The 1887 Michelson–Morley experiment found no significant change in light’s travel time as the apparatus orientation changed. The null result failed to reveal the expected effect of Earth moving through a hypothetical luminiferous aether.
Albert A. Michelson and Edward W. Morley used an interferometer to compare light traveling along perpendicular paths. If an aether wind affected light speed, rotating the instrument should have shifted the interference fringes. The predicted shift was not observed at the expected scale.
The result did not instantly prove special relativity or cause the aether idea to disappear. Physicists proposed additional explanations, including length contraction. In 1905, Einstein’s special theory of relativity made the aether unnecessary by treating the speed of light in vacuum as invariant for inertial observers.
The experiment is often described as proving that Earth’s motion had no effect on light. More precisely, it placed a strong limit on the expected directional variation under the classical aether model.