Suspended from the dome of the Pantheon in Paris in 1851, the pendulum designed by Léon Foucault was a first demonstration of the Earth’s rotation. Today it is the subject of a Google Doodle honoring the French physicist and his invention.
The original Foucault’s Pendulum consisted of a steel ball hung 22 feet (6.7 meters) on a steel swing and set swinging back and forth, kept in motion by a mechanical mechanism. As the Earth turned, the direction of the swing slowly revolved its plane of its motion to keep pace, demonstrating the planet’s rotation beneath the feet of Parisian observers.
The mesmerizing Google Doodle honors that discovery. Two sliders on the interactive feature allow a user to see how changing the local time or latitude affects how the pendulum swings.
Foucault’s Pendulum has been widely copied over the years, showing up in museums, science centers, and the like around the globe.
Foucault was born in Paris in 1819. He died in the same city in 1868.
In addition to his pendulum, he made an early calculation of the speed of light, discovered eddy currents, and is known for naming the gyroscope, although he didn’t invent it.
Foucault has an asteroid named after him and is one of 72 names inscribed on the Eiffel Tower.