Explain the tragedies of the masses with science

On November 6, 2021, in Houston (Texas), 8 people died out of passion during a rapper party Travis Scott Another 25 were taken to hospital with their injuries. NRG Park (where the event took place) was incredibly crowded; Several people started making their way through the crowd to get to the front row under the podium. The crowd that followed did the rest: a person fell and pushed one of them so as not to run over the miserable person, until the pressure reached the barriers that caused the tragedy.

dark story. This is not the first time such episodes have occurred: in 1979, 11 people lost their lives at the “He” show in Cincinnati and in 2009 9 more people died with the same dynamic while performing at Pearl Jam at Roskilde Festival in Denmark. Recently (April 2021), a crowd of people crushed 45 people during a religious ceremony in Meron, Israel.

And in Italy we remember the tragedy of the nightclub in Corinaldo (Ancona) in 2018, in which 5 teenagers and a young mother were killed, and the crowds in Piazza San Carlo in Turin in June 2017, when the crowd was raging. After the UEFA Champions League Final on a giant screen, 3 people cost their lives, as well as dozens of injuries.

Catastrophe science. Over the years, scientists have studied crowd dynamics for a long time, precisely with the aim of preventing such events from happening. One of the most analyzed disasters is the one that occurred during the pilgrimage to Mecca in January 2006: more than two million pilgrims take a predetermined route through the heart of the city, to the Jamarat Bridge, where the road narrows. Mob pressure increases dramatically and leads to the killing of 363 Sunni believers.

Dirk’s help N Anders Johansson From the University of Dresden he studied the videos of the tragedy for a long time and with the help of computers reconstructed the movements of the masses, he identified 3 stages.

At first, the crowd faces increasing pressure as the path narrows and begins to move in fits and starts. The movement advances, in the same direction as the people, like a wave. But the pressure continues: at this point, people are trying to escape persecution at all costs, fleeing in all directions and trampling on each other. According to scientists, this stage occurs when more than 6 people gather per square meter.

Watch out for the pogo. In Houston, the tragedy was not caused by a bottleneck, but by a different phenomenon known as crowd no hole, this is the “dance floor audience” who gather during performances under the stage to dance, jump, compete and bump into each other (eg, porkAs they say in the language of youth).

The mosh pit crowds have been carefully studied by Jesse Silverberg, a physics student at Cornell University with a passion for metal music. Using concert videos posted on Youtube, Jesse created a computer model that accurately tracks the movements of the audience on stage. There are the passive people, who sit idly even when a confrontation with the dancers occurs, and the active people, who are proactively looking for someone to bump into: that is pogo.

When the origins are in the majority, the crowd begins to act like a gas, with molecules randomly colliding with each other. But when two or more start moving in the same direction, real human vortices are created, engulfing every person they encounter with potentially dangerous consequences. Obviously, the researchers explain, the model greatly simplifies human behavior, but it has evolved enough to explain what might happen.

(dis) The human factor. Other studies, such as those of Dinesh Manchwa The University of Maryland includes psychological factors along with mechanical factors and calculates a safety limit of 4 people per square foot. At such intensity, explains Manchua, individual behaviors play a key role: Aggressive people, who start pushing or yelling, can be the spark that causes panic. With imaginable tragic consequences.