A History of the Aether in Physical Theory: Part III
Michelson-Morley
Click Here for an explanation of the Michelson-Morley Experiment.

Maxwell's Proposal
Shortly before his death, Maxwell argued that the only way to measure the earth’s velocity with respect to the
aether in a laboratory experiment is to look for variations in the velocity of light travelling back and forth between
two mirrors. He had thought of an astronomical determination of the solar system’s velocity with respect to the
ether, in which the effect to be measured was of order v/c.

Expectations from a Motionless Aether
If the aether is motionless, as Maxwell said it must, then all other matter, such as planets, such experience a
drag force. On earth we should be able to detect and aether "wind" as the earth moves through the aether. The
inverse motion of the ether with respect to the earth is often called the “ether drift".

The Null-Result
The experiment thus produced only a null result: no change in the speed of light was detected. In other words, it
failed to detect the motionless aether.

Michelson's (Correct) Interpretation
"The interpretation of these results is that there is no displacement of the interference bands. ... The result of the
hypothesis of a stationary ether is thus shown to be incorrect." (A. A. Michelson, Am. J. Sci, 122, 120 (1881))

Its Effect on the Aether Concept
The null result of the Michelson-Morley experiment--the non-detection of the aether wind, and thus the non-
detection of the motionless aether--was a fatal blow to the (monolithic) aether concept. Many attempts were
made, and continue to be made to salvage the aether concept, most notably, by Lorentz and Fitzgerald. These
attempts ultimately failed, and continue to fail, because the aether was and is (still) supposed to be monolithic
and the speed of light constant.
Lorentz-Fitgerald to Einstein