如何让一头大象爆炸——生命的尺度 2：英语精读讲义

Let's shrink an elephant to the size of a mouse and enlarge a mouse and make it the size of an elephant

让我们把大象缩小到老鼠那么大，再把老鼠放大到大象那么大，

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

因为这是我们的视频，我们想看看会发生什么。

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

首先，我们现在这只小象踉跄了几步，然后倒地身亡。

Tiny elephant buddy is very cold,

小象伙计感到非常冷，

frozen to death in minutes. 短語搭配

几分钟内就冻死了。

Our giant mouse looks very uncomfortable for a moment

我们巨大的老鼠有一瞬间看起来非常难受，

and then it explodes,

然后它爆炸了，

leaving hot mouse insides everywhere. 語法

留下到处都是滚烫的老鼠内脏。

Why?

为什么？

Because of size.

因为体型。

We are optimized to function precisely for the size we are

我们的身体经过优化，能精确适应我们现有的体型，

and would die horribly in any other environment.

如果换成其他体型，就会死得很惨。

But why exactly?

但究竟是为什么呢？

Why does our mouse explode

为什么我们的老鼠会爆炸，

and can we do this to our elephant too

并且如果我们努力尝试，

if we try hard?

能不能让大象也爆炸？

Life on this planet is based on cells.

地球上的生命都是由细胞构成的。

Cells do vary in size,

细胞的大小确实各不相同，

but they're pretty similar in their dimensions across all species.

但在所有物种中，它们的尺寸其实都相差无几。

A blue whale doesn't have bigger cells than a hummingbird, 語法

蓝鲸的细胞并不比蜂鸟的大，

just a lot more of them.

只是数量多了很多。

Cells have to do a lot of stuff to stay alive

细胞必须做很多事情才能保持存活，

and they need energy to be able to do so. 短語搭配

并且它们需要能量才能做到这一点。

To get this energy,

为了获取能量，

animal cells convert food and oxygen into usable chemical energy. 短語搭配

动物细胞将食物和氧气转化为可用的化学能。

This happens in our mitochondria,

这个过程发生在我们的线粒体中，

the powerhouse of the cell. 習語

即细胞的动力库。

They're like little coal engines that spit out tiny ATP batteries, 短語動詞

它们就像小型煤炭发动机，吐出微小的 ATP 电池，

which the cell can use for almost everything it needs to do.

细胞几乎可以用它来完成所有需要做的事情。

Just like an engine,

就像发动机一样，

mitochondria get really hot while working.

线粒体在工作时会变得非常热。

In human skin cells,

在人类皮肤细胞中，

they reach a scorching 50 degrees Celsius.

它们能达到 50 摄氏度的高温。

And some of our cells have up to 2,000 mitochondria,

我们有些细胞拥有多达 2000 个线粒体，

which are radiating their heat into the cell.

它们都在向细胞内散发热量。

So being alive generates a lot of heat.

因此，活着就会产生大量热量。

The more cells you have, 語法

你的细胞越多，

the more heat your body generates in total.

你的身体总体产生的热量就越多。

If our bodies didn't find ways of losing this heat, 語法

如果我们的身体找不到散发这些热量的方法，

we would be cooked from the inside and die.

我们就会从内部被煮熟并死去。

But this is a problem for bigger animals

但这对于大型动物来说是个问题，

because of the way bodies change as living beings scale up. 短語動詞

因为随着生物体型变大，身体的比例会发生变化。

Animals have three properties here that are important.

动物有三个重要的属性：

Their length,

它们的长度、

their outsides or skin,

外部（或皮肤），

and their insides, like organs, bones,

以及内部，比如器官、骨骼，

and hopes and dreams.

还有希望和梦想。

The thing that's hard to wrap your head around is 習語

难以理解的是，

that when things grow,

当物体变大时，

their insides grow faster than their outsides.

它们内部的增长速度要快于外部。

Imagine a fleshy cube.

想象一个肉乎乎的立方体。

If you double the length of its sides,

如果你将其边长增加一倍，

its surface and volume do not double.

它的表面积和体积并不会只增加一倍。

In fact, 表達脈絡

事实上，

the surface is now four times the original size 語法

表面积现在是原来的四倍，

and the volume of the cube eight times the original size.

而立方体的体积则是原来的八倍。

Which is called the square cube law 文化背景

这被称为平方立方定律，

and has been annoying nature for billions of years. 習語

几十亿年来一直让大自然很头疼。

So why is this a problem for big animals?

那么，为什么这对大型动物是个问题呢？

Because heat can only leave an object via its surface.

因为热量只能通过物体的表面散发。

So if we make our mouse the size of an elephant

所以如果我们把老鼠变得和大象一样大，

or 60 times longer,

或者说长度增加 60 倍，

it has 3,600 times more surface from which to lose heat. 語法

它的散热表面积增加了 3600 倍。

But it has 216,000 times more volume

但它的体积增加了 216000 倍，

filled with trillions and trillions of new hot mitochondria 短語搭配

里面充满了数以万亿计的全新的、滚烫的线粒体，

that produce more heat.

产生着更多的热量。

A lot more insides; 表達脈絡

内部增加了非常多；

not that much more skin.

皮肤却没有增加那么多。

Our mouse is very dead,

我们的老鼠死透了，

very fast.

而且死得非常快。

But big things like elephants exist,

但像大象这样的大型生物是存在的，

so how do they deal with the heat? 短語動詞

那么它们是如何处理热量的呢？

For one, 表達脈絡

首先，

they evolved ways to get rid of energy more easily, 短語動詞

它们进化出了更容易散发能量的方法，

like huge flat ears

比如巨大扁平的耳朵，

that have a lot of surface where heat can escape.

有着很大的表面积可以让热量散发。

But that's not enough.

但这还不够。

Nature's solution is actually very elegant.

大自然的解决方案其实非常巧妙。

Elephant cells are much, 語法

大象细胞的速度，比老鼠细胞要

much slower than mice cells.

慢得多。

The bigger an animal is, 語法

动物越大，

the less active its cells are.

其细胞的活跃度就越低。

If we classify animals by their metabolic rates 短語搭配

如果我们将动物按新陈代谢率分类，

and compare that to their overall mass, 短語搭配

并将其与它们的总质量进行比较，

it's clearly visible.

这一点就显而易见了。

It's not 100% accurate,

虽然不是 100% 准确，

but it is a good rule of thumb. 習語

但这是一个很好的经验法则。

Elephants are huge meat sacks

大象是巨大的肉袋子，

filled with trillions and trillions of little coal ovens. 習語

里面装满了数以万亿计的小煤炉。

So they keep the ovens just active enough to keep them running 語法

所以它们让这些炉子保持刚刚够用的活跃度，

and never at full power.

从来不全功率运行。

Their whole metabolism is slow.

它们的整体新陈代谢很慢。

Things move at a nice chill pace. 用詞

一切都以一种悠闲的节奏进行着。

Small animals need to go the exact opposite way. 短語搭配

小动物则需要走完全相反的路。

If you're small,

如果你很小，

you have a lot of surface area compared to not a lot of volume.

与很小的体积相比，你的表面积很大。

You don't have a lot of cell ovens

你没有那么多的细胞火炉，

and lose the heat they produce very fast.

并且热量散失得非常快。

So very tiny mammals came up with a very extreme solution. 短語動詞

因此，非常微小的哺乳动物想出了一个极端的解决方案。

Meet the Etruscan shrew, 表達脈絡

看看伊特鲁里亚鼩鼱，

the smallest mammal on Earth.

地球上最小的哺乳动物。

A mole-like thing

它长得像鼹鼠，

that's more closely related to hedgehogs than to mice. 語法

与刺猬的亲缘关系比老鼠更近。

With a body length of 4 cm, 語法

它体长 4 厘米，

it only weighs about 1.8 g,

体重只有约 1.8 克，

as much as a paperclip. 語法

和一个回形针差不多重。

It's a tiny ridiculous being.

这是一个荒谬的小生命。

It would basically cool off immediately,

它基本上会立刻变冷，

so its cells run on overdrive to stay warm. 習語

所以它的细胞要超负荷运转来保持温暖。

Its tiny ovens are filled at maximum capacity.

它的微型火炉都在满负荷燃烧。

Its heart beats up to 1,200 times a minute 語法

它的心跳每分钟高达 1200 次，

and it breathes up to 800 times a minute.

呼吸每分钟高达 800 次。

This creates an extreme need for energy,

这造成了对能量的极度需求，

so the shrew has to eat constantly.

所以这种鼩鼱必须不停地吃东西。

After only 4 hours without food,

只要 4 小时没吃东西，

it starves to death.

它就会饿死。

And while an African elephant consumes around 4% of its body weight in food each day,

虽然一头非洲象每天消耗的食物约占其体重的 4%，

our shrew needs 200% of its body weight in food a day just to survive.

我们的鼩鼱每天需要吃掉相当于其体重 200% 的食物才能生存。

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

想象一下每天要吃 2000 个巨无霸，

more than one a minute.

每分钟吃不止一个。

Fun for a while,

一开始可能挺好玩，

but then not so much. 語氣意圖

但之后就不怎么好玩了。

So a cubic centimeter of shrew

因此，一立方厘米的鼩鼱

needs 40 times more food than a cubic centimeter of elephant. 語法

需要的食物是一立方厘米大象的 40 倍。

If an elephant's cells suddenly become as active as the cells of a shrew, 語法

如果大象的细胞突然变得和鼩鼱的细胞一样活跃，

a crazy amount of heat would be generated.

就会产生疯狂的热量。

All the liquids in the elephant would suddenly start boiling

大象体内所有的液体会突然开始沸腾，

and then it would explode

然后它会爆炸，

in an impressive explosion of steaming hot burning elephant parts.

在一场壮观的爆炸中，炸出热气腾腾、燃烧着的大象碎块。

In reality, 表達脈絡

在现实中，

before an explosion occurred,

在发生爆炸之前，

the proteins making up our cells 短語動詞

构成细胞的蛋白质

would probably be denatured and stop producing heat. 用詞

可能会发生变性并停止产生热量。

But a meat explosion is much more fun

但肉块爆炸要好玩得多，

than melting an elephant into a massive hot goo.

比把大象融化成一大滩滚烫的黏液有趣。

Regardless, 表達脈絡

无论如何，

the scaling of the speed of metabolism happens everywhere,

新陈代谢速度与体型的比例关系无处不在，

even in places we don't expect,

甚至在我们意想不到的地方，

like pregnant women.

比如孕妇。

A baby in the womb of its mother

母亲子宫里的婴儿

behaves as if it were a part of her. 語法

表现得就像是她身体的一部分。

Its cells have about the same metabolic rate,

其细胞的新陈代谢率，

the same speed of life,

也就是生命的速度，

as its mother's organs.

和母亲的器官差不多。

It is truly a part of a bigger whole

它确确实实是一个更大整体的一部分，

rather than an individual. 語法

而不是一个独立的个体。

Until it's not anymore. 表達脈絡

直到它不再是。

The very moment a baby is born, 語法

在婴儿出生的那一刻，

a switch is flipped 習語

开关被按下，

and all its internal processes speed up rapidly. 短語動詞

它的所有内部生理过程迅速加快。

36 hours after birth,

出生 36 小时后，

the baby's cells have the same activity rate as a mammal its size.

婴儿细胞的活跃度就达到了同等体型哺乳动物的水平。

Babies literally transition from being an organ 短語搭配

婴儿真的是在短短几个小时内，

to being an individual in mere hours.

从一个器官转变成了一个独立的个体。

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

但在有一点上，大动物和小动物非常相似：

Heartbeats.

心跳。

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

哺乳动物一生中的心跳总数往往是相近的，

typically around 1 billion.

通常在 10 亿次左右。

So while the shrew and elephant are very different, 語法

所以，虽然鼩鼱和大象截然不同，

they share a similar number of heartbeats over the course of their lives. 短語搭配

但它们一生中的心跳次数却很相似。

Their speed of life is the opposite 表達脈絡

它们生命的速度截然相反，

and somehow still the same.

却在某种程度上依然相同。

And for a video in which we made elephants explode for no good reason, 短語搭配

作为一个无缘无故让大象爆炸的视频，

this is the most romantic ending we could come up with.

这是我们能想到的最浪漫的结局了。