# Léon Foucault

### By: Rebekah Drum

• Full name is Jean Bernard Léon Foucault
• Born in Paris on September 18, 1819
• He was a French physicist
• 194th Birthday
• Died on February 11, 1868

## what did he study?

Foucault began studying medicine, but he dropped out of medical school to study physics. Physics is the study of nature and properties of matter and energy. Foucault also worked on improving the photographic process while working for Alfred Donne.

## The Léon Foucault Pendulum

In 1851, Léon Foucault introduced The Foucault Pendulum. The Foucault Pendulum showed the rotation of the Earth. The first pendulum Foucault made was a 11 pound ball known as the Bob on a 6 ½ foot cable that spun clockwise. The pendulum shows that the Earth rotates because the ball that is going in a straight line changes directions because of the Earth's rotation. The forces that act on the pendulum are inertia, gravity, and air resistance. Inertia keeps the pendulum going straight out and gravity pulls the pendulum back in. Air resistance makes the pendulum swing in short straight arcs. The latitude of where you are effects which way the pendulum travels and how fast it travels.

This is the formula for the degrees of rotation:

n=360°sin of Latitude

## what did he give to science?

The Foucault Pendulum helped prove that the Earth has a rotation. The pendulum would not change the direction it was swinging, but the Earth would move underneath it. Léon Foucault was the first to show the Earth rotates without using the stars.

## Fun Facts

• Foucault was the first to take a photograph of the Sun.
• Armand Fizeau and Foucault learned that light travels through water slower than air.
• The asteroid 5668 Foucault was named after him.
• Foucault earned the Copley Medal of the Royal Society