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Spatial dimensions of our universe

  1. Aug 8, 2013 #1
    On the page 17 of this article by Max Tegmark http://arxiv.org/pdf/gr-qc/9704009v2.pdf, in figure 7, it has been argued that why spatial dimensions other than 3, is not possible for our universe. But in string theory, people are talking about 10, 11 or 26 spatial dimensions (even if these dimensions are thought to be in extremely small scale). Are these two contradicting? If no, why?
    Last edited: Aug 8, 2013
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  3. Aug 8, 2013 #2

    George Jones

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  4. Aug 8, 2013 #3
    We are living(!) on a universe that contains life. So our universe has to have 3+1 dimensions then. What is the difference between small scale dimensions and large scale dimensions? For example what would happen to general relativity and gravitation in that case (the universe with more than 3 dimensions)? Again does quantum theory predict these other dimensions?
  5. Aug 8, 2013 #4
    The small ones appear to be tightly wrapped...'compactified'.
    Nobody knows why some are small and others are large.

    quantum gravity and string theory are approaches trying to tackle such questions

    String theory suggests that 'particles' are strings...one dimensional extensions of point particles...whose characteristics, like energy,charge, spin are determined by the nature of the extra dimensions. Seems so far ten spatial and one time dimension are needed to account for the particle [string] characteristics we observe.
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