<human>:  When did the Michelson-Morley experiment take place?
<bot>: The Michelson-Morley experiment was conducted in 1887. The experiment measured the speed of light by bouncing light off of mirrors that were oriented perpendicular to the direction of the light. The experimenters found that the speed of light was the same regardless of the orientation of the mirrors. This experiment is still considered to be one of the most accurate measurements of the speed of light.