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Is the speed of light constant with time?

  1. Jun 10, 2014 #1
    In, BBC - Wonders of Universe, Professor Brian Cox explains that universe is stretching and the space that we live in is stretched from the early universe.

    If space is stretched as a result of Big Bang, and space is stretched at the speed of 74 km per second / megaparsec. is the speed of light through vacuum constant with respect to time?

    [Please close this thread. Due to observed red shift or increase in wavelength, speed of light should be constant, as frequency decreases to counter the increase in space. Even if speed of light is not constant in time, c is the speed of "gravitational waves"]
    Last edited: Jun 10, 2014
  2. jcsd
  3. Jun 10, 2014 #2


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    Gold Member

    Space does NOT "stretch". That is an analogy used in pop-science TV shows and has nothing to do with reality. Google "metric expansion" and/or see the link in my signature.
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