A French museum has apparently dropped the ball, quite literally, with one of Foucault’s original pendulums. The Times Higher Education newspaper reports that the pendulum, housed at the Musée des Arts et Métiers in Paris, came crashing down last month, after the cable holding its brass bob snapped. The 28 kilogram sphere smashed into the marble floor and has been irreparably dented, according to curator Thierry Lalande.

For those of you who have not suffered through a course in Newtonian mechanics, Foucault’s pendulum is one of the hardest, and frankly coolest, classical physics problems out there. The idea is this: make a really big pendulum and set it swinging back and forth. Now if the earth stood still, the pendulum would just keep on swinging like that forever. But because it spins, the pendulum’s plane of rotation keeps changing. Over the course of the day, the pendulum’s swing will precess 180 a certain number of degrees, depending on latitude. It’s all about conservation of momentum and angular coordinates and such.

Of course, when Focault demonstrated his pendulum in 1851, everybody already knew the earth was rotating, but the device was an impressive demonstration. From a physics perspective, the maths required to solve the pendulum problem are also key to understanding the rotation of hurricanes, orbital dynamics, space launches (especially ballistic missiles), and a lot of other stuff.

The Musée des Arts et Métiers seemed to have a spotty record of looking after its pendulum. In 2009, Lalande admitted that a party goer at a museum cocktail soiree had swung the ball into a security barrier. There aren’t a lot of details about how the cable snapped.

Anyway, a lesser Frenchman might have succumbed to ennui, but Lalande seems to have found the bright side of the situation: “It’s not a loss, because the pendulum is still there,” he says, adding that the accident was a failure on the part of the museum.

Fortunately, there’s still at least one other original Focault pendulum out there. An original bob still swings from the Panthéon in central Paris. And actually, there’s no reason the dented pendulum couldn’t swing on…

French coverage

Le pendule de Foucault décroche

Le pendule de Foucault perd la boule

Credit: Cdang/Wikipedia