Why all classical physicists expected light speed to vary...and why they were wrong.
The ONLY reason why classical physicists were expecting to see a variance in the speed of light for moving observers was because they were illogically applying Galileean relativity to waves, and added the speed of the observer to the speed of the wave, thus getting c+v or c-v as the speed of the wave in the observer's frame. If they didn’t all do that foolish thing, they would have NOT expected the speed of light to vary for moving observers ! Which means that, if they correctly understood and applied classical physics, they should have expected it to NOT vary, aka INVARIANCE instead of VARIANCE ! The latter is clearly wrong from a classical physics framework because the speed of the wave only depends on the properties of the medium, and because the wave has a PREFFERED FRAME which is the rest frame of the MEDIUM. Therefore it is illogical to use the rest frame of the Observer as the preffered frame of the wave, and then use Galileean additions to calculate the speed of the wave....