The video below shows a Foucault pendulum at the Science Museum of Virginia in Richmond. This device was conceived originally by French physicist Jean Bernard Léon Foucault in 1851 to demonstrate the rotation of the Earth. While the plane of oscillation of the pendulum remains constant, it nevertheless experiences an apparent deflection in its movement visualized here by the knocking down of the pegs on the ground. This deflection, which occurs clockwise in the Northern hemisphere and counterclockwise in the Southern hemisphere, is due to the rotation of the Earth under the pendulum. The deflection of the pendulum can also be used to calculate latitude.