The Michalson Morely experiment is famous for "disproving" the ether.
The ether theory goes back to alchemical days, and it was thought of as a scientific theory by Descartes, that it is the medium that light travels on.
It said that assuming the earth is moving, there should be a ether drift. There was no ether drift. The conclusion has to be either
1. That there is no ether
2. That we are on a stationary earth.
Because people assume the earth is moving they assume there is no ether.
However many scientist, including the inventor of vector calculus Oliver Heaviside, stated that there was an ether, and therefor transverse electromagnetic waves. Other scientist during the 20's and 30's stated there has to be a medium that light travels on. In maxwells equations the "displacement current" is used to describe how electricity can travel across a vacuum tube or capacitor with nothing but vacuum inside. How can electricity and light travel over vacuum or empty space? Light and electricity create force. So in a vacuum there must be a reactionary force to balance the forces. How can empty space or vacuum have a reactionary force as per Newton's laws, if there is nothing there.
Therefore there must be an ether, to react to the forces of light or electricity in a vacuum. Therefore we must be living on a stationary earth as per the Michalson Morely experiments!