Jean Bernard Leon Foucault

Jean Foucault (pronounced "Foo-Koh") was born on September 19, 1819 to a French Publisher.  Early on in his life, he showed skill in making mechanical toys.  In college, he studied medicine, but changed his focus to the Physical Sciences at the Paris Observatory.  He is credited with being one of the most versatile experimentalists of all time.

Foucault's life is marked by many distinguishing achievements.  He was the first scientist to photograph the sun.  He was able to measure the speed of light in a laboratory using a system of rotating mirrors.  He also proved that humans have binocular vision, with the brain combining images from the two eyes into a single image.  He is also credited with improvements on mirrors, lenses, prisms, arc lamps, telescopes, and gyroscopes.  He also developed the Foucault pendulum, with which he demonstrated the rotation of the earth.

Foucault died on February 11, 1868 in France.

So, how does the pendulum demonstrate the earth's rotation?