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Mosh Pit Physics, Chemistry Of The Bar

by Lauren K. Wolf
April 15, 2013 | A version of this story appeared in Volume 91, Issue 15


Credit: St. Petersburg Times/ZUMAPRESS/Newscom
People particles: Model likens mosh pits to an ideal gas.
This a photo of fans swirling in a mosh pit.
Credit: St. Petersburg Times/ZUMAPRESS/Newscom
People particles: Model likens mosh pits to an ideal gas.

When Matthew Bierbaum stepped up to the front of a crowded ballroom at the American Physical Society national meeting last month, he didn’t begin his research presentation in a conventional way.

“Who here has been to a metal concert?” the graduate student asked. “Throw up some horns!” he egged on attendees to simultaneously extend their pinkies and index fingers as a sign of heavy-metal love.

Bierbaum was in Baltimore not to discuss musical resonances, but to share his findings about mosh pits—formations at punk and heavy-metal concerts in which dancers slam into one another for fun. Together with fellow grad student Jesse L. Silverberg and professors James P. Sethna and Itai Cohen at Cornell University, Bierbaum analyzed and modeled the collective motions of the slam dancers on myriad YouTube concert videos. A paper summarizing their results is available on the preprint site ArXiv (

In a run-of-the-mill mosh pit, Bierbaum said, dancers collide with each other randomly and at a distribution of speeds that resembles particles in a two-dimensional gas. “How these supposedly intelligent beings behave like an ideal gas, I don’t know,” the physicist quipped.

Some moshers don’t move completely randomly, however. In circle pits, a subset of mosh pits, dancers collide in a vortexlike pattern. So Bierbaum and the other Cornell physicists described this behavior with a computer simulation based on flocking, a phenomenon that results when particles follow their neighbors.

Of the circle pits the team analyzed, 95% moved in a counterclockwise fashion, something Bierbaum tentatively attributes to humans’ dominant handedness.

After one audience member jokingly asked Bierbaum whether he was trying for an Ig Nobel Prize, the graduate student said, “We have this cool model, but there are serious implications.” The Cornell team hopes to use it to study how crowds move in emergency situations such as riots, he said.

“No funding from the government was used for this work,” he added. “We bought our own concert tickets.”

Another atypical research presentation took place last week at the American Chemical Society national meeting in New Orleans. During an Agricultural & Food Chemistry Division-sponsored symposium, “Chemistry of the Bar,” scientists talked about the chemicals responsible for the taste and smell of various cocktails.

Credit: Shutterstock
Hurricane: New Orleans cocktail is full of tasty chemicals.
This is a photo of the signature rum-based drink of New Orleans, the hurricane.
Credit: Shutterstock
Hurricane: New Orleans cocktail is full of tasty chemicals.

New Orleans’ signature rum-based drink, the hurricane, got the analytical treatment from Neil C. Da Costa, a researcher for International Flavors & Fragrances, in New Jersey. “I’m not here to tell you how to make the ideal hurricane,” Da Costa said. “There are more than enough bars in New Orleans to do that.”

But the British scientist did report the results of his investigation into the cocktail’s main, traditional ingredients: light and dark rum, lime juice, and passion fruit juice.

Although both light and dark rum are used in the cocktail, the dark version, aged in charred oak barrels, has more flavor than the light version, Da Costa said. Accordingly, he added, the brownish rum also contains heavier chemical compounds, such as phenolics. Passion fruit is also key to a hurricane’s taste because it enhances the citrus notes in the drink with sulfur-containing molecules such as mercaptoesters.

Overall, though, bartenders might improve the Big Easy’s darling drink by taking some cues from flavor chemistry, Da Costa said. “If they reduced the amount of alcohol and sugar,” which mask subtle notes like passion fruit, “they’d probably get more flavor out of the drink.”

Bourbon Street establishments reduce the amount of alcohol in their wares? Newscripts thinks chances are slim.

Lauren Wolf wrote this week’s column. Please send comments and suggestions to


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