News & Events

November 12th, 2006

Ski moguls move uphill…really!

David Bahr (INSTAAR Affiliate) and Tad Pfeffer have used time-lapse photography to demonstrate that ski moguls move uphill, a counterintuitive result. The uphill propogating "kinematic waves" are created by skiers that scrape off the downhill side of one mogul and then pile that snow on the uphill side of the next mogul. The net effect is that each mogul gains material on top, loses material on the bottom, and therefore migrates slowly uphill (centimeters a day). Mogul dynamics resemble other "self-organizing" systems like flocks of birds and LCD crystals. Furthermore, moguls move along ski trails like electrons on a wire. By treating each trail junction as a logic gate, a fully functional (albeit very slow) computer can be constructed from moguls. This research may help ski areas better plan how and where to place gates on trails. Ski racers might also benefit from understanding the physics of mogul movement. The bumps that the last racer is skiing are compressed toward them compared to the first skier. Bahr and Pfeffer's research is ongoing at the Mary Jane/Winter Park Ski Resort.