鳥類翅膀的運作原理（與飛機機翼比較）- Smarter Every Day 62：英語精讀講義

Hey, it's me, Destin,

嘿，我是Destin，

and welcome back to Smarter Every Day.

歡迎回到Smarter Every Day。

So, some of my favorite things to learn are those things that I've seen for several years

我最喜歡學的東西中，有一些是我已經看了好幾年的東西，

and I've made a lot of observations

我也做過很多觀察，

and I kind of think I get it, you know? 講解

然後我有點覺得我懂了，你知道嗎？

I mean, like really get it.

我是說，好像真的懂了。

And then I find out I don't. 片語動詞

但後來我發現自己並不懂。

So, when I first saw what I'm about to show you, 文法

所以，當我第一次看到接下來要展示給你們的東西時，

it blew my mind 慣用語

我大受震撼，

because it was so simple

因為它太簡單了，

I should have seen it my entire life 文法

我本應該早就發現的，

but I didn't.

但我並沒有。

Look at this bird.

看看這隻鳥。

The muscle that flaps the wing is here toward the center

拍打翅膀的肌肉在靠近中心的位置，

and he pushes down on the wing.

然後牠向下按壓翅膀。

But the feathers going out towards the edge of the wing

但是延伸到翅膀邊緣的羽毛

are overlapping in such a way 文法

以這樣一種方式重疊，

that they all push together on the downstroke, 用詞

使得在向下撲翼時它們全都緊緊貼在一起，

but on the backstroke

但在向上撲翼（回推）時，

they delaminate allowing them to open up like louvers 講解

它們會分層，像百葉窗一樣打開，

and allowing the wind to pass through them.

讓風從中穿過。

This means there's a lot less resistance on the backstroke.

這意味著向上撲翼時的阻力要小得多。

Basically, this bird wing is a biomechanical check valve. 表達脈絡

基本上，這鳥的翅膀就是一個生物力學單向閥。

That's amazing.

太不可思議了。

I've never thought about that

我以前從未想過這點，

but I saw it in the high-speed video in Peru

但我在秘魯的高速影片裡，

on the macaws for the first time.

首次在金剛鸚鵡身上看到了它。

This is why I've never seen it.

這就是我為什麼以前從未見過的原因。

Look how fast it happens.

看它發生得多快。

There's no way I could have observed that. 文法

我根本不可能用肉眼觀察到。

But watch the macaws in high-speed

但看看高速拍攝的金剛鸚鵡，

and you can see for yourself 片語搭配

你就能親眼看到，

clearly the feathers are delaminating on the backstroke.

羽毛在向上撲翼時明顯在分層。

On the downstroke

在向下撲翼時，

you can see that all the feathers overlap in such a way

你可以看到所有的羽毛以這樣一種方式重疊，

that they provide a firm boundary layer

形成一個堅固的邊界層，

that air can't pass.

空氣無法穿透。

But on the upstroke,

但在向上撲翼時，

look what happens.

看看發生了什麼。

You can see that the wing separates

你可以看到翅膀分開了，

and the feathers turn so that the air is flowing straight in between them.

羽毛發生偏轉，使得空氣直接從它們之間流過。

You can even see straight through the wing.

你甚至能直接透過翅膀看過去。

I think that's amazing.

我覺得這太神奇了。

So, he has a lot less resistance on the backstroke 文法

所以，牠向上撲翼時的阻力

than he does the downstroke.

比向下撲翼時要小得多。

Another thing he does to decrease this resistance on the backstroke

為了減少向上撲翼時的阻力，牠所做的另一件事

is he's performing more of an elliptical sweep with his wings 文法

是用翅膀進行更接近橢圓形的划動，

instead of just an up and down flap.

而不只是簡單地上下拍打。

So, what he's doing is

所以牠的動作是，

on the backstroke he's pulling that wing in

在向上撲翼時，牠把翅膀向內收，

and he's decreasing the length

並縮短翅膀的長度，

so he decreases the surface area of the total wing.

從而減小了整個翅膀的表面積。

That's pretty awesome as well.

這也非常棒。

So, one of the coolest misconceptions I had

所以，我曾有過最大的誤區之一，

is pretty clear to see on this red macaw.

在這隻紅色金剛鸚鵡身上可以看得很清楚。

I used to think that birds just flap down 文法

我以前以為鳥類只是往下拍翅膀，

and they create high pressure underneath them

在下方製造高壓，

and they push themselves up.

然後把自己推上去。

But if you look at this macaw,

但如果你看看這隻金剛鸚鵡，

something else is happening.

你會發現還有別的情況。

Look at the back of his wing here.

看看牠翅膀這裡的背面。

You can see that the feathers are being lifted up

你可以看到羽毛在向下撲翼時

on the downstroke.

被掀了起來。

What that means is 表達脈絡

這意味著

we have a low pressure situation there.

我們在那裡有一個低壓區。

It's like in engineering

就像在工程學中，

when we use something called computational fluid dynamics. 用詞

當我們使用一種叫做計算流體力学的技術時。

Basically, what we do is 文法

基本上，我們所做的是

we analyze the flow field

分析流場，

and we figure out what pressure situations 片語動詞

並找出在每個位置

we have at each location.

我們所面臨的壓力情況。

Now, you know that on an airplane wing

現在，你知道在飛機機翼上，

we have a low pressure situation on top.

上方會有一個低壓區。

That's exactly what's happening with this red macaw.

這正是發生在這隻紅金剛鸚鵡身上的情況。

So, look at his wing

所以，看看牠的翅膀，

and you can see that not only does he have a high pressure situation on the bottom

你會發現牠不僅底部有高壓區，

but the low pressure is so great 文法

而且頂部的低壓非常大，

that it's pulling those feathers off of his wing.

大到把那些羽毛從牠的翅膀上扯了起來。

That's amazing.

太不可思議了。

So, not only is he pushing down 文法

所以牠不僅在向下推，

but he's being pulled up on the same stroke.

而且在同一個動作中被向上拉。

That's pretty awesome.

這真是太棒了。

Now, this green parrot's doing the last thing

現在，這隻綠鸚鵡正在做最後一件事，

that I thought was pretty wild.

我覺得這也非常瘋狂。

If you notice

如果你注意觀察，

he is angling the tips of his wings

牠在向上撲翼時使翅尖傾斜，

on the backstroke and pushing back behind him.

並向後方推。

So, he's providing thrust. 用詞

這樣牠就產生了推力。

But one thing that's happening

但是正在發生的一件事，

that I don't really understand 語氣意圖

我並不太能理解，

but it looks like it could be true,

但看起來似乎是真的：

he's breaking his wing in half

牠在次級飛羽和初級飛羽之間，

between the secondary and primary feathers 用詞

把翅膀「折」成兩半，

and he's angling it

並讓其傾斜，

and it looks like he's diverting that flow down,

看起來像是在將氣流向下導流，

almost like a vertical takeoff Harrier jet. 文化背景

幾乎就像垂直起降的獵鷹式戰鬥機一樣。

It's pretty cool

這非常酷，

and I think it could be happening

我也覺得這有可能發生，

but I've never actually thought about a bird

但我從來沒真正想過鳥類

being able to provide downward thrust

能夠提供向下的推力

on a backward stroke.

在向後撲翼的時候。

That's pretty wild.

這太瘋狂了。

So, I thought I knew how flapping flight works 表達脈絡

所以，我原以為我知道撲翼飛行是怎麼回事，

but clearly I didn't.

但顯然我並不知道。

Send this to any of your buddies

把這個發給你任何一個

that like to think critically

喜歡批判性思考的朋友吧，

because they'll do what I do now.

因為他們會像我現在這樣做了。

Every time I see a bird against the sky, 文法

每次我看到天空中有鳥，

I watch his wing

我就會觀察牠的翅膀，

and on the downstroke

在向下撲翼時，

right at that point where he's pausing

就在牠停頓

to transition back to an upstroke, 片語搭配

準備過渡回向上撲翼的那個點，

if you watch you can see sunlight pop in between the feathers

如果你仔細看，能看到陽光從羽毛間隙穿過，

because he's opened it up

因為牠把翅膀打開了，

for lower air resistance on the backstroke.

以便在向上撲翼時減少空氣阻力。

And I think that's awesome

我覺得這棒極了，

because now I know how bird flight works.

因為現在我知道鳥類是如何飛行的了。

Anyway, I'm Destin

總之，我是Destin，

you're getting smarter every day

你每天都在變聰明，

and I'll leave you with this picture 片語搭配

最後留給你們看這張圖，

that my daughter made

這是我女兒做的，

by gluing homing pigeon feathers

她把信鴿的羽毛黏在

to a piece of paper

一張紙上，

to create her own bird.

創造了她自己的鳥。

You're getting smarter every day.

你每天都在變聰明。

Have a good one. 語氣意圖

祝你開心。

We're in the middle of a cotton field

我們現在在棉花地的中央，

in Alabama.

在阿拉巴馬州。

You've never seen it.

你肯定沒見過。

It's a really pretty sight.

風景真美。

What are we going to do here, son?

兒子，我們在這裡要做什麼？

Let this bird go.

把這隻鳥放走。

We're going to let this bird go. 文法

我們要把這隻鳥放走。

But before we let the bird go,

但在放走牠之前，

we're going to talk about his feathers,

我們要來談談牠的羽毛，

aren't we? 文法

對吧？