The bodily legal guidelines that govern the gang of the Sanfermines will enable to keep away from tragedies in agglomerations | Science | EUROtoday

Every July 6, at ten within the morning, the Municipal Police of Pamplona lets individuals cross to the Consistorial Square, which strikes freely from right here to there. But round half an hour earlier than the chupinazo marks the start of the San Fermín festivities, the person melts right into a dough that apparently strikes chaoticly. However, a research revealed Wednesday in Nature He has found that there are not any chaos, however fluid dynamics: a sequence of round actions starring more and more giant subgroups that orbit in intervals of 18 seconds. Physicists discover that the Sanferminera crowd follows Newton’s third regulation and this might serve to review the habits of crowds and till stopping tragedies in agglomerations.

The Pamplonica Square is an area of fifty by 20 meters. At 11:30 there are already greater than 5,000 individuals inside: as much as 9 individuals per sq. meter. But earlier than, when the gang reaches a threshold of 4 pedestrians per sq. meter, one thing adjustments. “After a critical density, the crowds have a spontaneous oscillatory movement,” says the professor of the Superior Normal School of Lyon (France) and co -author of this analysis, Denis Bartolo. “Even in the absence of external signals, people begin to move in synchrony,” provides this physicist devoted to the research of mass phenomena.

With cameras positioned on the roofs of the sq., this group of physicists studied the dynamics of the gang throughout the chupinazos of 2019, 2022, 2023 and 2024. The similar occurred yearly. When overcoming that threshold, the person melts within the crowd, forming subgroups of some hundred, with some turning to the left and others to the appropriate which might be rising in measurement (watch video). “At the beginning of the collective movement, the amplitude of these movements is small, but it grows as density increases, which results in circular trajectories of several meters. People move in mass, ”particulars the French physicist, who has studied dynamics from different crowds, such because the one within the Chicago marathon. It was the professor of the Department of Physics and Mathematics utilized to the University of Navarra, Iker Zuriguel, who instructed Bartolo that he needed to go see the Sanfermines.

“From four people per square meter, these sustained movements begin to occur, that is, an oscillatory movement with a frequency that is 18 seconds,” says Zuriguel. “The movement is not ahead and back as I believed. I was there of a kid and I had the feeling that it was ahead-Atrás, ”he recollects. But the dynamic is orbital, within the path of the clock needles some teams, in the other way others, and after these seconds, return to the location the place one was. “It is not chaotic, what we see is a pattern with a characteristic frequency,” provides the Spanish physicist, co -author of the research.

One of the phenomena they’ve noticed is that the dimensions of the subgroups grows by growing density. “As we approach Chupinazo, one thing we see, is that those regions in which everyone is rotating synchronized are growing. At first they are smaller areas and then in the end there is almost only one, ”says Zuriguel. In that course of, the totally different teams rotate in a single path and, periodically, change and accomplish that in the other way. The key to this temporal dynamic, thought that “it had to have to do with the size of the square,” ends the Navarrese physicist. But they needed to show it.

There are different circumstances of pedestrian dynamics that don’t slot in these seen in Pamplona. In manifestations or marathons there are dynamics of unemployment and march. In the middle of the large cities, pedestrians are likely to group and set up their march in double -meaning lanes, as in the event that they had been vehicles. But when on the lookout for examples with this modification from the person to the collective, they discovered it within the Love Parade. This Tecno Music Festival, began in Berlin in 1989, congregated hundreds and hundreds of attendees, and ceased to be held after the tragedy with about twenty useless that occurred within the 2010 version, occurred in Duisburg, additionally in Germany. Although the situation was very totally different, there with giant avenues, they discovered sure areas the place the density was equal to that noticed in Pamplona. “We estimate that region where there was a lot of density and we saw that the movements were exactly the same, newspapers,” says the physicist of the University of Navarra.

The ultimate affirmation of the validity of their idea had it once they returned to the Pamplona city corridor. After the chupinazo, dozens of chistularis come out of the city corridor on each side by the municipal ones with the results of dividing the dough into two. “They do the screen, the pressure waves do not cross the police and the pipers. When the place is leaving in two, there are two groups of different sizes, with a frequency, a different period, but that dividing by the size of the square came everything the same. The peaks are not so beastly, they are somewhat smaller, but the same movement is seen again, but at a different frequency, ”provides Zuriguel, which prior to now has studied pedestrians of pedestrians and evacuation of individuals, as on this experiment carried out With army making an attempt to get out of an enclosure: “The stronger you push, worse you.”

The research authors conclude within the article of Nature which collects its analysis the next: “Regardless of the microscopic mechanisms that promote the movement of people and dictate their interactions, the macroscopic dynamics of the crowd obeys a fundamental law: the conservation of linear momentum.” This is nothing aside from Newton’s third regulation. “The conservation of the linear momentum is nothing other than the mass by speed and has to be kept. That is Newton’s third law. Then, in any collision, mass per speed is preserved, ”recollects Zuriguel. The friction recreation between these current within the sq. follows a elementary regulation of physics.

Of the person to La Masa

The professor of the University of Wupertal (Alemamania), Antoine Tordeux, has additionally revealed in Nature A touch upon the work of Bartolo, Zuriguel and different colleagues. It highlights how what in precept is the motion of hundreds of autonomous brokers adjustments and turns into a collective with its personal dynamic through which the bodily dominates the social. “The social forces are the conventional behavior of pedestrians in low or medium densities, which consists mainly of avoiding collisions with the neighbors, trying to maintain a limit in a space,” he particulars in an electronic mail. Meanwhile, physicists “are forces of thrust and body compression that occur when pedestrians are in direct contact,” that’s, in dense crowds such because the one produced in Pamplona. “In the article of NatureBartolo and his co -authors observe an abrupt increase in the energy of the crowd when the density begins to overcome the critical density threshold of about 4 or 5 pedestrians/m², at which time the pedestrians begin to be in direct contact with each other ” , Tordeux states.

This transition from the individual to the collective is very well related to the physicist Iñaki Echeverría, also from the University of Navarra, and who has not participated in the study. In statements to the SMC Spain portal, it says: “It is the closest factor to being a tiny particle trapped in a dense, chaotic and fixed motion area …”. And he adds: “The relevance of this discovery transcends the festive anecdote. The phenomenon observed in Pamplona is a benign version of what can happen in extreme dangerous situations, such as the tragedy of the Love Parade in 2010 in Duisburg. ” The model built on those seen in Pamplona identifies a threshold from which danger situations could emerge.

Zuriguel, one of the authors, thinks that although accumulation of people causes that change in movement, it would not necessarily indicate that it is dangerous. “But in the long run they’re non -voluntary actions, so a little bit hazard is,” he says. Meanwhile, Bartolo, another of the authors, recalls that they have not studied accidents such as the stampede of MECA, in which hundreds of people died. “But the truth that the spontaneous dynamics of dense crowds are periodic makes it very simple to detect it very quickly, lengthy earlier than the amplitude of the motion can develop into harmful,” he says. And that data may very well be key to avoiding disasters similar to those who generally occur in mass agglomerations of individuals.