鸟类翅膀的工作原理（与飞机机翼对比）- Smarter Every Day 62：英语精读讲义

Hey, it's me, Destin,

嘿，我是Destin，

and welcome back to Smarter Every Day.

欢迎回到Smarter Every Day。

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

我最喜欢学的东西中，有一些是我已经看了好几年的东西，

and I've made a lot of observations

我也做过很多观察，

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

然后我有点觉得我懂了，你知道吗？

I mean, like really get it.

我是说，好像真的懂了。

And then I find out I don't. 短語動詞

但后来我发现自己并不懂。

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

所以，当我第一次看到接下来要展示给你们的东西时，

it blew my mind 習語

我大受震撼，

because it was so simple

因为它太简单了，

I should have seen it my entire life 語法

我本应该早就发现的，

but I didn't.

但我并没有。

Look at this bird.

看看这只鸟。

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.

然后它向下按压翅膀。

But the feathers going out towards the edge of the wing

但是延伸到翅膀边缘的羽毛

are overlapping in such a way 語法

以这样一种方式重叠，

that they all push together on the downstroke, 用詞

使得在向下扑翼时它们全都紧紧贴在一起，

but on the backstroke

但在向上扑翼（回推）时，

they delaminate allowing them to open up like louvers 講解

它们会分层，像百叶窗一样打开，

and allowing the wind to pass through them.

让风从中穿过。

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

这意味着向上扑翼时的阻力要小得多。

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

基本上，这鸟的翅膀就是一个生物力学单向阀。

That's amazing.

太不可思议了。

I've never thought about that

我以前从未想过这点，

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

但我在秘鲁的高速视频里，

on the macaws for the first time.

首次在金刚鹦鹉身上看到了它。

This is why I've never seen it.

这就是我为什么以前从未见过的原因。

Look how fast it happens.

看它发生得多快。

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

我根本不可能用肉眼观察到。

But watch the macaws in high-speed

但看看高速拍摄的金刚鹦鹉，

and you can see for yourself 短語搭配

你就能亲眼看到，

clearly the feathers are delaminating on the backstroke.

羽毛在向上扑翼时明显在分层。

On the downstroke

在向下扑翼时，

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

你可以看到所有的羽毛以这样一种方式重叠，

that they provide a firm boundary layer

形成一个坚固的边界层，

that air can't pass.

空气无法穿透。

But on the upstroke,

但在向上扑翼时，

look what happens.

看看发生了什么。

You can see that the wing separates

你可以看到翅膀分开了，

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

羽毛发生偏转，使得空气直接从它们之间流过。

You can even see straight through the wing.

你甚至能直接透过翅膀看过去。

I think that's amazing.

我觉得这太神奇了。

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

所以，它向上扑翼时的阻力

than he does the downstroke.

比向下扑翼时要小得多。

Another thing he does to decrease this resistance on the backstroke

为了减少向上扑翼时的阻力，它所做的另一件事

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

是用翅膀进行更接近椭圆形的划动，

instead of just an up and down flap.

而不只是简单地上下拍打。

So, what he's doing is

所以它的动作是，

on the backstroke he's pulling that wing in

在向上扑翼时，它把翅膀向内收，

and he's decreasing the length

并缩短翅膀的长度，

so he decreases the surface area of the total wing.

从而减小了整个翅膀的表面积。

That's pretty awesome as well.

这也非常棒。

So, one of the coolest misconceptions I had

所以，我曾有过的最大的误区之一，

is pretty clear to see on this red macaw.

在这只红色金刚鹦鹉身上可以看得很清楚。

I used to think that birds just flap down 語法

我以前以为鸟类只是往下拍翅膀，

and they create high pressure underneath them

在下方制造高压，

and they push themselves up.

然后把自己推上去。

But if you look at this macaw,

但如果你看看这只金刚鹦鹉，

something else is happening.

你会发现还有别的情况。

Look at the back of his wing here.

看看它翅膀这里的背面。

You can see that the feathers are being lifted up

你可以看到羽毛在向下扑翼时

on the downstroke.

被掀了起来。

What that means is 表達脈絡

这意味着

we have a low pressure situation there.

我们在那里有一个低压区。

It's like in engineering

就像在工程学中，

when we use something called computational fluid dynamics. 用詞

当我们使用一种叫做计算流体力学的技术时。

Basically, what we do is 語法

基本上，我们所做的是

we analyze the flow field

分析流场，

and we figure out what pressure situations 短語動詞

并找出在每个位置

we have at each location.

我们所面临的压力情况。

Now, you know that on an airplane wing

现在，你知道在飞机机翼上，

we have a low pressure situation on top.

上方会有一个低压区。

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

这正是发生在这只红金刚鹦鹉身上的情况。

So, look at his wing

所以，看看它的翅膀，

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

你会发现它不仅底部有高压区，

but the low pressure is so great 語法

而且顶部的低压非常大，

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

以至于把那些羽毛从它的翅膀上扯了起来。

That's amazing.

太不可思议了。

So, not only is he pushing down 語法

所以它不仅在向下推，

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

而且在同一个动作中被向上拉。

That's pretty awesome.

这真是太棒了。

Now, this green parrot's doing the last thing

现在，这只绿鹦鹉正在做最后一件事，

that I thought was pretty wild.

我觉得这也非常疯狂。

If you notice

如果你注意观察，

he is angling the tips of his wings

它在向上扑翼时使翅尖倾斜，

on the backstroke and pushing back behind him.

并向后方推。

So, he's providing thrust. 用詞

这样它就产生了推力。

But one thing that's happening

但是正在发生的一件事，

that I don't really understand 語氣意圖

我并不太能理解，

but it looks like it could be true,

但看起来似乎是真的：

he's breaking his wing in half

它在次级飞羽和初级飞羽之间，

between the secondary and primary feathers 用詞

把翅膀“折”成两半，

and he's angling it

并让其倾斜，

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

看起来像是在将气流向下导流，

almost like a vertical takeoff Harrier jet. 文化背景

几乎就像垂直起降的鹞式战斗机一样。

It's pretty cool

这非常酷，

and I think it could be happening

我也觉得这有可能发生，

but I've never actually thought about a bird

但我从来没真正想过鸟类

being able to provide downward thrust

能够提供向下的推力

on a backward stroke.

在向后扑翼的时候。

That's pretty wild.

这太疯狂了。

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

所以，我原以为我知道扑翼飞行是怎么回事，

but clearly I didn't.

但显然我并不知道。

Send this to any of your buddies

把这个发给你任何一个

that like to think critically

喜欢批判性思考的朋友吧，

because they'll do what I do now.

因为他们会像我现在这样做了。

Every time I see a bird against the sky, 語法

每次我看到天空中有鸟，

I watch his wing

我就会观察它的翅膀，

and on the downstroke

在向下扑翼时，

right at that point where he's pausing

就在它停顿

to transition back to an upstroke, 短語搭配

准备过渡回向上扑翼的那个点，

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

如果你仔细看，能看到阳光从羽毛间隙穿过，

because he's opened it up

因为它把翅膀打开了，

for lower air resistance on the backstroke.

以便在向上扑翼时减少空气阻力。

And I think that's awesome

我觉得这棒极了，

because now I know how bird flight works.

因为现在我知道鸟类是如何飞行的了。

Anyway, I'm Destin

总之，我是Destin，

you're getting smarter every day

你每天都在变聪明，

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

最后留给你们看这张图，

that my daughter made

这是我女儿做的，

by gluing homing pigeon feathers

她把信鸽的羽毛粘在

to a piece of paper

一张纸上，

to create her own bird.

创造了她自己的鸟。

You're getting smarter every day.

你每天都在变聪明。

Have a good one. 語氣意圖

祝你开心。

We're in the middle of a cotton field

我们现在在棉花地的中央，

in Alabama.

在阿拉巴马州。

You've never seen it.

你肯定没见过。

It's a really pretty sight.

风景真美。

What are we going to do here, son?

儿子，我们在这里要做什么？

Let this bird go.

把这只鸟放走。

We're going to let this bird go. 語法

我们要把这只鸟放走。

But before we let the bird go,

但在放走它之前，

we're going to talk about his feathers,

我们要来谈谈它的羽毛，

aren't we? 語法

对吧？