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Pendulum Types

Title 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.

Explanation

This explanation may be incomplete or incorrect: Created by CREEPING TENDRILS OF STARCH - Please change this comment when editing this page. Do NOT delete this tag too soon.

This comic shows and describes several pendulums. The first three are actual physics models, while the last one is made up for the comic.

The simple pendulum consists of a joint, rod, and weight, and when released, it swings in a regular fashion. These are used commonly in pendulum clocks to keep time.

The double pendulum consists of 2 joints, 2 rods, and a weight, and when released, it swings in a chaotic fashion. Interestingly, this follows by the mathematical definition of chaotic, being that small changes result in vast differences. This pendulum is thus nearly unpredictable. It does not have any real life applications.

The inverted pendulum consists of a simple pendulum that is placed upside down, with some apparatus underneath moving it side to side to keep it upwards. If left unpowered (or improperly controlled from positional feedback) it will fall, hence the "unstable" part. (The comic, however, appears to depict Kapitza's pendulum, a powered version that does not rely upon monitoring and feedback-control.)

The nightmare pendulum appears to be a double inverted pendulum with a regular pendulum in its weight, which is also adorned with archaic/mystical symbols. The comic claims that this pendulum summons Maxwell’s Demon, and jokingly implies that Maxwell’s Demon is an actual entity, and not a thought experiment.

The title text continues this joke explicitly, by referencing a real paper titled Vibro-levitation and inverted pendulum: parametric resonance in vibrating droplets and soft materials and implying that the paper ties the "creepy fingers" to Maxwell's (real) Demon. The paper only actually suggests that the phenomenon is related to inverted pendulum dynamics

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