Most people don't question the scientific accuracy of what goes on in the Marvel Cinematic Universe, like how Tony Starks' souped up Iron Man suits work or how Captain Marvel can whiz through outer space. But something in Marvel Studios' Avengers: Infinity War caught the attention of Saad Bhamla, an engineer at Georgia Tech, and his students.
At the end of the movie, mega-villain Thanos snaps his fingers while wearing the Infinity Gauntlet—a magical metal glove bedazzled with six almighty stones—and wipes out half of the planet's population. The scene inspired the engineers to ask: What are the physics of a finger snap? And was it possible for Thanos to snap while wearing the giant glove?
The answer is no, according to a new study published in the Journal of the Royal Society Interface this week. The team took a close look to explain the friction and other mechanics of snapping fingers.
"For the past few years, I’ve been fascinated with how we can snap our fingers," Bhamla says in a press release. "It’s really an extraordinary physics puzzle right at our fingertips that hasn’t been investigated closely."
Their analysis revealed that a snap occurs at a superhero-like speed of just seven milliseconds—20 times faster than the blink of an eye, reports Emily Conover for Science News.
Using high-speed video and sensors, Bhamla and his team analyzed the forces at play in different finger snaps. They tested snaps from three different people and studied what happens when tape is placed on different parts of the hand, like the wrist or knuckle. The designated snappers also wore different types of gloves and thimbles to test how the obejcts would affect the snap, reports Jennifer Ouellette for Ars Technica.
According to the press release, a snap has a rotational acceleration of 1.6 million degrees per second squared—nearly three times faster than a professional baseball pitcher's throwing arm.
"You get the data like, 'Oh, we’re hitting 1.6 million degrees per second squared, holy smokes. This is actually a pretty darn fast moment,'" Bhamla tells Elana Spivack for Popular Science. "We need to investigate how it is that we are able to generate such high extreme acceleration."
A finger snap has a latch-like mechanism in which potential energy is loaded up—by squeezing the middle finger and thumb together—and then quickly freed when the latch releases, or when the fingers slide past each other. Frog legs, mantis shrimp punches and chameleon tongues also use this energy-packed mechanism, reports Ars Technica.
When the team tested rubber thimbles, the snap had too much friction, and energy was lost during the snap. On the other hand, a slippery, lubricated glove didn't generate nearly enough energy. But two bare-skinned fingers created the perfect level, according to a comic created by Bhamla's lab.
"We need this Goldilocks zone, because too little friction, you can’t load up enough energy,” Bhamla tells Popular Science. "But if you have too high friction, you still have to have this dynamic motion of sliding past each other."
This research could improve the design of prosthetics to better simulate the human hand. Plus, the research provides insights into how friction plays a role in the way we interact with everyday objects, like unlocking a smartphone with fingerprint identification, Popular Science reports.
In the meantime, the team has an answer for their original question.
"Our results suggest that Thanos could not have snapped because of his metal armored fingers," says the paper's lead author Raghav Acharya, a Georgia Institute of Technology undergraduate student, in the press release. "So, it’s probably the Hollywood special effects, rather than actual physics, at play! Sorry for the spoiler."