Léon Foucault Catholicism that he previously abandoned. Foucault died of what was probably a rapidly developing case of multiple sclerosis on 11 February 1868 in Paris and was buried in the Montmartre Cemetery. The asteroid 5668 Foucault was named for him. His is one of the 72 names inscribed on the Eiffel Tower. Collected Works: Léon Foucault Jean Bernard Léon Foucault (; 18 September 1819 – 11 February 1868) was a French physicist best known for his demonstration of the Foucault pendulum, a device demonstrating the effect of the Earth's rotation. He also made an early measurement of the speed of light,
Pendulum observations, and a "pendulum mania" broke out, as Foucault pendulums were displayed in many cities and attracted large crowds. Around 1900 low-thermal-expansion materials began to be used for pendulum rods in the highest precision clocks and other instruments, first invar, a nickel steel alloy, and later fused quartz, which made temperature compensation trivial. Precision pendulums were housed in low pressure tanks, which kept the air pressure constant to prevent changes in the period due to changes in buoyancy of the pendulum due to changing atmospheric pressure. The best pendulum clocks achieved accuracy of around a second per year. The timekeeping