Humans snap their fingers more than 20 times faster than the blink of an eye, a study has found.
Using an amount of friction that is not too high and not too low, a snap of the finger produces the highest acceleration observed in humans, the research suggests.
One day the findings could inform the design of prosthetics meant to imitate the wide-ranging capabilities of the human hand.
Researchers had previously developed a general framework for explaining the powerful and ultrafast motions observed in living organisms.
The finger snap occurs in only seven milliseconds, more than twenty times faster than the blink of an eye, which takes more than 150 milliseconds
Dr Saad Bhamla
The framework, which proposes that organisms depend on the use of a spring and latching mechanism to store up energy they can then quickly release, seemed to naturally apply to the snap.
Undergraduate student at Georgia Tech, Raghav Acharya, and assistant professor Saad Bhamla of the School of Chemical and Biomolecular Engineering, were driven to apply this framework to a finger snap after seeing the movie Avengers: Infinity War – produced by Marvel Studios.
In it, the villain Thanos seeks to obtain six special stones and place them into his metal gauntlet.
After collecting them all, he snaps his fingers and triggers universe-wide consequences.
The researchers wondered if it would be possible to click snap while wearing an armour gauntlet.
When it came to the finger snap, they suspected skin friction played a more important role compared to other spring and latch systems.
And with the frictional properties of a metal gauntlet, they imagined it might be impossible.
Using a range of techniques, the researchers analysed a variety of finger snaps and explored the role of friction by covering fingers with different materials, including metallic thimbles to simulate the effects of trying to snap while wearing a metallic gauntlet.
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According to the study, an ordinary snap with bare fingers measured maximal rotational velocities of 7,800 degrees per second and rotational accelerations of 1.6 million degrees per second squared.
While the rotational velocity is less than that measured for the fastest rotational motions observed in humans, which come from the arms of professional baseball players during the act of pitching.
However, the snap acceleration is the fastest human angular acceleration measured, almost three times faster than the rotational acceleration of a professional baseball pitcher’s arm.
Dr Bhamla, who studies ultrafast motions in a variety of living systems, said: “When I first saw the data, I jumped out of my chair.
“The finger snap occurs in only seven milliseconds, more than twenty times faster than the blink of an eye, which takes more than 150 milliseconds.”
But when the fingertips of the subjects were covered with metal thimbles, their maximal rotational velocities decreased dramatically, confirming the researchers’ suspicions.
Mr Acharya, first author of the study, said: “Our results suggest that Thanos could not have snapped because of his metal armoured fingers.
“So, it’s probably the Hollywood special effects, rather than actual physics, at play. Sorry for the spoiler.”
Increasing the friction of the fingertips with rubber coverings also reduced speed and acceleration.
The researchers believe that the results open a variety of opportunities for future study, including understanding why humans snap at all, and if humans are the only primates to have evolved this ability.
Dr Bhamla said: “Based on ancient Greek art from 300 BC 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.
“This is the only scientific project in my lab in which we could snap our fingers and get data.”
The research is published in the Journal of the Royal Society Interface.