Reacción a "Analysis of how the human tide of the chupinazo in San Fermín moves, which could prevent accidents"

If there is one thing that someone born in Pamplona, like the author of this article, can assure you, it is that being inside the Town Hall Square during the San Fermín "chupinazo" is a unique experience. It is the closest thing to being a tiny particle trapped in a dense, chaotic, and constantly moving space—except that the other 'particles' are wearing red scarves and have likely had more wine for breakfast than advisable. But what was once just a personal impression has recently gained scientific backing.

A study published in Nature by a team led by Denis Bartolo, a professor at the École Normale Supérieure de Lyon, in collaboration with Iker Zuriguel from the University of Navarra, has analyzed this phenomenon rigorously for the first time.

These researchers have conducted a meticulous four-year observation of how thousands of people (around 5,000), packed like sardines in the Consistorial Square during the chupinazo, end up moving in a coordinated manner without any explicit guidance. According to their analysis, when the crowd reaches a critical density threshold (about four people per square meter), it transitions from a disordered state to an emergent phenomenon of collective oscillations, in which hundreds of individuals synchronize into a swaying, orbital movement.

The significance of this discovery goes beyond a mere festive anecdote. The phenomenon observed in Pamplona is a benign version of what can happen in extreme danger situations, such as the 2010 Love Parade tragedy in Duisburg, where the researchers also identified the presence of these oscillations before the deadly stampede that claimed 21 lives.

The study does not stop at mere empirical description. Based on principles of fluid mechanics, the researchers have developed a model that predicts how these oscillations emerge and how they could be monitored in real time. Simply put: if we can determine the point at which a crowd stops behaving as a collection of individuals and starts acting as a single oscillating entity, we could identify when a controlled situation might escalate into disaster.

For those of us who have experienced the chupinazo firsthand and have a background in physics, the idea that the crowd’s pushes and movements can be described by differential equations is both fascinating and unsettling. However, the study of crowd dynamics not only helps us understand the frenzy of San Fermín but also allows us to identify behavioral patterns that could be crucial in anticipating and preventing accidents at large-scale events. Being able to monitor and predict these collective flows is essential for ensuring safety and optimizing the management of massive gatherings.

So next time someone asks me what it feels like to be at the heart of the chupinazo, I won’t have to resort to vague metaphors. Now I can answer with precision: "It’s a density-driven phase transition that gives rise to collective oscillations." And then, raise a toast to it.