Foucault Pendulum

The Focault Pendulum is a famous experiment which is alleged to give simple, direct evidence of the earth's rotation. Introduced in the 1851, Léon Foucault claimed that the motions were proof the earth's rotation. Today Foucault Pendulums are popular displays in science museums and universities.

A common criticism is to point out that when the pendulum is put into motion it has often been seen at times to rotate in excess, in shortness, or in an opposite direction from the direction it should have traveled. Those who have repeated the experiment have asserted that “it was difficult to avoid giving the pendulum some slight lateral bias at starting.”

In the unmotorized Focault Pendulum experiment the pendulum is entirely unpredictabl. The pendulum will slow down due to air resistance and must be reset on a regular basis. In motorized Focault Pendulums, as seen in museum exhibits, it is the repetitive machinery which imparts a repeating lateral bias that creates the regular results seen.

Lady Blount provides the following:

Non-Uniform Variation
Samuel Birley Rowbotham informs us that the variation of the pendulum is often non-uniform and unpredictable:

The Wrong Direction
The Focault Pendulum is often seen to move in the wrong direction entirely. See the following quotes:

Mach's Principle
As an alternative explanation, Mach's Principle explains that if the earth was still and the all the stars went around the Earth then the gravitational pull of the stars would pull the pendulum. As Mach said "The universe is not twice given, with an earth at rest and an earth in motion; but only once, with its relative motions alone determinable. It is accordingly, not permitted us to say how things would be if the earth did not rotate."

External links:

 * Amir D. Aczel, Pendulum: Léon Foucault and the triumph of science