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  Visual proof of the rotation of the earth was first demonstrated in Paris in 1851 by the noted French physicist, Jean Bernard Foucault, who used a cannon ball for a pendulum and suspended it from the dome of the Pantheon by a wire about 250 feet long.

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  The pendulum you see at the Besser Museum is suspended from the ceiling above the main floor. A universal joint allows it to swing freely in any direction. A free swinging pendulum cannot change its plane (Newton's Law of Motion) and once started it will continue to swing in the same direction.

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  The pendulum is kept in motion by an electro-magnet which induces a current that supplies the necessary energy to overcome friction and air resistance to keep it swinging uniformly. Without an external power source, the length of the swing will decrease in a few hours almost to zero.

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  A pendulum placed at the North or South Pole will complete a 360 degree rotation in a 24 hour period. Alpena is located at the 45 parallel and the time required for the pendulum to return to the starting point is 33 hours and 56 minutes.

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  You can read more about Foucault's Pendulum here.