Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Speed of light.

  1. Mar 6, 2008 #1
    We know that light propagates in a constant speed c, but what if we are moving in an air plane and then turning on the light, why the speed of light remains constant?....
    Thank u.
  2. jcsd
  3. Mar 6, 2008 #2


    User Avatar

    Staff: Mentor

    Velocities don't "add" the same way in relativity as they do in classical physics.


    In the equation on the page above, let u' = c (velocity of the light with respect to the airplane) and see what you get for u (velocity of the light with respect to the ground).
  4. Mar 6, 2008 #3


    User Avatar
    Gold Member

  5. Mar 6, 2008 #4


    User Avatar
    Science Advisor

    The real answer is "because that's what experiment tells us". Everything else is derived from that.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook