Foucault pendulum

For the novel Foucault's Pendulum by Umberto Eco, See Foucault's Pendulum (book).

Foucault's Pendulum in the Panthéon, Paris

A Foucault pendulum, or Foucault's pendulum, is a tall pendulum free to oscillate in any vertical plane and capable of running for many hours. Its significance is that its motion demonstrates the Coriolis force and the rotation of the Earth. It is named after its inventor Léon Foucault, and was first exhibited in 1851 from the ceiling of the Pantheon in Paris.

At almost any location on Earth, it can be observed that the plane within which the pendulum swings slowly rotates. At either the North Pole or South Pole the plane of oscillation of a pendulum rotates once per sidereal day (in essence, the pendulum remains in the same plane while the Earth rotates underneath it). At other latitudes, the plane of oscillation of a pendulum rotates with an angular speed proportional to the sine of its latitude; thus one at 45° rotates once every 1.4 days and one at 30° every 2 days. At the equator the plane does not rotate at all.

External links

• "The Foucault Pendulum". California Academy of Sciences.
  • "About Foucault pendulums". California Academy of Sciences, 2003.
• "Foucault Pendulum". Smithsonian Institution.
• "South Pole Foucault Pendulum". Winter, 2001.
• Weisstein, Eric W., "Foucault's pendulum".