Foucault pendulum, Pendulum exhibit in the 5th arrondissement, Paris, France.
The Foucault pendulum consists of a 28-kilogram brass and lead sphere suspended from a 67-meter steel wire, swinging freely to demonstrate Earth's rotation through the gradual shift of its oscillation plane over time.
French physicist Léon Foucault first demonstrated this experiment in 1851 at the Paris Observatory before moving it to the Panthéon, providing direct observable proof of Earth's rotation without requiring astronomical observations.
The pendulum serves as a symbol of scientific inquiry and education, representing France's contributions to experimental physics and making complex planetary mechanics accessible to the general public through tangible visual demonstration.
The pendulum hangs under the dome of the Panthéon in the 5th arrondissement, where the copy installed in 1995 swings. Air friction limits each swing sequence to about six hours, so a magnetic mechanism keeps it moving; the original 1851 bob, damaged in 2010, is shown in a case at the Musée des Arts et Métiers.
The original 1851 bob, damaged when its cable snapped at the Musée des Arts et Métiers on 6 April 2010, is shown in a case beside the working pendulum there; the Panthéon has run an exact copy since 1995. At Paris's latitude of 48°52'N the swing plane turns clockwise about 11.3° per hour, a full circle in roughly 31 hours 50 minutes.
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