詹姆斯·韦伯如何改变了天文学：英语精读讲义

This is MIRI, the mid-infrared camera onboard the James Webb telescope. 文化背景

这就是MIRI，詹姆斯·韦伯望远镜上的中红外相机。

Watch what happens when light enters the camera.

看看光线进入相机时会发生什么。

A complex series of mirrors and filters direct and split the light up into different wavelengths,

一系列复杂的反射镜和滤光片将光线引导并分离成不同的波长，

which are then resized and directed onto the sensors.

然后调整其大小并将其投射到传感器上。

With this camera,

有了这台相机，

Webb can see extremely distant stars and galaxies

韦伯望远镜就能看到极其遥远的恒星和星系，

that are completely invisible to the human eye.

而这些对人类肉眼来说是完全不可见的。

This is only possible by cooling the camera down to just 6° above absolute zero. 文化背景

只有将相机的温度降至仅比绝对零度高6°，这一切才有可能。

But why does it need to be so cold?

但是它为什么需要这么冷呢？

In this video,

在这段视频中，

we're going to look at how Webb captures infrared light 文化背景

我们将了解韦伯是如何捕捉红外光的，

and how a simple sound like this

以及像这样简单的声音

is used to cool its camera all the way down to a mind-boggling temperature. 講解

是如何被用来将其相机的温度一路降至令人难以置信的水平的。

We'll also be giving away this LEGO ISS model,

我们还将送出这个乐高国际空间站模型，

so stick around to the end of the video 短語動詞

所以请看到视频最后，

to see how you could win.

看看你如何能够赢得它。

All of the cameras onboard James Webb detect infrared light,

詹姆斯·韦伯望远镜上的所有相机都能探测到红外光，

which is invisible to the human eye.

而这在人类肉眼看来是不可见的。

As light travels through space,

当光在太空中传播时，

its wavelength is constantly being stretched.

它的波长在不断被拉长。

If something is far enough away, 語法

如果某个物体足够遥远，

the light will be stretched so much that it is no longer visible by the time it reaches us. 語法

光线就会被拉伸得非常长，以至于在到达我们这里时就不再可见了。

This means there is a physical limit on how far we can see into space.

这意味着我们能够看到多远的太空存在着一个物理极限。

Since MIRI's sensors are made from arsenic and silicon,

由于MIRI的传感器是由砷和硅制成的，

it can detect this super stretched infrared light and see beyond that limit.

它可以探测到这种被极度拉长的红外光，从而突破这个极限。

These sensors work like regular camera sensors

这些传感器就像普通相机传感器一样工作，

by converting photons of light into an electrical signal.

通过将光子转换成电信号。

But in order to detect the faint signals of infrared light,

但是，为了探测到微弱的红外光信号，

the sensors on MIRI have to be extremely sensitive.

MIRI上的传感器必须极其灵敏。

Increasing the sensitivity, however, introduces a lot of noise. 用詞

然而，提高灵敏度会引入大量噪点。

Whenever we point a camera at something,

每当我们将相机对准某个东西时，

its sensor isn't just detecting what we want it to see.

它的传感器并不仅仅在探测我们想让它看到的东西。

There is so much more light bouncing around us that our eyes simply can't detect.

在我们周围有太多我们的眼睛完全无法察觉的漫反射光线。

This can trick the pixels in the sensor into registering random levels of light, 語法

这会让传感器中的像素误以为检测到了随机的光照强度，

creating a layer of noise in the image.

从而在图像上产生一层噪点。

If the thing you are looking at has a bright enough signal,

如果你在观察的物体具有足够明亮的信号，

it will stand out much more compared to the noise. 短語動詞

它在噪点面前就会显得非常突出。

However, if the thing you are trying to image is faint,

然而，如果你试图成像的物体很暗淡，

like the infrared light from a galaxy,

比如来自星系的红外光，

you'll need to increase the sensitivity of the sensor,

你就需要提高传感器的灵敏度，

which in turn will drastically increase the noise. 表達脈絡

但这反过来又会大幅增加噪点。

Since Webb is detecting infrared light,

由于韦伯正在探测红外光，

the problem gets even worse.

问题变得更加严重。

Every object in our universe emits heat energy,

我们宇宙中的每一个物体都会发出热能，

some of which is in the form of light.

其中一部分以光的形式存在。

Most objects aren't quite hot enough to emit visible light,

大多数物体还不够热，无法发出可见光，

but they do emit a lot of infrared light.

但它们确实会发出大量的红外光。

The hotter the object, 語法

物体越热，

the more infrared light it will emit,

它发出的红外光就越多，

which is essentially how thermal imaging cameras work.

这基本上就是热像仪的工作原理。

Because of this, James Webb itself would emit so much infrared light

正因为如此，詹姆斯·韦伯望远镜本身就会发出大量的红外光，

that its sensors would be completely drowned out. 短語動詞

以至于它的传感器会被完全淹没。

And so, in order to limit the amount of infrared light produced by the telescope,

因此，为了限制望远镜产生的红外光数量，

its cameras need to be kept at a temperature of -234°.

它的相机必须保持在-234°的温度。

That is extremely cool,

这简直太冷酷了，

just like Wondrium, the sponsor of today's video.

就像今天视频的赞助商Wondrium一样。

Wondrium is a learning platform where you can explore a variety of subjects,

Wondrium是一个学习平台，你可以在这里探索各种学科，

including some of my favorites,

包括我最喜欢的一些，

technology, science, and space exploration.

技术、科学和太空探索。

One of the best ones I came across was the search for exoplanets, 短語動詞

我偶然发现的最好的课程之一是关于寻找系外行星的，

which tells you all about the technologies and methods

它告诉你所有关于技术的和方法的知识，

used to discover new planets beyond our solar system,

这些技术和方法被用来发现我们太阳系以外的新行星，

just like those used on the James Webb telescope.

就像詹姆斯·韦伯望远镜上使用的那些一样。

Wondrium offers a diverse collection of videos, tutorials, and documentaries,

Wondrium提供了各种各样的视频、教程和纪录片，

giving you the opportunity to learn from experts and hear their firsthand experiences. 短語搭配

让你有机会向专家学习，并听取他们的第一手经验。

Plus, with new offers every month,

另外，通过每个月推出的新优惠，

you'll never run out of new and exciting things to discover. 短語動詞

你永远不会缺少可以发现的令人兴奋的新事物。

You can enjoy all of their courses ad-free from anywhere on any device.

你可以在任何设备的任何地方享受他们所有无广告的课程。

And best of all,

最棒的是，

they're offering the Primal Space community a free trial starting today.

他们从今天开始为Primal Space社区提供免费试用。

If you're looking to challenge yourself and expand your knowledge,

如果你想挑战自己并扩展自己的知识，

then Wondrium is the perfect place for you.

那么Wondrium是你完美的选择。

Don't wait any longer.

别再等了。

Head to the link in the description below for your Wondrium free trial.

点击下方描述中的链接即可获得Wondrium的免费试用。

In order for MIRI to operate at -267°, 語法

为了让MIRI在-267°下运行，

it's located behind the massive five-layer sunshield.

它被放置在巨大的五层遮阳板后面。

This alone reflects so much heat

单单这个就反射了如此多的热量，

and cools Webb's cameras down to around -234°.

并将韦伯相机的温度降至约-234°。

But, since MIRI is much more sensitive than the other cameras,

但是，由于MIRI比其他相机敏感得多，

it faces an even bigger problem, dark current. 文化背景

它面临着一个更棘手的问题：暗电流。

This is where the atoms inside the sensor itself vibrate and mistakenly register a photon of light, 表達脈絡

暗电流就是传感器内部的原子振动，并错误地记录为一个光子，

creating more noise.

从而产生更多的噪点。

Since temperature is just a measure of how fast an atom vibrates, 短語搭配

由于温度只是衡量原子振动有多快的一个指标，

lowering the temperature will lower the vibration and therefore reduce the amount of dark current.

降低温度将减缓振动，从而减少暗电流的数量。

Even at -234°,

即使在-234°，

the vibration of these atoms would be too much for MIRI's sensor.

这些原子的振动对MIRI的传感器来说也太大了。

And so, they have to be cooled all the way down to -267°,

因此，它们必须被一路降温到-267°，

just 6° above absolute zero.

仅比绝对零度高出6°。

At this temperature,

在这个温度下，

the atoms in the sensor are almost completely still,

传感器中的原子几乎是完全静止的，

drastically reducing the noise and allowing the faint infrared signals to shine through.

从而极大地减少了噪点，让微弱的红外信号能够透射出来。

But how did NASA take these sensors all the way down to -267°?

但是NASA是如何将这些传感器一路降至-267°的呢？

The cooling process all starts here,

降温过程都是从这里开始的，

at the bottom of the telescope,

位于望远镜的底部，

with a device called a pulse tube. 文化背景

有一个叫做脉冲管的装置。

Inside these tubes are two pistons,

这些管内有两个活塞，

which move back and forth to compress the helium into the pulse tube. 短語搭配

它们前后移动以将氦气压缩到脉冲管中。

Since this movement would create a lot of unwanted vibration,

由于这种运动会产生大量不必要的振动，

these pistons have to move in the exact opposite direction

这些活塞必须在完全相反的方向上移动，

with precision timing to cancel out each other's movement. 短語動詞

并拥有精确的计时，以抵消彼此的运动。

These pistons move very quickly,

这些活塞移动得非常快，

just like a speaker,

就像扬声器一样，

to create a low-frequency sound wave with a frequency of 30 Hz.

产生频率为30 Hz的低频声波。

This sound wave travels down the tube

这种声波顺着管道传播，

and gets compressed once it reaches the end,

一旦到达末端就会被压缩，

creating an area of higher pressure.

从而形成一个较高压力的区域。

Then, as it bounces back in the opposite direction,

然后，当它沿相反方向反弹时，

it expands, creating an area of low pressure

它会膨胀，形成一个低压区域，

before being compressed once again.

然后再一次被压缩。

If the next wave is sent out exactly as the previous one returns, 語法

如果下一个波的发出恰逢上一个波的返回，

it means the frequency perfectly matches that of the tube. 語法

这意味着频率与管道的频率完全匹配。

This creates a standing wave 文化背景

这就产生了一个驻波，

where the areas of high and low pressure remain in the same place.

高压区和低压区停留在同一个地方。

By tripling the frequency,

通过将频率提高到三倍，

it causes the waves to combine and create a stationary wave

这会使波形组合，并形成一个驻波，

with multiple areas of high and low pressure.

具有多个高压和低压区域。

Since temperature and pressure are related,

由于温度和压力是相关的，

this also leads to areas of high and low temperature.

这也会导致出现高温和低温区域。

This alone wouldn't change the overall temperature

单靠这一点并不会改变整体温度，

because the hot and cold parts simply cancel each other out.

因为高温和低温部分仅仅是相互抵消了。

But, if there was a way to extract the hot parts, 語法

但是，如果有办法把高温部分提取出来，

then the temperature would start to drop.

那么温度就会开始下降。

And so, three heat exchangers

因此，三个热交换器，

made of thin metal sheets 短語搭配

由薄金属片制成，

are placed at the points where the hot and cold gas meet.

被放置在冷热气体交汇的地方。

These allow the gas to pass through whilst also absorbing some of its temperature, 用詞

它们允许气体通过，同时也吸收了它的一些温度，

causing a heat gradient to form. 語法

从而形成温度梯度。

The heat from the hot side is pulled out

热端的热量被抽取出来，

and sent to the radiators via a heat exchanger.

并通过热交换器送到散热器中。

Then, the cold temperatures on the other side are also drawn out. 短語動詞

然后，另一侧的低温也随之被抽调。

This causes the temperature to drop from 27° all the way down to -256°

这就导致温度从27°一直下降到-256°

at the final heat exchanger.

在最后一个热交换器处。

But how is this used to cool the sensors located at the opposite end of the telescope?

但这是如何被用来冷却位于望远镜另一端的传感器的呢？

Next to the pulse tube is another set of pistons

脉冲管旁边是另一组活塞，

that compress helium in a completely separate line of tubing.

它们在一条完全独立的管道中压缩氦气。

This line passes through the cold parts of the pulse tube's heat exchangers,

这条管线穿过脉冲管热交换器的寒冷部分，

cooling the helium all the way down to around -256°.

把氦气一路冷却到约-256°。

But still the helium isn't quite cold enough. 語法

但是，氦气依然不够冷。

From there, the helium goes on a long journey,

从那里，氦气开始了漫长的旅程，

winding its way up through 10 m of thin tubing until it reaches the cold head assembly. 習語

蜿蜒盘旋穿过10米的细管，直到到达冷头组件。

Inside, there is another heat exchanger and a tiny hole less than 1 mm in diameter. 短語搭配

在里面，有另一个热交换器和一个直径小于1毫米的小孔。

The helium is pushed through the hole

氦气被推过这个孔，

and undergoes something called the Joule-Thomson effect. 文化背景

经历了一种叫做焦耳-汤姆孙效应的过程。

As the gas moves through the hole,

当气体穿过这个孔时，

it gets compressed before quickly expanding on the other side. 語法

它先是被压缩，然后在另一侧迅速膨胀。

This rapid expansion causes the pressure to drop, 語法

这种迅速的膨胀导致压力骤降，

cooling the gas very quickly.

从而非常迅速地冷却气体。

This is why blowing air through our mouth is colder

这就是为什么通过嘴巴吹气会比较凉快，

if we make a smaller hole with our lips.

只要我们用嘴唇撅成一个小一点的孔。

On James Webb,

在詹姆斯·韦伯望远镜上，

this cools the helium all the way down to just -267°.

这能将氦气一路冷却至仅-267°。

From here, the helium flows on to copper plates attached to the back of MIRI's sensors,

从这里开始，氦气流向附在MIRI传感器背面的铜板，

cooling them down to the required temperature.

将它们冷却到所需的温度。

After that, the helium has done its job 習語

在那之后，氦气就完成了它的工作，

and it flows back down the telescope where the entire process begins again.

然后它回流到望远镜底部，整个过程又重新开始。

When NASA began designing James Webb,

当NASA开始设计詹姆斯·韦伯望远镜时，

no cryocooler with this level of cooling existed.

这种制冷水平的低温冷却器还不存在。

And so, engineers had to really push the boundaries of physics, 習語

因此，工程师们必须真正突破物理学的界限，

all while conforming to the limits of fitting it into a space telescope. 語法

同时还要克服将其塞进太空望远镜的尺寸限制。

And now,

那么现在，

time for something really special.

到了一个特别的环节。

The winner of the previous giveaway is Daniel Weinman.

上一期抽奖的赢家是Daniel Weinman。

Congratulations.

恭喜你。

But, as always,

但是，像往常一样，

we'll be giving away another awesome space prize in the next video.

我们将在下一个视频中送出另一个超棒的太空奖品。

To win this amazing LEGO space station model,

为了赢得这个超赞的乐高空间站模型，

sign up at the link below

请在下方的链接注册，

and leave a comment saying how long you think James Webb will operate for. 語法

并留下评论，说说你认为詹姆斯·韦伯望远镜将运行多长时间。

Thank you very much for watching

非常感谢您的观看，

and I'll see you in the next video.

我们在下个视频见。