Towering Scientists: Foucault’s pendulum and Earth’s rotation
In 1851, the French physicist Léon Foucault provided an experimental proof of the Earth’s rotation using a pendulum. Although Foucault is best known for this ingenious experiment, he also made several important contributions to physics including the discovery of eddy currents as well as measuring the speed of light. Foucault is one of the 72 scientists whose names are engraved on the sides of the Eiffel tower.
At the Arts et Métiers museum in Paris, visitors can witness Foucault's pendulum experiment in action twice daily. The setup features a 17-meter metal cable suspended from the ceiling, with a brass-encased lead sphere attached to its lower end. As the pendulum swings, it gradually knocks over wooden pegs arranged on a circular table below, demonstrating the Earth's rotation.
According to Maela Levigne of the Arts et Metiers museum, “the pendulum starts to oscillate in the direction in which it is launched with no lag observed. The oscillation period (of this pendulum) is between seven and eight seconds. Between each oscillation, the Earth shifts by one millimetre.”
She explained that despite the pendulum never shifting from its plane of oscillation, it manages to knock out the skittles because of the shifting of the earth below it.
What moves is the earth which will shift, relative to the plane of oscillation of the pendulum. “By shifting, the Earth moves the table, which moves the skittles that are laid on the table. They then come into contact with the pendulum and end up falling.”
Foucault's Pendulum
More Than Just an Experiment
Read more on RFI English
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