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The drops that run down the inside of a glass after wine is swirled – called “legs” or “tears” – are caused by a shock wave interrupting the ring of fluid that sticks to the glass.
We know that a film of wine can flow up the side of a glass after swirling because the water in wine evaporates faster than the alcohol, creating a difference in surface tension that drives liquid upward. But exactly what caused wine tears to form was a mystery until now.
Hangjie Ji at the …
source: newscientist.com