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The Ether

  1. Mar 26, 2007 #1

    Pythagorean

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    The skepticism thread reminded me of a question I had for the professionals here.

    A lot of Electrodynamics (especially the idea of displacement current) was developed by Maxwell with the idea of Ether in mind.

    I'm not trying to argue that the ether-as-we-know-it actually exists, but the whole idea behind it is that space has properties. It seems almost like political fear (in the form of skepticism) prevents knowledgeable people from further exploring this idea because they don't want to be labeled crackpots.

    When we brought this up to our teacher, he wouldn't comment on it one way or the other. What do you guys think?

    specifically:

    a) why do Maxwell's equations still work if they were formulated with an ether in mind, yet there's no ether

    b) does space have properties?

    c) Could something like the ether (but a new beast) exist as a property of space?
     
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  3. Mar 26, 2007 #2

    ZapperZ

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    Er.. Maxwell Equations do not "work" all the time. It is non-covariant under galilean transformation. In other words, if you're on an airplane and you see someone on the ground "applying" Maxwell equation to a phenomenon, your set of Maxwell equations will predict nonsensical results that won't match what you (or the other person) saw! That was the whole impetus for Einstein to examine it.

    Zz.
     
  4. Mar 26, 2007 #3
    Think about it this way Pythagorean, what would you gain by postulating some kind of ether?

    The theory of general relativity has shown that we can build a theory that does not require any notion of an ether.
    In that case Ockham's razor applies. :smile:
     
  5. Mar 26, 2007 #4

    Pythagorean

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    It's Occam's razor, and the postulation is that it could lead to new predictive ideas, in which Occam's razor becomes a personal decision (like I use Occam's razor with string theory, because I don't care about string theory, but I don't expect string theorists to use Occam's razor, because they're trying to find a way to make new predictions with it.)

    That makes a bit more sense. I'm only in my second semester of Electrodynamics and we're just now getting into retarded potentials in Griffith's. I'm assuming I'll learn more about this pretty soon then (I hope).
     
  6. Mar 26, 2007 #5
    I think it is more likely that his name was Ockham rather than Occam but that is an entirely different discussion. :smile:

    Anyway, if you can demonstrate we need some kind of ether in order to predict anything new, I am all eyes, but please forgive me for not holding my breath. :biggrin:
     
  7. Mar 26, 2007 #6

    Pythagorean

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    I'm not one of those people who asks questions on here because I want to argue it or convince people to go pursue this. I'm more looking for where my misunderstanding is coming from because I'm sure I'm not the first to wonder about this, and if it hasn't been changed, so all the wondering before me didn't mean anything I guess.

    I think it would be of cosmological interest if anything. It was more just a mild curiosity. In class, I wondered 'if ether was eliminated why didn't any adjustments have to be made to the displacement current?'.

    I'm not trying to revolutionize science or anything...
     
  8. Mar 26, 2007 #7
    Why not? :tongue:
     
  9. Mar 26, 2007 #8
    Correct me if I'm wrong, but I was under the impression that Maxwell's Equations will predict accurate results under a transformation of reference frame, but that the mechanisms may differ. The classical example I've heard is a bar magnet moving through a loop of wire. In the magnet's frame of reference, a magnetostatic explanation will show that the moving charges in the wire will undergo a Lorentz force and create a charge. Whereas in the wire's frame of reference, a changing magnetic flux through the loop will produce an electric field whose line integral around the loop is nonzero (resulting in a net EMF). Therefore in different reference frames, Maxwell's Equations falsely attribute the current through the loop to different phenomena, but predict an accurate result nonetheless.

    Is this correct?
     
  10. Mar 26, 2007 #9

    JasonRox

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    What journal did you get this published in? Because it sounds like complete rubbish to me.
     
  11. Mar 26, 2007 #10

    ZapperZ

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    I don't think so. I remember doing a couple of HW assignments eons ago whereby you use both newtonian laws (which are covariant under galilean transformation) and one of the maxwell equations, and the maxwell equation predict a different answer.

    Zz.
     
  12. Mar 26, 2007 #11
    Wait, I figured out what's going on. Maxwell's Equations are consistent with special relativity, not the Galilean transformations. Sorry, I guess I was confusing the Galilean and Lorentz transformations for awhile there.
     
    Last edited: Mar 26, 2007
  13. Mar 26, 2007 #12

    Pythagorean

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    who are you trying to mischaracterize here, just for clarity?
     
  14. Mar 26, 2007 #13

    JasonRox

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    Haha! Not you. :rofl:

    Just an imaginary person. :tongue:
     
  15. Mar 26, 2007 #14

    Pythagorean

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    ahhhhh....
     
  16. Mar 26, 2007 #15

    Stingray

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    To add a little to Zz's comments, people noticed that the experimentally-inspired equations of electromagnetism did not satisfy Galilean relativity. So it was assumed that the equations only held in a special reference frame which was called the ether. We were supposed to be moving slowly with respect to this frame (compared to the speed of light).

    Of course, that wasn't true. Einstein realized that it was possible to redefine the concept of a reference frame (and ideas of space and time) such that Maxwell's equations always worked.
     
  17. Mar 26, 2007 #16

    Pythagorean

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    So, I had an misunderstanding of what ether was. That's why I asked my other questions which went unanswered.

    So can we say that space has properties? that it's a thing? because it bends and curves?

    I remember Brian Greene talking about Newton's Bucket had some implications too, but I lost interest when he started going into string theory (in Fabric of the Cosmos)
     
  18. Mar 27, 2007 #17

    russ_watters

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    Yes, space has properties - just not the position/motion properties of a fluid medium.
     
  19. Mar 27, 2007 #18

    Pythagorean

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    Is studying the properties of space a relativity thing or an astronomy thing or what?
     
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