Editing Luminiferous aether (section)

===Aether drag===
{{Main|Aether drag hypothesis}}
The two most important models, which were aimed to describe the relative motion of the Earth and aether, were [[Augustin-Jean Fresnel]]'s (1818) model of the (nearly) stationary aether including a partial aether drag determined by Fresnel's dragging coefficient,<ref group=A name=fresnel /> and [[George Gabriel Stokes]]' (1844)<ref group=A name=stokes />
model of complete aether drag. The latter theory was not considered as correct, since it was not compatible with the [[aberration of light]], and the auxiliary hypotheses developed to explain this problem were not convincing. Also, subsequent experiments as the [[Sagnac effect]] (1913) also showed that this model is untenable. However, the most important experiment supporting Fresnel's theory was [[Hippolyte Fizeau|Fizeau]]'s 1851 [[Fizeau experiment|experimental confirmation]] of [[Fresnel]]'s 1818 prediction that a medium with [[refractive index]] ''n'' moving with a velocity ''v'' would increase the speed of light travelling through the medium in the same direction as ''v'' from ''c''/''n'' to:<ref group=E name=Fizeau1 /><ref group=E name=michel2 />

{{block indent|<math>\frac{c}{n} + \left( 1 - \frac{1}{n^2} \right) v.</math>}}

That is, movement adds only a fraction of the medium's velocity to the light (predicted by Fresnel in order to make [[Snell's law]] work in all frames of reference, consistent with stellar aberration).  This was initially interpreted to mean that the medium drags the aether along, with a ''portion'' of the medium's velocity, but that understanding became very problematic after [[Wilhelm Veltmann]] demonstrated that the index ''n'' in Fresnel's formula depended upon the [[wavelength]] of light, so that the aether could not be moving at a wavelength-independent speed. This implied that there must be a separate aether for each of the infinitely many frequencies.