如果把大象從摩天大樓上扔下去會發生什麼事？生命與體型 1：英語精讀講義

Let's start this video by throwing a mouse, 表達脈絡

讓我們在影片一開始先扔一隻老鼠，

a dog,

一隻狗，

and an elephant from a skyscraper onto something soft.

和一頭大象，從摩天大樓上扔到柔軟的東西上。

Let's say a stack of mattresses. 表達脈絡

假設是一堆床墊吧。

The mouse lands and is stunned for a moment

老鼠落地後先是懵了一會兒，

before it shakes itself off and walks away 片語動詞

然後抖了抖身子走開了，

pretty annoyed 用詞

並且非常生氣，

because that's a very rude thing to do.

因為這真是一件很粗魯的事。

The dog breaks all of its bones

狗全身骨折，

and dies in an un-spectacular way,

死狀平平，

and the elephant explodes into a red puddle of bones and insides

而大象則爆炸成了一灘由骨頭和內臟組成的紅色血水，

and has no chance to be annoyed.

連生氣的機會都沒有。

Why does the mouse survive,

為什麼老鼠活下來了，

but the elephant and dog don't?

而大象和狗卻死了？

The answer is size.

答案是體型。

Size is the most under-appreciated regulator of living things. 用詞

體型是生物界中最被低估的調節因素。

Size determines everything about our biology,

體型決定了我們生物學的一切，

how we're built,

我們的身體構造，

how we experience the world,

我們如何體驗這個世界，

how we live and die.

以及我們如何生存和死亡。

It does so because the physical laws are different for different sized animals.

它是如此重要的原因在於，物理定律對不同體型的動物是不同的。

Life spans seven orders of magnitude 用詞

生命的跨度橫跨七個數量級，

from invisible bacteria to mites,

從隱形的細菌到蟎蟲，

ants, mice, dogs, humans,

螞蟻、老鼠、狗、人類，

elephants, and blue whales.

還有大象和藍鯨。

Every size lives in its own unique universe 慣用語

每種體型的生物都生活在各自獨特的宇宙中，

right next to each other,

它們比鄰而居，

each with its own rules,

每個宇宙都有著自己的規則，

upsides and downsides. 片語搭配

以及各自的優缺點。

We'll explore these different worlds in a series of videos.

我們將透過一系列影片探索這些不同的世界。

Let's get back to the initial question. 表達脈絡

讓我們回到最初的問題。

Why did our mouse survive the fall?

為什麼我們的老鼠在墜落中倖存下來了？

Because of how scaling size changes everything,

因為體型比例的縮放改變了一切，

a principle that we'll meet over and over again.

這是一個我們將會一再遇到的原理。

Very small things,

非常小的東西，

for example,

舉個例子，

are practically immune to falling from great heights

對高處墜落幾乎免疫，

because the smaller you are, 文法

因為你的體型越小，

the less you care about the effect of gravity.

就越不用在乎重力的影響。

Imagine a theoretical spherical animal the size of a marble.

想像一個理論上的球形動物，大小像一顆玻璃彈珠。

It has three features:

它具有三個特徵：

its length,

它的長度，

its surface area which is covered in skin,

覆蓋皮膚的表面積，

and its volume or all the stuff inside it

以及它的體積或者說是裡面的所有東西，

like organs, muscles, hopes and dreams.

比如器官、肌肉、希望和夢想。

If we make it 10 times longer,

如果我們把它變長10倍，

say the size of a basketball,

假設變成籃球那麼大，

the rest of its features don't just grow 10 times.

它的其他特徵可不僅僅是跟著增長10倍。

Its skin will grow 100 times and its insides

它的皮膚會增長100倍，而它的內臟，

or its volume grows by 1,000 times.

或者說它的體積會增加1000倍。

The volume determines the weight or more accurately mass of the animal. 表達脈絡

體積決定了動物的重量，或者更準確地說是質量。

The more mass you have,

質量越大，

the higher your kinetic energy before you hit the ground,

你在撞擊地面之前的動能就越高，

and the stronger the impact shock.

撞擊的衝擊力也就越強。

The more surface area in relation to your volume or mass you have, 片語搭配

你的表面積相對於體積或質量越大，

the more the impact gets distributed and softened,

衝擊力就越能被分散和緩衝，

and also the more air resistance will slow you down.

並且空氣阻力也能更好地讓你減速。

An elephant is so big that it has extremely little surface area in ratio to its volume,

大象實在太大了，所以它的表面積與體積的比值非常小，

so a lot of kinetic energy gets distributed over a small space

這意味著巨大的動能集中在很小的區域上，

and the air doesn't slow it down much at all.

而且空氣幾乎無法讓它減速。

That's why it's completely destroyed in an impressive explosion of goo when it hits the ground.

這就是為什麼它砸到地面時會變成一場驚人而黏稠的爆炸並被完全毀滅。

The other extreme, 表達脈絡

另一個極端是，

insects, have a huge surface area in relation to their tiny mass,

昆蟲的表面積相對於它們微小的質量來說是巨大的，

so you can literally throw an ant from an airplane

所以你完全可以把一隻螞蟻從飛機上扔下去，

and it will not be seriously harmed.

它也不會受重傷。

But while falling is irrelevant in the small world, 表達脈絡

但是，雖然墜落在這個微小世界裡無足輕重，

there are other forces that are harmless for us,

卻有其他一些對我們來說毫無危險的力，

but extremely dangerous for small beings.

對小生物而言極其致命。

Like surface tension,

比如表面張力，

which turns water into a potentially deadly substance for insects.

它把水變成了對昆蟲來說潛在的致命物質。

How does it work?

它是如何運作的？

Water has the tendency to stick to itself. 片語搭配

水有黏在一起的傾向。

Its molecules are attracted to each other through a force called cohesion, 講解

它的分子透過一種被稱為內聚力的力量相互吸引，

which creates a tension on its surface that you can imagine as a sort of invisible skin. 慣用語

這在水的表面產生了一種張力，你可以把它想像成一種看不見的皮膚。

For us, this skin is so weak that we don't even notice it normally. 文法

對於我們來說，這種皮膚太微弱了，通常我們甚至注意不到。

If you get wet,

如果你弄濕了，

about 800 g of water or about 1% of your body weight sticks to you.

大概有800克的水，也就是你體重的1%會黏在你身上。

A wet mouse has about 3 g of water sticking to it,

一隻濕透的老鼠大約會有3克水黏在身上，

which is more than 10% of its body weight.

這超過了它體重的10%。

Imagine having eight full water bottles sticking to you when you leave the shower. 表達脈絡

想像一下你洗完澡出來時身上掛著八滿瓶水的感覺。

But for an insect,

但對昆蟲來說，

the force of water's surface tension is so strong that getting wet is a question of life and death. 慣用語

水的表面張力是如此之強，以至於被弄濕是個生死攸關的問題。

If we were to shrink you to the size of an ant and you touch water, 文法

如果我們把你縮小到螞蟻大小，然後你碰到水，

it would be like you were reaching into glue.

那感覺就像你伸進了膠水裡。

It would quickly engulf you,

它可以迅速吞噬你，

its surface tension too hard for you to break, 文法

它的表面張力大到你無法打破，

and you drown.

然後你就會被淹死。

So insects evolved to be water repellent. 用詞

因此，昆蟲演化出了疏水的特性。

For one, 表達脈絡

一方面，

their exoskeleton is covered with a thin layer of wax, 片語搭配

它們的外骨骼上覆蓋著一層薄薄的蠟，

just like a car.

就像汽車一樣。

This makes their surface at least partly water repellent because it can't stick to it very well.

這使得它們的表面至少有部分是防水的，因為水很難附著在上面。

Many insects are also covered with tiny hairs that serve as a barrier. 片語搭配

許多昆蟲身上還覆蓋著細小的絨毛，作為一道屏障。

They vastly increase their surface area and prevent the droplets from touching their exoskeleton 文法

它們極大地增加了表面積，阻止水滴接觸到外骨骼，

and make it easier to get rid of droplets. 片語動詞

同時也使得甩掉水滴變得更容易。

To make use of surface tension, 片語搭配

為了利用表面張力，

evolution cracked nanotechnology billions of years before us. 慣用語

演化在人類出現前的數十億年就已經破解了奈米技術。

Some insects have evolved a surface covered by a short and extremely dense coat of water-repelling hair.

有些昆蟲演化出了覆蓋有短且極其濃密的拒水毛髮的表面。

Some have more than a million hairs per square millimeter.

有些每平方毫米有多達一百多萬根毛髮。

When the insect dives underwater,

當昆蟲潛入水中時，

air stays inside their fur and forms a coat of air.

空氣會留在牠們的皮毛裡，形成一件空氣外套。

Water can't enter because the hairs are too tiny to break its surface tension.

水進不去，因為這些毛髮太細小，無法打破水的表面張力。

But it gets even better. 表達脈絡

但更絕的還在後頭。

As the oxygen of the air bubble runs out, 片語動詞

當氣泡裡的氧氣耗盡時，

new oxygen diffuses into the bubble from the water around it 用詞

新的氧氣會從周圍的水中擴散進氣泡，

while the carbon dioxide diffuses outwards into the water.

同時二氧化碳會向外擴散到水中。

And so the insect carries its own outside lung around

因此，這隻昆蟲隨身帶著自己外部的肺，

and can basically breathe underwater thanks to surface tension. 片語搭配

而且多虧了表面張力，基本上能在水下呼吸。

This is the same principle that enables pond skaters to walk on water,

這就是讓水黽能在水面上行走的原理，

by the way. 表達脈絡

順便說一句。

Tiny anti-water hairs.

微小的抗水毛髮。

The smaller you get,

你的體型越小，

the weirder the environment becomes.

所處的環境就越怪異。

At some point, even air becomes more and more solid. 文法

在某種程度上，連空氣也會變得越來越固態。

Let's now zoom down to the smallest insects known, 表達脈絡

現在讓我們把鏡頭對準已知最小的昆蟲，

about half the size of a grain of salt,

大概只有鹽粒的一半大小，

only 0.15 mm long,

只有0.15公釐長，

the fairyfly.

纓小蜂。

They live in a world even weirder than other insects.

牠們生活在一個比其他昆蟲更怪異的世界裡。

For them,

對牠們來說，

air itself is like thin Jell-O, 文化背景

空氣本身就像稀薄的果凍，

a syrup-like mass surrounding them at all times. 用詞

一種糖漿狀的物質無時無刻不在包圍著牠們。

Movement through it is not easy.

在其中移動並不容易。

Flying on this level is not like elegant gliding.

在這個層級飛行可不像是優雅的滑翔。

They have to kind of grab and hold on to air. 講解

牠們必須想辦法抓住並攀附在空氣上。

So their wings look like big hairy arms rather than proper insect wings. 文法

所以牠們的翅膀看起來像毛茸茸的大手，而不像正常的昆蟲翅膀。

They literally swim through the air 慣用語

牠們真的就像在空氣中游泳一樣，

like a tiny gross alien through syrup.

就像一個微小噁心的外星人在糖漿中穿梭。

Things only become stranger from here on 片語搭配

從這裡開始，事情只會變得越來越奇怪，

as we explore more universes of different sizes.

隨著我們探索更多不同尺度的宇宙。

The physical rules are so different for each size

每個體型的物理規則是如此不同，

that evolution had to engineer around them over and over 用詞

以至於在過去十億年裡，隨著生命體型的增長，

as life grew in size in the last billion years.

演化不得不在這些規則周圍一次又一次地重新設計。

So why are there no ants the size of horses? 表達脈絡

那麼，為什麼沒有馬一樣大的螞蟻呢？

Why no elephants the size of amoeba?

為什麼沒有變形蟲一樣大的大象呢？

Why?

為什麼呢？

We'll discuss this in the next part.

我們會在下一部分討論這個。

We have a monthly newsletter now.

我們現在有一份每月的電子報。

Sign up if you don't want to miss new videos

如果你不想錯過新影片的話請訂閱，

and for bonus videos.

還有更多獎勵影片。