# Mosh Pit Math: Physicists Analyze Rowdy Crowd

Mar 21, 2013
Originally published on March 22, 2013 5:55 am

Physics and heavy metal don't seem to have a lot in common, but Matt Bierbaum and Jesse Silverberg have found a connection. Both are graduate students at Cornell University. They're also metal heads who enjoy going to concerts and hurling themselves into mosh pits full of like-minded fans.

About five years ago Silverberg took his girlfriend to her first gig. "Usually I would jump in the mosh pit," he says. "But this time I wanted her to be safe and have a good time, so we stayed out on the side and watched things from there."

While he was watching, he realized that the motion of people in a mosh pit looks kind of like molecules moving in a gas.

"It was basically just this random mess of collisions, which is essentially how you want to think about the gas in the air that we breathe," he says.

Physicists have worked out the basic rules that describe this kind of motion, so Bierbaum and Silverberg decided to look for the rules of motion in moshing. They went to concerts and studied videos from YouTube. Silverberg emphasizes that no tax dollars went toward buying concert tickets — the study is a labor of love.

Using just a few variables, like how fast people moved and how dense the crowd was, Bierbaum and Silverberg created a mathematical model that they presented at this week's March meeting of the American Physical Society. Using a mixture of simulated moshers and standing fans, they could reproduce mosh pits, circle pits and other common collective motions that take place at metal concerts. You can try some simulations for yourself in their mosh pit simulator below.

It's not just the metal heads that obey these kinds of basic mathematical rules, says Andreas Bausch, a researcher at the Munich Technical University in Germany. Flocks of birds and schools of fish do similar things. So do car drivers. Now concertgoers can be added to the list, he told NPR in an email. "This is indeed cool stuff."

The new mosh pit research could be interesting for another reason. In emergencies people panic, and the movement rules they follow change. Mosh pits might provide clues about the new rules.

"We hope that this will provide a lens into looking at other extreme situations such as riots and protests and escape panic," Bierbaum says.

They plan to continue their research, while rocking on.

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Transcript

STEVE INSKEEP, HOST:

This week, thousands of physicists flock to Baltimore for an annual event, the largest physics conference in the world. The topics have included topological insulators and frustrated magnetism. Frustrated magnetism. Many of us have had that problem, I'm sure. There was also a paper presented on death metal.

NPR's Geoff Brumfiel went to Baltimore to find out what hardcore rock was doing at a physics conference.

GEOFF BRUMFIEL, BYLINE: Meet Jesse Silverberg, a graduate student in physics at Cornell University.

JESSE SILVERBERG: So lately I've been listening to a lot of Killswitch Engage. And also a band out of Germany which is relatively young and new, they're called We Butter The Bread With Butter.

(SOUNDBITE OF MUSIC)

BRUMFIEL: He presented the research on heavy metal with fellow grad student Matt Bierbaum.

MATT BIERBAUM: I've been listening to a lot of Nintendocore and some hardcore too. So that's Bear vs. Shark and HORSE the Band, and stuff like this.

(SOUNDBITE OF MUSIC)

BRUMFIEL: By day, Matt studies regular metals and Jesse looks at something called soft matter physics. By night, they mosh. Moshing is basically hurling yourself headfirst into a crowd of rowdy metal heads.

SILVERBERG: Everyone is running around and bumping into each other and pushing and shoving. And there's loud music and it's fast and the lights are flashing. And probably some people are drunk. And yeah, it's pretty chaotic and pretty messy.

(SOUNDBITE OF MUSIC)

BRUMFIEL: Physicists are always searching for simple patterns in messiness. And five years ago, Jesse had a eureka moment when he took his girlfriend to her first metal gig.

SILVERBERG: Usually I would jump in the mosh pit and run around and spend the show there. But you know, this time I wanted her to be safe and, you know, have a good time, so we stayed out on the side and watched things from there.

BRUMFIEL: While he was watching, he realized that peoples' motion in a mosh pit looks kind of like molecules in a gas.

SILVERBERG: It was basically just this random mess of collisions, which is essentially how you want to think about the gas in the air that we breathe.

BRUMFIEL: Physicists have worked out the basic rules describing this kind of motion. And similar rules apply to flocks of birds and schools of fish. So Matt and Jesse decided to look for the rules of motion in moshing. Using just a few variables, like how fast people move and how dense the crowd was, Matt and Jesse created a mathematical model that they presented at this conference. And yeah, moshers do move kind of like molecules in a gas.

But it's not just the metal heads that obey these kinds of basic mathematical rules. We went to a balcony to watch people milling around in the conference center, and Matt and Jesse thought of something else.

BIERBAUM: There's several groups of three. And then between them there's a lot of people that are forming lanes and trying to navigate their way through the matrix of physicists.

SILVERBERG: And it reminds me of the motion of fluid through a porous medium, like a sponge.

BRUMFIEL: Could some kind sponge equation describe a physics meeting? Maybe. We all obey some basic rules when we're moving around. This is where the new mosh pit research gets interesting. In emergencies people panic. The rules they follow change and mosh pits might provide clues about the new rules.

BIERBAUM: Metal concerts are a very unique situation. They're very extreme. It's loud. It's dense. We've described all the collisions that are happening - how rough it is. And so we hope that this will provide a lens into looking at other extreme situations, such as riots and protests and escape panic.

BRUMFIEL: Jesse and Matt are planning to continue their mosh pit modeling. And, Jesse says, it's changed his concert-going experience.

SILVERBERG: I'm now completely distracted by what's going on around me in the crowd. And sometimes it's just hard to pay attention to the band on stage.

BRUMFIEL: Physics has ruined heavy metal for you. That's so sad, Jesse.

SILVERBERG: You know, I can't think of a worse fate.

(LAUGHTER)

BRUMFIEL: I can. Being in a mosh pit myself.

Geoff Brumfiel, NPR News

INSKEEP: Covering all the news in the world, it's MORNING EDITION from NPR News. Transcript provided by NPR, Copyright NPR.