Google’s latest doodle marks the birthday of Jean Bernard Léon Foucault, the French physicist and inventor of a pendulum that demonstrated the rotation of the earth.
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. Initially, the primary focus of his research was into LJM Daguerre’s photographic processes, while he was also an assistant to the bacteriologist Alfred Donne in the course of his work on microscopic anatomy.
After collaborating with his fellow physicist Hippolyte Fizeau on a series of investigations into the intensity of the light of the sun, he made his name at the Panthéon in Paris in 1851 with a demonstration that involved suspending a 67-metre, 28kg pendulum suspended from the building’s dome.
The plane of its motion, with respect to the earth, rotated slowly clockwise. The experiment sparked a pendulum-mania across Europe and the United States, and crowds were attracted to observe so-called “Foucault pendulums” in major cities on both sides of the Atlantic.
Later achievements included devising a method of testing the mirror of areflecting telescope to determine its shape, the so-called “Foucault knife-edge test”.
By way of recognition for his achievements, Foucault was made a member of the Bureau des Longitudes, of the Royal Society of London and of the Legion d’Honneur.
The physicist, whose name is one of 72 French scientists, engineers, and mathematicians engraved on the Eiffel Tower, died in Paris in 1868.