should you walk and spend more time in the rain?

你應該慢慢走，多花點時間在雨中嗎？

Or should you run, which means you'll be hitting more raindrops from the side?

還是應該跑步，表示你身體兩側會碰到更多雨滴呢？

Assuming you haven't been fully soaked yet and you aren't jumping into puddles, the answer is simple.

假設現在的你還沒變成落湯雞，也沒踩到水坑，答案很簡單。

As you move out of the way of one falling raindrop, you move into the way of another.

當你從一個雨滴下離開，同時就進入了另一個雨滴的地盤。

So, the amount of rain hitting the top of you is constant, regardless of how fast you're going.

所以說，淋到你頭上的雨量不管你走多快都是一樣的。

To see this, you can picture that the raindrops themselves are stationary, and you and the earth beneath you are moving upwards through the rain.

想要了解這個現象，想像一下雨滴都停止不動，而你和所站的地面都在往雨中上移動。

And since the volume of a parallelepiped⏤that's a 3D parallelogram⏤doesn't depend at all on its slant,

而由於平行六面體（立體的平行四邊形）的體積不會取決於其傾斜角度，

then no matter how fast you're moving horizontally, the same amount of rain will land on top of you each second.

無論你水平移動得多快，每一秒鐘落在你身上的雨量都會一樣。

Now, if you're not moving, the rain from the top is all you'll get.

那如果你是靜止不動的，會落在你身上的只有正上方的雨。

But if you are moving, you'll also run into raindrops from the side and you'll get wetter.

但如果你在移動，你同時也會跑向來自兩側的與，只會變得更濕。

So, in any given second, you stay driest by standing still, and the faster you move the wetter you become.

所以在任何時刻，靜止不動相對較乾，而移動得越快則越容易濕。

But if you're trying to get from point A to point B, then standing still won't do you much good.

但是如過你是要從 A 點移動到 B 點，原地站著對你不會有好處。

And en route from point A to point B, the total amount of rain you run into from the side has nothing to do with how fast you're going.

而從 A 點到 B 點的途中，身體接觸的總雨量跟你移動的速度快慢完全無關。

Just like how a snowplow will plow the same amount of snow from a stretch of road regardless of the exact speed it drives.

這和除雪機的道理是一樣的，無論除雪機開得多快，同一條路上鏟的雪量都是相同的。

In the case of running through the rain, you can figure that out using parallelepipeds again.

以雨中奔跑的情況來看，可以再用平行六面體來解釋。

So, over a given period of time, the same amount of rain will hit you from the top, regardless of how fast you're going.

相同的時間範圍內，從上方落到你身上的雨量是相同的，無論你行進速度多快。

And over a given distance, you'll hit the same amount of rain from the side, again, regardless of how fast you're going.

而在相同的距離內，身體接觸到的雨量也是一樣，同樣不會因為速度影響。

So, your total wetness is equal to the wetness per second for rain from the top times the amount of time you spend in the rain,

所以說，你淋濕的程度等於「每秒淋的雨量」乘以「待在雨中的時間」，

plus the wetness per meter for rain from the side times the number of meters you travel.

加上「每公尺接觸的雨量」乘以「在雨中的移動的總距離」。

So, to stay driest getting from one point to another, you should try to minimize the amount of water falling onto you from above.

所以，要保持最乾的狀態，應該要把上方淋到身上的雨量降到最低。

And quite simply, that means getting out of the rain as fast as possible.

而簡單地說，就是盡快找到避雨的地方。