It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
Léon Foucault’s 1851 experiment remains a mesmerizing evidence that the Earth does, in fact, rotate. Scientists were aware of this, but the fact that the pendulum swings through many degrees of a circle over the course of a day provides tangible proof that we are on a planet spinning in space. (The actual number of degrees that the Earth rotates underneath the pendulum is equal to the Earth’s rotation rate multiplied by the sine of the pendulum’s latitude; a Foucault’s pendulum installed at the poles would move through 360 degrees, while in Paris, only three-quarters of a revolution (270 degrees) occurs in a 24-hour period.)
The Umberto Eco novel, Foucault’s Pendulum, made the mid-19th-century physics demonstration famous. The novel even opens at the Musée des Arts et Métiers. The pendulum played a key role in the high-literary conspiracy involving the Knights Templar at the heart of the novel.
The experimental apparatus consists of a tall pendulum free to oscillate in any vertical plane. The direction along which the pendulum swings rotates with time because of Earth's daily rotation. This is because the plane of the pendulum's swing, like a gyroscope, tends to keep a fixed direction in space, while the Earth rotates under it. The first public exhibition of a Foucault pendulum took place in February 1851 in the Meridian Room of the Paris Observatory. A few weeks later, Foucault made his most famous pendulum when he suspended a 28 kg bob with a 67 meter long wire from the dome of the Panthéon, Paris. The plane of the pendulum's swing rotated clockwise 11° per hour, making a full circle in 32.7 hours. In May 2010, the cable suspending the bob in the Musée des Arts et Métiers snapped doing irreparable damage to that copy of the pendulum.
In 1851 it was well known that Earth rotated: in addition to the passage of the sun and stars overhead, scientific evidence included Earth's measured polar flattening and equatorial bulge. However, Foucault's pendulum was the first simple proof of the rotation in an easy-to-see experiment, and it created a sensation in the academic world and society at large.
At either the North Pole or South Pole, the plane of oscillation of a pendulum remains fixed with respect to the fixed stars while Earth rotates underneath it, taking one sidereal day to complete a rotation. So relative to Earth, the plane of oscillation of a pendulum at the North or South Pole undergoes a full clockwise or counterclockwise rotation during one day, respectively. When a Foucault pendulum is suspended on the equator, the plane of oscillation remains fixed relative to Earth. At other latitudes, the plane of oscillation precesses relative to Earth, but slower than at the pole; the angular speed, α (measured in clockwise degrees per sidereal day), is proportional to the sine of the latitude, φ:
Originally posted by serbsta
Not that I am happy this has occurred, nor am I saying that it isn't a valuable instrument, but the practical reasons behind its operations are pretty much defunct in this day and age.