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Is there plank speed?

  1. Apr 5, 2013 #1
    If plank time is the time it takes a photon to travel a plank length and speed is d/t or meters/second. then is the speed of light c plank speed? is the constant speed of light evidence of plank time?
  2. jcsd
  3. Apr 5, 2013 #2


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    Science Advisor
    Homework Helper

    Yep, I guess.

    Note however, that the speed of light is a physical constant and in fact the meter is defined in terms of it. A unit like the Planck time and Plank length are also defined in terms of other fundamental constants, e.g. [itex]t_\mathrm{P} = \ell_\mathrm{P} / c[/itex] where [itex]\ell_\mathrm{P} = \sqrt{\hbar G c^{-3}}[/itex] is defined in terms of c and two other fundamental constants. So it's basically by construction, which I wouldn't call "evidence".
  4. Apr 5, 2013 #3


    Staff: Mentor

    What does that mean? Do you need evidence of ounces, or teaspoons? What does it mean to have evidence of a unit?
  5. Apr 5, 2013 #4
    Meter is a definition, second is. (Teaspoons also). So it is better to set c as 1. And lp as 1.

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