For humans, it's a coffee mug and for elephants, a kitchen trash can.

對人類來說，這是一個咖啡杯，對大象來說，這是一個廚房垃圾桶。

An elephant's bladder is 400 times the size of a cat's,

大象的膀胱是貓的400倍。

but it doesn't take an elephant 400 times longer to pee.

但大象尿尿並不需要400倍的時間。

So, how does this work?

那麼，這是如何操作的呢？

The answer lies in what scientists call the “Other Golden Rule.”

答案就在於科學家所說的 "另一條黃金法則"。

It applies to mammals, which pee out some of their wastes in a yellowy liquid.

它適用於哺乳動物，它們會將一些廢物以黃色液體的形式尿出來。

Other classes of animals use different systems and methods to excrete waste.

其他類別的動物使用不同的系統和方法來排洩廢物。

The Rule describes how urinary organs and forces change with body size,

規則》介紹了泌尿器官和力量隨體型變化的情況。

enabling a range of mammals to achieve similarly rapid relief.

使一系列的哺乳動物能夠實現類似的快速緩解。

There are two main factors contributing to urination speed:

導致排尿速度的因素主要有兩個。

bladder pressure and gravity.

膀胱壓力和重力。

Bladder pressure is created when mammals contract their muscles

當哺乳動物收縮肌肉時，就會產生膀胱壓力。

to squeeze urine out.

以擠出尿液。

This pressure is equal to the applied muscular force per unit area but,

這個壓力等於組織、部門面積所施加的肌肉力量，但。

since these factors scale proportionally,

因為這些因素按比例縮放。

bladder pressure doesn't actually change much depending on body size.

膀胱壓力其實並不會因為體型的不同而有太大的變化。

Meanwhile, the effects of gravity do vary across species.

同時，重力的影響在不同的物種中確實有所不同。

Mammals have a pipe-like organ called the urethra

哺乳動物有一個類似管道的器官，叫做尿道口。

that transports urine from a higher elevation to a lower one—

將尿液從較高的地方輸送到較低的地方。

specifically, from the bladder down to where urine exits the body.

具體來說，從膀胱一直到尿液排出體外的地方。

In doing so, the urethra harnesses the power of Torricelli's Law,

這樣一來，尿道就利用了托里切利定律的力量。

which states that flow rate increases with container height.

其中指出，流量隨容器高度增加而增加。

Take these two containers holding the same volume of liquid.

取這兩個盛有相同體積液體的容器。

When identically punctured at the bottom,

當相同的刺破底部時。

the vertical container drains nearly twice as fast.

垂直容器的排水速度幾乎是其兩倍。

This is because the water's falling from a greater elevation difference.

這是因為水的落差較大。

By transporting urine from high to low, the urethra has a similar effect.

通過將尿液從高處運送到低處，尿道也有類似的作用。

The urethra is probably not perfectly vertical,

尿道可能不是完全垂直的。

so its length doesn't tell us exactly how far the urine falls.

所以它的長度並不能準確地告訴我們尿液的落差有多大。

However, it's a good approximation.

不過，這是一個很好的近似值。

The urethra's diameter also affects flow rate.

尿道的直徑也會影響流速。

When that vertical container's exit hole has a larger diameter,

當該垂直容器的出口孔直徑較大時。

the water drains out even faster.

水排得更快。

The length and diameter of an animal's urethra varies

動物尿道的長度和直徑各不相同

depending on its species and whether it has a penis or vagina.

取決於它的種類和是否有陰莖或陰道。

For example, a female elephant has a meter-long urethra

例如，一頭雌性大象的尿道有一米長

with a thirty-five millimeter diameter.

直徑為三十五毫米。

A person with a vagina has a urethra that is more than 20 times shorter

有陰道的人，其尿道縮短20多倍。

and 5 times thinner.

和5倍的薄。

The elephant's longer, wider urethra is what allows it to urinate

大象的尿道較長、較寬，所以它才能排尿。

for a comparable amount of time as a human.

在與人類相當的時間內。

Indeed, if an elephant had the urethra of a housecat,

的確，如果一頭大象有家貓的尿道。

it might take it about 2 hours to drain its bladder.

它可能需要2個小時才能排出膀胱。

It's hypothesized that the Other Golden Rule

據推測，另一個黃金法則就是

is conserved because quicker pees may both reduce vulnerability to predators

因為更快的排卵既可以減少對捕食者的脆弱性，又可以保護自己的身體。

and flush out disease-causing pathogens.

並排出致病病原體。

But the Rule has limitations.

但該規則有其侷限性。

It's only been shown to apply to non-aquatic mammals.

它只被證明適用於非水生哺乳動物。

And the Rule doesn't apply to mammals under three kilograms.

而且該規則不適用於三公斤以下的哺乳動物。

They actually pee in droplets, not continuous streams,

他們其實是以水滴的形式撒尿，而不是連續不斷的尿流。

because surface tension breaks up their tiny jets of urine.

因為表面張力打破了他們的微小的尿液噴射。

Even within non-aquatic mammals above three kilograms,

即使在三公斤以上的非水生哺乳動物內。

different behaviors disrupt the Other Golden Rule.

不同的行為擾亂了其他金科玉律。

Male dogs don't always fully empty their bladders

公狗並不總是完全排空膀胱。

and will instead tinkle in short spurts to mark their territory.

而會在短時間內叮叮噹噹地標記自己的領地。

Male pandas sometimes pee in handstands, marking bark higher up on trees

雄性大熊貓有時會用手臺尿尿，在樹上較高處的樹皮上做記號。

in order to broadcast their scent to potential mates.

以便向潛在的配偶傳播它們的氣味。

Handstand pees take longer because urine must work against gravity.

由於尿液必須在重力的作用下工作，所以站立小便需要更長的時間。

Underwater pees are also lengthier

水下的小便也比較長

because the external water pressure counteracts the internal forces

因為外在的水壓抵消了內在的力量。

resulting from elevation difference.

由高差造成的。

Whether it's with the intensity of a fire hydrant or a squirt gun,

不管是用消火栓還是水槍的力度。

this system swiftly delivers our urine to the outside world.

這個系統迅速地將我們的尿液輸送到外界。