When Marco Polo heard it in China, he suspected evil spirits. When residents of Copiapo, Chile, heard it emanating from a sandy hill, they dubbed the peak El Bramador, for its roars and bellows.
Scientists today call it “singing sand,” but they’re all referring to the same thing: As sand grains shuffle down the slopes of certain sand dunes, they produce a deep, groaning hum that reverberates for miles.
A trio of Parisian biophysicists think they know the answer. It’s not necessarily the motion of the sandy ocean that determines the pitch of the note—it’s the size of the grains, though why the size matters is still unknown.
This was sort of expected, at least it makes sense. They already knew that different dunes made different tunes. The authors describe the noise as millions of little shocks as the grains bump together. Pretty cool stuff. Singing sands have been one of those Fortean mysteries that I sort of knew eventually science would tease appart and figure out. There are more…