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xkcd #2924: Pendulum Types
(imgs.xkcd.com)
Alt text:
The creepy fingers that grow from a vibrating cornstarch-water mix can be modeled as a chain of inverted vertical pendulums (DOI:10.1039/c4sm00265b) and are believed to be the fingers of Maxwell's Demon trying to push through into our universe.
It works with double pendulums too
https://youtu.be/gnn21smGVrQ