For 10 points, name this now-discredited theoretical substance that was thought to be the medium that carries light.
This substance's namesake "drag theory" gained support in the Fizeau experiment. Lorentz transformations were first proposed to scale from this substance's "rest system" to a "moving system." The existence of this substance was discredited by the null result of the Michelson-Morley experiment. For 10 points, name this now-discredited theoretical substance that was thought to be the medium that carries light.
This substance's namesake "drag theory" gained support in the Fizeau experiment.
{luminiferous ether} [or {aether}]