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A query regarding Ether wind

  1. Nov 14, 2011 #1
    Michelson Morley experiment was sought to find out earth's motion through ether, which allegedly produced ether wind. Thus the time required for two rays of light would be different, thereby producing interference pattern. Since earth revolves arouns sun, and sun revolves around something else, and our galaxy is rotating, revolving. So is it not that if there was any ether wind, it would be the resultant of all these motion, and not just earth's motion around sun. The equations in the text books take into account only the earth's motion. I agree it is not possible to take into account all these motions while calculating ether wind. But I think it would render the calculations made for these experiments invalid. Had M&M factored this in their experiment..I am confused
     
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  3. Nov 14, 2011 #2

    Matterwave

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    They detected NO ether wind, period. So, either the Earth with all these combined motions is somehow "absolutely stationary" wrt to this ether, or there is no such thing as ether.
     
  4. Nov 14, 2011 #3

    ghwellsjr

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    Isn't it possible that the combination of all the motions you described resulted in such a low value for the ether wind that the accuracy of the MMX instrument couldn't detect it?

    Actually, you left out the most important motion which is the surface of the earth caused by its rotation. So even if all the motions added to zero at some point in time, twelve hours later, it should have been large enough for the instrument to measure.

    Michelson concluded that since he couldn't measure any ether wind, the earth must be dragging the ether along with it. He proposed repeating the experiment at the top of a high mountain to minimize the drag.

    But before he could carry out his proposal, some other scientists explained the null result of the experiment, not by discarding the idea of an absolute stationary ether, but by concluding that lengths must contract along the direction of motion through the ether. And that is exactly the same "explanation" that you get when you use Special Relativity to define any inertial Frame of Reference and see what happens when the surface of the earth and thus the MMX instrument are moving in that FoR.

    So if Special Relativity comports with reality, it also comports with the idea of an absolute stationary ether as it only affirms the fact that its state cannot be determined. It is discarded on philosophical preference, not on the result of any measurement.
     
  5. Nov 14, 2011 #4

    jtbell

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    They also tried it at different times of year, when the earth is at different points in its orbit, so the earth's orbital velocity was in different directions with respect to the supposed "ether wind" and the two would add differently.
     
  6. Nov 14, 2011 #5

    Dale

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    If the aether breaks wind in the forest and there is nobody around to hear, is the speed of light still c?
     
  7. Nov 14, 2011 #6

    ghwellsjr

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    Don't you mean "smell"?
     
  8. Nov 14, 2011 #7

    Dale

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    Hehe, I was debating which to say.
     
  9. Nov 14, 2011 #8

    ghwellsjr

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    It's a tough philosophical question but I recommend using Occam's razor to cut the wind.
     
  10. Nov 15, 2011 #9
    Yes totally correct. Guess I was confused about what I was exactly confused about. The thing that keeps nagging me is how M&M experiment is described in textbooks. I mean if the ether wind can arise anyhow, then isn't it naive to assume that the light ray travelling in the direction of motion would be travelling slowly compared that with the light ray travelling perpendicular to it. Wasn't it possible that due to uneven ether wind, the speed of light travelling perpendicular to motion would be faster?

    I know that this notion about ether has been abandoned now. But I am looking at it just for sake of that experiment. Can anybody elucidate me on this (I hope I am being clear, coz this is as articulate as I can be)
     
  11. Nov 15, 2011 #10

    ghwellsjr

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    Remember that a round trip of light is always involved so even if the light ray traveling in the direction of motion is slowed down, the light ray that is reflected back will be sped up, making the round trip take the same time as the rays involved in the perpendicular direction. But this requires that the mirrors be closer together along the direction of motion compared to the mirrors along the perpendicular.
     
  12. Jan 18, 2012 #11
    It's funny how relativist like to talk about "null results" in M&M experiment but "forget" about Dayton Miller's "Ether-Drift Experiments at Mount Wilson"
     
  13. Jan 18, 2012 #12

    Doc Al

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  14. Jan 18, 2012 #13

    ZapperZ

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    And just in case people missed it, Doc Al's reference clearly falsify the notion that we "forget" about Miller's result. People who make such claim clearly haven't done their homework.

    Zz.
     
  15. Jan 18, 2012 #14

    zonde

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    Speed of light in direction of motion is c-v for forward trip and c+v for backward trip. So the round trip speed is [itex]c(1-v^2/c^2)[/itex].
    In perpendicular direction speed for forward trip and backward trip is the same - [itex]\sqrt{c^2-v^2}[/itex]
    or [itex]c\sqrt{1-v^2/c^2}[/itex] and it is faster.

    So it is correct that the speed of light travelling perpendicular to motion would be faster.
    This actually has nothing to do with aether. It's about Galilean transformation.
     
  16. Jan 20, 2012 #15
    This interpretation is based on the concept that the ether is stationary and unmoving. Other interpretarions are possible if the ether is considered to exist and have the ability to move. Why are these other interpretations taboo?
     
  17. Jan 20, 2012 #16

    ghwellsjr

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    The whole idea of an ether is that it is what undulates or what waves. Just like waves on the surface of the water medium, the light wave travels at some speed, but the medium itself stays put. Having a medium that can move around would create more problems than it would solve.

    By the way, prior to Einstein, most if not all scientists still believed in an absolute stationary ether. They explained the fact that no ether wind could be detected because their apparatus shrunk along the direction of motion through the ether and clocks would run slower when moving through the ether. This idea, called Lorentz Ether Theory or LET explains everything just as well as Special Relativity but it affirms the existence of the ether. Only problem is, no one knows where its rest state is so it has been deemed of no consequence, whether or not it actually exists.
     
  18. Jan 20, 2012 #17
    Lorentz Ether Theory also assumes an absolute stationary ether. The CMBR is a good starting point for consideration as the rest frame of the ether. If it is not the correct rest frame it is the very next best thing for consideration.

    If a quanta of ether contained energy, why would not that quanta be accelerated by a gravitational field exactly the same as any other object having mass or energy equivalent mass? It should be since the acceleration caused by a gravitational field is independent of the mass or energy equivalent mass of the body being accelerated.

    In short, other than not being the mainstream consensus, why is the concept of moving space wrong?
     
  19. Jan 20, 2012 #18

    Dale

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    Because it has failed every experimental prediction that it has made.

    Also, if the idea is that light is a vibration in the aether medium then the aether needs to be solid since light is a transverse wave and fluids don't support transverse waves, and it needs to be both very rigid and low-density to get waves propagating at c.
     
  20. Jan 20, 2012 #19

    ghwellsjr

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    LET, like SR, does not include and, in fact, ignores gravity, which means they don't apply to the whole universe or anything as big as CMBR.

    In any case, both LET and SR do not consider a frame (or ether) to contain anything that could be quantized and as I said before, having a moving frame (or ether) in which parts of it can move around would create problems that the simple construct of a frame couldn't handle.

    If something isn't mainstream consensus, there's usually a good reason.
     
  21. Jan 20, 2012 #20
    Because the (old) theory of "complete aether drag" is incompatible with
    a) Aberration of light
    b) Sagnac effect due to Earth's rotation (included in GPS)

    This was the reason, why the Fresnel-Lorentz idea of a stationary aether was preferred - until it was refuted by Michelson-Morley, so that the only remaining choice was special relativity.

    http://en.wikipedia.org/wiki/Aether_drag_hypothesis
    http://en.wikipedia.org/wiki/Michelson–Gale–Pearson_experiment

    Regards,
     
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