Implications of negative Michelson-Morley result

[cianfa72]

In the MM experiment, assuming the existence of aether, the analysis is carried out using the Galilei-Newton model of spacetime that boils down to the existence of an absolute time $t$ (spacetime is an affine fiber bundle over the absolute time $t$) .

The experimental negative results imply one of the following:

1. the Galilei-Newton spacetime model is not appropriate to describe the physical world
2. the aether actually does not exist and the principle of relativity extends also for light propagation (speed of light does not depend on source velocity -- like the sound -- and it is inertial-frame invariant $c$)

As far as I can understand, point 2. is incompatible with point 1. therefore forces us to give up it and assume the spacetime with a different structure (i.e. Minkowski structure).

By the way, if we assume point 1. true, is possible to develop a theory consistent with the aether existence ?

 

[Vanadium 50]

@cianfa72, this is based on incorrect assumptions.

The experiment measured the "ether wind" - the speed of the ether with respect to the apparatus. It measured zero. Six months later, it still measured zero, but now the earth is moving in the other direction.

"There is no ether" is one possible explanation. "The earth drags the ether with it as it moves".

As a general rule, it's not good to post things you are not sure of in other people's threads.

 

[cianfa72]

"The earth drags the ether with it as it moves".

Do you mean the above is another possible explanation for the MMX's experimental results ?

 

[Ibix]

Do you mean the above is another possible explanation for the MM's experimental results ?

Yes.

 

[cianfa72]

"The earth drags the ether with it as it moves".

Ok, therefore in principle we could retain the Galilei-Newton spacetime model by combining it with the Earth's aether dragging hypothesis.

 

[Histspec]

Do you mean the above is another possible explanation for the MM's experimental results ?

Another example: The Fitzgerald-Lorentz contraction hypothesis was initially introduced in order to save the "stationary" aether from being refuted by MMX.
This should remind us that one experiment (such as MMX) alone can never be the reason for adopting a theory. Indeed, the strength of special relativity lies in the fact, that it not only explains MMX, but a range of very different experiments without introducing auxiliary hypotheses.

 

[Ibix]

Ok, therefore in principle we could retain the Galilei-Newton spacetime model by combining it withe the Earth's aether dragging hypothesis.

...if it weren't for all the other lines of evidence like stellar aberration and Fizeau's experiments with water. Michelson-Morley is a key plank in ruling out ether hypotheses, but it is not sufficient on its own.

 

[cianfa72]

Michelson-Morley is a key plank in ruling out ether hypotheses, but it is not sufficient on its own.

Just to be clear: the Earth's aether dragging hypothesis is compatible with the principle of special relativity (restricted to inertial frames).

 

[Ibix]

the Earth's aether dragging hypothesis is compatible with the principle of special relativity

No. The speed of light is only isotropic in the ether rest frame just like in a naive ether model, but experiments attached to the Earth's surface are at rest in that frame if the ether is dragged by Earth. Thus the Michelson-Morley experiment would give a null result.

 

[cianfa72]

No. The speed of light is only isotropic in the ether rest frame just like in a naive ether model, but experiments attached to the Earth's surface are at rest in that frame if the ether is dragged by Earth. Thus the Michelson-Morley experiment would give a null result.

Ah ok, so if we switch to an another inertial frame coasting with constant velocity w.r.t. the inertial rest frame of the Earth (the aether dragged by Earth), then the light propagation process will not be longer isotropic and occurring with the same fixed speed $c$ (as measured in that inertial frame).

 

[Ibix]

Presumably, yes.

 

[A.T.]

Do you mean the above is another possible explanation for the MMX's experimental results ?

Here is a possible explanation for the MMX's experimental results, that was falsified by other experiments:
https://en.wikipedia.org/wiki/Emission_theory_(relativity)

 

[cianfa72]

Coming back to the null MMX result, one can claim that it experimentally confirms (or at least is compatible) that the two-way speed of light is isotropic (even though it might be in principle not frame invariant).

Then one of the postulate of Einstein's SR claims that such a two-way speed of light is actually frame invariant too.