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Pendulum Army Synchs Up

According to a common story (which may be a sort of physics folk tale as far as I know) the physicist Christiaan Huygens was sick in bed idly watching a pair of pendulum clocks on his wall when he noticed that they were swinging in perfect harmony (anti-harmony actually, because they swung in opposite directions, like mirror images of each other). When he set them swinging out of sync, they would always manage to eventually adjust their periods until they were swinging perfectly together again.

Although Huygens never figured out exactly what was going on, we now know that the two pendulums were coupled through tiny motions transferred through the wall they were both attached to. It's too bad Huygens never thought to do an experiment like the one in the video here.

If you have a little over four minutes to kill, check it out. I'm sure this demo would have totally blown Huygen's mind. I think it's just cool.


  1. It's not cool, it's scary. Regimented uniformity. A model for the militarized state.

    1. It is kind of ominous. I wouldn't read into it too much, though. People are a lot more complicated than metronomes.

  2. cosmic variance has a nice explanation of the effect here:

    also a video of a python simulation:

    since the metronomes are arranged on a 2D plane, an interesting question would be where on the table the synchronization is fastest.

    makes me wonder what other things could synchronize in this way. How about the heartbeats of twins in the same womb?

    1. Thanks for the info, I love Cosmic Variance. It was interesting reading the info for the simulation (python refers to the programming language, not the snake, for anyone reading along). It makes it clear that some damping is need for the synchronization. For undamped pendulums and metronomes, the phases shift around in interesting ways, but don't synch up for long, if at all. Of course, to keeping it going, you need driving as well to prevent all the motion from damping out eventually.


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