the Fizeau-Foucault experiment

The Fizeau-Foucault experiment measured the speed of light using rotating gears and mirrors. Light from a source is directed toward a mirror some distance away. It reflects back through a rotating wheel with teeth. If the wheel is stationary, light passes through and returns unchanged. When rotating, the teeth partially block or allow the light, depending on its speed. By adjusting the wheel’s rotation, researchers determined how fast light travels by observing when the returning light was blocked or allowed through. This experiment confirmed that light travels at a constant speed and helped establish that the speed of light is finite and measurable.