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Trouble for discrete space-time?

  1. Mar 31, 2003 #1


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  2. jcsd
  3. Mar 31, 2003 #2
    One must first explain the disagreement between the theoretical energy density of spacetime, 1093 gm/cm3, and the measured value, 10-28 gm/cm3.
  4. Mar 31, 2003 #3


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    The cited reference is not the article. It is a paraphrase of the paper, and the paraphrasing is not accurate at all.

    Quantum mechanics (QM) does not predict any kind of blurring of light as described in the article. Relativity does not make that prediction either. So failure to detect the "blurring" experimentally is not a problem for existing accepted theory.

    On the other hand, such blurring may be a prediction of some of the new classes of unified field theories which are being floated. If so, such theories might be ruled out by this experiment.

    Essentially, QM has managed to fend off 75 years of attacks from all quarters. Current theory is remarkably consistent with all experimental evidence. As to the comment about energy density being off by 135 powers of 10, I don't think this is a disparity that everyone agrees even exists. But I guess it is open to debate.
  5. Apr 1, 2003 #4


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    The vacuum energy problem is more of a desire than a fact. Physicists would like to think that they can compute vacuum energy density, so they devised a heuristic argument from QM and got that huge number... so the question is "is there really a huge vacuum energy we haven't detected", "does the idea of vacuum energy even make sense", or "what is the missing piece to the argument that gives reasonable results".

    In all likelyhood, the "yes" answer goes to the last of those 3 questions, since it seems reasonable that an accurate vacumm energy theory would require general relativity which has resisted integration with quantum theories, so the heuristic argument breaks because it is based on a realm where we have no consistent theory.

  6. Apr 1, 2003 #5
    I haven't read the whole article, but String Theory could explain this. You see, Quantum Mechanics does predict powerful fluctuations of spacetime, but these occur at sizes smaller than a Planck's size. String Theory dictates that - while this would happen, at sizes smaller than a Planck's size - there is nothing smaller than a Planck's size.
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