Archive for the ‘physics’ Category


Human wave physics goes pragmatic

April 16, 2007

Hajj, Jabarat Bridge For some years, specialists in fluid dynamics have taken an interest in wave phenomena in crowds, analogous to the well-known compressible fluid dynamics that create stop and go vehicular traffic. The most vivid motivation has been the fact that trampling deaths have become more common as more and more pilgrims attend the Hajj. Rather than a few tens of thousands, millions now seek to make their way across the Jamarat bridge near Mecca. Now there’s been a lifesaving breakthrough. As Science News reports:

In collaboration with Saudi authorities, physicists at Dresden University of Technology in Germany studied video recordings of the 2006 stampede. They wrote visual-recognition software to track and measure the motion of individuals in the crowd and, by following those individuals, analyzed the crowd’s movements as the disaster unfolded…”We tried dozens of different measurements,” says team member Anders Johansson, but he and his colleagues found only one factor, which they called crowd pressure, that proved useful. It combines crowd density and the rate of change in the velocity of the flow.

The team found that critical thresholds in crowd pressure correlate with the onset of stop-and-go patterns and turbulence. The findings are due to appear in Physical Review E.

…Salim Al-Bosta, a civil engineer in the Saudi government, says that measures based on the research helped the Hajj run smoothly this year. Image-recognition software now tracks the flow of pilgrims and warns organizers to slow the influx of pilgrims to the site when crowd pressure approaches a critical value, he says.

This would be very cool just as pure research. That it also has such a positive human benefit plasters a huge grin on my beak.

Next challenge for the physicists: model and provide corrections for the dynamic which inexplicably lowers average IQ by forty points when large numbers of Americans enter voting booths.