/****************************************************************************** Foucault's Pendulum - Proof of the rotation of the earth by Russ Jones - rjones@southwind.net Leon Foucault (1819-1868) became a famous man in 1851 by his pendulum experiment to demonstrate the Earth's rotation. It was suggested to him by the chance observation that a steel rod, clamped in the chuck of a lathe, tended to vibrate in the same plane when the lathe was slowly turned. After trials with a seven-foot pendulum in his own cellar and with a 36-foot one in the Paris Observatory, Foucault carried out a dramatic public exhibition. A contemporary, one C. A. Young described it thus: "From the dome of the Pantheon of Paris he suspended a heavy iron ball about a foot in diameter by a wire more than 200 feet long. A circular rail some 12 feet across, with a little ridge of sand on it, was placed under the pendulum in such a way that a pin attached to the swinging ball would just scrape the sand and leave a mark on each vibration. The ball was drawn aside by a cotton cord and allowed to come absolutely to rest; then the cord was burned, and the pendulum set to swinging in a true plane; but this plane seemed to deviate slightly towards the right, cutting the sand in a new place at each swing and shifting at a rate which would carry it completely around in about 32 hours if the pendulum did not first come to rest. In fact, the floor of the Pantheon was seen turning under the plane of the pendulum's vibration." This experiment, which is today shown in many planetariums and museums (I've seen a Foucault's pendulum in museums in Chicago, San Diego, Denver, New York City, and Washington), made a sensation in 1851. Foucault was awarded the Cross of the Legion of Honor and, at the instigation of Emperor Napoleon III, was appointed to the staff of the Paris Observatory as a physicist, where he turned his attention to the improvement of reflecting telescopes. This rendering is based both on Mr. Young's description, and from an engraving to be found in A. Berget's "Le Ciel," 1923. I have been unable to obtain any information on the dimensions of the Pantheon of Paris, but I rather doubt that it had a dome that extended to "more than 200 feet" in height. Nevertheless, I have rendered the wire a full 200 feet in length. It's angle of vibration is less than two degrees, and appears to be nearly vertical here. ********************************************************************************/