This is scientific American 60 second science.

I'm Christopher Intagiyata.

Nuckles, Cracking.

You may not mind the sound, you may despise it, or you could study it.

Couple years back, Vinny Sujo was taking a biomechanics class at the French Polytechnic

school outside Paris, and he was on the hunt for the perfect class project.

Even though they suggested many projects, I couldn't find one which is both practical and that I could

complete within the framework of this class.

So in frustration, I was cracking my knuckles one day and that's when I realized, huh,

that's interesting.

And so a project was born, the physics of knuckle cracking.

It's actually a subject of intense scientific investigation.

Back in 1971, scientists figured they knew how it worked.

The cracking sound was caused by bubbles popping. 21 scientists figured they knew how it worked.

The cracking sound was caused by bubbles popping

within the fluid surrounding the knuckles.

Or so they thought, because in 2015, shots were fired

in the form of MRI visualization of the knuckles post-cracking.

In fact, the bubbles were still there.

The whole process happens too fast for imaging technology to visualize in real time.

You'd need to shoot at 1,200 frames per second,

10 times faster than the best x-ray and MRI machines on the market.

...