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The Minivilization

@theminivilization.bsky.social

424 followers 693 following 50 posts

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The Minivilization @theminivilization.bsky.social · 12/05/2025

Whoops; here's the second image with white bg and no alpha channel so the text is actually visible

File:Mechanical disk integrator.svg, uploaded to Wikimedia Commons by DMGualtieri

https://commons.m.wikimedia.org/wiki/File:Mechanical_disk_integrator.svg

A diagram depicting the operating mechanical principles of the ball-and-disk integrator. See source page and/or alt text of the previous image for fuller description.

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The Minivilization @theminivilization.bsky.social · 12/05/2025

My vote is for the ball-and-disk integrators that were used in Kelvin's harmonic analyser to compute the tides, and in US naval vessels during WWII to compute distance traveled over variable velocities. Absolutely ingenious design.

File:Harmonic analyser disc and sphere.jpg, uploaded to Wikimedia Commons by Andy Dingley

https://commons.wikimedia.org/wiki/File:Harmonic_analyser_disc_and_sphere.jpg

Two ball-and-disk integrators in William Thompson (Lord Kelvin)'s harmonic analyser, an analog computer designed in the 1870s and 1880s to compute tidal schedules. Each integrator consists of a metal ball that could be slid horizontally along one axis, representing the input variable, and can roll freely around an axis parallel to the direction of the aforementioned sliding. The ball rests on a metal disk, which, when spun at a fixed rate, rolls the ball at a rate proportional to its distance from the center of the disk, so the total rotation of the ball is an antiderivative of its horizontal position. The ball's rotation is transferred to a rolling pin which moves an arm (not depicted here) which graphs that antiderivative, thereby integrating the input as it runs. When the disk is spun back and forth in a sinusoidal oscillation, the rotation imparted on the pin becomes one of the two dimensions of the input's Fourier transform.

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The Minivilization @theminivilization.bsky.social · 13/04/2025

Permian synapsids are so goddamn cool, I'm so glad kids are being given these opportunities to learn about them instead of just pretending like dinosaurs are the only extinct animals that ever existed

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