彩虹的科学！……以及为什么耳机线总是缠在一起。：英语精读讲义

Hey Vsauce,

嘿，Vsauce，

Michael here and I'm celebrating the holidays in my mom's basement.

我是 Michael，我正在妈妈家的地下室里欢度佳节。

But a few days ago,

不过几天前，

MadmegzOfEpic @tweetsauce this question.

MadmegzOfEpic 向 @tweetsauce 提了这个问题。

Now at first I was like, 用詞

我一开始心想：

"The end of a rainbow?

“彩虹的尽头？

Of course you can't get there.

你当然不可能走到那里。

Everybody knows that."

这谁都知道啊。”

But then I said,

但接着我又问自己：

"Why?

“为什么？

I mean, 語氣意圖

我是说，

what would happen if I saw a rainbow and I fired a camera bullet at the rainbow? 語法

如果我看到一道彩虹，再朝它发射一台子弹摄像机，会发生什么？

What would the footage look like?" 語法

拍到的画面会是什么样？”

Well,

其实，

I found that in this impossible journey to a rainbow,

我发现，在这场不可能实现的彩虹之旅中，

you can learn a lot.

你能学到很多东西。

For instance,

比如，

the rainbow that you see is unique to you. 短語搭配

你看到的彩虹是专属于你的。

That's right.

没错。

Anybody nearby will also see a rainbow,

附近的其他人也会看到彩虹，

but their rainbow will be slightly different.

但他们看到的会略有不同。

There's a different rainbow for everybody.

每个人都有一道不同的彩虹。

And that's because rainbows are apparent phenomena. 用詞

这是因为彩虹是一种表观现象。

Where you are dictates where the rainbow will appear to you. 語法

你所在的位置决定了彩虹会出现在你眼中的什么地方。

Rainbows happen because sunlight behind your body

彩虹之所以会出现，是因为你身后的阳光

enters into raindrops in front of you

进入了你面前的雨滴，

that then reflect it back into your eyeballs.

然后被反射回你的眼球。

And there's a rainbow because raindrops not only reflect light, 語法

之所以会形成彩虹，是因为雨滴不仅会反射光，

they also refract it.

还会折射光。

Refraction occurs whenever any type of wave enters a new medium

每当任何一种波进入新的介质，

where its speed is changed.

并在其中改变传播速度时，就会发生折射。

And in order to change speed, 短語搭配

而要改变速度，

that wave must change direction.

这种波就必须改变方向。

So when white light from the sun enters a raindrop,

所以，当太阳的白光进入雨滴时，

it is refracted.

光就会发生折射。

It changes direction.

它会改变方向。

And different wavelengths of light,

而不同波长的光，

which means different colors, 表達脈絡

也就是不同颜色的光，

are refracted differently.

折射的程度也不一样。

So they get separated into what we know as ROY G. BIV. The geometry of a spherical raindrop means 文化背景

于是，它们便分散成我们熟知的 ROY G. BIV。球形雨滴的几何结构意味着，

that this spectrum of colors will only be visible to you

这道色谱只有在

from a very specific angle relative to where you are. 短語搭配

相对于你所在位置的一个特定角度，才能被你看到。

And that angle is about 40 to 42 degrees

这个角度约为 40 到 42 度，

from the angle of your head to your head's shadow.

也就是从你的头部到头部影子这一方向算起。

Here's a way to think about it. 表達脈絡

你可以这样理解。

The spectrum of a rainbow is firing out of raindrops

彩虹的色谱会从雨滴中射出，

between the angle of 40 and 42 degrees.

角度介于 40 到 42 度之间。

So if you move forward,

所以，如果你向前移动，

you'll just see that rainbow coming from different drops,

你只会看到同一道彩虹改由不同的雨滴呈现，

except light that reflects more than one time inside the raindrop.

不过，在雨滴内部反射不止一次的光又是另一回事。

Now,

那么，

in order for this light to get to your eyes, 語法

要让这种光进入你的眼睛，

it has to reflect at a very specific angle.

它必须以一个非常特定的角度反射。

So it's only visible about 50 to 53 degrees from your perspective. 短語搭配

所以从你的视角看，只有大约 50 到 53 度的角度才能看到它。

And this, my friends,

而这，朋友们，

is the double rainbow.

就是双彩虹。

Now again,

同样，

because of spherical geometry,

由于球体几何结构，

these raindrops are not going to be able to reflect light to your eyeballs

这些雨滴无法把光以

between 42 to 50 degrees,

42 到 50 度之间的角度反射进你的眼球，

which means that the area between a primary and secondary rainbow

这意味着主虹与副虹之间的区域

is darker than the rest of the sky.

会比天空的其他部分更暗。

This area is known as Alexander's dark band. 短語搭配

这个区域叫作亚历山大暗带。

Oh, and there's way more than we can even cover here.

噢，关于彩虹，还有太多内容是我们在这里讲不完的。

For instance,

比如，

if the sun is already set,

如果太阳已经落山，

but the moon is behind you producing enough light,

但你身后的月亮能提供足够的光，

you can get a moonbow.

你就可能看到月虹。

Also cool,

还有一种也很酷的现象：

reflection rainbows.

反射虹。

If one of these occurs with a normal rainbow,

如果反射虹和普通彩虹同时出现，

you'll have two rainbows that don't line up, 短語動詞

你会看到两道对不齐的彩虹，

that aren't parallel.

它们并不平行。

The reason is that one of these rainbows is not coming from sunlight behind the viewer, 語法

这是因为其中一道彩虹的光并非来自观察者身后的太阳，

but instead from sunlight reflected from the lake below.

而是来自下方湖面反射的阳光。

Because you can only see a rainbow from a certain angle,

由于只有在特定角度才能看到彩虹，

if you move your body,

当你移动身体时，

you will continue to see that rainbow from the same angle,

你还是会在同一个角度看到那道彩虹，

which means the rainbow will move with you.

也就是说，彩虹会跟着你移动。

It will appear to be following you. 語法

它看起来会一直跟着你。

Now this is particularly apparent when you're flying in an airplane

当你坐在飞机上时，这种现象尤其明显，

high above the ground, moving quickly.

因为你在高空飞行，而且移动得很快。

Now because you're so far off the ground,

由于你离地面非常远，

the rainbow,

这道彩虹

which is centered around your shadow, 短語搭配

以你的影子为中心，

is actually 100% completely visible,

实际上会百分之百完整地显现出来，

which means none of it is hiding below the horizon,

也就是说，它没有任何部分藏在地平线以下，

which means you see a circular rainbow.

所以你看到的是一圈圆形彩虹。

And as you can see, 表達脈絡

正如你所看到的，

as the plane flies through the clouds,

飞机穿过云层时，

the rainbow continues to be in the same apparent position.

彩虹看起来仍然停留在同一个位置。

So if I fired a bullet camera right at a rainbow,

所以，如果我朝着彩虹发射一台子弹摄像机，

the rainbow would not get closer.

彩虹并不会越来越近。

Instead,

相反，

it would appear to recede just as fast as the camera approached it. 語法

摄像机多快接近它，它看起来就会以同样的速度后退。

Rainbow is a classic compound word, 用詞

英文单词 rainbow 是一个典型的合成词，

a word that is made up of two or more words that can stand on their own. 講解

也就是由两个或更多能够独立成词的词组成。

So let's unpack these a bit beginning with bow, 習語

那我们就拆开看看，先说 bow，

a decorative knot.

也就是装饰用的蝴蝶结。

Here are some brand new headphones.

这里有一副全新的耳机。

They're perfectly together,

两边整整齐齐地放在一起，

everything's fine,

一切都很好，

and uh they're perfectly straight.

而且，呃，耳机线完全是直的。

But quickly,

但用不了多久，

after being in my pocket or in a backpack,

在口袋或背包里放过之后，

headphones inevitably tie themselves up into weird knots.

耳机就免不了自己缠成奇怪的结。

The same goes for Christmas tree lights and electrical wires. 短語搭配

圣诞树灯串和电线也一样。

Why does that happen?

为什么会这样？

I mean,

我是说，

are there some kind of like weird evil elves sneaking around

难道有什么古怪又邪恶的小精灵偷偷溜过来，

when we're not looking

趁我们没注意时

tying wires into knots?

把电线打成结吗？

Hmm.

嗯。

Maybe,

也许吧，

but probably not.

但多半不是。

Instead,

其实，

the answer lies in mathematics. 習語

答案就在数学中。

Mathematicians have jiggled strings around inside boxes

数学家曾把绳子放进盒子里反复晃动，

to determine not only what types of knots will randomly occur, 語法

以弄清会随机出现哪些类型的结，

but how often they will.

以及这些结出现的频率。

And of course,

当然，

what they found is that it's much more likely for a string to fall into a knotted position 語法

他们发现，绳子最终处于打结状态的可能性

than a relatively rare unknotted one.

远高于处于相对少见的无结状态。

Furthermore,

此外，

once a string is knotted,

绳子一旦打结，

it resists being untied, 語法

就不容易被解开，

which is pretty much the definition of a knot. 短語搭配

而这差不多正是“结”的定义。

So,

所以，

it'll remain knotted and twisted up until a person comes along and unties it. 短語動詞

它会一直打着结、缠成一团，直到有人来把它解开。

But what about rain? 表達脈絡

那么，rain（雨）又是怎么回事？

Well,

嗯，

we know that rain is part of what's responsible for the visual experience of a rainbow. 用詞

我们知道，雨是形成彩虹视觉体验的原因之一。

But what about the olfactory sensation of rain? 用詞

那么，雨带来的嗅觉体验呢？

The smell of rain.

也就是雨的气味。

There's actually a name for the way rain smells.

其实，雨的这种气味有一个专门的名字。

It's called petrichor. 用詞

它叫作 petrichor。

Naturalists have given the smell of rain a name

博物学家为雨的气味取了这个名字，

because they have found a specific cause for the smell of rain.

因为他们发现了这种气味产生的具体原因。

During dry times,

在干旱时期，

plants exude in oil.

植物会分泌一种油。

And the point of this oil is to slow down seed germination and plant growth 講解

这种油的作用是延缓种子萌发和植物生长，

so they can wait until there's more water.

让它们等到水分更充足时再生长。

But once the rain comes, 語法

但雨一落下，

this oil is washed into the air and we smell it,

这种油就会被雨水带入空气中，被我们闻到，

creating petrichor, 語法

从而形成 petrichor，

the smell of rain.

也就是雨的气味。

So the next time you smell rain,

所以下次闻到雨的气味时，

think about this word petrichor and where it comes from.

想一想 petrichor 这个词，以及它的由来。

You're not just smelling nature or certain plant oils,

你闻到的不只是大自然或某些植物油的气味，

you are smelling by definition 短語搭配

按照这个词的本义，你闻到的是

the blood of stone. 習語

石头的血。

The blood of the earth,

大地的血，

of the ground.

地面的血。

And as always,

一如既往，

thanks for watching.

感谢观看。