"The Michelson–Morley experiment, one of the most important and famous experiments in the history of physics, was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University. It is generally considered to be the first strong evidence against the theory of a luminiferous aether.
At any given point on the Earth's surface, the magnitude and direction of the aether wind would vary with time of day and season. By analyzing the return speed of light in different directions at various different times, it was thought to be possible to measure the motion of the Earth relative to the aether.
Instead of providing insight into the properties of the aether, Michelson and Morley’s article in the American Journal of Science reported the measurement to be as small as one-fortieth of the expected displacement but “since the displacement is proportional to the square of the velocity” they concluded that the measured velocity was approximately one-sixth of the expected velocity of the Earth’s motion in orbit and “certainly less than one-fourth.” Although this small “velocity” was measured, it was considered far too small to be used as evidence of aether, and it was later said to be within the range of an experimental error that would allow the speed to actually be zero."
So with the 'failure' of this experiment, scientists moved away from the idea of a luminiferous aether (which is a bit of a shame as it's such a lovely pairing of words). Spacetime replaced the luminiferous aether. Now that spacetime has been disproved (well, for me anyways) - I wonder if we should return to some of the old ideas, and experiments, regarding the mysterious luminiferous aether.
It appears Newton thought that the aether IS the vaccum...."Is not the heat of the warm room convey'd through the vacuum by the vibrations of a much subtler medium than air, which after the air was drawn out remained in the vacuum?"
It also appears that Einstein still maintained thoughts about the qualities of the aether, even as he replaced it with spacetime - "Einstein's conclusion about the existence of Ether after he developed the General relativity - a fact missing in the scholar Physics textbooks. In 1920 Albert Einstein stated :
page 16: But on the other hand there is a weighty argument to be adducted in favor of the ether hypothesis. To deny the ether is ultimately to assume that empty space has no physical quality whatever. The fundamental facts of (quantum) mechanics do not harmonize with this view.
page 23: Recapitulating, we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense."
In the late 19th century, Maxwell's equations of electromagnetism were formulated. They predicted that the speed of light (and of electromagnetic waves in general) in vacuum is 300,000 km/s. In a Universe where light can travel at any speed, why does light choose to travel in a vacuum at 300,00km/s? Could it be that a luminiferous aether regulates the speed at which electromagnetic radiation travels in a vacuum? Is the aether only applicable within the Schumann cavity - or perhaps the Earth's magnetic field - or even the solar system's magnetosphere? ( I guess one more question on the pile won't hurt) - Is the luminiferous aether illustrating the electric effect of the Sun upon the Earth?