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What is aether (ether) actually? Is it space-time fabric curve or is it anti-matter? If not this what is it then, does it exist? Why is the concept disregarded after Einstein's theory of Relativity? But Ether experimentally satisfies maxwell's equation and is it due to ether we define relative permitivity?

Qmechanic
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DASH_quanta
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It is some hypothetical material substance that permeates the universe. More precise definition depends on the particular theory of aether.

With regard to electromagnetism its hypothetical material substance in which electromagnetic waves propagate in analogy to propagation of waves in water or sound in air. Because Maxwell theory is not invariant under Galilean transformations, the equations are written only for one particular frame of reference. The aether was supposed to define this frame.

The problem is, that if Maxwell equations pick out one special reference frame in which they are written, we should expect electromagnetic phenomena to work differently in different inertial frames. This was not observed. Moreover, Einstein showed, that we can write the EM theory without aether. Because we didnt find preferred inertial reference frame and we managed to explain electromagnetism without aether, we have no need for it and dropped the idea of aether as useless. Its not that it was refuted, we just realized it is unobservable and it needlessly complicated the theory and we stopped using it.

This is of course in the light of special theory of relativity. I do not know whether aether idea can be kept alive in quantum field theory or general relativity or if these two theories actually refute the idea of aether altogether.

Umaxo
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  • " Its not that it was refuted", and what about the Michelson Morley experiment that destroyed the concept of the luminiferous aether?https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment . It is not all thought experiments ! – anna v Jun 09 '21 at 12:17
  • @annav Michelson Morley experiment is well explained by Lorentz-Maxwell theory, that refers to the special reference frame (i.e. aether frame). In this theory, the clocks and measurement apparatus gets dilated/contracted in different frames due to the fact that they work on EM principle and EM field gets deformed in different frames in just a way to make the special inertial frame unobservable. Mathematically its equivalent to STR (as far as I know - I read only one book that talks about this, The Special Theory of Relativity by David Bohm). – Umaxo Jun 09 '21 at 12:30
  • "The MM experiment was performed between April and July 1887 " , they , E and B,just justified the measured effect with mathematics. in 1917 Einstein was born in 1879 and Bohm in 1917, – anna v Jun 09 '21 at 12:42
  • @annav can you state your point explicitly? – Umaxo Jun 09 '21 at 12:44
  • That it was the experiment by MM that refuted the luminiferous ether, not theoretical reformulations that came to justify the experimental measurement. – anna v Jun 09 '21 at 12:46
  • @annav I dont understand your argument. If something refutes something, the timestamp is irrelevant. It either does it or does not. Proponents of aether theory made a prediction before 1887, this prediction was refuted by the experiment. Then Lorentz (and others) came and realized they did not account for an influence the earth movement has on our clocks and metersticks and all EM fields in general and updated the prediction. I am not denying that MM refuted the original prediction, I am just saying that it did not refute the aether. – Umaxo Jun 09 '21 at 12:59
  • well, " Einstein's use of the word "aether" found little support in the scientific community, and played no role in the continuing development of modern physics." https://en.wikipedia.org/wiki/Luminiferous_aether#Einstein's_views_on_the_aether is what I am talking about. – anna v Jun 09 '21 at 13:17
  • Sorry I didnt knew my question was so bas that I got -3 votes – DASH_quanta Jun 11 '21 at 11:53