 Michelson-Morley experiment

An interferometer compares round-trip light travel times along perpendicular arms as its orientation changes. The absence of the classical stationary-aether fringe shift at the expected scale constrains orientation dependence of the round-trip speed of light. The result is consistent with special relativity, but alone does not select it uniquely from every alternative theory.^[ref]

The instrument's stone support and floating mounting allowed the experimenters to change its orientation while limiting mechanical disturbance. The measured quantity was the fringe shift produced as the apparatus rotated, rather than a direct timing of a single light pulse.^[ref]

The Michelson-Morley experiment, conducted in 1887 by Albert A. Michelson and Edward W. Morley, is one of the most famous experiments in physics, primarily designed to detect the existence of the luminiferous aether—a hypothetical medium through which light waves were thought to propagate, much like sound waves travel through air. ### Purpose of the Experiment: The experiment aimed to measure the Earth's motion through this aether.

Published as On the Relative Motion of the Earth and the Luminiferous Ether.