The latest Google Doodle marks the 194th birthday of Jean Bernard Léon Foucault, the French physicist and inventor of a pendulum that demonstrated the rotation of the earth.
While it had long been known that the Earth rotated, the introduction of the Foucault pendulum in 1851 was the first simple proof of the rotation in an easy-to-see experiment.
Foucault’s most famous pendulum consisted of a 28kg brass-coated lead bob on a 67-metre long wire hanging from the dome of the Panthéon in Paris. The plane of the pendulum’s swing rotated clockwise 11° per hour, making a full circle in 32.7 hours.
Today, Foucault pendulums are popular displays in science museums and universities. The United Nations headquarters in New York City has one, while the largest Foucault pendulum in the world, Principia, is housed at the Oregon Convention Center.
Foucault is also credited with making an early measurement of the speed of light and with the discovery of eddy currents: electric currents induced within conductors by a changing magnetic field in the conductor, which are sometimes called Foucault currents.
The son of a publisher, Foucault was born in Paris in 1819, where he initially studied medicine but soon switched to physics due to a fear of blood.