Researchers at Georgia Institute of Technology used high-speed cameras and state-of-the-art force sensors to record the speed and acceleration of finger snapping and investigate the little-known physics that makes it possible.
They discovered that a finger snap is the quickest human body acceleration ever recorded.
Their findings, published in the Journal of the Royal Society Interface on Nov. 17, show that the finger snap’s maximum rotational velocities are 7,800 degrees per second and the maximum rotational acceleration is 1.6 million degrees per second squared, which is three times the acceleration produced by a professional baseball player’s arm.
“The finger snap occurs in only seven milliseconds — more than 20 times faster than the blink of an eye, which takes more than 150 milliseconds,” said study senior author Saad Bhamla, an assistant professor of chemical and biomolecular engineering at the Georgia Institute of Technology, said in a statement.
After seeing the 2018 Marvel Studios film “Avengers: Infinity War,” in which Thanos, an 8-foot (2.4 meter) purple warlord from Saturn’s moon Titan, seeks out six powerful “Infinity Stones” that will grant him the ability to bend and reshape the fabric of the universe according to his will, Bhamla was inspired to conduct research. Thanos planned to wipe out half of all living species in the cosmos with a single snap of his fingers by encasing the stones in a metal “Infinity Gauntlet.”
But for some of the scientists, performing a finger snap while wearing a metal gauntlet was the step too far.
The scientists used a high-speed camera to evaluate a series of finger snaps while covering the snapping hand with various materials to investigate the physics underpinning the motion. They discovered the best physical explanation for how snaps happen and its most essential component: friction, by fitting their experimental results to a variety of mathematical models.
According to the study, finger snaps work by employing arm muscles as a motor to load elastic potential energy into spring-like tendons in the fingers and arms, which is then quickly released to cause the amazing acceleration of the snap. By securing the middle finger to the thumb and preventing it from moving, friction between the thumb and middle finger serves as a critical latch. The friction is overcome once enough energy has been built up, and the thumb and middle finger slip past each other, releasing the snap.
If the amount of friction is too low or too high, too much energy is released as heat rather than motion, according to researchers. This “Goldilocks zone” sits between the two extremes.
The researchers, of course, didn’t have a working Infinity Gauntlet, so they used metal thimbles to cover the subjects’ fingertips. A rubber glove was shown to be as harmful to a successful finger snap as Thanos’s gauntlet because it supplied too much friction, dissipating too much of the snap as heat; and the rigid gauntlet because it delivers too little, never enabling the snap to fully build up. Thanos’ snap-happy fingers would also have a significantly reduced touch area because of the metal armor protecting them.
Finger snapping may have applications in understanding other biomechanical behaviors, such as how ants and termites store up energy to snap their mandibles, researchers said. Other academics may now look into the anthropological factors underlying human finger snapping as a result of this research.
“Based on ancient Greek art from 300 B.C., humans may very well have been snapping their fingers for hundreds of thousands of years before that, yet we are only now beginning to scientifically study it,” Bhamla said.
“This is the only scientific project in my lab in which we could snap our fingers and get data.”
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