彩虹的科學！……還有為什麼耳機線總是纏在一起。：英語精讀講義

Hey Vsauce,

嗨，Vsauce，

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

我是 Michael，正在我媽家的地下室裡歡度佳節。

But a few days ago,

不過幾天前，

MadmegzOfEpic @tweetsauce this question.

MadmegzOfEpic 向 @tweetsauce 提了這個問題。

Now at first I was like, 用詞

一開始我心想：

"The end of a rainbow?

「彩虹的盡頭？

Of course you can't get there.

當然不可能走得到。

Everybody knows that."

這誰都知道啊。」

But then I said,

但接著我又問自己：

"Why?

「為什麼？

I mean, 語氣意圖

我的意思是，

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

如果我看到一道彩虹，再朝它發射一台子彈攝影機，會發生什麼事？

What would the footage look like?" 文法

拍到的畫面會是什麼樣子？」

Well,

其實，

I found that in this impossible journey to a rainbow,

我發現，在這趟不可能實現的彩虹之旅中，

you can learn a lot.

你可以學到很多東西。

For instance,

比方說，

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

你看到的彩虹是專屬於你的。

That's right.

沒錯。

Anybody nearby will also see a rainbow,

附近其他人也會看到彩虹，

but their rainbow will be slightly different.

但他們看到的會略有不同。

There's a different rainbow for everybody.

每個人都有一道不同的彩虹。

And that's because rainbows are apparent phenomena. 用詞

這是因為彩虹是一種表觀現象。

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

你所在的位置決定了彩虹會出現在你眼中的哪個地方。

Rainbows happen because sunlight behind your body

彩虹之所以會出現，是因為你身後的陽光

enters into raindrops in front of you

進入你面前的雨滴，

that then reflect it back into your eyeballs.

再被反射回你的眼球。

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

之所以會形成彩虹，是因為雨滴不只會反射光，

they also refract it.

也會折射光。

Refraction occurs whenever any type of wave enters a new medium

每當任何一種波進入新的介質，

where its speed is changed.

並在其中改變傳播速度時，就會產生折射。

And in order to change speed, 片語搭配

而要改變速度，

that wave must change direction.

這種波就必須改變方向。

So when white light from the sun enters a raindrop,

因此，當太陽的白光進入雨滴時，

it is refracted.

光就會發生折射。

It changes direction.

它會改變方向。

And different wavelengths of light,

而不同波長的光，

which means different colors, 表達脈絡

也就是不同顏色的光，

are refracted differently.

折射的程度也不一樣。

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

於是，它們便分散成我們熟知的 ROY G. BIV。球形雨滴的幾何結構代表，

that this spectrum of colors will only be visible to you

這道色譜只有在

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

相對於你所在位置的特定角度，才能被你看到。

And that angle is about 40 to 42 degrees

這個角度大約是 40 到 42 度，

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

也就是從你的頭部到頭部影子這個方向算起。

Here's a way to think about it. 表達脈絡

你可以這樣想。

The spectrum of a rainbow is firing out of raindrops

彩虹的色譜會從雨滴中射出，

between the angle of 40 and 42 degrees.

角度介於 40 到 42 度之間。

So if you move forward,

所以，如果你向前移動，

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

只會看到同一道彩虹改由不同的雨滴呈現，

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

不過，在雨滴內部反射不只一次的光又是另一回事。

Now,

那麼，

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

要讓這種光進入你的眼睛，

it has to reflect at a very specific angle.

就必須以一個非常特定的角度反射。

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

所以從你的視角來看，只有大約 50 到 53 度的角度看得到它。

And this, my friends,

而這個，朋友們，

is the double rainbow.

就是雙彩虹。

Now again,

同樣地，

because of spherical geometry,

由於球體幾何結構，

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

這些雨滴無法把光以

between 42 to 50 degrees,

42 到 50 度之間的角度反射進你的眼球，

which means that the area between a primary and secondary rainbow

這表示主虹與副虹之間的區域

is darker than the rest of the sky.

會比天空其他部分更暗。

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

這個區域稱為亞歷山大暗帶。

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

喔，關於彩虹，還有太多內容是我們在這裡講不完的。

For instance,

比方說，

if the sun is already set,

如果太陽已經下山，

but the moon is behind you producing enough light,

但你身後的月亮能提供足夠的光，

you can get a moonbow.

你就可能看到月虹。

Also cool,

還有一種也很酷的現象：

reflection rainbows.

反射虹。

If one of these occurs with a normal rainbow,

如果反射虹和一般彩虹同時出現，

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

你會看到兩道對不上的彩虹，

that aren't parallel.

它們並不平行。

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

這是因為其中一道彩虹的光並非來自觀察者身後的太陽，

but instead from sunlight reflected from the lake below.

而是來自下方湖面反射的陽光。

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

由於只有在特定角度才能看到彩虹，

if you move your body,

當你移動身體時，

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

還是會在同一個角度看到那道彩虹，

which means the rainbow will move with you.

也就是說，彩虹會跟著你移動。

It will appear to be following you. 文法

它看起來會一直跟著你。

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

當你搭飛機時，這種現象尤其明顯，

high above the ground, moving quickly.

因為你在離地很高的空中快速移動。

Now because you're so far off the ground,

由於你離地面非常遠，

the rainbow,

這道彩虹

which is centered around your shadow, 片語搭配

以你的影子為中心，

is actually 100% completely visible,

實際上會百分之百完整地顯現，

which means none of it is hiding below the horizon,

也就是說，沒有任何部分藏在地平線下方，

which means you see a circular rainbow.

因此你看到的是一圈圓形彩虹。

And as you can see, 表達脈絡

正如你所看到的，

as the plane flies through the clouds,

當飛機穿越雲層時，

the rainbow continues to be in the same apparent position.

彩虹看起來仍在同一個位置。

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

所以，如果我朝彩虹發射一台子彈攝影機，

the rainbow would not get closer.

彩虹並不會變得更近。

Instead,

相反地，

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

攝影機靠近得多快，它看起來就會以同樣的速度後退。

Rainbow is a classic compound word, 用詞

英文單字 rainbow 是一個典型的複合詞，

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

也就是由兩個以上能獨立成詞的字組成。

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

那我們就來拆開看看，先從 bow 開始，

a decorative knot.

也就是裝飾用的蝴蝶結。

Here are some brand new headphones.

這裡有一副全新的耳機。

They're perfectly together,

兩邊整整齊齊地放在一起，

everything's fine,

一切都沒問題，

and uh they're perfectly straight.

而且，呃，耳機線完全是直的。

But quickly,

但沒過多久，

after being in my pocket or in a backpack,

放進口袋或背包之後，

headphones inevitably tie themselves up into weird knots.

耳機就免不了自己纏成奇怪的結。

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

聖誕樹燈串和電線也一樣。

Why does that happen?

為什麼會這樣？

I mean,

我的意思是，

are there some kind of like weird evil elves sneaking around

難道有什麼古怪又邪惡的小精靈偷偷溜過來，

when we're not looking

趁我們沒注意時

tying wires into knots?

把電線打成結嗎？

Hmm.

嗯。

Maybe,

也許吧，

but probably not.

但多半不是。

Instead,

其實，

the answer lies in mathematics. 慣用語

答案就在數學裡。

Mathematicians have jiggled strings around inside boxes

數學家曾把繩子放進盒子裡反覆晃動，

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

以弄清會隨機出現哪些類型的結，

but how often they will.

以及這些結出現的頻率。

And of course,

當然，

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

他們發現，繩子最後處於打結狀態的機率

than a relatively rare unknotted one.

遠高於處於相對少見的無結狀態。

Furthermore,

此外，

once a string is knotted,

繩子一旦打結，

it resists being untied, 文法

就不容易被解開，

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

而這差不多正是「結」的定義。

So,

所以，

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

它會一直打著結、纏成一團，直到有人來把它解開。

But what about rain? 表達脈絡

那麼，rain（雨）又是怎麼回事？

Well,

嗯，

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

我們知道，雨是形成彩虹視覺體驗的原因之一。

But what about the olfactory sensation of rain? 用詞

那麼，雨帶來的嗅覺體驗呢？

The smell of rain.

也就是雨的氣味。

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

其實，雨的這種氣味有一個專門的名稱。

It's called petrichor. 用詞

它叫做 petrichor。

Naturalists have given the smell of rain a name

博物學家替雨的氣味取了這個名字，

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

因為他們找到了這種氣味產生的具體原因。

During dry times,

在乾旱時期，

plants exude in oil.

植物會分泌一種油。

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

這種油的作用是延緩種子發芽和植物生長，

so they can wait until there's more water.

讓它們等到水分更充足時再生長。

But once the rain comes, 文法

但雨一落下，

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

這種油就會被雨水帶入空氣中，被我們聞到，

creating petrichor, 文法

從而形成 petrichor，

the smell of rain.

也就是雨的氣味。

So the next time you smell rain,

所以下次聞到雨的氣味時，

think about this word petrichor and where it comes from.

想想 petrichor 這個詞，以及它的由來。

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

你聞到的不只是大自然或某些植物油的氣味，

you are smelling by definition 片語搭配

按照這個詞的本義，你聞到的是

the blood of stone. 慣用語

石頭的血。

The blood of the earth,

大地的血，

of the ground.

地面的血。

And as always,

一如往常，

thanks for watching.

謝謝收看。