Living the Scientific Life (Scientist, Interrupted)

Foucault’s Pendulum

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This video features physics and astronomy professor Jim LaBelle, as he discusses the truly fascinating science behind a classic physics experiment, Foucault’s pendulum, while seated next to Dartmouth University’s pendulum in Fairchild Tower.


While scientists already knew that the Earth had a rotation, they had struggled to come up with a way of definitively proving this was so. In 1851, French scientist Leon Foucault gave a sensational demonstration in the Paris Pantheon proving that the Earth revolved around its axis — known as diurnal motion — before a group of dignitaries that included Napoleon III. He suspended a heavy brass bob by a wire from the Pantheon’s ceiling to create a pendulum and let it swing freely in any direction along its vertical axis. As time passed, the swings rotated in response to the Earth’s rotation.

The pendulum was such a simple proof of the theory, it became one of Foucault’s most famous contributions to science.