A Foucault of a day

Image Rémih CC BY-SA 3.0

In 1851, Frenchman Léon Foucault devised an experiment that would demonstrate the rotation of the earth. He hung a metal ball on a wire from the centre of the great dome of the Panthéon. By setting in motion and then tracking its horizontal variation from a fixed arc over the period of a day, the rotation of the earth was effectively graphed for all to see. It’s actually a bit more complicated than that. Truth be told(ish), if you want actual facts, you may be reading the wrong blog. Anyway, despite being very popular with the easily impressed Parisians, Foucault’s experiment tended to get in the way of the endless cycle of solemn consecrations and deconsecrations, so they took it down after a couple of years.

These days the experiment is a staple of science museums the world over. You might also remember that Umberto Eco wrote a book called Foucault’s Pendulum, in which southern belle Scarlett O’Hara falls in love with humble Italian pendulum maker, Raffaele Butler. They overcome adversity, and swing off into the sunset together. I’m going from memory on this.

You can imagine the delight - nay, ecstasy - of this humble devotee of big-shiny-things-that-move when I discovered Foucault’s pendulum had been reinstalled in 1995. Actually it was a copy, because the original had gone to the Musée des arts et métiers. Now, I’m normally a one-Foucault-a-day man, but feeling energised by the ghost of Victor Hugo, I abandoned the Panthéon (after some hours of staring at the big ball swinging back and forth whilst sucking my thumb) and toddled off in search of the original sacred* Foucault’s pendulum. 
* Okay, I don’t think it’s actually sacred, but I had plans to conduct my own personal canonisation service.

The Musée des arts et métiers is big-shiny-things-that-go-ping-heaven-on-a-stick. First thing I see, of course, was the original-only-it-actually-fell-off-and-this-is-a-copy pendulum doing its thing. I immediately settled in for several more hours of watching the ball. 

I started feeling sleepy. Very sleepy. 

Here’s a video I found on YouTube. I suggest you put it on endless loop: