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Either Ether or no Ether

  1. Sep 18, 2013 #1
    The theory of relativity makes an 'ether' superfluous, but does it challenge the existence of an 'Ether'. Could the ether be an electromagnetic field or some other unknowable? Or is space-time a kind of ether? Its hard to understand light or even probability waves without a medium in which they are propagated. And whilst sound can travel faster than sound when propagating through
    a moving medium, perhaps the fact that light does not do so, tells us something about the light medium. I'm sure these things have been considered millions of times I just wondered what peoples thoughts were.

  2. jcsd
  3. Sep 18, 2013 #2
    The fact that people find hard to conceive a wave that propagates without a medium comes to show that the untrained mind is not fully prepared to understand how physics work. Does not mean that the physical models are incorrect though. It's a limitation of the mind, not the model.
  4. Sep 18, 2013 #3


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    Nature is indifferent to whether we can understand it or not.
  5. Sep 18, 2013 #4


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    Yes, quite strongly. There are many different kinds of ether models with varying experimental predictions. Most of those have been definitively excluded by experiment. The only remaining ether models which are not excluded are those which are, by ad hoc design, made completely unobservable. This puts it in a category even less scientifically relevant than the Easter Bunny and Santa Claus.
  6. Sep 18, 2013 #5


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    Does a medium need to be a physical medium? I'm assuming the EM field isn't considered a medium because it isn't physical?
  7. Sep 18, 2013 #6


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    Why isn't the EM field physical? Last time I used it to stick a baloon on a wall it sure seemed physical to me.
  8. Sep 18, 2013 #7


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    Hard to understand, perhaps, but not impossible if you think about the way that Maxwell's equations suggest that a falling electric field will produce a rising magnetic field, and a rising magnetic field will produce a rising electric field that can then fall again to keep the cycle going. And if you follow that line of thought, you reach a theory that explains experimental observations more cleanly and usefully than the the ether theories - which is why special relativity was received with general enthusiasm.

    Indeed it does... it tells us that light behaves more as if it doesn't need a physical medium.
  9. Sep 18, 2013 #8


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    well, the question Michaelson and Morley must have asked themselves is how is it that we believe in the existence of a physical phenomenon when this phenomenon displays no measurable attributes. it could exist in some form in which it does nothing and makes no difference, but then what's the point? it's the Aether-of-the-Gaps theory.

    this is the same question i ask in the Cosmology forum when people bring up the Multiverse as an explanation of some difficult question that is otherwise hard to answer.

    so if i'm holding a charge and you're holding a charge of opposite polarity, does the fact that you can feel your charge pulled toward my charge indicate that there's a material medium in between? is it hard to understand that, even with a vacuum or total nothingness in between, that it's simply the nature of our two charged bodies to attract each other?

    relative to the medium, the speed of sound is the same.

    but if the experiment shows that no matter what direction the Earth is moving, we measure no difference in the speed of EM propagation, then what does that tell you? it could mean that, somehow, the aether is moving around the Sun along with the Earth in such a way that we aren't moving through it. it does that 12 months a year. and then for the folks who live on the planet Zog, the aether moves around their sun along with them. or maybe not, maybe the Zichaelson-Zorley experiment they performed turned out different than ours? but that would be hard for me to believe.
  10. Sep 18, 2013 #9
    Thanks everyone. Nugatory I must look into Maxwells equations :) Dalespam I think I was envisioning the unobservable type of mediums. Perhaps there is something none physical we can't comprehend. Is the em field everywhere? Sorry guys I think I just need to read more about the subject...
    Many thanks
  11. Sep 18, 2013 #10


    Staff: Mentor

    Perhaps, but if so then it doesn't matter if we ignore it. Since it is unobservable we will never be wrong by acting as though it doesn't exist.
  12. Sep 19, 2013 #11
    Yes, all field are everywhere. That's kind of part of the definition of a field. Of course it might be (classically) equal to zero at places but that doesn't mean it's not there.
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