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I Gravitational Waves Vs. Aether Wind

  1. Jun 12, 2016 #1
    The Michelson-Morley Experiment (as depicted in the scishow YouTube video "The Greatest Failed Experiment Ever") which was used to test for the effects of 'Aether Wind' appears to be almost, if not completely, the same setup as the one used in a gravitational-wave observatory. Why is the success of the experiment now used as evidence for something very different from what it would have, so long ago, proven a completely different theory? How can we be sure that this doesn't just mean that there is an aether but our tools were incapable of measuring it back then, instead of verifying Einstein's theories?

    For reference, this is the video describing The Michelson-Morley Experiment:
     
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  3. Jun 12, 2016 #2

    Orodruin

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    The signals are completely different.
     
  4. Jun 12, 2016 #3

    Nugatory

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    That's because interferometers are the most accurate way of measuring both small changes in speed and small changes in distance. Thus, you shouldn't be surprised to find them in experiments that depend on either kind of measurement.

    But as Orodruin says, the type of signal is completely different. There's no way that the fluctuations observed by LIGO could be explained by an ether wind.
     
  5. Jun 13, 2016 #4

    pervect

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    The Michelson Morely inteferometer was designed to keep the distance between the mirrors in its arms constant. The mirrors were not allowed to move relative to the rigid frame of the interferometer, but rigidly attached to the rigid frame. . The mirrors on the Ligo interferometer are not attached to the frame. They're attached to test masses, which are levitated suspended to support the mirrors against Earth's gravity, but are otherwise free to "slide around". One of the challenges of the design is to isolate the test masses so that other enviromental influences other than gravity waves cause as little motion as possible.

    There are no test masses in the Michelson morely interferometer - the mirrors are attached to the frame of the interferometer directly.

    [add]There are some details on the final stage of the suspension system for advanced ligo (aLigo) at https://www.advancedligo.mit.edu/sus.html. Basically, there is a multiple-pendulum system (three to four pendulums). There is some sort of possible active "sesmic isolation system" [SEI] in addition - the pendulums are hung from the sesmic isolation system. I haven't found any details on the SEI though..
     
    Last edited: Jun 13, 2016
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