When the Mongols returned a few years later with an even bigger army, another typhoon showed up and turned the invading fleet into driftwood.

幾年後，當蒙古人帶著更龐大的軍隊捲土重來時，又一場颱風把入侵的艦隊變成了浮木。

Thinking their emperor had summoned the storms to rescue them, the Japanese named these typhoons Divine Wind, or Kamikaze.

日本人以為他們的天皇召喚風暴來拯救他們，是以將這些颱風命名為 "神風 "或 "神風"。

Native cultures in the Caribbean and Central America, like the Taino and Maya, told stories of Uruk-Han, a god who brought wind and storms.

加勒比海和中美洲的土著文化，如泰諾人和瑪雅人，講述著烏魯克-漢的故事，他是一個帶來風和風暴的神。

Their ancient artifacts tell us that they'd deduced these storms' spiral shapes long ago, something Western scientists wouldn't figure out until 1831.

他們的古代文物告訴我們，他們很早就推斷出了這些風暴的螺旋形狀，而西方科學家直到 1831 年才發現這一點。

Tropical cyclones are called by different names in different oceans, but Atlantic hurricanes, like Katrina and Sandy, are probably the most famous.

熱帶氣旋在不同的大洋有不同的名稱，但像卡特里娜和桑迪這樣的大西洋颶風可能是最著名的。

These storms are some of the nastiest monsters that Earth's game makers throw our way.

這些風暴是地球上的遊戲製作者拋給我們的一些最噁心的怪物。

A fully formed hurricane can reach more than 100 miles across, walls of clouds and ice can extend up through the entire lower layer of our atmosphere, but how does a storm that big even happen?

完全形成的颶風直徑可達 100 多英里，雲牆和冰牆可以延伸到整個大氣層的下層，但這麼大的風暴是如何形成的呢？

The basic ingredients for a hurricane are pretty simple, heat and wind.

颶風的基本要素非常簡單，就是熱和風。

The wind is easy, wherever we find low air pressure, air wants to move from the outside in to fill that low pressure.

風很簡單，只要發現氣壓較低，空氣就會從外向內流動，以填補低氣壓。

This is what creates a hurricane's super strong winds, but it doesn't explain why they spin.

這就是颶風產生超強風力的原因，但並不能解釋颶風為什麼會旋轉。

A hurricane's winds want to move in a straight line, but their path is deflected thanks to the Coriolis effect.

颶風本想沿直線前進，但由於科里奧利效應，其路徑發生了偏轉。

If Earth wasn't spinning, hurricanes wouldn't either.

如果地球不旋轉，颶風也不會旋轉。

A 100 mph wind blowing north near the equator is also moving east, along with the direction of Earth's rotation.

赤道附近向北吹的時速 100 英里的風也隨著地球自轉的方向向東移動。

Because Earth is basically a sphere, the closer we get to the poles, the slower the rotation, so as that wind moves north, the atmosphere and the Earth below it aren't spinning as fast, and the sideways motion of the wind outruns Earth's rotation, pushing it east.

由於地球基本上是一個球體，越靠近兩極，自轉速度就越慢，是以，當風向北移動時，其下方的大氣層和地球的自轉速度就沒有那麼快，風的側向運動就會超過地球的自轉速度，將其推向東方。

The same thing happens for the winds on the other side, except they're moving slower, so they get pulled to the west.

另一側的風也會發生同樣的情況，只不過它們的移動速度較慢，所以會被拉向西邊。

This is why cyclones spin clockwise in the southern hemisphere, and counterclockwise in the northern hemisphere, or anticlockwise, or whatever.

這就是為什麼氣旋在南半球順時針旋轉，而在北半球逆時針或逆時針旋轉的原因。

It's also why hurricanes can't form too close to the equator, there isn't enough difference in rotation at low latitudes to start them spinning.

這也是颶風無法在赤道附近形成的原因，因為低緯度地區的自轉差異不足以讓颶風開始旋轉。

Moving in closer to the eye, hurricane winds increase in speed because of angular momentum, just like how a figure skater spins faster when they pull their arms in.

在靠近風眼的地方，颶風的速度會因為角動量而增加，就像花樣滑冰運動員在旋轉時拉緊手臂，速度會更快一樣。

The second key ingredient is heat, from warm water.

第二個關鍵要素是來自溫水的熱量。

A hurricane works a lot like an engine.

颶風的工作原理很像發動機。

Not the engine in your car, but an ideal engine, like the one developed by French physicist Nicolas Carnot.

不是你車上的發動機，而是理想的發動機，比如法國物理學家尼古拉-卡諾開發的發動機。

First, a piston rises.

首先，活塞上升。

Normally, reducing the pressure cools a gas, but in a Carnot engine, heat is added, so the temperature remains constant even as the pressure drops.

通常情況下，降低壓力會使氣體冷卻，但在卡諾發動機中，熱量會增加，是以即使壓力降低，溫度也會保持不變。

But what happens if we turn off the heat, and keep dropping the pressure?

但是，如果我們關掉加熱裝置，繼續降低壓力，會發生什麼呢？

The gas cools.

氣體冷卻。

Next, let's reverse the first step, lowering the piston.

接下來，讓我們反轉第一步，降低活塞。

We'd expect this higher pressure to heat up the gas, but in our engine we've got a device to draw heat out so the temperature remains the same.

我們本以為壓力升高會使氣體升溫，但在我們的發動機中，有一個裝置可以將熱量排出，是以溫度保持不變。

And finally, we keep compressing the piston, but we stop taking away heat, so the temperature rises along with pressure.

最後，我們繼續壓縮活塞，但不再帶走熱量，是以溫度會隨著壓力升高而升高。

Ideal engines like this don't exist in the real world, but a hurricane is one of the closest things we've got.

現實世界中並不存在這樣的理想引擎，但颶風是最接近的引擎之一。

As winds flow towards the center of a hurricane, we'd expect the low pressure to cool them.

當風流向颶風中心時，我們會預期低氣壓會冷卻它們。

But the air is kept warm thanks to massive amounts of water evaporating it.

但由於大量水分蒸發，空氣保持溫暖。

I mean massive.

我的意思是巨大的。

An average hurricane can carry more than 100 billion pounds of water.

平均一場颶風可攜帶超過 1000 億磅的水。

So how does evaporation keep wind warm?

那麼，蒸發是如何讓風保持溫暖的呢？

Changing water from liquid to vapor, to rip those molecules apart and let them fly free, takes energy.

把水從液態變成氣態，把這些分子撕裂開來，讓它們自由飛翔，這需要能量。

This is why you feel cool when you get out of the pool, it's what happens to a bowl of soup that's left out too long.

這就是為什麼你從泳池出來後會感覺涼爽，這就是一碗湯放太久的後果。

Evaporating water takes heat with it.

蒸發的水會帶走熱量。

That heat is stored in the wind, so the temperature stays the same even as the pressure goes down.

這些熱量儲存在風中，是以即使氣壓降低，溫度也不會改變。

It's just like that first step of our ideal engine.

這就像我們理想引擎的第一步。

Then, as the air rises, our heat source is gone, so water vapor condenses into liquid again, releasing its stored heat into the atmosphere.

然後，隨著空氣上升，我們的熱源消失了，於是水蒸氣再次凝結成液態，將儲存的熱量釋放到大氣中。

The temperature is actually higher on top of a hurricane, thanks just to the heat released by condensing water vapor.

颶風頂部的溫度實際上更高，這只是由於水蒸氣凝結釋放的熱量。

High up, the air releases radiation into space as it flows out and down, just like step 3.

在高處，空氣在向外和向下流動時會向太空釋放輻射，就像步驟 3 一樣。

And finally, that air sinks back to Earth, compressing and getting warmer, and the hurricane engine is ready for another cycle.

最後，空氣下沉回到地球，壓縮並變暖，颶風引擎又準備好了新一輪的循環。

This feedback loop turns hurricanes into self-sufficient engines of destruction.

這種反饋迴路將颶風變成了自給自足的破壞引擎。

A typical tropical cyclone consumes the same amount of power as the entire United States.

一個典型熱帶氣旋的耗電量相當於整個美國的耗電量。

As long as there's enough warm water, it keeps feeding itself, getting larger and larger until… well, is there a limit to how powerful a hurricane can be?

只要有足夠的暖水，颶風就會不停地哺育自己，變得越來越大，直到......那麼，颶風的威力有極限嗎？

Size and rainfall are the biggest predictors for how bad a storm will be, but hurricane intensity is rated by wind speed.

風力大小和降雨量是預測風暴嚴重程度的最大依據，但颶風強度是根據風速來評定的。

Category 1 are the weakest, while anything over 157 mph is lumped in category 5.

第 1 類是最弱的，而任何超過 157 英里/小時的物體都被歸入第 5 類。

Using equations for Carnot's ideal engine and data about Earth's climate, scientists say 190 mph should be the maximum theoretical wind speed.

科學家們利用卡諾理想發動機方程和地球氣候數據，認為 190 英里/小時應該是理論上的最大風速。

But after Typhoon Haiyan hit 195 in 2013, does that mean it's time to add a category 6?

但在 2013 年臺風 "海燕 "襲擊了 195 個國家之後，這是否意味著是時候增加一個 6 級颱風了？

Let's get real.

讓我們面對現實吧。

After a certain wind speed, all destruction pretty much looks the same, so it really doesn't make sense to add another category of bad.

風速達到一定程度後，所有的破壞看起來都差不多，所以再增加一個壞的類別實在沒有意義。

But it gives us something to think about.

但它給了我們一些思考。

As Earth's climate warms, we're putting more heat, more fuel, into these engines of destruction.

隨著地球氣候變暖，我們為這些破壞引擎注入了更多的熱量和燃料。

And it's another reason to take our foot off the gas pedal.

這也是我們不踩油門的另一個原因。

Stay curious.

保持好奇心

If you want a chance to win a super-stylin' It's Okay To Be Smart t-shirt, just email us with your answer to this question.

如果您想有機會贏得一件超有型的 "It's Okay To Be Smart "T恤，只需給我們發送電子郵件，告訴我們您對這個問題的答案。

There's a huge spinning storm in Jupiter's southern hemisphere, the Giant Red Spot.

木星南半球有一個巨大的旋轉風暴--巨紅斑。

Jupiter spins in the same direction as Earth, but the Red Spot storm spins counterclockwise, the opposite direction of southern hemisphere hurricanes.

木星的旋轉方向與地球相同，但紅斑風暴卻是逆時針旋轉，與南半球颶風的旋轉方向相反。

Why is that?

為什麼會這樣？

We'll randomly choose five correct responses to receive one of these, and we'll give you the answer in a future video.

我們將隨機抽取 5 個正確答案，並在今後的視頻中告訴您答案。