If we derive the speed of light from the Maxwell equations we will find it's a function of the permittivity and permeability of the medium.

Now let's play with the thought that we are living in a substance that behaves like vacuum (eg. no mechanical drag) but have different permittivity and permeability, thus different speed of light.

If we would perform MM experiment inside that substance would it detect wind?

Or in other words can we distinguish between "real" and "fake" vacuum by testing the postulates of special relativity in it?


1 Answer 1


Yes it would. Indeed it has been done as this is exactly what Fizeau's water tube experiment shows.

The predicted magnitude of the effect is different for ether theories and special relativity, so the measurement can be used to show that SR is the correct description of the light propagation.


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