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The magical chain fountain

posted by Jason Kottke   Mar 06, 2014

Ok quiet down, we’re going to science right now. (That’s right, I verbed “science”.) If you take a long chain of beads, put them in a jar, and then throw one end of the bead chain out, the rest of the beads will follow *and* this bead fountain will magically rise up into the air over the lip of the glass.

As the guy’s face in the video shows, this is deeply perplexing. For an explanation, slow motion video, and a demonstration of a preposterously high chain fountain, check this video from the NY Times out:

The fountain, said Dr. Biggins, which he had never seen before the video, was “surprisingly complicated.” The chain was moving faster than gravity would account for, and they realized that something had to be pushing the chain up from the container in which it was held.

A key to understanding the phenomenon, Dr. Biggins said, is that mathematically, a chain can be thought of as a series of connected rods.

When you pick up one end of a rod, he said, two things happen. One end goes up, and the other end goes down, or tries to. But if the downward force is stopped by the pile of chain beneath it, there is a kind of kickback, and the rod, or link, is pushed upward. That is what makes the chain rise.

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