Demonstrating Earth's rotation through pendulum plane precession
In 1851, French physicist Léon Foucault demonstrated Earth's rotation by suspending a 28 kg iron ball from a 67-meter wire in the Paris Panthéon. The pendulum's swing plane appears to rotate relative to the floor, but it's actually the floor (and Earth) rotating beneath it. The rate of precession depends on latitude—faster near the poles, zero at the equator.
At the North Pole, the plane completes a full rotation in about 24 hours. At Paris (48.9°N), it takes approximately 32 hours. In the Northern Hemisphere, the plane rotates clockwise (viewed from above); in the Southern Hemisphere, it rotates counter-clockwise.