Sunday, July 11, 2010


The double pendulum: Hypnosis for physicists

Sometimes, when I'm not busy blogging or saving the world, I'll build things. So today my friend Jeff and I built a double pendulum. It's essentially a large pendulum, with a smaller one swinging beneath. Unlike a regular pendulum, which is fairly easy to quantify, the double pendulum is a chaotic system! Practically speaking, it means it looks crazy and amazing when you watch it swing. Jeff and I used instructions given in MAKE. It took about an hour or two (albeit with guidance by an enlightened expert handyman), and the awesomeness-of-project to time-spent-building ratio is extremely high. If you're so inclined, you can even make one yourself.

I'll probably give this one a wider base and make a few other improvements. (I'll post about those as they happen.) If I can, I'll also put up some video of the pendulum in action. In the meantime, content yourselves with these pictures of the pendulum in action!


  1. You probably don't need a wider base as much as a heavier base.

    And how did you connect the pendulums? There aren't a whole lot of ways to connect them and still minimize friction/maximize swing.

  2. They used skateboard bearings.

    And I've seen it: it is incredibly cool! Though I do think adding some LEDs would make it even cooler...


  3. Wow... That's pretty ghetto :-P

    And it doesn't need LEDs, it needs a mustache. IMHO

  4. Needs videos. Also a long-exposure picture of a double pendulum with led lights on it would be awesome.