The Michelson-Morley Experiment

The Michelson-Morley experiment, conducted in 1887, aimed to detect Earth's motion through the "aether," a hypothetical medium thought to carry light waves. They used a special device called an interferometer to compare the speed of light in different directions. If Earth moved through the aether, the light's speed should vary depending on direction. Surprisingly, the experiment found no difference, suggesting no such aether exists. This result challenged existing ideas and was a key step toward Einstein's theory of special relativity, which explains that the speed of light is constant for all observers.