A swinging weight in a Paris dome gave the first direct proof the Earth spins

Copernicus and Galileo had argued the Earth rotates, but no experiment had shown it directly. In 1851, Léon Foucault suspended a 28kg pendulum from the dome of the Panthéon and let it swing freely for hours. Its path slowly rotated relative to the floor beneath it, not because the pendulum turned, but because the building, and the whole Earth, was turning under it.

— Léon Foucault, Physical Demonstration of the Rotation of the Earth — 1851, Panthéon, Paris