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.

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This post is background for another post I'm doing tomorrow or possibly later this week. It involves that old standby of freshman physics, the pendulum. We want to find out the period of a pendulum, the length of time the pendulum spends making one complete back-and-forth cycle.
Some time ago I was looking for materials to possibly build a foucault pendulum. Of course the first step is google. There was a site that suggested two old issues of Scientific American, and it happens that we have tons of old Scientific Americans in the store room.
I've finally buckled down and started reading Neal Stephenson's Baroque Cycle