mathematical (and valid), but in physics it is important to tie them in with experiments. Or at least clearly show their "speculative character." Here, it sounds like string theory is already a given fact... Awolf002 01:26, 6 Apr 2004 (UTC)
I like that added "hint" about missing tests. Much better now Steuard, right? Awolf002 19:04, 8 Apr 2004 (UTC)
Two questions and clarifications
I'm new at this, and a little confused, but intrigued. The article says, "string theories are able to avoid problems associated with the presence of pointlike particles in a physical theory. Detailed study of string theories has revealed that they contain not just strings but other objects, variously including points, membranes, and higher-dimensional objects."
Can anyone explain to me what sort of problems string theories are able to avoid?
Also, how is it possible that each string "contains" other objects? I thought the whole point of a string theory is that the strings are the smallest, indivisible building blocks (as opposed to conventional physical models, which hold that the smallest building blocks are three-dimensional)?
I'd love to understand this better.
--Seneca644 03:56, 6 Jul 2004 (UTC)
- One of the most obvious (to physicists) problems has to do with the infinities that show up when you try to describe a point charge. With a finite amount of electric charge concentrated at a single infinitely small point, the electric field at that point is infinitely large. If the same charge is instead distributed continuously along a string, no infinitely small point along the string has a non-zero charge, so the problem goes away. (The actual calculations used in string theory are rarely this straightforward, but I think the principle is pretty much the same.)
- As for your second question, that's just an unclear phrase in the article (embarassingly, I think I wrote it). The strings don't contain other objects, the theories do. I've just changed the word "contain" to "describe", which should make the meaning much clearer.--Steuard 22:21, Jul 9, 2004 (UTC)
I don't know about other people's hoses, but my garden hose has 3 dimensions, one more than this article seems to indicate. Is it some kind of gateway to another universe perhaps? Is it leaking into another brane like gravitons supposedly do? Infradig (andrew) 04:46, 1 Sep 2004 (UTC)
Image
Is anyone able either to obtain royalty-free string images like those cool ones on that nova documentary, or render something? That'd add to the article. [maestro] 04:47, 4 Dec 2004 (UTC)
"String theory, as with any current theory of quantum gravity, is unverifiable, and therefore it is also unfalsifiable."
GAHHH!!! I just had a two hour argument with my agnostic friend (I am an atheist) about this.
Just because an idea is created does not make it unfalsifiable! Theists always use this argument and it is flawed. It is the exact point of the Invisible Pink Unicorn--that becuase it is created, you can not disprove it, even though we all know she is a falsehood (blessed be her holy hooves). It's because the moment an idea is created, and you vehemently defend it, people say it can not be disproven.
By this token, Gimli exists, because I say so, and therefore, it is unfalsifiable.
Lockeownzj00 20:13, 5 Feb 2005 (UTC)
- I think you misunderstand something here. Unfalsifiability is bad, from a philosophical viewpoint, for the reasons you stated above. Of course, an Invisible Pink Unicorn cannot exist, because invisibility precludes colour. *shakes head* BovineBeast
By Rob: JUST because the grasp of the human mind cannot process a consept and theory so complicated, doesn't make it untrue!, But what we perceve is what we belive.
Superstring theory
Shouldn't this article be titled "Superstring theory"? The phrase "string theory" is a popular shortening of the original term. --User:Brian0918/sig 02:41, 1 Mar 2005 (UTC)
what about the philosophy of a sphere?
we know , a mathematical back ground concerning the origin of any sphere is a bit complex too ,a sphere is that it has no start and no end ,. absolutely we can find the end of a sphere [ sphere of radius R ] it is a preety simple question [ if parameters of diff.. eq n provide] ; but are our minds are ready enough to find the origin of any sphere. if we say a point matter then also that same is too a sphere , if we say a differential of a space then the ouestion is redirected to the constant k of our space time concept. here word sphere ,i mean to say any originating ball or a body [equivalently], a potential field, uniform lump matter of same constituent originating in space time co-ordinates . what ever we do , how hard we try , my above question is a question to all explorers of fundamental science, including me.
- i think , as per mathematics says, we can only talk about matter formation[ hence energy] or the meta physics, if and only if the above puzzle is cracked through mathematics , hence getting nearer and nearer to the truth . this will certainly risk free the possibility of any wrong truth/ model of any prediction what ever we make towards universe.
further questions; connect: e2t_solar@rediffmail.com
do you have a problem : i too is having a part of problem
let us solve together [ contact me if interested in my question] (unsigned I prabhat)
I say improving the article will make masses happier. --Cool Cat 
My Talk 15:47, 20 Mar 2005 (UTC)
Trouble with this article
I think this article is very biased.
"As of 2005, string theory is unverifiable. It is by no means the only theory currently being developed which suffers from this difficulty; any new development can pass through a stage of unverifiability before it becomes conclusively accepted or rejected. As Richard Feynman noted in The Character of Physical Law, the key test of a scientific theory is whether its consequences agree with the measurements we take in experiments. It does not matter who invented the theory, "what his name is", or even how aesthetically appealing the theory may be—"if it disagrees with experiment, it's wrong."
String theory's perdiction of cosmological constant is wrong. (55 orders of magnitude)
In fact, some would argue string theory is not even a theory given that even if the amazing particle accelerators which would supposedly show evidence of the smaller dimensions could be built, string theorists still don't predictions on what exactly would be seen.
Please see http://www.math.columbia.edu/%7Ewoit/strings.pdf
Question about time
Time is not a dimension, right? Right? Can somebody please explain, when I search information some sites tell me that time is the fourth dimension and some tell that it's not a dimension. Is it a matter of opinion until we understand a little more about how the world works?
- It is the perspective of essentially all theoretical physics since Einstein that time is a dimension. However, you should probably find an actual discussion forum if you want a more complete explanation (perhaps you could try the Usenet group "sci.physics", which you can access through Google Groups (http://groups.google.com/)); this page is only intended for discussion of how to improve the content of the article on String theory.--Steuard 20:52, Apr 21, 2005 (UTC)
garden hose thing
thank god. without the garden hose thing i'd have been lost. 70.177.90.39 03:06, 11 May 2005 (UTC)
Question
Recently someone made a new theory based on the sting theory and the kazula klein theory, where everything is explained only using flexion of the space. I cant remember who this is. Does anybody know this theory?
How does string theory explain matter/anti-matter anihilation?
As a non-physicist following string theory through Scientific American and Nova, one question I've always wanted to ask about string theory is "How does string theory describe the anihilation of matter and anti-matter". I would expect that there must be some mathematical symetry between the vibration mode of a string that results in an electron vs. that of a string that results in a positron. When two such vibrating strings collide, just what happens?
Thanks,
Mark Z.
Extra Dimentions
I read with interest the theory that extra spatial dimentions exist. However, this view is at variance with one expressed by Professor Stephen Hawking, who remarks that "if there were more than three spatial dimentions, the orbits of planets around the sun or electrons around a nucleus would be unstable and they would tend to spiral inward" --Derek R Crawford.
- That description of gravity would certainly be accurate if the extra spatial dimensions were "accessible" to us in the same way that the usual three are: the (approximate) force of gravity in D spatial dimensions falls off at large radius r as r^-(D-1). (I suspect that the comments about electron orbits aren't as relevant once quantum mechanics gets involved: QM doesn't allow for "spiraling inwards" at that scale.) But we already know that any extra dimensions would have to be different somehow, because we can't see them.
- The most common explanation in string theory is that the extra dimensions are "curled up" in small circles (or some other compact space). I've tried to explain that concept a little bit on this slide (http://www.slimy.com/~steuard/research/MITClub2004/slide09.html) in an overview of string theory that I wrote. The slide compares a human being's perception of a tightrope to an ant's: the person can move in only one dimension, but the ant can move in two.
- If that were the case, then measurements on very small scales in our universe would see gravity falling off faster than r^-2. But once the radius of the extra dimension became small compared to r, we would be back to r^-2 again (you can imagine that the small circle has "filled up" with gravitational field: there's nowhere else for it to dissipate in that direction). Last I heard, direct measurements have only verified that r^-2 gravity holds down to about 0.1 mm (which is quite large, when you think about it). So there's lots of room for the extra dimensions required by string theory.--Steuard 19:41, Jun 21, 2005 (UTC)