Michelson had a vision to detect the absolute motion of the Earth using light. The theory of light propagation depends on what was known about the transmission of any energy in some present medium. It is based on observance of macro wave phenomenon in nature. We understand how sound is transmitted in water, air, and solids. We can see how energy is transmitted in waves when a stone is dropped in a still pond. For light to transmit energy in a vacuum, it was a general consensus that a medium must be present. That medium was named the "aether". It was assumed to be very tiny, undetectable, and motinonless, with bodies moving frictionless thru it. As such it represented an absolute reference frame. Michelson reasoned that the velocity of a body could be added and subtracted to the velocity of light rays emitted from the body, assuming Euclidean geometry, or Galilean Relativity, applies. In order to detect this, he invented the interferometer.
Here is a Diagram of the interferometer:
To improve performance, light bounced up and down the legs of the device several times.
The goal was to detect the Earth's velocity in the ether, or an absolute reference frame. Assuming the Earth's motion around the Sun, testing was done at 6 month intervals to get a relative speed difference between the two. This picture from the Journey Movie draws all the elements together.
And this depiction:
Michelson started tests in 1881. It was surmised that the westbound beam would travel slower, according to the assumptions of the Fresnel Drag Theory of the ether at the time, and the light beams would develop a large interference pattern. This diagram depicts the two light beams one travelling into the ether movement and the other perpendicular. This axis of the interferometer would be pointing to the North Star during the experiment
The Earth's velocity is supposed to be about 66000mph. He was unable to detect this velocity but did get a small nominal shift however indicating some small detectable amount of motion. This is thought to be a wobble in the rotation of the universe around the earth, in the Geocentric theory. This small motion was completely ignored by Einstein in the development of the Special Relativity Theory and all of modern science for the most part. The slight motion detected was said to be a "Null Result", but is strange to ignore since it is large compared to the apparatus' high level of precision, down to fractions of light wavelength. But it essentially confirmed Airy and Arago's experimental results of the earth not moving, undermining the Copernican Principle. Published in American Journal of Science, 1881, Michelson states:
Morely joined him improving the device and completed the experiment in 1887.
19th century scientists always seemed to at least talk about the Tycho-Ptolemy concept of the Earth at the center of the universe, as if their experiments showed it. By the 20th Century, the concept of small objects in space orbit big objects seems to have complete control of the thinking process. When I received my physics degree in 1973, the consensus reached was that the Michelson and Morely experimental results showing a so-called Null effect (not true) meant that there was NO ether and no absolute reference frame. Light self propagated thru a pure vacuum, no medium required. Special relativity ruled, then, with light speed a constant independent of inertial reference frames (i.e. motion, v+c was a no-no), and objects simply shrank in the direction of motion, with no explanation or causal effect. Einstein said it was just a property of matter. They could not bring science to the possibility that the Earth was motionless and of course light needed a medium to propagate. Instead they ran to adopt Relativity, comprised of un-provable adhoc explantion after adhoc explantion that are a total violation of causal science, undermining scientific method, essentially illogical and insane. Object shrink with relative speed? Preposterous. Even though Special Relativity is embedded in calculations of any scientific experiment requiring light measurement today, this effect of shrinking object lengths has never been shown or detected in an independent test. Time dilation experimental results are questionable. It is easily disproven by a simple thought experiment with its Twin Paradox. The use of special relativity to explain Mercury's orbit discrepancies from the classical Newtonian gravity equations was touted as proof by Einstein, but there are many better explanations ( M. Bowden Relativity Fraud @ 10:28
Lorentz at least tried to explain the length contraction as forced by ether pressure. But this is contradictory to simple observations of objects in motion tend to stay in motion thru the ether, and therefore must be frictionless, But as the rise of quantum mechanics took hold, we have learned now of the quantum void, quantum vacuum, quantum foam and the zero point energy field, where one cup of normal vacuum of space contains enough energy to boil all the water off the face of the Earth several times over. They actually had to give it another name kowtowing to Special Relativity taking it away. But this is the ether by any other name, and it is back, make no mistake. They figure that the size of an ether particle is 10 to the -33 cm, a Planck distance. With nuclei and electrons at 10 to -13, this object is still 20 orders of magnitude smaller. You can only imagine the particles of course can pass thru matter as we know it quite easily, as if we are a ghost to it.
Recapping, so as long as we continue to find proof that the ether exists as the light propagation medium, all experiments with light by Arago, Airy, Fresnel, Fizeau, Michelson, Morely, Sagnac, and Gale have found that the Earth does not move through it with any appreciable velocity. Funny how Einstein just declared with Relativity that you cannot use light to find absolute motion, there is no such thing as an absolute reference frame, the speed of light is constant and not dependent on the speed of the emitter, that the ether doesn't exist, that time dilates, length contracts, and mass increases with velocity, and it is desperately embraced in order to avoid the dreaded conclusion of a motionless Earth, when to do so is in complete violation of causal science and scientific method. When you really think about it, it truly is the Bizzaro fantasy they have us believing in...
Pictures from the Journey Movie