The Order of Chaos - Data Week


By Timothy Dillon

Photo courtesy of dr_zoidberg

For anyone who has been to a rough concert, the sensation of being part of a mosh pit is quite familiar. Anyone who has never moshed is missing out on a full sensory experience. First, you and everyone around you, is packed together. Sweat is common, as all that close contact tends to turn up the heat. And of course, with sweat comes body odor; your nasal passages are filled with the hundreds of people you are all mashed together with, so much so, that you can almost taste it.

It can be difficult to focus on anything as your eyes are being bombarded with a sea of faces. That sea of faces moves too and moves you along with it. The mosh pit sways to the music and people are splashed one way and another, never letting anyone in its grasp settle in one spot for too long.

Being part of a mosh pit is a disorienting experience that some people actively seek out. It can be enjoyable to feel like part of a large organism, but for those who don’t share this affection, it just seems like absolute madness. Perhaps it is, but this chaos is not without order beneath it.

Matt Bierbaum and Jesse Silverberg are a couple of heavy metal, hardcore loving, mathematicians. Graduate students at Cornell University, Bierbaum and Silverberg have spent the last couple of years studying how people in large crowds act and move. Using a large set of coupled Ordinary Differential Equations (ODEs) they were able to create a simulation of various types of mosh pits.

“I just couldn’t believe what I was seeing,” Silverberg tells BTR. “From the classes I had taken, I had studied a little bit about how air molecules move around, and there I was, watching the mosh pit, and it looked exactly like the picture that I had sort of dreamt up.” When you step back from the crowd these people seem to flow and bounce just like the air around us.

After recognizing a system to this, they set out to try and define the parameters of a mosh pit. Getting technical, but not too esoteric, Bierbaum explains that they basically treated the people like single particles interacting with each other. “All we’re choosing are the forces that we want to use to allow our particles to propagate,” Bierbaum explains.

In their analysis, they consider different types of forces, like a flocking force as seen in birds, and of course, the forces of particles colliding with one another. The nature of the force within a mosh pit presents itself in a variety of ways as well. There is the traditional swarm of people and then there are circle pits, when the flock moves and rotates within a larger crowd. Much of this was trying to create a model for how people behave in these types of extreme situations.

Behavior is a bit tricky. When asked if a person could use their model to help navigate a mosh pit, Bierbaum and Silverberg considered this as something that remains unknown. While their mathematical model is good at predicting behavior to a certain extent, how people make decisions, on the psychological level, is something they still hope to explore and study to improve their model.

Photo courtesy of Adrian Purser

“You have to be careful when you try to map simulation parameters onto a real group of people,” says Silverberg. “We definitely need to work more with people who study the sociology of crowds and really try to capture the underlying dynamics of human psychology.”

Later this summer, Bierbaum and Silverberg plan on filming a heavy metal show in order to extract a lot of real world data and apply it to their model. They have used YouTube videos to analyze crowds, however, the video is often shaky, or has a limited view. With a better set of recordings from various angles, they would be able to map the path and trajectories of the particles (people), and possibly recreate the crowd itself in simulation.

Their research has not gone unnoticed either. Besides their own desire to find where they fit in the greater world of science, they also see the real world applications of their findings. There are companies working with crowd control and large groups of people who would be interested in seeing more accurate models of crowd movements. When asked if there were any shows in particular they would like to film and study they laughed.

“All of them. If someone wants to help us get in to metal shows to film these things, I mean what better mix of work and pleasure, could I ever imagine? I don’t know,” Silverberg laughs.

Though experiencing a mosh pit and circle pit is discombobulating, there is actually a serious amount of order coordinating how the crowd moves. The constraints of the other people and the enclosure or environment changes as the crowd reacts and changes over time. In time, Bierbaum and Silverberg hope to improve their model so that they can accurately predict human crowd behavior. Guess that means more metal for these mathematicians is all in a days work.

For some fun, check out this epic mosh pit compliments of Andrew WK: