Because this is our video, and we want to see what happens.

因為這是我們的影片，我們想知道會發生什麼。

First, our now tiny elephant stumbles around and then drops dead.

首先，這隻迷你象會跌跌撞撞的，然後會摔死。

Tiny elephant buddy is very cold, frozen to death in minutes.

迷你象會很冷，然後在幾分鐘之內凍死。

Our giant mouse looks very uncomfortable for a moment, and then it explodes, leaving hot mouse insides everywhere.

而我們的巨鼠會看起來很不舒服一陣子，然後牠會爆炸，把留有餘溫的內臟弄的到處都是。

Why?

為什麼？

Because of size.

因為牠們的大小。

We are optimized to function precisely for the size we are, and would die horribly in any other environment.

我們完美地適應了自身的身體大小來運作，而在其他情況下，我們則會死得慘不忍睹。

But, why exactly?

但是，到底是為什麼呢？

Why does our mouse explode, and can we do this to our elephant too, if we try hard?

為什麼我們的巨鼠會爆炸？如果我們努力一點的話，也可以讓大象爆炸嗎？

Life on this planet is based on cells.

這個星球上的生命都是源於細胞。

Cells do vary in size, but they're pretty similar in their dimensions across all species.

細胞的大小的確有所不同，但在細胞方面，所有物種卻都非常相似。

A blue whale doesn't have bigger cells than a hummingbird, just a lot more of them.

藍鯨的細胞沒有比蜂鳥的更大，只是多了很多細胞而已。

Cells have to do a lot of stuff to stay alive, and they need energy to be able to do so.

細胞需要做很多事情維持生命，因此它們需要能量。

To get this energy, animal cells convert food and oxygen into usable chemical energy.

為了得到這個能量，動物的細胞將食物和氧氣轉化為可用的化學能。

This happens in our mitochondria, the powerhouse of the cell.

這會在我們的細胞中的粒線體發生，也就是細胞的發電廠。

They're like little coal engines that spit out tiny ATP batteries, which the cell can use for almost everything it needs to do.

它們就像一台小小的煤礦發電機，會吐出三磷酸腺苷電池，這個電池可以提供細胞幾乎全部所需的東西。

Just like an engine, mitochondria get really hot while working.

跟發動機一樣，粒線體在運作的時候會變得很熱。

In human skin cells, they reach a scorching 50 degrees Celsius.

在人類皮膚細胞內，它們的溫度高達攝氏 50 度。

And some of our cells have up to 2,000 mitochondria, which are radiating their heat into the cell.

而我們有一些細胞有差不多 2,000 多個粒線體，它們會發散熱能進入細胞中。

So, being alive generates a lot of heat.

因此，活著這件事會產生大量的熱能。

The more cells you have, the more heat your body generates in total.

如果你有越多的細胞，你的身體會產生越多的熱能。

If our bodies didn't find ways of losing this heat, we would be cooked from the inside and die.

如果我們的身體不能找到方式散熱，我們就會因體內熱到被煮熟而熱死。

But this is a problem for bigger animals, because of the way bodies change as living beings scale up.

這對於體積較大的動物是一個問題，因為隨著動物的體積變大，散熱的方法也會改變。

Animals have three properties here that are important.

動物有三個重要的屬性。

Their length, their outsides or skin. And their insides, like organs, bones, and hopes and dreams.

它們的長度、外部或皮膚。以及他們的內部，例如內臟、 骨頭，希望和夢想。

The thing that's hard to wrap your head around is that when things grow, their insides grow faster than their outsides.

你很難去理解的是，當東西開始成長時，它們內部的生長速度其實快過外部。

Imagine a fleshy cube.

想像一個肉肉的正方體。

If you double the length of its sides, its surface and volume do not double.

如果你將它的邊長變為二倍，它的表面和體積則不變。

In fact, the surface is now four times the original size, and the volume of the cube eight times the original size.

事實上，它的表面就會是現在的四倍，而它的容量會比原來的大八倍。

Which is called the Square Cube Law, and has been annoying nature for billions of years.

這就是所謂的平方立方法則，這個法則幾十億年來一直困擾著大自然。

So why is this a problem for big animals?

那麼為什麼這對於體型大的動物是一個問題呢？

Because heat can only leave an object via its surface.

因為熱能只能透過一個物體的表面散發。

So if we make our mouse the size of an elephant, or 60 times longer, it has 3,600 times more surface from which to lose heat.

所以如果讓我們的老鼠變得跟大象一樣大，或 60 倍長， 牠就會有比原先多 3600 倍的表面來散熱。

But it has 216,000 times more volume filled with trillions and trillions of new hot mitochondria that produce more heat.

但它的體積則會大 216,000 倍，裡面充滿著數萬億的粒線體來產生更多的熱能。

A lot more insides, not that much more skin.

內部體積相較於外部皮膚增加了更多。

Our mouse is very dead, very fast.

老鼠會死的很快。

But big things like elephants exist.

但地球上存在像大象這樣的大傢伙。

So how do they deal with the heat?

牠們是怎樣處理熱能的呢？

For one, they evolved ways to get rid of energy more easily, like huge flat ears, that have a lot of surface where heat can escape.

首先，牠們進化出容易散發能量的方式，像是巨大的耳朵，就會有更多的表面讓熱能散出。

But that's not enough.

但這還不夠。

Nature's solution is actually very elegant.

大自然的解決方法其實很優雅。

Elephant cells are much, much slower than mice cells.

大象有更多的細胞，但這些細胞卻比老鼠的細胞慢得多。

The bigger an animal is, the less active its cells are.

動物越大，細胞的活性越小。

If we classify animals by their metabolic rates, and compare that to their overall mass, it's clearly visible.

如果我們通過新陳代謝的速度分類動物，並且比較它們的總質量，這點就顯而易見了。

It's not 100% accurate, but it is a good rule of thumb.

雖然不是 100％ 準確，但它是一個很好的方法。

Elephants are huge meat sacks filled with trillions and trillions of little coal ovens.

大象是一個被億萬個小煤爐填滿的大肉袋。

So, they keep the ovens just active enough to keep them running and never full power.

因此，煤爐的效率只需要能恰好支撐它們身體的運作就行了，所以從來不會火力全開。

Their whole metabolism is slow.

牠們整體的新陳代謝很慢。

Things move at a nice chill pace.

以一個很悠閒的速度運作。

Small animals need to go the exact opposite way.

然而小動物卻需要完全相反的方法。

If you're small, you have a lot of surface area compared to not a lot of volume.

如果你很小，相較於外部皮膚，內部體積較小。

You don't have a lot of cell ovens, and lose the heat they produce very fast.

你沒有太多的細胞煤爐，所以會很快失去熱能。

So very tiny mammals came up with a very extreme solution.

因此，極小的哺乳動物想出了一個非常極端的解決方案。

Meet the Etruscan Shrew, the smallest mammal on Earth.

來看看小臭鼩，牠是世界上最小的哺乳動物。

A mole-like thing that's more closely related to hedgehogs than to mice.

這種長得像鼹鼠的動物比起跟老鼠，其實和刺蝟更相近。

With the body length of four centimeters, it only weighs about 1.8 grams, as much as a paperclip.

牠的體長四公分，大約只有 1.8 克，跟迴紋針差不多重。

It's a tiny, ridiculous being.

牠是這樣一個又小又荒謬的存在。

It would basically cool off immediately, so its cells run on overdrive to stay warm.

一般來說，牠會很快地就降溫，所以牠的細胞會超速運行，以保持溫暖。

Its tiny ovens are filled at maximum capacity.

牠小小的烤爐已經以最大功率的方式運作著。

Its heart beats up to 1,200 times a minute, and it breathes up to 800 times a minute.

牠的心臟一分鐘跳動 1200 次，一分鐘呼吸 800 次。

This creates an extreme need for energy, so the shrew has to eat constantly.

這需要大量的能量，因此，小臭鼩必須不斷地吃。

After only four hours without food, it starves to death.

如果牠四個小時不吃東西的話，就會死亡。

And while an African elephant consumes around 4% of its body weight in food each day, our shrew needs 200% of its body weight in food a day just to survive.

非洲象只攝取其體重約 4% 的食物，小臭鼩卻為了生存每天需要其體重 200% 的食物。

Imagine having to eat 2,000 Big Macs a day.

想像一下每天吃 2000 個大麥克。

More than one a minute.

每分鐘要吃多於一個。

Fun for a while, but then not so much.

一開始可能會覺得很有趣，但之後會感覺很不適。

So, a cubic centimetre of shrew needs 40 times more food than a cubic centimetre of elephant.

因此，一立方公分的小臭鼩需要比一立方公分的大象多 40 倍的食物。

If an elephant's cells suddenly become as active as the cells of a shrew, a crazy amount of heat would be generated.

如果一頭大象的細胞突然變得跟小臭鼩的細胞一樣活躍，將會產生令人難以置信的熱能。

All the liquids in the elephant would suddenly start boiling, and then it would explode in an impressive explosion of steaming hot burning elephant parts.

大象體內的所有液體將會立即沸騰，然後身體的部位都會被蒸得滾燙，最後牠就會在這樣的情況下爆炸。

In reality, before an explosion occurred, the proteins making up our cells would probably be denatured, and stop producing heat.

現實中，在牠爆炸之前，組成我們細胞的蛋白質可能就會先失去活性， 並且停止產生熱能。

But a meat explosion is much more fun than melting an elephant into a massive hot goo.

但是爆炸的肉會比融化成塊狀的大象更加有趣。

Regardless, the scaling of the speed of metabolism happens everywhere.

無論如何，這種新陳代謝速度的縮放無時無刻都在發生。

Even in places we don't expect, like pregnant women.

就連我們預料外的地方也會發生，像是孕婦。

A baby in the womb of its mother behaves as if it were a part of her.

子宮內的嬰兒就像屬於孕婦的一部分在運作著。

Its cells have about the same metabolic rate, the same speed of life, as its mother's organs.

它的細胞有跟它媽媽的器官一樣的新陳代謝速度，一樣速度的生命。

It is truly a part of a bigger whole, rather than an individual.

他們是一體的，並不是分開的。

Until it's not anymore.

直到它不再是媽媽肚子裏的小嬰兒。

The very moment a baby is born, a switch is flipped, and all its internal processes speed up rapidly.

在嬰兒出生的那一刻，一個開關被打開了，其內部所有細胞的運作過程會迅速加快。

Thirty-six hours after birth, the baby's cells have the same activity rate as a mammal its size.

出生後 36 小時，寶寶的細胞具有跟一般哺乳動物一樣的活躍性。

Babies literally transition from being an organ to being an individual, in mere hours.

僅在短短幾小時，嬰兒就從一個器官變成一個獨立的個體。

But there's one thing where big and small things are very similar:

但有一個東西，無論體積大或小，都是相似的：

Heartbeats.

心跳。

Mammals tend to have a similar amount of heartbeats, over their lifetime.

哺乳動物的一生中往往有相似的心跳總量。

Typically around one billion.

通常約十億左右。

So, while the shrew and elephant are very different, they share a similar number of heartbeats all the course of their lives.

所以，就算臭鼩和大象非常不一樣，在他們的一生中，牠們也有著相似的心跳總量。

Their speed of life is the opposite and somehow still the same.

儘管他們的生命的速度是相異的，但某種程度上仍然是相同的。

And, for a video in which we made elephants explode for no good reason, this is the most romantic ending we could come up with.

本部影片裡，我們讓大象無緣無故爆炸，這已經是我們可以想出最浪漫的結局。