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Why exacly 11 dimensions?

  1. Sep 5, 2004 #1
    Can anyone explaine to me why there is exacly 11 dimensions :bugeye: , why not 13 or 7? I have searched a lot but I have not found it anywhere.

  2. jcsd
  3. Sep 5, 2004 #2
    look under the "strings, branes, LQG" section of PF. I know I've seen that same question asked.

    Paden Roder
  4. Sep 5, 2004 #3
    Well i assume than you are talking about M-theory which says there must be 11 dimensions according to the approximate equations worked about by witten when he combined previous 5 theories into one theory

    I think you might like to use one of the folliwng resources


    It is about 35 minutes of a lecture I wrote with help from some members here including selfAdjoint

    I also have a powerpoint that goes with it
    but this lecture was meant to be stand alone if you would like to kind of follow along with the powerpoint
    the powerpoint is here


    also a transcript of the speech itself is avaliable here


    If you just want a quick answer just keep reading

    if you need more information
    one ask me
    two go to the string forum
    three read the elegant universe
    Last edited by a moderator: May 1, 2017
  5. Sep 5, 2004 #4
    i believe tom has summed it up rather nicely but really more than 11 dimensions COULD exist although as of now they arent needed and therefore we dont add them. really i would just wait until m theory's full calculations have been done before i said that only 11 can exist.
  6. Sep 9, 2004 #5
    wow very interesting,,
  7. Sep 11, 2004 #6
    So what would you say if there is a theory that can explain ALL the forces of nature as only the consequences of ONE property of VERY LIMITED number of fundamental particles and consistently predicts quantization of electron energy inside an atom, radiation interaction with material, the existance of other particles and their "binding energy", the wiglling of star motion and includes the gravity forces together on equal footage interpreting with few postulates why there is no repultion of masses and there is an static electomagnetic field around our earth using only three dimensions of the "natural" space and the universal time and give "relativistic-like" conclusions only within "classical-like" mechanics and give all physics the unity it deserves?
    I DO NOT mean www.thefinaltheory.com but I mean the Unity Theory of Amr M. Morsi who was one of my students in EM theory at Ain Shams Univ. (where I'm an LA) and then an electronics eng. colleague and finally a personal physics tutor and friend.
    However there is another Egyptian Prof. Mohammed-Saladdin ElNashaei (I don't know how his name appears in literature) who I met in Cairo Univ. open lecture and talked about his infinite dimension theory where time is just like anyone of them out of his study of the deterministic chaos. but I did not read anything he wrote (because I cannot spell his english name and my tight time. so if anyone can guide me on his theory my mail is open to receive documents at sifeddinpapers@yahoo.com)
    There are still this John Carolle of Camdridge Univ. who claims there are three time dimensions as well asa the three space dimensions that allow to give space-time vortices that explains why there is no isolated magnetic charge.
    So how many dimensions do think live in? Would you like to be Mr. Square or Lady Sphere or may be Mr. 4WD!
  8. Jan 27, 2005 #7
    My question is, are these extra dimensions in any particular "order" or would they be of different "classes"? For instance, it seems to me that the dimensions "length", "width", and "height" exist in relation to each other and would therefore be of one "class" of dimensions (spatial). Then we have "time", which seems to be its own kind of dimension. Then we have these "extra" spatial dimensions. Could an object theoretically exist in some dimensions but not others? Could there be a one-dimensional object (using the term "object" loosely) that only exists in, say, time, or one of the unknown dimensions?
  9. Jan 28, 2005 #8
    "My question is, are these extra dimensions in any particular "order" or would they be of different "classes"? For instance, it seems to me that the dimensions "length", "width", and "height" exist in relation to each other and would therefore be of one "class" of dimensions (spatial). Then we have "time", which seems to be its own kind of dimension. Then we have these "extra" spatial dimensions. Could an object theoretically exist in some dimensions but not others? Could there be a one-dimensional object (using the term "object" loosely) that only exists in, say, time, or one of the unknown dimensions?"

    Well acording to the M-Theory, the extra dimensions are claimed to be extremly small, Where every object exists in all the extra dimensions its just to small for us to even notice. These extra dimensions are just curled up into the 3 standed height, length and width ones.
  10. Jan 28, 2005 #9


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    The dimensions are in two classes; time, and space. One dimension is time, and all the others are space dimensions. As such they would be interchangeable (as length, width, and height are, really; you can mark those on the edges of a box and then rotate the box any way you want). The thing that breaks the interchangeability symmetry is that seven of the space dimensions are compacted (curled up small). But there isn't any special way to choose which space dimensions become small, it's just a fact of life which are.
  11. Jan 28, 2005 #10
    Ain't 11 dimensions used for the strong & weak forces and electromagetism to be along the same strenth at one point in time. I'm sure I read something like that somewhere.
  12. Jan 29, 2005 #11


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    I think that's ten dimensions; supersymmetric GUTs that unify those three forces (without strings) require ten dimensions, and tend to compact them just as string theorists do.
  13. Jan 30, 2005 #12


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    Why 10 dimensions? Well, 4 usual space/time dimensions and 6 compactified ones. Plus an extra M theory one that is kinda taken to be fuzzy (hard to define a length on it).

    So why 10 dimensions? Well it turns out, this number is fixed. You can't deviate from it at all in order for the theory to be consistent. If someone in 10 years says "well we really need 14 dimensions to describe nature', then that something is not string theory. In conformal field theory, much of the mathematics of string theory, quantum anomaly conditions must match precisely and this number outputs 10 dimensions. No more, no less.
  14. Feb 1, 2005 #13

    Hey guys have you ever thought though that m theory and supersymetry are the deluded ravings of mathemeticians who are being driven slowly insane by the wierdness of qm :wink:

    String theory too could be just an imagined nonsense :wink:

    Let's maintain some sort of scientific approach to these mathematical sophistries at least until the evidence for them is there :smile:

    I think we should be wary of claiming that there are any more than 4 dimensions unless we can prove the existence of them we're in danger of dissapearing up our own backsides with this sophistry.

    Fantasticaly interesting and clever theories and to be praised and encouraged, but lets not forget that's all they are: theories; actually thinking about it there not even theories there hypothesis since there is no evidence for any of them :biggrin:

    I love mathemeticians kinda like ufo nuts with too much spare time and too little scientific experimentation.

    Step outside of the envelope people after all the answers in the post

    Me just then, A.Smartarse feb 2005 :smile:
  15. Feb 1, 2005 #14
    I prefer the 4 dimensional universe over the 10 or 11. But we shouldn't cut the strings just yet.
  16. Aug 28, 2005 #15
    Assuming we accept the 11 dimensional calabi-yau model, does this model REQUIRE that the other three dimensions be very large or is this just a bonus?

    Either way, is there a minimum size needed for the 4 large dimensions to make this model work?
  17. Aug 29, 2005 #16
    Why three dimensions ?

    Would there be any reason why three spatial dimensions is such a good start in physics?
    It is well known that 2 dimensions would be quite difficult to live in.
    But why are we so happy with 3?
  18. Aug 29, 2005 #17
    We started with three because we only directly experience three. The other spacial dimensions are too small for even the atoms of our bodies to move in and out of. We've only recently discovered more than three because we've only recently started studying things small enough to have some free movement in the other dimensions.
  19. Aug 30, 2005 #18

    I totally agree that 3D is a direct experimental evidence.

    But, I was wondering if some people had come with temptative explanations / interpretations about the number of 3 'obvious' dimensions.

    Of course, if the 11 dimensions are definitively proved, and if -indeed- a bunch of these are microscopic dimension, then it is factual reasons that lead us to 3 dimensions in our daily lifes. By the way, are the reasons for 11 dimensions factual or more fundamental? Does a 11D space have special properties as compared to other spaces?

    Finally, let me note that if I had to choose -by myself- an hypothetical dimension for the scene of physics, I would choose the infinite. I have the feeling that this would open a lot of possibilities ...
  20. Aug 31, 2005 #19

    Well, from calculations, more specifically, equations they have actually found out that using the curved model of the fifth dimension. The resulting equations would be somewhat similiar to those of electromagnetism.

    For clarifications, their model of curved dimensions actually only has the fourth dimension large enough to be felt, straight in the face right?
    With the speculations that the fifth and above dimensions would be smaller then planck's constant, thus it being almost impossible to be detected :confused:
  21. Jul 4, 2008 #20
    I see that this thread has lain dormant for about three years now, but i'm chipping in with my small change on this because it seems to end right about where my thoughts have been wandering lately. If a moderator prefers to turn this into a new thread, that's ok by me.

    Fallaciousmiles mentions that there has been speculation that the dimensions beyond the familiar spacial three are somehow smaller than the Planck length. When hearing that these dimensions are curled up (or wound up? -- another speculation of mine) so that they are too small to be detected, i've wondered how small that might be. Specifically, what i am most curious about is whether there has been any serious speculation that anything other dimensionally could be going on at sub-Planck lenths. [Don't throw anything!] Yes... I do appreciate that the Planck length represents a limit beyond which we can't calculate, [Right?] but i've always had difficulty reconciling that with a lot of other thinking cluttering up my mind. I suspect any serious speculation along such lines could only be going on amongst those with greater maths knowledge than i possess (with my historian/librarian + curiousity background), so i bring my quandary up here.
    My thinking along these lines connects with my suspicions that 'existence' must extend by infinite scales of magnitude both towards smaller and larger -- a suspicion i base mostly on the philosophical rationale that either 'all' has ultimately had some sort of beginning ex nihilo [defying our common experience], or there must be an infinite regress of cause and effect [defying nothing in our experience, but challenging our ability to imagine anything as actually infinite].
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