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B How does LIGO measure gravitational waves

  1. Oct 25, 2017 #1
    I'm aware that the LIGO system uses interferometry but I'm confused how it works in this case. Do they test both beams of light? Or do they use one beam to test the wavelength of the other and see the difference? Also it is sensitive up to 10 e-18 meters, is that for the change in wavelength or change in the length of the beam?
  2. jcsd
  3. Oct 25, 2017 #2


    Staff: Mentor

  4. Oct 25, 2017 #3

    stefan r

    User Avatar
    Gold Member

    It is one beam of light. It gets split. The wavelength of light does not change. Interference changes the amplitude measured not the frequency.

    Check these two ideas:

    Beam Splitter.
    Destructive interference.
  5. Nov 5, 2017 #4
    I'm puzzled that the stretching of space by a gravitational wave stretches the LIGO arm but not the light within it. Because we are told that the red shift of a distant galaxy is caused by light being stretched by the expansion of space (the universe).
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