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

I How good an inertial reference frame is the Earth?

  1. Mar 25, 2016 #1
    Special relativity is one of the most tested theories in physics. A central postulated of SR is that the speed of light is the same for all observers in inertial reference frames, and this leads to time dilation and the other effects that have been tested with a high degree of precision.

    We know, however, that the earth is rotating and revolving around the sun, the sun is revolving around the galactic center etc. So at any given time there is a net acceleration of any earthbound reference frame and it is therefore not strictly inertial. Is this such a small effect as to be totally negligible for testing of SR, at least to the precision of testing to date?

    I'm thinking in particular of the Michelson-Morley experiment. If the lab frame of reference has a net acceleration in some direction, wouldn't the speed of light be different parallel and perpendicular to that direction? Is this effect totally negligible?
  2. jcsd
  3. Mar 25, 2016 #2


    User Avatar
    Science Advisor

    The Earth's surface has 1g upwards proper acceleration. That's what mostly makes it non-inertial in the relativistic sense.
  4. Mar 25, 2016 #3


    Staff: Mentor

    It depends on the specific experimental set up. The MMX design is simply not sensitive to the rotation, and in the horizontal plane it is not sensitive to the uniform vertical acceleration. A Sagnac interferometer is sensitive to the rotation. Other experiments are sensitive to the vertical acceleration.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted