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[时差N小时] 时差N小时:咖啡渍的奥秘（上）
Next time you spill a little, let the coffee dry before wiping it up. You’ll notice that after it dries there is a darkish ring around the very edge of the spill, whereas the middle disappears2012-01-13 编辑：beck
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[时差N小时] 时差N小时:咖啡渍的奥秘(下)
Why is that? It’s because the edges of the spill are where the fluid is at its thinnest. A spill sitting on a flat surface is something like a pancake. Big in the middle and thin on the rim. As2012-01-16 编辑：beck
