時差N小時:咖啡漬的奧秘(上)

　　Next time you spill a little, let the coffee dry beforewiping it up. You’ll notice that after it dries there is adarkish ring around the very edge of the spill,whereas the middle disappears almost entirely.What’s going on here? Robert Deegan and SydneyNagel at the University of Chicago looked into thisphenomenon, and they discovered somethingpretty interesting. The coffee puddle leaves a ringbecause it doesn’t simply dry where it sits. As thespill begins to dry, it actually creates its ownoutward motion, drawing the insides of the puddletoward the edges.

　　下一次你灑出一點咖啡，在擦掉前讓咖啡變干。你會注意到，咖啡干后在溢出的邊緣處有一圈淺黑的邊，而中間的咖啡幾乎全揮發(fā)了。這到底是怎么回事?芝加哥大學(xué)的羅Robert Deegan 和Sydney Nagel研究了這一現(xiàn)象，他們發(fā)現(xiàn)了一些非常有趣的事?？Х鹊尾皇呛唵蔚負]發(fā)掉，它實際上產(chǎn)生了自身的向外運動，將水滴中間的咖啡推向邊緣。