I was recently reading about how physicists were heavily relying on the existence of Luminiferous Aether for their physics to work. I read about how the Michelson-Morley experiment attempted to prove the existence of the Luminiferous Aether by causing different light beams to travel upwind and downwind in a way that would create a shift in the interference pattern, that is if the ether existed.
Bare with me for a second and pretend that the ether actually existed and that the experiment was successful and showed the desired results. I still don't understand how this would prove the existence of the ether.
I mean, the results definitely seem to agree with the theory of the Luminiferous Aether but it doesn't necessarily prove it. Because if the ether wind didn't exist, shouldn't the shift in the interference pattern be observed either way because the earth, the mirrors, and the detectors all move relative to the light beams and (considering the speed of light respects the Principle of Galilean Relativity) depending on the direction of movement of Earth, the light beam would pick-up or lose speed c +/- v.
What I mean is, in a sense, after the light beams have been 'launched' from their sources, and due to the movement of the Earth, one of the mirrors would 'move' closer to the light beam, and hence decreasing the distance the light needs to travel, while the other mirror moves further and hence increasing the distance the light needs to travel.
So basically light, if it followed the Principle of Galilean Relativity as was postulated back then, would experience some form of 'earth movement shift', regardless of whether the ether existed or not.
What am I missing? Did they consider that the 'launched light' would have some original velocity added to it due to the movement of Earth, treating light as some sort of mechanical particle, and therefore the 'Earth shift' wouldn't matter and the results would point directly to the Ether Wind?
Or alternatively, if light was proven to follow Galilean Relativity, was there any consequential relationship between the principle of Galilean Relativity and the Luminiferous Aether that would prove the existence of the ether once light was noticed to follow Galilean Relativity?