It belonged in a museum

…and thankfully, that’s exactly where the original Foucault’s Pendulum was: the Musee des Arts et Metiers (the Museum of Arts and Industry) in Paris. It’s still there, only in mid-May its cable snapped, sending the weight crashing through the floor of the museum.

It was only about 160 years ago that many people were still not convinced the Earth rotates on its own axis. After all, we don’t feel the motion; the Sun, Moon and stars seem to wheel around us, we don’t spin around like a top. Otherwise we’d get seasick on land, surely? Even when it became fairly common belief that the Earth orbited the Sun, the idea that the Earth also spun didn’t have much going for it. What’s to keep us from flying off?

We can be all superior about it now and talk about how the attractive force of the Earth’s gravity is far stronger than any angular momentum we might experience from it’s spin, or about frames of reference, or anything else, but we wouldn’t all have such concrete knowledge of these ideas without the work of Léon Foucault.

No relation to the philosopher and historian Michel Foucault, the physicist Jean Bernard Léon Foucault achieved all manner of great things: he measured the speed of light (with pretty good accuracy, much better than his predecessors), vastly improved the quality of telescopes, and named the gyroscope. But his most famous invention was a large, free-rotating pendulum, suspended in the Panthéon, which slowly changed the direction of its oscillation as the Earth rotated.

Many other such pendulums have been built, and I saw one when I was a boy, set up in the Queen Victoria Building in Sydney. I remember being quite obsessed with it at the time, reading up about its significance, enjoying the rich history of the same experiement being carried out over more than a century and across vast distances. I didn’t know it was only a temporary exhibit until I tried to find it on a trip back to Sydney in 2008, but I relived the joy when I saw another one in operation late last year at the Boston Museum of Science – suspended over a Mayan calendar!

Even the pendulum in the Panthéon was not Foucault’s first, but it was this one that caused a sensation in both scientific and lay circles – and which was irreparably damaged in May. Imagine it in the context of the time: a definite, physical demonstration of the Earth’s rotation! Today, a comparable feat would be to set up a simple demonstration  showing direct evidence of anthropogenic global warming. It’s easily possible to show that even a small amount of CO2 causes an increase in temperature – the wonderful Intelligent Life Magazine recently ran a great article showing you how – and perhaps building such a demonstration in public would silence some of the critics, but it’s hard to imagine it having quite the same impact as Foucault’s simple and elegant experiment did back in 1851.

There’s still a pendulum in the the Panthéon, a replica of the original, and given that party-goers at the Musee des Arts et Metiers had previously pushed the pendulum around, perhaps it’s better to go see the replica. That’s the wonderful thing about science – and indeed art: you might destroy the artefact, but the idea lives on. And if you really want to see a pendulum in action, you can find them all over the world.

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