United Nations Photo

A view of the Foucault Pendulum which is installed in the main lobby of the General Assembly building at United Nations Headquarters in New York, showing the 200-pound gold-plated sphere suspended from the ceiling 75 feet above the floor of the lobby and over a raised metal ring, some six feet in diameter and containing an electromagnet in the centre.

A gift to the U.N. from the Government of the Netherlands, the Pendulum offers visual proof of the rotation of the earth. The sphere, 12 inches in diameter, is held by a stainless steel wire which allows the weighted ball to swing freely in any plane. It swings directly over the raised metal ring, its plane shifting slowly in a clockwise direction. A complete cycle will take approximately 36 hours and 45 minutes. The pendulum utilizes the principle first demonstrated by the noted French physicist, Jean Barnard Leon Foucault, in Paris in 1851, when he suspended a heavy sphere from the dome of the Pantheon by a 220-foot wire. [July 1969]