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Michaelson Morely

  1. Mar 31, 2008 #1
    In the MM experiment how come the experiment didnt detect the movement of earth or did it ? or wasnt it accurate enough to measure it as I nkwo the velocity of the earth is much slower than C a few ppm?
  2. jcsd
  3. Mar 31, 2008 #2


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    The "aim" of the Michelson-Morley experiment was to measure the movement of the earth through the ether, and the effect of the generated "ether wind" on the speed of light. However, no effect was found, and thus the idea of an ether was thrown away. See here or here for detailed information on the experiment.
  4. Mar 31, 2008 #3


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    In relativity there is no such thing as "the velocity of the earth". The Earth has different velocities in different frames, with all these frames equally valid, and the speed of light the same in each frame.
  5. Mar 31, 2008 #4


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    The question the OP is asking, though, is was the MM experiment sensitive enough to measure the effect it claims to have [not] measured. Obviously, yes - that would be an obvious error if the experiment wasn't sensitive enough to measure the effect it was attempting to detect. But here are the numbers for you: http://en.wikipedia.org/wiki/Michelson-Morley_experiment

    It says in the link that the precision of the experiment was to within about 1/25th of the effect they were trying to measure and the measured magnitude of the effect was within that level of precision away from zero.

    In addition, the experiment has been performed - and improved upon - thousands of times since M&M originally performed it.
    Last edited: Mar 31, 2008
  6. Apr 1, 2008 #5
    As the rate of time is a function of absolute velocity, direction is irrelevant, the phyisics of measurent must be different in diff frames of ref. Different frames of ref will give diff results for the same measurement

    for example measuring a meter using a clock and light
    man1 is in a plane flying east at 100 kph
    man2 is in a plane flying west at 100 kph
    lest say our galaxy is moving east at 100 kph

    in effect the absolute velocity of man 1 is 200 kph, man2 is stationary. Time passes for each at a different rate so they will get a diff result for a meter measurement or will they?
  7. Apr 1, 2008 #6
    sorry i forgot something from my last post

    the men are using exactly the same technique to measure an exact meter which is the distance light travles in 1/c seconds

    caos they are travelling at diff velocities there clocks are out of kilter
  8. Apr 1, 2008 #7
    the physics isnt the same as time passess at a diff rate in diff frames which is a function of absolute velocity
  9. Apr 1, 2008 #8


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    You're wrong, it is the same because each measures their own clock to move at a normal speed while the other guy's clock seems to be slowed down in proportion to the other guy's velocity--there is no way to determine whose clock is "really" running slower, not if they are both moving inertially (no acceleration). The idea that the laws of physics work the same way in all inertial frames is a very basic part of relativity, and no experiment has contradicted it, you really need to study the issue a little before jumping to the conclusion that it's wrong (in any case, if you read this thread on the rules of this forum, you'll see that this is not the place to try to debate mainstream physics theories, just to try to understand them and their consequences better. If you have questions about how the theory works that's fine, but definitive statements that the theory is wrong--when you obviously haven't studied it much at all--will get the thread locked).
  10. Apr 1, 2008 #9
    You have to read more on SR, or at least understand it.

    The laws of physics are no different in other reference frames.
  11. Jun 29, 2008 #10
    The Aether itself is not observable, you can't say - here, lets take a look at this piece of aether! - because it is immaterial. Real but not in spacetime, hence, not directly observable. This is why MMX (the Michelson-Morley experiment) failed so miserably. But you can measure its effects; things like inertia, gravity, magnetism, electricity... etc.

    From the MMX results we should conclude that the aether is immaterial and directly unobservable. Now, if there was an empty space, independently from the universe, before there was matter, isn't the classical vacuum immaterial and directly unobservable too? Can we take a direct measurement of something which is not matter? The only thing proven by the MMX was that they didn't understand the Aether's nature. You want to measure drag caused by the Aether? Just measure a moving object's momentum... or measure the force needed to accelerate any object... that's aether caused drag!
  12. Jun 29, 2008 #11
    Hello cyberdyno.

    This may be releavant.

    Fresnel and, seperately Stokes both tried to explain the negative result of the MM experiment by some sort of ether condensation or ether drag effect. Both were proved to be unworkable explanations.

    Reference: Historical introduction to a translation of The Principle of Relativity: an Original Paper by A Einstein and H Minkowski. These facts probably appear in many other histories of the subject.

    With regard to the presence of empty space independently of the uiverse i believe the accepted view is that before the universe "began" there was not even empty space.

    If the ether is unobservable i would take this to mean it is undetectable. So it must have no measureable properties. So there is no nature of the ether to be understood or misunderstood.

    If you, however, do understand this undetectable ether, please excuse my ignorance of the subject and give me your explanation of it. No references please, just your interpretation.

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