The sailing stones of the Racetrack Playa, a dry lakebed in Death Valley, have been the subject of a mystery since the 1940s. The playa is dotted with stones, some as large as 700 pounds (320kg), with long tracks behind them, as though they have been performing a synchronised dance.
Although there have been many theories about how the rocks might be moving on their own — including dust devils, hurricane-force winds, films of slippery algae or thick sheets of ice — none had ever been confirmed, nor had any human seen the rocks actually moving.
Until now, that is. A team of researchers from the Scripps Institution of Oceanography at UC San Diego decided they were going to solve the mystery once and for all. In the winter of 2011, they brought in a high-resolution weather station to measure wind at one-second intervals, and brought in 15 rocks fitted with GPS devices (since the National Parks Service would not allow them to use the native rocks).