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A snap of the fingers is a metaphor for something easy.
Like, you can do it in a snap.
But researchers who really buckled down to study the physics of
finger snapping found... it’s actually a pretty impressive feat.
And understanding it could help us study things from insect jaws to prosthetics.
In a study published in 2021 in Journal of the Royal Society Interface,
researchers figured out the physics of the finger snap
using high speed cameras and force sensors.
The inspiration for the study came after seeing a movie where
the villain snaps his fingers while wearing a metal glove.
Six guesses for which one that is.
The researchers wondered whether that would be possible,
because the metal wouldn’t have much friction.
Well, according to the study, the perfect snap can be
broken down into three phases.
The first is loading, where the thumb and middle finger
store up kinetic energy, or energy of motion.
Then comes the unlatching, where the fingers start to slide past one another.
And finally, unlatching movement [snap] is when the fingers move at
ultra-fast speeds until the middle finger hits the palm,
creating shock waves that make the ‘snap’ sound.
The whole thing happens in less than 7 milliseconds,
20 times faster than the blink of an eye.
And during that unlatching movement phase, your fingers are rotating
at up to 7,800 degrees per second, almost as fast as a
professional baseball player rotates their arm during a pitch.
All this means, finger snapping is one of the fastest,
most explosive movements our bodies can muster!
But whether those three phases add up to a snap or
silence comes down to one key element: friction.
Friction is the resistance between two objects moving over one another.
And it turns out that snapping requires a sort of Goldilocks zone of friction.
You see, you want friction to help build up the kinetic energy in the loading phase.
But you have to overcome the friction when it
comes time to release during unlatching.
Researchers figured out just how much friction contributes
to snapping by rigging how slippery and squishy a person’s fingers were.
To make them more slippery, participants in the
study wore lubricated nitrile gloves.
And when they did, their fingers didn’t create enough
friction and they could not store up enough energy for a forceful and loud snap.
If their fingers were instead made more grippy by wearing a latex rubber glove,
then participants couldn’t release their fingers and the snap also flopped.
The researchers also wanted to see whether the
squishiness of someone’s fingers, or how compressible they were,
had anything to do with the friction that built up.
So some participants wore a hard metal thimble with a nitrile glove on top.
And it turns out fingers need to be at least a little
squishy to help build up that friction.
So snapping with a metal glove on? Not possible for people.
Maybe possible if you have infinity stones or something.
The researchers, who had previously studied super-fast motion in
other animals, took all this information and combined it into a
mathematical model that could now be used to help in other fields of science.
For example, it could help biologists understand the snaps of, say,
Panamanian termite soldiers.
Those are insects that snap their jaws together ultrafast to defend their hive.
And the researchers propose the mechanism might be similar to finger snapping.
Plus, understanding the dynamics of the finger snap
could help engineers fine tune the movement of prosthetics.
Which you gotta say, isn’t just fun, but pretty [snap] snappy research indeed.
It’s funny how we don’t really understand things like finger snapping until
someone goes “But how does that actually work?”
and they decide to do some science about it.
But to learn more about the physics of the everyday, from bridges to fridges,
you might like Brilliant’s course Physics of the Everyday.
Or any one of the math, science, engineering, and computer
science courses they have available.
Because if you’ve decided you want to learn new things in the new year,
Brilliant is a great resource.
Their interactive courses focus on letting you participate
rather than learning by rote.
Right now, if you sign up at brilliant.org/scishow, you can save 20 percent
off an annual premium subscription to Brilliant.
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