(Newser)
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Sand exhibits so many unexplainable physical properties that some think granularity is a form of matter unto itself, Wired reports. Granular matter acts like a solid, a liquid, or a gas depending on the circumstance. “You walk on the beach, and the sand supports your weight,” said physicist Heinrich Jaeger. “Pick up a handful, and it runs through your fingers, like a liquid. But you can’t walk on water.”
A recent study of the physics of falling sand shows the grains forming into droplets like water, even though the forces of cohesion in granular materials are 100,000 times weaker than in liquids. Jaeger thinks understanding granular materials, which exist everywhere in industry, is paramount. “Physicists have a rich toolbox for dealing with solids, liquids and gases,” he said. “But we don’t have a manual for when the old categories don’t apply.”
