Last modified on August 20, 2019, at 13:19

Foucault's Pendulum

Diagram of a simple pendulum showing the amplitude of its swing.
The precession of the plane of a Foucault pendulum. The speed of the precession is highly exaggerated.

Foucault's pendulum is a weight, usually a sphere, suspended by a wire that is attached at the ceiling with a joint that allows the weight to swing in any direction.

The motion of this pendulum proves that the earth is rotating underneath the pendulum. The angle of the rotation of the pendulum per hour remains fixed at any location and equals:

where q is the latitude of the observer. At the equator, the plane in which the pendulum moves does not change.

The physicist Jean Bernard Léon Foucault demonstrated this in the church Le Pantheon in Paris in 1851.

Other uses

Foucault's Pendulum is also the English name for an Italian novel by Umberto Eco.