1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

C = 299 792 458 m/s and uncertainty

  1. Feb 4, 2007 #1
    c is 299 792 458 m/s without uncertainty? doesn't work the Heisenberg uncertainty principle for fotons?
  2. jcsd
  3. Feb 4, 2007 #2
    The distances typically involved in measuring c are sufficently big that quantum fluctuations are ignored.

    Also, the length of 1m is defined by the distance light travels in a certain amount of time. Because of this definition, we're effectively defining light's speed, not measuring it, so it is exact.
  4. Feb 5, 2007 #3
    we define 1m, but we must still measure in how much time light crosses 1m; we measured c but it can be less or more, right?
  5. Feb 5, 2007 #4


    User Avatar

    Staff: Mentor

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook