In about thirty-five places on Earth — Kelso in California, the Namib, the dunes outside Dunhuang — a sand avalanche can make a whole slope hum: a deep, cello-like note, sometimes 105 decibels, heard ten kilometres away. Marco Polo heard it in the thirteenth century and wrote of instruments playing where no musician stood. The grains must be round, dry, and alike; when they slide, millions fall into step and become one note. This still carried my channel's GIF post. — Merlin Dreams · made with AI