Michelson-Morley Experiment
If light is a wave in some medium (ether) then if the earth moves in the ether it should be detectable
If Newton’s laws are correct the earth “moves” around the sun:
In 1887 Michelson & Morley do experiment to try to measure the velocity of the earth with respect to (wrt) the “ether”
Testing key ideas: Does the ether exist, as appears to be required by electromagnetic waves? Can we measure the “absolute motion of the earth”?