為什麼太空人在月球上留下了反射鏡！(ft. MinutePhysics) - Smarter Every Day 73：英語精讀講義

It's me Destin.

我是 Destin。

Welcome back to Smarter Every Day.

歡迎回到 Smarter Every Day。

So, did you know that in the '60s and '70s, 表達脈絡

那麼，你知道在 60 和 70 年代，

when the astronauts went to the Moon in the Saturn V rocket,

當太空人乘坐農神 5 號火箭登月時，

they actually left experiments on the surface of the Moon?

他們其實在月球表面留下了一些實驗設備嗎？

In fact, there's one that's still there today 表達脈絡

事實上，有個設備今天還在那裡

and it's still operating.

並且仍在運作。

We're still getting data out of it.

我們依然能從中獲取數據。

But before I explain

但在我解釋

that, I kind of need to go to the bathroom. 語氣意圖

那個之前，我得先去趟洗手間。

All right.

好吧。

Here where I went to grad school,

這是我讀研究所的地方，

we shared this building with NASA,

我們和 NASA 共用這棟大樓，

which is interesting because every time I go wash my hands 文法

這很有趣，因為每次我去洗手

after using the bathroom,

（上完洗手間後），

I think about the Moon.

我都會想到月球。

Check this out. 語氣意圖

來看看這個。

On one wall,

在一面牆上，

we have a mirror,

我們有一面鏡子，

and on the other wall we have a mirror and they're lined up.

而在另一面牆上我們也有一面鏡子，而且它們對齊了。

Now, all this makes for some pretty interesting fun stuff. 片語動詞

現在，這一切構成了非常有趣的現象。

But what I want to talk about today is right here. 表達脈絡

但我今天想談的是這裡。

Look at that.

看那個。

No matter where you go in the room, 文法

無論你走到房間裡的哪個地方，

you always see the camera lens

你總是能看到相機的鏡頭

right in the corner of the mirror.

正好在鏡子的角落裡。

This has pretty serious implications 片語搭配

這有著相當重要的意義

for NASA science on the Moon.

對於 NASA 在月球上的科學研究來說。

Now, it's so important that I've asked Henry from MinutePhysics

這非常重要，所以我請來了 MinutePhysics 的 Henry

to explain it to you.

來為你們解釋。

Let's check it out.

我們來看看吧。

A corner reflector like this one

像這樣的角反射器

is an ingenious and beautifully simple device.

是一個巧妙又極具簡單美感的裝置。

It takes advantage of the fact that a mirror mirrors one dimension of the world. 片語搭配

它利用了鏡子能鏡像反映世界一個維度的原理。

If you have a second mirror,

如果你有第二面鏡子，

you can reverse back to how you started.

你就可以反轉回最初的樣子。

But if the second mirror is at 90° to the first,

但如果第二面鏡子和第一面呈 90 度角，

now when you mirror back,

現在當你反射回去時，

the world will have rotated 180°.

世界將旋轉 180 度。

So, if you send a beam of light into a corner reflector,

所以，如果你把一束光射入角反射器，

regardless of what direction you send it in 文法

不管你射入的方向為何，

or what direction the corner reflector is oriented,

或者角反射器的朝向為何，

it'll come back rotated 180°

它都會旋轉 180 度返回

into a parallel return path to its source.

進入一條平行於光源的返回路徑。

If you look here at the top of the camera,

如果你看看相機頂部，

you can see that my name is mirrored.

你可以看到我的名字被鏡像反轉了。

But if I bring it over here to the side in the corner,

但如果我把它拿到這邊的角落裡，

look at that.

看看這個。

You can read it.

你可以讀出來了。

You can probably see it a little bit better with my shirt.

看我的衣服可能會看得更清楚一點。

Can't read it?

讀不出來？

Now you can.

現在你可以了。

That's because you're seeing a reflection of a reflection.

這是因為你看到的是反射的反射。

But look at this.

但看看這個。

If I look back at the corner and then I tilt the camera up,

如果我看著角落然後把相機向上傾斜，

I'm no longer aligned. 文法

我就不再對齊了。

I can't see the lens anymore.

我再也看不到鏡頭了。

Now, that tells me that I'm not in a true return path 表達脈絡

這告訴我，我不在一條真正的返回路徑上

like he tried to explain to me.

就像他試圖向我解釋的那樣。

That's because those mirrors

這是因為這些鏡子

are only reflecting in the two horizontal directions.

只在兩個水平方向上反射。

There's no mirror reflecting back to you in the vertical direction.

沒有鏡子在垂直方向上向你反射。

If you have a third mirror at a right angle, 片語搭配

如果你有成直角的第三面鏡子，

everything will be mirrored,

一切都會被鏡像，

reversed,

反轉，

and mirrored again.

然後再被鏡像。

So, your name will be backwards.

所以，你的名字會倒過來。

But at least now you can move your camera or eyes around however you want. 文法

但至少現在你可以隨心所欲地移動相機或眼睛。

And as long as you can still see all three mirrors, 文法

只要你還能看到全部三面鏡子，

you'll see a reflection of yourself in the middle.

你就會在中間看到你自己的反射。

Mathematically, if you want to reverse a vector, 文法

從數學上講，如果你想反轉一個向量，

you need to reverse each of its components,

你需要反轉它的每一個分量，

and so you need three mirrors

所以你需要三面鏡子

to get full retroreflection in 3D. 用詞

來實現 3D 的全向逆反射。

One mirror for each dimension.

每個維度一面鏡子。

Oh, this is just like the reflectors on the road.

喔，這就像路上的反光鏡一樣。

If you look real close at this one that my wife hit with a lawn mower,

如果你仔細看看這個被我妻子用割草機撞過的東西，

you can see that they're actually just little bitty corner reflectors. 用詞

你可以看到它們其實就是小小的角反射器。

Exactly,

沒錯，

but those are imperfect on purpose 片語搭配

但它們是故意做得不完美的，

because a high precision corner reflector would bounce the light back 片語動詞

因為高精度的角反射器會把光反彈回

to your car's headlights and not your eyes.

你汽車的車頭燈裡，而不是你的眼睛裡。

Oh!

喔！

Well, I just happen to have an array of high precision corner reflectors 片語搭配

好吧，我剛好有一組高精度的角反射器

here with me in Germany.

帶在我身邊，在德國。

And what's that?

那是啥？

It's Johan,

這是 Johan，

the laser guy from the Netherlands.

來自荷蘭的雷射達人。

You remember him, right?

你還記得他吧？

This corner reflector is so precise,

這個角反射器非常精確，

I can set it here on this bridge,

我可以把它放在這座橋上，

go all the way upriver to the next bridge,

一路逆流而上到下一座橋，

hit it with a laser,

用雷射照射它，

and I'll still get a reflection even though it's snowing. 文法

儘管在下雪，我仍然能看到反射。

Check it out.

來看看。

What are you doing, Johan?

你在幹嘛，Johan？

I'm warming up my laser. 片語動詞

我在預熱我的雷射。

All right.

好吧。

And uh why are you doing that?

呃，你為什麼要那樣做？

To get it to the right temperature because it's very temperature sensitive. 講解

為了讓它達到合適的溫度，因為它對溫度非常敏感。

Oh, okay.

喔，好的。

All right.

好吧。

Can you ping the reflector? 用詞

你能照射一下反射器嗎？

There it is.

在那兒呢。

Clearly,

很明顯，

you're getting a return.

你收到了返回的光。

That's what, like 500 m away,

大概有 500 公尺遠吧，

would you say? 語氣意圖

你覺得呢？

350.

350。

How do you know that?

你怎麼知道的？

I counted the steps.

我數了步數。

Okay,

好的，

so here's the question. 表達脈絡

那麼問題來了。

If Johan is able to get a really good reflection

如果 Johan 能夠在

at 350 m away in the snow

350 公尺外，在雪地中

with a handheld laser

用手持雷射

that he's having to blow on to keep alive, 慣用語

（甚至還要對著它吹氣來保持溫度），獲得極好的反射，

then what are we able to do if we put

那麼如果我們把

a high precision laser reflector on the Moon?

一個高精度雷射反射器放在月球上，我們能做到什麼？

In fact,

事實上，

that's what Apollo

那正是阿波羅計畫

did. What was it?

所做的。那是幾號來著？

Apollo what?

阿波羅幾號？

Apollo 11,

阿波羅 11 號，

14,

14 號，

and 15.

和 15 號。

They put retroreflectors on the Moon,

他們在月球上放置了後向反射器，

and we're still using it for experiments to this day. 片語搭配

而且直到今天我們仍在使用它們進行實驗。

Right.

對的。

Experiments like monitoring the distance to the Moon.

諸如監測地月距離這樣的實驗。

If you count how long it takes a photon to get to the Moon and back, 文法

如果你計算一個光子到達月球並返回需要多長時間，

you can just multiply by the speed of light,

你只需乘以光速，

divide by two,

除以二，

and figure out the distance to the Moon within centimeters. 片語動詞

就能將地月距離精確到公分級別。

Exactly,

完全正確，

Henry.

Henry。

So, if you shoot the Moon with a laser,

所以，如果你用雷射射向月球，

2.56 seconds later,

2.56 秒後（返回），

divided by two,

除以二，

1.28 light seconds to the Moon.

到月球就是 1.28 光秒。

So, if you do the math, 片語搭配

所以，如果你算一下，

that ends up to about this far from the Earth.

大概就是離地球這麼遠的距離。

Anyway,

不管怎樣，

this is useful for understanding

這有助於理解

the detailed nuances of the Moon's rotation and orbit,

月球自轉和軌道的細微變化，

measuring movement of tectonic plates here on Earth,

測量地球上板塊的運動，

and even testing

甚至可以用來檢驗

the fundamental principles of general relativity.

廣義相對論的基本原理。

Corner reflectors are not just used in optics. 文法

角反射器不僅用於光學。

You can also use it for any type of reflected electromagnetic radiation.

你也可以將它用於任何類型的反射電磁輻射。

Here in Frankfurt, Germany,

在德國法蘭克福這裡，

there's a bridge with long posts

有一座橋，長長的柱子

coming off the big pylons there under the bridge.

從橋下那些巨大的橋墩上伸出來。

We've got a big boat about to go under the bridge. 文法

有一艘大船正準備從橋下經過。

And if you look at the very end,

如果你看最末端，

there's corner reflectors.

那裡有角反射器。

Only they're not mirrors, 表達脈絡

只是它們不是鏡子，

they're just metal.

只是金屬而已。

He's using a radar

他正在使用雷達

to guide off of those corner reflectors,

依靠那些角反射器來導航，

so he doesn't hit the bridge.

這樣他就不會撞到橋上。

It's basically a passive lighthouse, 慣用語

它基本上是一個無源燈塔，

only it's not light,

只不過發出的不是光，

it's radar.

而是雷達。

Cool.

酷。

So, corner reflectors are like a lighthouse

所以，角反射器就像一座燈塔

that tells you its distance,

告訴你它的距離，

except better because they don't need their own source of power. 講解

只是更好，因為它們不需要自己的電源。

That's why they were a good experiment to leave on the Moon. 表達脈絡

這就是為什麼把它們留在月球上是個很棒的實驗。

Actually,

實際上，

the Apollo astronauts left other junk on the Moon, too. 用詞

阿波羅太空人還在月球上留下了其他的廢品。

Come over to my channel,

來我的頻道，

MinutePhysics,

MinutePhysics，

and I'll tell you all about it.

我會告訴你關於它的一切。

That's how the Apollo guys

這就是阿波羅的太空人們

went to the bathroom in the command module.

在指令艙裡上洗手間的方式。

How'd they do it on the lunar module?

他們在登月艙裡是怎麼解決的？

Imagine it's fairly similar.

我想應該挺相似的。

Oh.

喔。

Do you realize that there might be poop on the Moon.

你意識到月球上可能有便便嗎。

We gotta think this through! 講解

我們得好好想想這個！

Wow.

哇。

I didn't even think about that.

我甚至都沒想過那個。

We always talk about the other stuff that they sent.

我們總是談論他們送上去的其他東西。

Did they leave their poop on the Moon?

他們把便便留在月球上了嗎？

I imagine they must 文法

我想他們肯定是

have because like why would you bring that back? 語氣意圖

留了，因為你幹嘛要把它帶回來？

When I go hiking,

當我去健行時，

I try to find the perfect spot.

我試圖尋找最完美的景點。

That guy has won that game.

那個傢伙贏得了那場遊戲。

That's like the most distant porta-john. 文化背景

那就像是最遙遠的流動廁所。

The most distant porta-john

最遙遠的流動廁所

On the lunar landers on the Moon.

在月球上的登月艙裡。