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14 dimensions?

  1. May 21, 2008 #1
    I was told by my old physics teacher that there is proof (mathematically) for around 14 dimensions or something crazy like that. I think he said it was in relation to string theory and the amount of dimensions they need to oscillate as we think

    but seriously, we have x,y,z planes and time

    what more could we need?
    so what does dimensions 5-14 cover?
  2. jcsd
  3. May 21, 2008 #2
    Eleven dimensions is needed in string theory.
  4. May 21, 2008 #3
    It covers more spatial dimensions. I'm 90% sure that no matter how many spatial dimensions there are, there is only one time dimension.
  5. May 21, 2008 #4
    I don't think one time dimension is absolutely necessary for a hypothesis to be sound.
    The extra dimensions(5-10 spacial) are only needed for strings to be able to move in different fashions.
    Consider a one-dimensional universe. There exist two strings on that plane, both charged electrically positive. Some force pushes them together(the means by which they come together is not important). As they come together, more and more repulsion occurs, and the points want more and more to separate in some way. The force that is pushing them together, however, is too strong to fight, and so the string bend into another dimension.

    Or, for an example that's commonly used for plate tectonics, pretend I have two folded towels on a table. I push them together, and eventually they bend up due to the forces acting on them.

    Without the extra dimension that they bend into, the theory breaks down. Keep in mind this is not a great metaphor.
  6. May 21, 2008 #5
    That is a great metaphor. But, theoretically what you just stated, means that we could force two things together and they would move into a fourth spatial dimension?
  7. May 21, 2008 #6
    Very theoretically. However, for our purposes, three dimensions is enough. Only at a very small scale do things start to need more room to act.
  8. May 21, 2008 #7
    check out the kaluza-klein theory. it too talks of more than 4 dimensions(3 spatial ad 1 of time). according to it, the extra dimensions have curled up on themselves to such a degree to be hardly noticable. something like taking a rectangular piece of paper(2 dimensions) and rolling it up a lot so that it becomes a tube with a very small radius. so it has effectively become a line(1 dimension).
  9. May 22, 2008 #8
    if there were more than 3 dimensions then why can i not move in more than 3 directions (neglecting the 0.5d of time)
  10. May 22, 2008 #9
    The count actually runs something like this. String theories requires 10 dimensions. Super Symmetry requires 11 dimensions. The two theories come together in some fashion in an 11 dimensional points theory, or M theory, or brane theory.

    At one time it was said that string theory required either 10 or 24 dimensions. As near as I can understand, the extra 14 dimensions are still around but thought of as internal degress of freedom.

    These extra dimensions--over 4, impliment the 4 forces.
    Last edited: May 22, 2008
  11. May 22, 2008 #10
    so if these other dimensions represent forces, does that mean we exist in more than 4 (or 3.5) dimensions as well?

    it is really hard to visualize as we are so use to our 4
    reminds me of trying to visualize the 'singularity' hahah

    there is some experiment too where you take a strip of paper, and you turn one end upside down, then bring it back to meet the other end so that you have a 1d shape (only one surface). is that like the paper tube one posted before?
  12. May 22, 2008 #11
    Aftermath. It's difficult to visualize this of course, but, yeah we're already there, and as jablonski says adding one rolls up like a tube of very small circumference.
    Where does this 3.5 dimension stuff come from? surely not from established physics or any significant thought.
    Last edited: May 22, 2008
  13. May 22, 2008 #12
    I've never seen anyone say it before but I'm guessing some people might consider time to be only half a dimension because we only move in one direction through it.
  14. May 22, 2008 #13
    So far as you know...
  15. May 22, 2008 #14


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    There has been talk (not sure how much research or study into) of more than one time dimension. I think it simply stems from asking why there shouldn't be another time dimension, and considering the ramifications of another one. After all, I would argue we hardly understand time at all, so the possibility certainly isn't off limits.
  16. May 22, 2008 #15
    I think I know what you are saying about having more than one time dimension, there is a theory that states that all electrons in existence are exactly the same because they are all copies of each other. Some are just going backwards in time, and some are going forwards, but when this forward-backward time movement happens, things can make carbon copies of themselves. I read this in the book, Beyond Einstein- The cosmic quest for the theory of the universe. by Michio Kaku. http://www.amazon.ca/Beyond-Einstei...=sr_1_3?ie=UTF8&s=books&qid=1211509815&sr=1-3
    This theory would suggest the two, forward and backward time dimensions.
  17. May 22, 2008 #16


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    I'm not really sure how serious to take Kaku anymore. Seems he just writes a lot of pop-sci books and does NOVA specials these days. :(
  18. May 22, 2008 #17
    Yes, he does, but he is still a reputable physicist and a very good one at that, a person who writes pop-sci books can still be very reputable. And, his books do go considerably in depth.
  19. May 22, 2008 #18
    Is the rolled piece of paper analogy an example of only one extra dimension?

    Electrons can be at multiple places at one time. Is this one of the reasons why we need more dimensions?

    Are these extra dimensions simply answers to unexplained movement, ie. when something behaves contradictory to how is is expected. Like if physical laws say it will do one thing in 4 space, but it does not, so it must be operating under physical law, but just in more dimensions than previously thought?
  20. May 22, 2008 #19
    Agreed. There is nothing wrong with attempting to spread a few shreds of truth to the masses. Neil Degrass Tyson is a good example.

    Also Kaku started with physics and ended up on t.v... not the other way around.
  21. May 22, 2008 #20
    no, the rolled paper analogy is for many dimensions. atleast this is how i read it in a book loong back(i ll dig it up).

    as far as i know, all these theories sprang up because of inconsistencies in quantum physics at the time. 'infinities springing up all the time' is a well advertised problem. another motivation was in trying to unify GR with quantum physics.

    and as mentioned earlier, the extra dimensions are not of space.
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