Editing Michelson–Morley experiment (section)

=== Most famous "failed" experiment ===
[[File:Michelson Morley 1887 Figure 6.png|thumb|300px|Michelson and Morley's results. The upper solid line is the curve for their observations at noon, and the lower solid line is that for their evening observations. Note that the theoretical curves and the observed curves are not plotted at the same scale: the dotted curves, in fact, represent only one-eighth of the theoretical displacements.]]
After all this thought and preparation, the experiment became what has been called the most famous failed experiment in history.<ref group=A name=blum /> 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 (Fig.&nbsp;7), but "since the displacement is proportional to the square of the velocity" they concluded that the measured velocity was "probably less than one-sixth" of the expected velocity of the Earth's motion in orbit and "certainly less than one-fourth".<ref name=michel2 /> Although this small "velocity" was measured, it was considered far too small to be used as evidence of speed relative to the aether, and it was understood to be within the range of an experimental error that would allow the speed to actually be zero.<ref group=A name=staley /> For instance, Michelson wrote about the "decidedly negative result" in a letter to [[Lord Rayleigh]] in August 1887:<ref group=A name=shankland2 />

{{Quote|The Experiments on the relative motion of the earth and ether have been completed and the result decidedly negative. The expected deviation of the interference fringes from the zero should have been 0.40 of a fringe – the maximum displacement was 0.02 and the average much less than 0.01 – and then not in the right place. As displacement is proportional to squares of the relative velocities it follows that if the ether does slip past the relative velocity is less than one sixth of the earth’s velocity.}}

From the standpoint of the then current aether models, the experimental results were conflicting. The [[Fizeau experiment]] and its 1886 repetition by Michelson and Morley apparently confirmed the stationary aether with partial aether dragging, and refuted complete aether dragging. On the other hand, the much more precise Michelson–Morley experiment (1887) apparently confirmed complete aether dragging and refuted the stationary aether.<ref group=A name=Jan /> In addition, the Michelson–Morley [[null result]] was further substantiated by the null results of other second-order experiments of different kind, namely the [[Trouton–Noble experiment]] (1903) and the [[experiments of Rayleigh and Brace]] (1902–1904). These problems and their solution led to the development of the [[Lorentz transformation]] and [[special relativity]].

After the "failed" experiment Michelson and Morley ceased their aether drift measurements and started to use their newly developed technique to establish the wavelength of light as a [[Length measurement|standard of length]].<ref name=michel3 /><ref name=michel4 />