時(shí)差N小時(shí):雨滴的多種形狀

When it's raining, it may seem that every raindrop isthe same—same size, same basic shape, samewetness. But if you could compare and measureraindrops, you'd find that they're not all the samesize or shape. In fact, raindrops vary from one to sixmillimeters in diameter and come in all sorts ofshapes. When they first fall from clouds, raindropsare surprisingly large—in rare cases, some are aswide across as a baseball. So what happens to breakthese monster drops into many smaller drops ofdifferent sizes?

下雨時(shí)，似乎每一滴雨都是一樣的——一樣的大小，一樣的基本形狀，一樣的濕潤。但如果你能比較和測量雨滴，就會(huì)發(fā)現(xiàn)它們的大小、尺寸并不完全相同。實(shí)際上，雨滴的直徑從一毫米到六毫米不等，形狀和尺寸也各不相同。當(dāng)雨滴第一次從云端落下時(shí)，它們出奇的大——在很少見的情況下，某些雨滴甚至?xí)捜绨羟?。那么是什么讓這些“怪獸”雨滴破碎成許多大小不一的小雨滴呢?

Scientists used to think it was the result of drops colliding and splintering as they fell. But onestudy has found that although individual large drops do indeed break up into smaller shards, ithas nothing to do with mid air collisions. Instead, drops shatter all on their own. Frenchscientists observed the phenomenon when they used a high speed camera to capture dropsfalling from a nozzle to simulate rainfall.

過去，科學(xué)家認(rèn)為這是由雨滴在下落過程中相互碰撞、不斷分裂所致。但一項(xiàng)研究發(fā)現(xiàn)，大雨滴確實(shí)分裂成為較小的碎片，但這與半空中的碰撞無關(guān)。實(shí)際上，雨滴是自動(dòng)破裂的。法國科學(xué)家觀察到這一現(xiàn)象，他們用噴嘴模擬降雨，用高像素的相機(jī)捕捉到了水滴下落時(shí)的鏡頭。

As it falls from the nozzle or cloud, the drop flattens. Then it seems to inflate like a balloon.Finally, after a few milliseconds, the upward pressure of air causes the drop to explode intohundreds of watery bits. The researchers created mathematical models to demonstrate thatthe shattering of individual drops explains why raindrops come in different sizes. Now, math isalways useful—but to really get a sense of how raindrops shatter, you have to see it up close.

隨著水滴從噴嘴或云端不斷下降，雨滴趨于平緩。然后，它們像氣球一樣膨脹。最后，幾毫秒過后由于空氣的上行壓力，雨滴爆炸成上百個(gè)小水滴。單個(gè)雨滴的爆炸解釋了為什么雨滴的大小各異，研究人員還創(chuàng)建了數(shù)學(xué)模型來加以說明。現(xiàn)在，數(shù)學(xué)總是能派上用場——但想要真正了解雨滴是如何分裂的，你必須近距離觀察它。