Wherever dense crowds gather, an eruption of panic can have deadly consequences, as in the stampede that killed hundreds during a mass pilgrimage to Mecca in 2006. With methods from the physics of fluids, scientists have now dissected the events of that tragic day and come up with recommendations that may have contributed to making this year’s pilgrimage proceed smoothly.
Every year toward the end of the week-long Hajj pilgrimage, millions of pilgrims visit the place in the desert outside Mecca, Saudi Arabia, where Abraham is said to have thrown stones at the devil. Every able-bodied Muslim is supposed to make the trip at least once. When they arrive, pilgrims throw pebbles at three walls, which symbolize three apparitions of the Evil One.