A swinging weight in Paris proved the Earth turns

In 1851, physicist Léon Foucault hung a 28-kilogram bob from a 67-meter wire in the Panthéon in Paris and let it swing freely. Over hours, its path appeared to rotate relative to the floor, not because the pendulum changed course but because the building slowly turned beneath it. It was the first experiment to demonstrate Earth's rotation using ordinary mechanics rather than astronomical observation.

— Léon Foucault, Foucault pendulum — Demonstrated at the Panthéon, Paris, 1851