The Fizeau experiment, conducted by the French physicist Armand Fizeau in 1849, aimed to measure the speed of light in moving water. Fizeau directed a light beam toward a distant mirror and reflected it back through a rotating cogwheel placed in front of the light source. The light traveled through a tube filled with water flowing in the same direction as the light beam. By adjusting the rotation speed of the wheel, Fizeau could observe interference patterns. This allowed him to calculate the difference in the speed of light in still water and moving water. The Fizeau experiment provided early evidence supporting the wave theory of light and contributed to our understanding of the propagation of light in different media.