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No existence of the aether

  1. Nov 23, 2008 #1
    While it is widely accepted that there is no existence of the aether, what does this say about Dirac's argument which contradicts mainstream belief? This comes about 50 years after it was suggested that there was no aether. Is this a special case?

    I was told that aether theory is not excluded by experiments or theoretical reasons, it is just relatively ugly.

    So to say that the Michelson-Morley experiment disproves the luminous aether too strong of a statement?
  2. jcsd
  3. Nov 24, 2008 #2


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    Re: Aether

    The MM experiments exclude a classical aether which would cause 'aether drag'. If there were an aether that did not cause this, we could not detect it, it would have no effect on measurements, and thus it would be pointless to include it in any theory.

    There is some speculation that the quantum vacuum, with its zero-point fields could be a sort of aether for light etc to propagate through - but that's off the mainstream.
  4. Nov 24, 2008 #3


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    Re: Aether

    Mentz114, maybe you meant 'ether drift'. MM experiments would be perfectly consistent with the earth dragging along a bubble of ether. Ether drag seems to be incompatible with other experiments (stellar aberration?), but not with MM ones.
  5. Nov 24, 2008 #4


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    Re: Aether

    The Michelson-Morley experiment disproved the original "Galilean" notion of an aether, but Lorentz and others were able to formulate a modified version of the aether that was compatible with Michelson-Morley.

    Einstein came along with his own interpretation which rendered the Lorentzian aether unnecessary. He didn't actually disprove it; he provided another explanation that almost everyone (eventually) found simpler and aesthetically superior. Lorentz's aether theory and Einstein's relativity were mathematically equivalent but philosophically very different. Einstein's postulates naturally cover the whole of physics, whereas Lorentz's theory needed to be separately adapted to each branch of physics.

    The problem with Lorentz's version of the aether was that there was no way of detecting it. We didn't know how fast we were moving relative to it, and it didn't matter because we got the same answer regardless. Something that couldn't be detected and whose speed didn't matter seemed a redundant concept, when there's another theory (Einstein's) that gives the same answer without it.

    I know nothing about Dirac's "aether", but a quick Google suggests his notion was something different altogether from Lorentz's aether; it just happened to use the same name, I think.

    I agree, MM itself doesn't disprove dragging of a Galilean aether, but dragging would cause "refraction" that could be (but isn't) astronomically observed.
  6. Nov 24, 2008 #5


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    Re: Aether

    Nomenclature aside, the effect I was referring to is when changing our direction wrt to the aether would result in different relative speeds of light. Drift or drag, I don't know ( nor does it matter in the light of subsequent remarks).
  7. Nov 24, 2008 #6
    Re: Aether

    Closely related to this description is the fact that aether theory led to no other key insights, nothing else seemed to be resolved except (maybe) the constant speed of light. Einstein's theory, in contrast, did lead to all sorts of new insights a number of which could be experimentally proved..length contraction and time dilation in special relativity, the curving of light in gravitational fields in general relativity, the orbit of mars, for example.
  8. Nov 24, 2008 #7


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    Re: Aether

    "Dirac's argument which contradicts mainstream belief?"
    Dirac had many theories, but which argument are you referring to?
  9. Nov 24, 2008 #8
  10. Nov 24, 2008 #9
    Re: Aether

    This thread will soon be closed and anyone who posted here will receive infractions, but I am going to post this anyways because I find this topic very interesting and believe the purpose of this forum is to discuss and learn about topics such as this one.

    Have a look at some of Fresnel's work in aether from respected and peer-reviewed sources.

    http://journals.royalsociety.org/content/33k51640261jm242/ [Broken]


    Some of his work addresses this question and not surprisingly, some of it concurs with special relativity.

    No it isn't. A lot of physicists did work in aether but as what was suggested above, it didn't provide much insight into anything so it was abandoned. Tesla, for example used the theory of aether to explain many of his experiments even though mainstream science had already adopted GRT and SRT.

    Also, aether hasn't been entirely abandoned. It's still under investigation by a select few. For example this recent publishing (2008) from the APS,

    http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000100000015153902000001&idtype=cvips&gifs=yes [Broken]
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