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The Foucault Pendulum

A prominent feature of the General Assembly Lobby is the Foucault pendulum, given by the Netherlands to the United Nations in 1955. The Foucault pendulum, named after the French physicist Jean Bernard Leon Foucault, gives visual proof of the rotation of the Earth.

It consists of a gold-plated sphere, partly filled with copper, suspended from the ceiling 75 feet above by a stainless steel wire. A universal joint allows it to swing freely in any direction. An electromagnet under the pendulum counteracts the friction in the air, thus keeping the pendulum swinging uniformly. During the course of a day, the direction in which the pendulum swings appears to change due to the rotation of the Earth. It takes the sphere 36 hours and 45 minutes to complete its cycle.

Copyright 2001 United Nations