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Why Planck scale?

  1. Dec 1, 2011 #1
    What are the reasons for scientists believing the planck scale is the smallest unit of length? I have been hearing a lot of this length scale recently and i know we cant even do expiremental research at these small of levels. I'm wondering where they got the idea that strings [from string theory] exist at this level.

    thanks guys!
  2. jcsd
  3. Dec 1, 2011 #2


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    It's the scale at which the effects of gravity and quantum mechanics become comparable. Crudely, one might suppose that fluctuations in the metric become comparable to the metric itself, and so the concept of distance needs modification. People do talk about a "trans-Planckian" regime, even smaller than the Planck length, but as you say, what happens at such distances is highly speculative, at this point well out of reach of both theory and experiment.
  4. Dec 1, 2011 #3


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    Above describes subject. In particular note that the question you are raising is related to particular theories uniting Gen. Rel. and quantum theory.
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