pendulum with a long wire; can swing in any direction; the change in the swing plane demonstrates the earth's rotation
A pendulum that varies in the direction of its swing as the Earth rotates. Used to demonstrate that it is Earth that rotates and not the sky.
A Foucault pendulum is a simple pendulum (a weight on a long string attached to a support) that tracks the rotation of the Earth. As the pendulum swings, the Earth rotates under the pendulum, so the pendulum seems to rotate. It was first demonstrated by Jean Bernard Léon Foucault, in 1851 at the Paris World's Fair.
A pendulum with precession, relative to an observer fixed to the earth, produced by the effect of Coriolis acceleration. If set swinging at the North Pole in a given plane in space, its linear momentum perpendicular to the plane is zero, and it will continue to swing in this invariable plane while the earth rotates beneath it with a period of one day. At a latitude L, the frequency of precession is 1/T sin L where T is one day.
The Foucault pendulum, or Foucault's pendulum, named after the French physicist LÃ©on Foucault, was conceived as an experiment to demonstrate the rotation of the Earth; its action is a result of the Coriolis effect. It is a tall pendulum free to oscillate in any vertical plane and ideally should include some sort of motor so that it can run continuously rather than have its motion damped by friction. The first Foucault pendulum exhibited to the public was in February 1851 in the Meridian Room of the Paris Observatory, although Vincenzo Viviani had already experimented with a similar device in 1661, .