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Explanation of m&m experiment through sr

  1. Apr 2, 2013 #1
    Hello friends,

    We all know that Michelson-Morley conducted an experiment which led to the proof that ether doe not exist. I don't know whether there is an alternative experiment of this,if there is i mean this experiment(http://www.youtube.com/results?sear...46.1525.1j5j2j1.9.0...0.0...1ac.1.JO2rBQAXZaU , 4th link.)

    What would Michelson-Morley Experiment look like in the IRF of an observer who is at rest(This observer will be in space)
  2. jcsd
  3. Apr 2, 2013 #2


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    They assumed that they were not at rest but Einstein pointed out that they could legitimately make that assumption and that would explain why they could not detect any ether wind. (They did not prove that ether does not exist. That's impossible.)
  4. Apr 2, 2013 #3
    see the 4th video. It said like that. And they said that ether does not exist.
  5. Apr 2, 2013 #4
    i will take back this answer!!
  6. Apr 2, 2013 #5
    watch that video.then they conducted the experiment in other way.they conducted experiment by thinking that they are moving opposite to ether wind.so light should have travelled slower speed and both would not have reached the the beam split mirror at the same time.but light travelled constant.so ether does not exist
  7. Apr 2, 2013 #6
    this is not my question.will the light reach at the same time in the beam splitter in the IRF frame of observer who is at rest.this guy should be outside earth's orbit
  8. Apr 2, 2013 #7
    Note that both the observer and the system are not in an IRF.
  9. Apr 2, 2013 #8
    why the observer? I said that he is out of the orbit so that he remains in rest.ok then.consider earth as moving uniform motion with reference to that observer.then what change can we observe?
  10. Apr 2, 2013 #9


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    I am not on a system that can view videos right now. I'll take a look later when I get a chance.
  11. Apr 2, 2013 #10
    yes.me too!! That is why i gave that link instead of that video itself.but don't worry. You can open it with the help of your mobile. It works.
  12. Apr 2, 2013 #11
    Sorry, I missed that, yes when the observer is in space he is in an IRF. By the way if he is in orbit he is also in an IRF.
  13. Apr 2, 2013 #12
    yes.. Ok. I know. When you said like that,i itself got confused.. Now can you give me answer? And can you see the video that i said?
  14. Apr 2, 2013 #13


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    You'll hear people saying this all the time. They're being sloppy.

    The MM experiment demonstrated that we do not observe certain effects that are predicted by the most common and simplest class of ether theories, and therefore that those theories could not be correct.

    (In general, any time that you hear someone say that an experiment "proves" something, they're being a bit sloppy. Experiments don't prove theories, they disprove competing theories).
  15. Apr 2, 2013 #14
    "absence of evidence is not evidence of absence"
  16. Apr 2, 2013 #15


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    Everytime I click on the video link, I get a different set of videos so I"m not sure which is the one you want but I think it is the one with the serial number XavC4w_Y9b8.

    My comments will be with regard to that video. You have to pay real close attention to what they said. They never said that MMX proved that ether does not exist. At around 6:50 into the video they said "in complete disagreement with the idea of earth moving through the ether". Then at 7:15 they say "the experiment had failed to detect the ether". This is different than saying they proved the ether does not exist.

    As I said earlier, Einstein showed that no matter what inertial state they were in, they could consider themselves to be at rest with the respect to the ether. So the experiment would have the same result even if they were in a legitimate IRF but I'd hate to be around all the mercury in a weightless environment.

    I think I'm totally missing the significance of your question.
  17. Apr 2, 2013 #16


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    Well stated.
  18. Apr 2, 2013 #17


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    A regular M&M is a peanut M&M moving very fast.
  19. Apr 2, 2013 #18
    I mean this video :
    Last edited by a moderator: Sep 25, 2014
  20. Apr 2, 2013 #19
    Yes.you are right. Experiments disprove two conflicting theories.. Thank you for your response!
  21. Apr 2, 2013 #20
    I would like to understand this: Since earth is moving, time slows down(moving with respect to observer who is outside the earth). When time slows down, There will be change in simultaneous events. Like they conducted experiment like this: They sent a beam,splits into two when encountered beam splitter (I think that is a beam splitter) One travels perpendicular to it,other goes straight.they too hit the two mirrors at the same time and come back to the beam splitter. This happened to them. So i wanted to ask this: Will those two split light hit the two mirrors at the same time in reference to observer outside earth's orbit? But i think even this happens,it will reach the beam split mirror at the same time.
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