Foucault Gyroscope

In 1851, Léon Foucault used a pendulum to demonstrate the rotation of the Earth. Despite his success, he was not fully satisfied with the pendulum experiment because of the dependency on the sine of latitude, which the public found difficult to understand. He later designed a device which he named ‘gyroscope.’

A spinning gyroscope keeps a constant axis of rotation in space, so it should slowly rotate with respect to an observer attached to the rotating Earth. The challenge was technical; it would need to have minimal friction, and it has to be able to spin for a sufficient duration so that the precession due to Earth’s rotation can be observed.

Gustave Froment helped Foucault to build the device. Using a hand crank and four stages of gearing, the gyroscope can be launched with the initial speed of 12000 rpm, allowing the rotation to persist for 10 minutes. It was sufficient to observe the precession due to Earth’s rotation, using a microscope.