Thanos: I will destroy this universe! Physics: No, you can't.

Written by Skin

Want to set an extraordinary sports record? It turns out that not only athletes can set this record: all you have to do is snap your fingers!

A recent study published by a team at Georgia Tech shows that when we perform a perfect finger snap, we produce the highest angular acceleration ever observed in the human body - 1.6 million °/s². This speed is faster than the rotational acceleration of a professional baseball pitcher's arm.

“Humans have been snapping their fingers since 300 B.C., but it’s only now being studied scientifically.” | doi.org/10.1098/rsif.2021.0672

Before setting a world record, you may need to know the principle of snapping fingers so that you can develop your own "secret of snapping fingers".

When we snap our fingers, the middle finger and thumb are squeezed together, the two fingers push in opposite directions, and then the middle finger hits the muscle at the base of the thumb. However, snapping fingers requires more than just the middle finger and thumb, and the "snap" sound does not come from the two fingers.

In the snapping gesture, the pinky and ring fingers form a resonant cavity with the other fingers, while the middle finger and thumb form a trumpet shape. When the middle finger hits the muscle, the air in the cavity will vibrate repeatedly, producing a sound.

Therefore, if you want to make a crisp and loud snap, you must first adjust your hand posture to ensure that there is a cavity between your fingers. Another "secret" is to achieve a near-perfect friction between the thumb and middle finger.

The story all started with a movie. After watching "Avengers: Infinity War", two students from Georgia Institute of Technology suddenly became curious about the scene in which Thanos snaps his fingers. In the movie, when Thanos snaps his fingers wearing a metal glove, half of the life in the world will disappear.

But in fact, according to the principles of physics, Thanos cannot snap his fingers.

Thanos: I have installed all the gems and you are telling me this? | Giphy

Snapping fingers is a high-speed sport. In fact, it is not just humans who have mastered the secret of this high-speed sport. **Many organisms use this sport as their survival skill. **For example, when the leaves of the Venus flytrap are stimulated, they close quickly in about 100ms. Therefore, researchers have developed a general framework for these sports: latch- mediated spring actuation (LaMSA).

Before snapping your fingers, press your middle finger with your thumb. The middle finger is like the spring in the picture. When it is pressed, it stores a lot of elastic potential energy. When the spring is suddenly released, according to the kinetic energy theorem, the elastic potential energy accumulated in the middle finger is converted into kinetic energy, and the middle finger will accelerate and snap open.

The "spring and latch" framework for snapping fingers. The middle finger acts as the spring. | doi.org/10.1098/rsif.2021.0672

When the middle finger "spring" reaches equilibrium, it reaches its maximum speed. The researchers used 4082fps high-speed imaging to capture the movement of snapping fingers, and they found that the action of snapping fingers only takes 7ms to complete. In other words, it is more than 20 times faster than the time it takes to blink an eye (150ms).

This snap of the fingers reached a maximum rotation speed of 7800°/s and a rotation acceleration of 1.6 million°/s² within 7ms.

In addition, in the LaMSA system of snapping fingers, the friction between the fingers plays a decisive role in the speed of snapping fingers.

The researchers used different materials to control the coefficient of friction between the fingers. To simulate sweaty hands, they put lubricated nitrile gloves on the fingers. Secondly, they used latex gloves to simulate a higher coefficient of friction. Of course, to prove that Thanos couldn't snap his fingers, the researchers also put metal gloves on the fingers.

Snap your fingers with rubber gloves on. | Georgia Tech

The data found that when sweaty hands reduce friction, it also reduces the energy stored before snapping the fingers. But surprisingly, the rubber gloves that increase friction also greatly reduce the speed of snapping the fingers, because high friction will cause the stored energy to dissipate.

The metal finger sleeves make the originally soft fingers lose their compressible properties, which means that the elastic force of the "spring" is greatly reduced.

The perfect finger snap requires just the right amount of skin friction and compression. | Wiki

In the LaMSA system of snapping fingers, if the friction is too small, the energy stored in the early stage will be smaller; but if it is too large, it will hinder the release of energy.

In short, to perform a perfect snap, the friction and compression between the fingers must be optimal. In the "just right" friction range, the maximum force will be stored before the snap, and the energy dissipation will be reduced during the snap.

So if you adjust your posture but still can't snap your fingers, you might as well wipe your hands to keep your fingers dry and smooth.

The trajectory of the middle finger when snapping your fingers. | doi.org/10.1098/rsif.2021.0672

But while the research was inspired by Thanos, there is more to it than that. The model in this study not only illustrates the importance of friction, but also gives us a new understanding of other organisms and ourselves.

Many insects and animals do not have enough muscle force to support their rapid movements. However, they are able to accumulate elastic potential energy and then convert it into kinetic energy through the "spring and latch" model mentioned above. An ant called Mystrium camillae uses this "snapping finger" technique to make a mandibular movement 5,000 times faster than blinking, setting a world record in the animal kingdom.

The mandible movement of the Camilla ant. It may look slow, but this was captured at 480,000 fps. In fact, it is 5,000 times faster than the blink of an eye. | doi.org/10.6084/m9.figshare.7375436.v1

This research also provides important reference for the future field of bionic hands and prosthetics.

But in addition to being cool, playing accompaniment, and being used by Thanos to destroy the world, snapping fingers can really be used for more important things. For example, blind people can locate themselves and identify their surroundings in an unknown environment by snapping their fingers or flicking their tongues.

In the era of intelligence, researchers have also used finger snapping as a unique biometric feature that can replace passwords and fingerprints to unlock smartphones. However, the prerequisite is that you must first learn the skills of snapping your fingers and make a snap that works.

Unlock your phone with a snap of your fingers? Have you ever considered the feelings of those of us who don't know how to snap our fingers? | Pixabay

Physics saves the world! Thanos: I *&%……%**((&

Cover source: doi.org/10.1098/rsif.2021.0672

Reference: https://docs.qq.com/doc/DU3VIbld3SmVVS0x4

Source: Bringing Science Home