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太空很久以前是橙色的!! – 译学馆
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太空很久以前是橙色的!!

Cosmic Microwave Background Explained | Space Time | PBS Digital Studios

外太空看起来是漆黑一片
Outer space looks black,
然而事实上整个宇宙曾经是这个颜色
but the entire universe used to be this color.
怎么会是这样的呢
How’s that possible?
让我们来找出答案
Let’s find out.
星球和星系是没有排名的
Stars and galaxies is not with standings,
宇宙是黑桃色的
space is peach black.
因此选择一个黑点然后将一个模拟卫星圆盘天线指向它
So pick a dark spot in the sky and point an analog satellite dish at it.
你可能以为什么都得不到 但是不是这样
You might expect to get nothing, but you don’t.
你产生了静电
You get static.
挑选另一个点 得到更多的静电
Pick another point and more static.
再移动你的圆盘天线指向另一个黑点 又得到静电
Move your dish yet again, static.
还要算上各种可能的干扰
Even accounting for all possible types of interference,
无论你怎么定位圆盘天线
no matter how you orient your dish,
静电潜在的微波环形带是不变的
there’s this constant underlying microwave band static
它恰好总是在漆黑的宇宙中那里
that’s just always there in the darkness of space,
以同样的方式发散下去
emitting the same pattern over and over.
现在既然我们已经从各个可以看到的方向识别到这种神秘的静电
Now since we pick up this mysterious static from every direction we look,
而这些静电似乎的来源存在于太空中的每个角落
it would seem to be coming from a source that exists literally everywhere on the sky.
问题是 我们不知道这种来源会在哪个地方
Problem is, we don’t know of any source
发射这种可以观察到的微波发射
anywhere that would emit this observed pattern of microwave emission,
所以它来自哪里呢
so where’s it coming from?
外星人
Aliens.
不 这不是外星人
No, it’s not aliens.
也不可能是外星人
It’s never aliens.
但是如果我告诉你静电的来源 就是我们称之为
But what if I told you that the source of static, which we call
宇宙微波背景 或者宇宙微波背景辐射
the cosmic microwave background, or CMB,
它是在大约13.5百亿年前
was the process that formed the first atoms in the universe
宇宙第一次大爆炸中形成的
almost 13 and 1/2 billion years ago?
并且如果我告诉你宇宙微波背景辐射的来源
And what if I also told you that the source of the CMB
同样是导致整个宇宙成千上万年看起来都是橘色的原因你会怎么办
also caused all of space to look orange for millions of years?
是的 宇宙曾经是橙色的
That’s right, the universe used to be orange.
为了了解到这如何成为事实的
To understand how this could be true,
我们首先需要用一个简短的迂回来说明 回到你的面包机上
we first need to take a brief detour into your toaster.
打开你面包机
Turn on your toaster.
加热元件发出苍白微红的光
The heating elements glow a pale, reddish color.
发光并不是面包机的环境发光反射
That glow isn’t ambient light reflecting off the toaster,
它是面包机本身发出的光
it’s light being emitted by the toaster itself.
如果你要用仪器来分析这种光
If you were to analyze that glow with instruments
会比用眼睛来看的容易
less limited than human eyes, you
你会发现面包机不仅是发出苍白 红色的光
would realize that the toaster isn’t just emitting pale, red light.
它发射出的所有有波长的电磁波
It’s emitting electromagnetic waves of all wavelengths.
此外 不同的波长强度
Moreover, the intensity at different wavelength
有着非常具体的比例
is in very specific proportions that trace out
可以用来画出一个跟这个很相近的跟踪图来看
a graph very close to this.
发射模式可以用图来表示
That emission pattern represented by the graph
可以称为烤面包机的热谱或者
is called the toaster’s thermal spectrum or really
可以认为这是一个真正的理想化的热谱可以称为黑体谱
an idealization of a thermal spectrum called a black body spectrum.
现在 所有的东西都有了温度
Now, everything has a temperature,
所以每个事物都有自己的热谱了
so everything has a thermal spectrum,
并且他们会发射出电磁波的波长
and it emits all electromagnetic wavelengths.
你 墨西哥煎玉米卷 太阳 所有的一切
You, a taco, the sun, everything.
实际上 这叫热谱
In fact, it’s called a thermal spectrum
因为光线是由材料中的粒子随机运动产生
because the light is generated by the random motions of particles in the material.
这些随机运动是它们对温度的反应
And those random motions are themselves a reflection of temperature.
现在 如果你的温度已经将的够低了
Now, if you go really low in temperature,
降到绝对零度以上的2.7度
down to 2.7 degrees above absolute zero,
微波波长峰值的变化
the peak shifts way into microwave wavelengths
还有 你瞧 和宇宙微波背景辐射值相符
and, lo and behold, exactly matches the CMB,
我是说真的
and I mean exactly.
宇宙微波背景辐射是最接近的事物之一
The CMB is one of the closest things
在数学上完美的热谱
to a mathematically perfect thermal spectrum that
还没有被观察到
has ever been observed.
问题是 宇宙里大部分都是空的
Problem is, space is pretty much empty.
那里没有真的有温度的事物
There’s nothing really in there to have
更不用是具体的2.7开尔文的温度了
a temperature, much less the very specific temperature of 2.7 Kelvin.
那么为什么宇宙微波背景辐射图看起来完全像是个热谱
So why does the CMB look like a thermal spectrum at all?
为了回答这个问题和理解太空为何过去曾经是橙色的
To answer that and to see why space used to be orange,
我们需要时光倒转回大约四十万年前
we need to turn the clock back to about 400,000 years
在大爆炸以后 得到或者释放了一些东西
after the Big Bang, give or take.
在那个时期
During that era,
一个增压粒子带着几千度高的温度渗透了整个太空
a supercharged particle with a temperature of several thousand degrees permeated all of space.
在这样的温度下 对于电子和质子来说太热了
At this temperature, it’s too hot for electrons and protons
即使对于合成的原子来说也太热了 更别说对于星星
to even coalesce into atoms, let alone stars,
行星和星系来说了
planets or galaxies.
这被称作等离子电离汤
This ionized soup is called a plasma.
就像烤面包机 人和炸玉米片
And just like toasters, people and tacos,
这是发射的电磁波的温度分布
it was emitting a thermal distribution of electromagnetic waves.
但是因为这里没有中性原子
But because there were no neutral atoms yet,
光线发射出的等离子体
the light the plasma emitted just
在遇到一个电子之前
couldn’t travel very far before it
不能漫游到很远的地方 而且这像弹跳球游戏一样
would run into an electron and ricochet like in a pinball game.
那么如果你让这个电子回到这个区域
So if you took the Tardis back to this era
并且能帮助防止它融化
and could somehow keep it from melting,
你没有办法从遥远的取景屏看到
you wouldn’t be able to see very far on the viewscreen,
也许是几千光年 听起来像是很久的样子
maybe a few thousand lightyears, which sounds like a lot,
但是在天文学里面这是基本单位的能见距离
but it’s basically zero visibility in astronomical terms.
所以在这个时刻 它看起来就像是在太空里
So at this moment, it was as if flash bulbs were constantly
时常可以看到的灯泡
going off everywhere in space,
但是这个光会被雾掩盖
but the light was being snuffed out by a fog.
等这种等离子冷却后 它的温度甚至
Now as this plasma cooled, its temperature eventually
它的温度甚至会降到低于3000度或者更低
its temperature eventually dropped below the 3,000 or so degree mark,
低到中性原子可以最终形成
where neutral atoms could finally form.
没有更多的自由电子可以重新发射光
With no more free electrons to redirect the light,
宇宙第一次变得透明
the universe became, for the very first time, transparent.
等离子发射出来的光
The light that the plasma had emitted then
在中和之前这是它最后一次欢呼 最后一次的闪烁
just before neutralized was one last hurrah, one final flash
无限的橙色灯泡爆炸了
of an infinite number of orange bulbs going off
在宇宙中每个地点或多或少都留下了痕迹
at every point in the universe more or less simultaneously.
现在那种光可以永远自由的在宇宙中流通
And now, that light could free stream through the universe forever.
在这个大爆炸前 中 后的过程中宇宙空间扩大了
Before, during and after this event, space was expanding.
这就是等离子体变稀薄的原因 并且首次降温的原因
That’s what thinned out the plasma and made it cool down in the first place.
但是向我们前一集有谈到的
But as we talked about in a prior episode
你可以在这里重温下 扩大空间
that you can revisit here, expanding space
通过y一种名叫宇宙学红移的过程
stretches the wavelength of free streaming light
增长了自由波光的波长
through a process called cosmological redshift.
所以在几百万年的过程中
So over the course of a few million years,
这种橙色光的热谱
that orangey thermal spectrum of light
由于红移变得波长越来越长
was redshifted to longer and longer wavelengths,
变成考面包机红 最后变成红外线了
becoming toaster red and eventually infra-red,
所以对于人类的眼睛来说 最后太空变成黑色了
so that to human eyes, the sky eventually turned dark.
如果你再给太空另外一个13亿年
If you throw in another 13 plus billion years
来进行扩张 所有的光
of space expansion, all that light
就会红移到q微波波段
has redshifted into the microwave band
就会成为今天我们所说的宇宙微波背景辐射
to become what we today perceive as the CNB.
所有这些原子都是从等离子体分出来的
And all those atoms from that plasma?
好吧 它们设法集中在一起 汇聚成恒星 星系
Well, they managed to clump, become stars, galaxies,
并且通过一个复制的宇宙循环过程
and through a complicated process of cosmic recycling, us.
所以宇宙微波背景辐射 或者更具体地说
So the CNB, or more specifically,
是宇宙热谱的行形状
the shape of its thermal spectrum,
对说到宇宙的颜色
is pretty compelling evidence that when
是很有力的证明 黑色是新的橙色
it comes to the color of space, black is the new orange.
既然宇宙微波背景对于除了
Now, the CNB is interesting for a lot
其热性质以外的其它原因来说是特别的
of other reasons besides its thermal character,
那么我信息你们一定会有疑问
so I’m sure you guys will have questions about.
我会尽我所能在下一期”时空”专辑里面进行处理
I’ll tackle as many as I can on the next episode of ‘Space Time.’
上周 我给了你们一个关于用福克斯滚筒稳定陀螺驱动行星的挑战
Last week, I challenged you to stabilize a gyro-driven Star Fox barrel roll.
很多人发邮件来回答这个问题 并且许多人 都回答正确
A lot of you emailed in responses, and a lot of you got it right.
在发来的邮件中回答正确的前五名
The first five of you who emailed correct
我先提前说声抱歉
answers, and I apologize in advance
如果我有拼错你的名字的话 他们分别是
if I mispronounce your name, were
马库斯·卡瑟琳 卡梅隆·莫兰 马蒂亚斯·奥拉 托马斯·许
Markus Kesselring, Cameron Moran, Mattias Olla, Thomas Hsu
以及雅各布·施蒂克
and Jacob Stueck.
干的不错
Good work.
余下其他人的答对的人的名字会在下方滚动出现
The rest of your names will be scrolling below
我们寻找的答案正如我解释的一样
as I explain the answer we were looking for.
诀窍是去除所有中间的角
The trick was to cancel out all the intermediate angular
作为飞轮产生动态向量
momentum vectors produced as a flywheel
加上向前的角向量
with forward-pointing angular momentum
旋转得到向后指向角动量
rotates to end up with backward-pointing angular momentum.
解决方案是用2个飞轮
And the solution is to have two flywheels,
俩个都带有向前指向的角动量让你
both with forward-pointing angular momentum that you
在相反的方向感觉是在相反的方向旋转
rotate into the reverse orientation in opposite senses.
这样 任何侧面中间角动量
That way, any sideways intermediate angular momentum
就会被消除
that gets produced is canceled out.
这里有个简短的YouTube视频演示了
The short YouTube video here shows a demo
这一动态的原理
of this principle in action.
你们提交的一个答案的技术原理
An answer that some of you submitted that technically
不是错误的 但是不是我们要的答案
isn’t wrong, but wasn’t we were going for,
只要找到其中一个已经旋转的飞轮
is to take the already spinning flywheel, just one of them,
然后减缓它的自旋
and slow down its spin.
作为回应 整个飞船就会以另外一种方式扭曲
In response, the ship would have to be torqued the other way.
以这种技术原理工作 但是你们
And technically that works, but you
不需要用那么应用多转矩阵或者杠杆原理
don’t get nearly as much torque application or leverage
实际上你旋转一个陀螺仪的时候没有改变它的旋转
as you do from actually rotating a gyroscope without changing its spin.
你们中有些人问 难带不会有额外的陀螺仪质量
A few of you asked, wouldn’t the extra mass of the gyroscopes
就像是额外的燃料质量一类的东西吗
weigh just as much as extra mass from fuel?
答案是 不一定
Answer– not necessarily.
如果我们假设 光真的很强
If some fictitious, really light but really strong
材料可以足够快的旋转
material could be spun sufficiently fast,
你就可以用很少的质量
you could store up a lot of angular momentum
存储大量的角动量
with very little mass.
对于那些指出我们会得到副翼的人
And to everyone who pointed out that we got the aileron flap
已经在视频被指出是错误的了
directions wrong in the video, noted,
视频已经添加了解释 谢谢你让我们保持准确性
annotation added and thanks for keeping us accurate.
[音乐响起]
[MUSIC PLAYING]

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