Foucault

Google celebrates Léon Foucault’s 194th birthday with pendulum Doodle

 Ryan Whitwam BySep. 18, 2013 12:48 pm

Jean Bernard Léon Foucault was a 19th century French physicistwho made contributions to a number of areas like photography and polarization. However, he is probably best known for the creation of the Foucault Pendulum, which is the the focus of today’s interactive Google Doodle on what would have been Foucault’s 194th birthday. When the pendulum was first displayed in Paris in 1851, it captured the world’s attention. The Foucault Pendulum was the first experiment that demonstrated the Earth’s rotation in an observable way.

The Foucault Pendulum is like all the other pendulums you’ve ever seen, except the notable rotation effect is only visible when the wire is at least 40 feet long. The pendulum swings back and forth with the heavy metal bob at the end. As the does its thing, the actual plane of swing appears to rotate relative to the Earth. Thus, the path of the bob changes over time. The dominoes placed around the perimeter are a way to visualize the movement.

The so-called plane of oscillation changes based on the latitude the pendulum is at. At the north pole, the apparent rotation would be a full 360° circle in 24 hours because the rotation of the Earth has little to no impact. Move a bit south, and the rotational influence of the Earth begins to figure in. The rotation of the Earth moves the pendulum and everything around it in a larger circle about its axis (because Earth is roughly spherical). The farther south you go, the slower the apparent rotation. Get the below the equator, and the rotation begins to pick up again, but in a counter-clockwise direction. You can use the sliders in the Google Doodle to play with the variables.

Foucault built his original pendulum bob out of a solid chunk of lead coated in brass. It still exists in the Musée des Arts et Métiers. An exact replica of the original has been swinging under the dome of the Panthéon in Paris where the original demonstration took place.