posted by Tom Hu .
What is the Michelson and Morley experiment?
Please don't give me Wikipedia
It was an experiment to determine if the speed of light depends upon the direction of the light. Until then, it was believed that light consisted of vibrations in a massless fluid called ether that fills the universe. If this were true, the Earth would be travelling through it with some velocity, and the speed of light would depend upon the direction of the light compared to that of the Earth's motion.
No dependence upon direction was found. The experiment helped support Einstein's Theory of Relativity.
I am sure you can find many links that describe how the experiment was done, including the one Ms. Sue provided.