Mathematician Calculates Rotational Speed of Fidget Spinner in Fidgets Per Second

iStock // fullempty
iStock // fullempty

How fast does a fidget spinner spin? It's a simple question with a simple answer, but a complex path to that answer. The issue lies in analyzing an extremely fast-moving object with simple tools, like a smartphone.

In the video below, mathematician Matt Parker turns to a spectrogram sound-analyzing app to solve this problem. Spectrograms are visual representations of sound, allowing the viewer to pick out certain frequencies within an audio clip and measure their intensity. By figuring out the sound the fidget spinner makes, Parker can sort out how many Hertz (cycles per second) the spinner is rotating at.

The first task is making the spinner itself stable, so it's easy to spin and becomes a reliable target for audio recording. Parker attaches the device to a drinking glass, and mounts the smartphone above it, with the microphone pointed at the edge of the spinner. Then by blowing the fidget spinner with compressed air, the mathemagic happens.

Parker calculates the absolute speed of the tips of the fidget spinner, as well as the speed of the spinner in revolutions per minute—the latter is roughly 3750 rpm! (For comparison, a typical car engine runs around 2000-3000 rpm when cruising.) The video is full of further analysis and methodology.

Tune in for some delightful applied mathematics...and be sure to wear your safety gear!

Incidentally, Parker used the SpectrumView app, though there are others like it. He also posted a screenshot of the spectrogram, as seen in the video, in case you want to test your own spinner.

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The Truth Behind Italy's Abandoned 'Ghost Mansion'

YouTube/Atlas Obscura
YouTube/Atlas Obscura

The forests east of Lake Como, Italy, are home to a foreboding ruin. Some call it the Casa Delle Streghe (House of Witches), or the Red House, after the patches of rust-colored paint that still coat parts of the exterior. Its most common nickname, however, is the Ghost Mansion.

Since its construction in the 1850s, the mansion—officially known as the Villa De Vecchi—has reportedly been the site of a string of tragedies, including the murder of the family of the Italian count who built it, as well as the count's suicide. It's also said that everyone's favorite occultist, Aleister Crowley, visited in the 1920s, leading to a succession of satanic rituals and orgies. By the 1960s, the mansion was abandoned, and since then both nature and vandals have helped the house fall into dangerous decay. The only permanent residents are said to be a small army of ghosts, who especially love to play the mansion's piano at night—even though it's long since been smashed to bits.

The intrepid explorers of Atlas Obscura recently visited the mansion and interviewed Giuseppe Negri, whose grandfather and great-grandfather were gardeners there. See what he thinks of the legends, and the reality behind the mansion, in the video below.