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如何给黑洞拍照?

A Picture of the Milky Way's Supermassive Black Hole

This video is sponsored by KiwiCo,
本视频由KiwiCo赞助播出
more about them at the end of the show.
相关详情视频末有介绍
This is a picture of the supermassive black hole
图上是一个超大质量的黑洞
at the center of our Milky Way galaxy
它就是人马座A*
known as Sagittarius A*.
位于银河系的中心
The black hole itself doesn’t emit light
黑洞本身不发光
so what we’re seeing is the hot plasma swirling around it.
所以我们看到的是绕黑洞旋转的热等离子体
This is only the second picture of a black hole ever.
这是史上第二张有关黑洞的照片
It was taken by the Event Horizon Telescope Collaboration,
由事件视界望远镜合作组织拍摄
the same people who brought you this image of the supermassive black hole
这张M87星系中心的超大质量黑洞照片
at the center of galaxy M87.
也是出自该团队之手
Now, their original plan was to image Sagittarius A* first.
他们初始计划计划是拍摄人马座A*
Since it’s in our own galaxy,
因为人马座A*位于银河系
it is 2,000 times closer than M87*,
比M87*的距离近2000倍
but it’s also over 1,000 times smaller
但人马座A*也比M87*小1000多倍
so from Earth,
所以从地球上看
it appears only slightly larger than M87*.
人马座A*似乎只比M87*稍大一点
And there are a number of additional challenges to observing it.
而且观察人马座A*还有一些额外的困难
First of all, there is a lot of dust and gas
首先 在我们和银河系中心之间
between us and the center of our galaxy
存在大量尘埃和气体
so you can’t even see it with visible light.
所以你甚至无法用可见光看到人马座A*
In this video from the European Southern Observatory,
在欧洲南方天文台的这段视频中
we zoom in on our Galaxy’s core.
我们将银河系的核心放大
As we get closer and closer,
随着镜头的推进
at some point we have to switch over to infrared light
放大到一定地步 我们必须切换成红外光
which can better penetrate the debris,
红外光可以更好地穿透碎片
allowing us to see it from Earth.
让我们能从地球上看到人马座A*
Over the past three decades,
在过去的三十年里
we’ve been able to peer into the heart of the Milky Way
我们已经能够窥视银河的中心
and witness something truly amazing.
并见证一些真正令人不可思议的景象
A collection of stars zipping around on all kinds of eccentric orbits.
我们会看到一群在各种偏心轨道运行的恒星
They go incredibly fast.
它们的速度非常之快
One of the stars was clocked
据测算 其中一颗恒星
going 24 million meters per second.
运行速度达到每秒2400万米
That’s 8% the speed of light.
是光速的8%
All these stars appear to be orbiting something incredibly massive and compact,
所有恒星似乎都绕一个极其巨大致密的物体运行
but this object isn’t glowing brightly like a star.
但是这个物体并不像恒星一样发光
If you watch closely, you can see it flicker now and then.
如果仔细观察 你可以看到它时不时闪烁一下
This is what we believe to be a supermassive black hole.
这个就是我们认为的超大质量黑洞
From the motion of the stars around it,
从恒星围绕黑洞运行的情况
we can infer that the black hole’s mass is about 4 million times that of our Sun
我们能推断出黑洞质量约是太阳的400万倍
but all crammed down into a tiny point—the singularity.
但超大行星物质会被塞进一个小点——奇点
Anything including light that comes
包括光在内的任何东西
within a Schwarzschild radius of this point
一旦进入这个奇点的史瓦西半径之内
can’t escape and ends up in the singularity.
就无法逃脱 在奇点终结
So for us to see any radiation from the black hole,
我们看到的任何来自黑洞的辐射
it must come from further out than this,
都来自史瓦西半径之外的地方
usually from superheated plasma as it falls in.
通常来自落入黑洞的过热等离子体
But for its size,
就大小而言
Sagittarius A* doesn’t consume much matter.
人马座A*消耗的物质并不多
It’s unusually quiet and dark.
它异常静谧 黑暗
The supermassive black hole at the center of M87 in contrast is much more active,
相比之下 M87中心的超大质量黑洞要更活跃
gobbling up matter from its accretion disk.
它通过吸积盘吞噬物质
Plus, since it’s over 1,000 times bigger,
另外 它比人马座A*大1000多倍
it takes 1,000 times longer for objects to orbit it.
所以物体绕它一周需要1000倍的时间
And that means from Earth, its appearance over time
这意味着从地球上看
is more consistent in contrast to Sagittarius A*
M87的外观会更稳定
where things can change on the order of minutes.
而人马座A*则会在几分钟内发生变化
These visualizations are from Luciano Rezzolla
这些图像来自法兰克福歌德大学的
and colleagues at Goethe University Frankfurt.
Luciano Rezzolla及其同事
But the biggest challenge of all in making an image
但是 就拍摄超大质量黑洞图像而言
of either supermassive black hole is that these objects are so compact
最大的困难是这些天体非常致密
and so far from Earth,
而且离地球非常远
in the sky, they appear very, very tiny.
在天空中 它们看起来非常的小
To get a sense of just how tiny,
为了让大家了解它到底有多小
take the whole sky and divide it into 180 degrees.
我们把整个天空分成180度
The Andromeda galaxy spans about three degrees.
仙女座星系的跨度约为3度
Then divide one degree into 60 arcminutes
然后将一度分成60弧分
and one arc minute into 60 arcseconds.
一弧分等于60弧秒
Divide an arcsecond into 100,
将一弧秒除以100
into a 100 again and into 100 once more.
再除以100 继续除以100
And this is the size of the black holes on the sky.
这就是天空中黑洞的大小了
It’s equivalent to taking a picture of a donut on the moon.
就相当于给月球上的一个甜甜圈拍照
Now, there is no optical telescope on Earth that could produce such an image.
目前地球上尚无能够制作这种图像的光学望远镜
So in this video, I wanna answer two questions.
那么在这个视频中 我想回答大家两个问题
How did they do it?
他们是如何拍到黑洞照片的?
And what are we actually looking at?
而我们看到的东西到底是什么?
So starting with,
那我们来解决第一个问题:
how did they make these images of black holes?
黑洞照片是如何拍出来的呢?
Well, the first thing to know is they weren’t made with visible light.
首先我们要知道照片并非由可见光制作
They were made using radio waves with a wavelength of 1.3 millimeters.
是由波长为1.3毫米的无线电波制作
So all the observations were taken by radio telescopes
所有对黑洞的观察都是通过射电望远镜进行
which essentially look like huge satellite dishes.
望远镜的外观就像巨大的卫星天线
When a source emits radio waves,
信号源发射无线电波
they travel out radially in all directions,
无线电波会向四面八方辐射出去
but Earth is so far away
但是地球太遥远了
that by the time they reach our planet,
所以当无线电波到达地球时
the wavefronts are almost completely flat and parallel.
波阵面几乎是完全平滑且平行的
This is known as a plane wave.
这就是所谓的平面波
A radio telescope works by scanning back and forth across the sky.
射电望远镜的工作原理是来回扫描天空
When it is pointed directly at a radio source,
当它直接对准某个信号源时
it produces a bright spot.
就会产生一个亮点
That’s because all the radio waves travel the same distance,
那是因为所有的无线电波传播的距离相同
bounce off the dish, and are received at the same time
经过卫星反射后在同一时间被接收
so they are in phase meaning peaks line up with peaks and troughs with troughs.
它们是同相的 波峰波谷一致
They constructively interfere.
同相无线电波相长干涉
As the telescope moves past the source,
当射电望远镜扫描信号源时
some of the radio waves now travel farther than others
一些无线电波会比其它无线电波传播得更远
and therefore they meet up out of phase, destructively interfere,
因此它们会异相相遇 产生相消干涉
and the intensity of the signal drops to zero.
信号强度下降到零
To make a sharp image, you want this drop off to be as steep as possible
此时为了获得清晰图像 这种下降要尽可能大
so the telescope produces peak intensity
这样只有在直接瞄准信号源时
only when aimed directly at the source
望远镜才会产生峰值强度
and then the intensity drops rapidly
只要望远镜向任何方向移动一点
when the dish is moved just a tiny bit in any direction.
强度就会迅速下降
There are two ways of achieving this.
有两种方法可以实现这一点
One is to observe higher frequency radio waves.
一个是观察更高频率的无线电波
That way any slight movement of the telescope represents a greater fraction of a wavelength.
望远镜任何轻微移动都能观测到更大一部分波长
This causes destructive interference to occur sooner.
但这会导致更容易受到相消干涉
The other way is to increase the diameter of the telescope,
另一种方法是增加望远镜的直径
and this increases the difference in path length
望远镜进行一定的角度调整
between radio waves on opposite sides of the telescope for a given angular adjustment.
这增加了其对面的无线电波的路径长度差异
How narrowly a telescope can identify the source
望远镜的角分辨率就是
of radio waves is known as its angular resolution.
其能识别无线电波源的范围
You can think of it as
你可以把它想象成
the size of the spot on the sky that the telescope is sensitive to.
望远镜对天空中光点大小的敏感度
It is proportional to wavelength,
它与波长成正比
and inversely proportional to the diameter of the telescope.
与望远镜的直径成反比
The challenge with making a picture of a black hole is
制作黑洞照片的难度在于
that you’re trying to see the structure in a tiny area of the sky.
要在天空的一小块区域内看到黑洞的结构
Imagine scanning a radio telescope across the center of a black hole.
试想一下 用射电望远镜扫描黑洞的中心
You would want to see the bright spot as the telescope passes over the left edge
当望远镜经过黑洞左边缘时 会看到亮点
and then a dark spot
接着是一个黑点
and then another bright spot as it passes the right edge.
然后经过黑洞右边时又是一个亮点
The problem is, for any individual radio telescope on Earth,
问题是 就地球上任何一台射电望远镜而言
the angular resolution is too large.
其角度分辨率都太大了
So as it passes over the black hole,
所以当射电望远镜扫描黑洞时
it would still be receiving radio waves from the left side
它从右侧接收无线电波时
as it begins receiving radio waves from the right side.
会同时从左侧接收无线电波
The resolution isn’t high enough to tell
望远镜分辨率不够高的话
if there’s a ring structure there as we’d expect with a black hole,
我们就无法判断那里是否有我们要找的黑洞环状结构
or if it’s just a blob.
还是只是一个斑点
Observing at shorter wavelengths isn’t really an option
用更短的波长进行观测 这种方法是行不通的
because that light is blocked either by our atmosphere or by the matter around the black hole.
因为光线会被大气层或黑洞周围的物质阻挡
So if you wanna improve resolution,
所以如果你想提高分辨率
the only way you can do it is by increasing the diameter of the telescope.
唯一的方法就是增加望远镜的直径
But if you actually do the calculation,
但是如果你真的做了计算的话就会发现
you find that the telescope you’d need would have to be the size of the Earth in order to see the ring of a black hole,
必须地球那么大的望远镜才能看到黑洞光环
which is obviously impossible,
这显然是不可能的
but there is a way to do something that’s almost as good.
但是还有一种方法可以做到这一点
You don’t need a complete dish the size of the Earth,
你不需要一个地球大小的镜面
just pieces of it.
你需要的是许多小镜面
Individual radio telescopes that are separated by distances
只需保证每个射电望远镜之间的距离加起来
up to the Earth’s diameter.
等于地球直径即可
As long as you can properly combine the signals from all these distant telescopes,
只要正确组合所有这些远距离望远镜的信号
you get the constructive and destructive interference required
就可以得到所需的相长干涉和相消干涉
to achieve the same angular resolution as an Earth-sized dish.
以达到地球大小射电望远镜的角度分辨率
This technique is called very long baseline interferometry.
这种技术被称为甚长基线干涉测量法
So the event horizon telescope is not just one telescope
因此 事件视界的望远镜不是一台望远镜
but a global network of radio observatories.
而是一个全球性的无线电天文台网络
All these telescopes observe Sagittarius A* at the same time.
所有这些望远镜同时观测人马座A*
Unlike a single telescope,
与单一的望远镜不同的是
you can’t bounce all the radio waves to a central receiver
你无法把所有无线电波反射到同一中央接收器
and add them up in real time.
然后实时叠加起来
So instead each telescope records the signal at its location
因此每个望远镜都会记录其所在位置的信号
and the exact time down to the femtosecond.
以及精确到飞秒的时间
Petabytes of data are generated.
产生数十亿字节的数据
But now that data needs to be brought together,
数据现在需要被整合在一起
and the fastest way to do it was actually to carry hard drives as hand luggage to centralized locations.
最快的方法是将硬盘放进手提箱带回中心
Now, think about the data we’ve got.
现在看一下我们得到的数据
Electrical signals and precise timings from a number of radio telescopes around the world,
全世界这么多个望远镜的电信号和精确计时
but none of those radio telescopes
但是没有一个射电望远镜
has enough angular resolution to see the ring of the black hole.
能有足够的角度分辨率来观察黑洞光环
So how do you combine that data and get finer detail than any of the inputs?
那如何组合这些数据并获得更详细信息呢?
Well, there is additional information in the relative distances between these telescopes
突破点就在这些望远镜之间的相对距离
and in the time delays between when a wavefront hits one telescope relative to the others.
以及相对于其他望远镜的波前时间延迟中
Imagine combining the signals from two distant telescopes.
若将两台相距较远的望远镜的信号结合起来
Let’s say they both received the same wave at the same time
假设他们同时接收到同一个无线电波
so those waves were coming in phase.
那么这些波是同相位的
Well, then the source must have been located directly between them.
这样的话 信号源肯定就在它们之间
The radio waves would’ve traveled the same distance
之所以无线电波会经过相同的距离
to each telescope to arrive at the same time,
在同一时间到达每个望远镜
except with just two telescopes,
是因为只有两台望远镜
that only narrows it down to a line in the sky
所以能将信号源的范围缩小到
that is equidistant from both telescopes.
天空中与两台望远镜等距的一条线上
The source could have been anywhere on that line.
信号源可能在这条线上的任何地方
And it’s actually worse than that.
实际上比这种情况更糟糕
It’s possible that the source could be exactly one wavelength closer to one of the telescopes
因为信号源可能正好离其中一个望远镜更近一个波长
and that way the radio waves would still arrive perfectly in phase.
这样无线电波仍然会以同相位到达
Or the difference could be two or three or four wavelengths, but you get the point.
更近两个三个或四个波长也是这样 你懂得
So from one pair of telescopes, the information we get about the source
从一对望远镜中我们得到的信息源
is actually a series of bright and dark fringes.
实际上是一系列明暗条纹
Telescopes that are close together produce wide fringes,
距离很近的望远镜会产生很宽的条纹
while those that are far apart produce narrow fringes.
而那些相距较远的望远镜会产生窄条纹
So to make an image, you need pairs of telescopes
因此 要拍摄一幅图像 就需要成对的望远镜
at all different orientations and different distances apart.
它们处于不同的方位 相距不同的距离
Each pair makes a different interference pattern.
每一对望远镜会产生不同的干扰图案
And then by combining all these patterns,
然后把所有这些图案结合起来
we get an image of the black hole which created them.
我们就得到了黑洞图像
But now that we have this picture,
现在我们得到了这样一幅图
what exactly is it showing us?
它的内容是什么呢?
Well, this is how I explained it when the first image of a black hole was released.
请容我解释第一张黑洞图片
So here is my mock black hole of science.
这是我的黑洞模型
And this sphere represents the event horizon.
这个球体代表事件视界
Once you’re inside here,
一旦你进入事件视界
there is no coming back, not even for light.
就再也回不来了 光也无法逃脱
The radius of the event horizon is known as the Schwarzschild radius.
事件视界的半径被称为史瓦西半径
Now, if we were just to look at a black hole with nothing around it,
如果黑洞周围什么都没有
we would not be able to make an image like this
那我们就无法制作出这样的图像
because, well, it would just absorb all electromagnetic radiation that falls on it,
因为黑洞会吸收落于其内的所有电磁辐射
but the black hole that they’re looking at has matter around it in an accretion disk.
但是我们看到的黑洞 周围存在吸积盘
In this accretion disk, there is dust and gas swirling around here very chaotically.
在这个吸积盘中 尘埃 气体非常混乱地旋转
It’s incredibly hot. We’re talking millions of degrees.
里面的温度非常高 大概有几百万度
And it’s going really fast,
它旋转得非常快
a significant fraction of the speed of light.
差不多能达到光的速度
And it’s this matter that the black hole feeds off
这就是黑洞赖以生存的物质
and gets bigger and bigger over time,
随着时间的推移 这些物质变得越来越大
but you’ll notice
但你会注意到
that the accretion disk does not extend all the way in to the event horizon.
即使这样吸积盘也没有延伸到事件视界
Why is that?
这是为什么呢?
Well that’s because there is an innermost stable circular orbit,
那是因为黑洞里面有一个稳定的圆形轨道
and for matter around a non-spinning black hole,
对于围绕非旋转黑洞的物质来说
that orbit is at three Schwarzschild radii.
这个轨道的长度是三个史瓦西半径
Now, in all likelihood, the black hole at the center of our galaxy will be spinning.
但十有八九 银河系中心的黑洞是会旋转的
But for simplicity,
话说回来
I’m just considering the non-spinning case.
我们只考虑黑洞不旋转的情况
You can see my video
如果你想了解更多
on spinning black holes if you wanna find out more about that.
可以看我那一期关于旋转黑洞的视频
So this is the innermost orbit for matter going around a black hole.
言归正传 物质围绕黑洞最里面的轨道
If it goes inside this orbit,
一旦进入这个轨道
it very quickly goes into the center of the black hole and we never hear from it again,
它很快会被吸入黑洞中心 音讯全无了
but there is something that can orbit closer to the black hole,
但是有一种东西可以在轨道上比较靠近黑洞
and that is light.
那就是光
Because light has no mass,
光没有质量
it can actually orbit at 1.5 Schwarzschild radii.
所以它可以在1.5倍史瓦西半径处存在
Now here, I’m representing it with a ring,
现在在这里 我用一个环来代表史瓦西半径
but really this could be in any orientation.
但实际上这可以是一个任何方向的环
So it’s a sphere of photon orbits.
这是一个光子轨道的形成球体
And if you were standing there,
如果你站在那里
of course you could never go there,
当然了你不可能去那里
but if you could, you could look forward and actually see the back of your head
但假设可以的话 你向前看会看到你的后脑勺
’cause the photons could go around and complete that orbit.
因为光子可以绕着轨道运行
Now, the photon sphere is an unstable orbit
光子球是一个不稳定的轨道
meaning eventually either the photons have to spiral into the singularity
这意味着光子最终要么螺旋式进入奇点
or spiral out and head off to infinity.
要么螺旋式飞出去 奔向无限远
Now, the question I want to answer is,
现在我要回答的问题是
what does this black, quote unquote, shadow in the image
图片中的这个黑色阴影
correspond to in this picture of what’s actually going on around the black hole?
对应的是黑洞的哪一部分?
Is it the event horizon? Are we simply looking at this?
是事件视界吗?我们只能看到它吗?
Or is it the photon sphere
是光子层吗?
or the innermost stable, circular orbit?
还是最里面的稳定的圆形轨道?
Well, things are complicated.
事情很复杂
And the reason is, this black hole warps space-time around it
因为这个黑洞扭曲了它周围的时空
which changes the path of light rays
改变了光线的路径
so they don’t just go in straight lines like we normally imagine that they do.
所以它不像我们通常想象的那样走直线
I mean, they are going in straight lines,
我是说 光是直线前进的
but space-time’s curved so yeah, they go in curves.
但时空是弯曲的 所以光也是弯曲的
So the best way to think of this is maybe
所以我们最好这样思考
to imagine parallel light rays coming in from the observer
平行光线从望远镜里射进来
and striking this geometry here.
打在这个几何图形上
Of course, if the parallel light rays cross the event horizon,
当然 如果平行光线穿过事件视界
we’ll never see them again so they’re gone.
我们就再也见不到它们了 它们消失了
That will definitely be a dark region,
那这里肯定会是一个黑暗的区域
but if a light ray comes in just above the event horizon,
但是如果一束光线刚好从视界上方射进来
it too will get bent and end up crossing the event horizon.
它也会弯曲并穿越事件视界
It ends up in the black hole.
最终会进入黑洞
Even a light ray coming in the same distance away as the photon sphere
即使是与光子层距离相同的光线
will end up getting warped into the black hole
最终也会被扭曲到黑洞中
and curving across the event horizon.
并弯曲着穿过事件视界中
So in order for you to get a parallel ray which does not end up in the black hole,
所以平行光线要想不落入黑洞里
you actually have to go out 2.6 radii away.
必须走到2.6个史瓦西半径以外
If a light ray comes in 2.6 Schwarzschild radii away,
如果一束光线从2.6倍史瓦西半径外射进来
it will just graze the photon sphere at its closest approach and then it will go off to infinity.
它就会擦过光子层 然后飞向无穷远
And so the resulting shadow that we get looks like this.
所以我们得到的阴影就像这样
It is 2.6 times bigger than the event horizon.
它是事件视界的2.6倍
And you say, what are we really looking at here?
你会问 我们看到的到底是什么?
What is this shadow?
阴影部分代表什么?
Well in the center of it is the event horizon.
它的中心是事件视界
It maps pretty cleanly onto the center of the shadow.
事件视界非常清晰地映射到阴影的中心
But if you think about it,
但是如果你仔细想想
light rays going above or below also end up crossing the event horizon,
向上或向下的光线最终也会穿过事件视界
just on the backside.
就在后面
So in fact, what we get is the whole backside of the event horizon
所以我们实际看到的是事件视界的整个背面
mapped onto a ring on this shadow.
映射到这个阴影上的一个环上
So looking from our one point in space at the black hole,
所以从太空中的一个点观察黑洞
we actually get to see the entirety of the black hole’s event horizon.
我们可以看到整个黑洞的事件视界
I mean, maybe it’s silly to talk about seeing it
我的意思是 也许说能看到它是愚蠢的
because it’s completely black,
因为是它是全黑的
but that really is where the points would map to on this shadow.
但事件视界确实是会映射到阴影上的这部分
It gets weirder than that because the light can come in and go around the back and,
比这更奇怪的是 光可以进来 绕到后面
say, get absorbed in the front,
然后在前面被吸收
you get another image of the entire horizon next to that in another annular ring
你会在旁边另一个环形圈 看到整个全景图像
And then another one after that and another one after that.
一圈接一圈 再一圈接一圈
And you get basically infinite images of the event horizon
当你接近这个阴影的边缘时
as you approach the edge of this shadow.
你会得到无限个事件视界的图像
So what is the first light that we can see?
那么我们能看到的第一道光是什么?
It is those light rays that come in at just such an angle
就是以这样的角度进入的光线
that they graze the photon sphere
它们擦过光子层
and then end up at our telescopes, and they produce a shadow
然后到达我们的望远镜
which is 2.6 times the size of the event horizon.
它们产生的阴影是事件视界的2.6倍
So this is roughly what we’d see
如果垂直于吸积盘观察
if we happen to be looking perpendicular to the accretion disk,
我们就会看到这样的概况
but more likely
但更有可能的是
we will be looking at some sort of random angle to the accretion disk.
我们会以某种随机视角观察吸积盘
We may be even looking edge on.
我们甚至可能在吸积盘的边缘观察
And in that case, do we see this shadow of the black hole?
在这种情况下 我们会看到黑洞的阴影吗?
You might think that we wouldn’t,
你可能认为我们看不到吸积盘
but the truth is
但事实是
because of the way the black hole warps space time and bends light rays,
由于黑洞扭曲时空和弯曲光线的方式
we actually see the back of the accretion disk.
我们实际上看到了吸积盘的背面
The way it works is light rays coming off the accretion disk bend over the top
其原理是从吸积盘上下来的光线在顶部弯曲
and end up coming to our telescopes.
最终到达我们的望远镜
So what we end up seeing is something that looks like that.
所以我们最终看到的是这样的东西
Similarly, light from the bottom of the accretion disk comes underneath,
同理 来自吸积盘底部的光线到达下面
gets bent underneath the black hole and comes towards us like that.
在黑洞下面弯曲 就像这样向我们射来
And this is where we get an image that looks something like the interstellar black hole.
这看起来就像《星际穿越》里的黑洞了
It gets even crazier than this
比这更疯狂的是
’cause light that comes off the top of the accretion disk here can go around the back of the black hole,
从吸积盘顶部发出的光会绕过黑洞的背面
graze the photon sphere, and come out the bottom right here
擦过光子层 从底部出来
producing a very thin ring underneath the shadow.
在阴影下面产生一个非常薄的环
Similarly, light from underneath the accretion disk in the front can go underneath
同样地 来自前面吸积盘下方的光线
and around the back and come out over the top,
可以从下方绕过后面 从上方射出
which is why we see this ring of light here.
所以我们在这里看到了这个光环
This is what we could see if we were very close to the black hole,
这是我们非常接近黑洞时所能看到的
something that looks truly spectacular.
一些看起来非常壮观的东西
One other really important effect to consider is
另一个要考虑的非常重要的影响是
that the matter in this accretion disk is going very fast,
这个吸积盘中的物质运行速度非常快
close to the speed of light.
接近光速
And so if it’s coming towards us,
所以如果它向我们走来
it’s gonna look much brighter than if it’s going away.
看起来就会比它离开时更亮
That’s called relativistic beaming or Doppler beaming.
这被称为相对论波束或多普勒波束
And so one side of this accretion disk is going to look much brighter than the other,
所以这个吸积盘的一边看起来会比另一边亮得多
and that’s why we’re gonna see a bright spot in our image.
所以我们会在图像中看到一个更亮的地方
So hopefully this gives you an idea of
希望本期视频能带你了解
what we’re really looking at when we look at an image of a black hole.
看一个黑洞的图像时 我们到底在看什么
Hey, this video was sponsored by KiwiCo,
嘿 这个视频是由KiwiCo赞助的
creator of awesome hands-on projects for kids.
它是一个儿童动手项目的创造者
You know, I’ve used KiwiCo with my own kids for years.
实不相瞒 我用和孩子一起用了KiwiCo很多年
They have nine different subscription lines targeted at different age groups,
他们有9个不同的订阅频道 针对不同的年龄
all the way down to newborns.
一直到新生儿都有
The way it works is every month a box shows up at your door
它的工作方式是每个月给你邮寄一个盒子
and inside it is everything you need to complete the project.
里面是你完成项目所需的材料
That means no extra trips to the store.
这意味着你无需再去商店跑一趟
And when I show my kids the box,
当我给我的孩子看盒子的时候
they jump at the chance to make it with me,
他们很乐意和我一起玩
and we can spend hours building something,
我们可以花几个小时建造一些东西
playing with it, and learning about STEAM concepts together.
一起玩儿 一起学习蒸汽概念
There really is no substitute for getting your hands dirty
实践是检验真理的唯一标准
and making something to figure out how it actually works.
做一些东西来弄清楚它的工作原理吧
Plus, it’s a ton of fun.
另外 这个过程乐趣多多
And to me, that’s how learning should be.
对我来说 这就是学习的方式
I want my kids to approach learning as play.
我希望我的孩子把学习当成游戏
And I have seen how this fosters their curiosity and sparks new ideas.
我也看到了这是如何培养他们的好奇心和激发新想法的
KiwiCo have been long-time supporters of the channel.
KiwiCo是本频道的长期支持者
I’ve visited their offices,
我参观过他们的办公室
which really seem like a giant playground for adults like me.
对我这样的成年人来说 那里像巨大的游乐场
And I’ve met their expert project designers
我见过他们的专业项目设计师
and seen how thoroughly they test and iterate their designs.
看到他们如何不厌其烦地测试和重复设计
Now, for viewers of this channel
对于这个频道的观众来说
KiwiCo are offering 30% off your first month of any kit.
KiwiCo将为您提供首月30%的折扣
Just go to kiwico.com/veritasium30.
快去kiwico.com/veritasium30一睹真颜吧
I will put that link down in the description.
我会在简介中写下链接
So I wanna thank KiwiCo for supporting Veritasium,
感谢KiwiCo公司对本节目的支持
and I wanna thank you for watching.
感谢大家的收看

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视频概述

黑洞本身不发光,那么天文学家如何观测黑洞,甚至拍摄到黑洞的照片呢?一起来一探究竟吧~

听录译者

收集自网络

翻译译者

ccz

审核员

审核员XY

视频来源

https://www.youtube.com/watch?v=Q1bSDnuIPbo

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