The fascinating thing about the Michelson-Morley interferometer experiment is that they were attempting to validate the aether hypothesis, and measure the Earth

The fascinating thing about the Michelson-Morley interferometer experiment is that they were attempting to validate the aether hypothesis, and measure the Earth's absolute velocity relative to the aether. Instead they failed to do so, and the experiment showed that the speed of light is the same in all directions relative to all observers regardless of motion. A quite shocking and non-intuitive result that served as a foundation for the theory of relativity. Even today most non-scientists do not understand or appreciate this result, they still operate within a mental model of the universe involving absolute frames of reference.