《那些古怪又讓人憂心的問題》第134期:雨滴(2)
For five or six seconds, nothing is visible. Then, the base of the cloud begins to bulge downward. For a moment, it looks a little like a funnel cloud is forming. Then the bulge widens, and at the ten-second mark, the bottom of the drop emerges from the cloud.
The drop is now falling at 90 meters per second (200 mph). The roaring wind whips up the surface of the water into spray. The leading edge of the droplet turns to foam as air is forced into the liquid. If it kept falling for long enough, these forces would gradually disperse the entire droplet into rain.
現在水滴的下落速度已經達到了每秒90米。呼嘯而過的大風將表層水吹成水霧。隨着越來越多的空氣被強行擠入水滴內部，水滴的下沿開始變成泡沫狀。如果水滴繼續以這個速度下落足夠長的時間，這些力會漸漸把整個水滴分解成雨滴。Before that can happen, about 20 seconds after formation, the edge of the droplet hits the ground. The water is now moving at over 200 m/s (450 mph). Right under the point of impact, the air is unable to rush out of the way fast enough, and the compression heats it so quickly that the grass would catch fire if it had time.
但在那發生之前，在水滴形成後約20秒，水滴的下沿接觸到了地面。現在水滴的下落速度超過每秒200米。在接觸點的正下方，空氣無法及時排開，被壓縮的空氣迅速產生大量熱量，假如有時間的話，下面的草叢是會着火的。
Fortunately for the grass, this heat lasts only a few milliseconds because it's doused by the arrival of a lot of cold water. Unfortunately for the grass, the cold water is moving at over half the speed of sound.
好消息是，這些熱量只持續了幾毫秒的時間，隨後它就被大量冰冷的水淹沒了。壞消息是，急速而來的冰冷水滴速度超過音速的一半。If you were floating in the center of this sphere during this episode, you wouldn't have felt anything unusual up until now. It'd be pretty dark in the middle, but if you had enough time (and lung capacity) to swim a few hundred meters out toward the edge, you'd be able to make out the dim glow of daylight.
如果之前你一直漂在整個水滴的正中央，你直到此時此刻纔會發現一些異樣。水滴的中央非常暗，如果你有足夠的時間（和肺活量）游上幾百米來到水滴邊緣，你會看到黯淡的光線。As the raindrop approached the ground, the buildup of air resistance would lead to an increase in pressure that would make your ears pop. But seconds later, when the water contacted the surface, you'd be crushed to death-the shockwave would briefly create pressures exceeding those at the bottom of the Mariana Trench.
隨着水滴離地面越來越近，不斷增加的空氣阻力會產生越來越大的壓強，你的耳朵會感到脹痛。幾秒後，當水滴接觸到地面時，你就會因擠壓而死——衝擊波會在瞬間產生超過馬裏亞納海溝底部的壓強。The water plows into the ground, but the bedrock is unyielding. The pressure forces the water sideways, creating a supersonic omnidirectional jet1 that destroys everything in its path.
整個水滴一頭撞上地面，不過地面上的基岩是不可撼動的。由此產生的壓力將水推向四側，產生一股超音速全向射流，1摧毀一切沿途的物體。
