了解宇宙是如何运行的（2010）

How the Universe Works S06E06

Part 1 Dec. 22, 2021, 7:22 p.m.

我们银河系的命运悬而未决
The fate of our galaxy hangs in the balance.
银河系正在消亡，而我们不知道是什么原因
The Milky Way is dying, and we don't know why.
我们的星系，像所有其他星系一样，寿命是有限的
Our galaxy, like all galaxies, has a limited life-span.
一旦死去什么都熄灭了
After that, it's lights out.
寻找星系杀手的竞赛开始了
The race is on to find a smoking gun.
现在可以肯定地说，有很多方法可以杀死一个星系
It's safe to say right now there are many ways to kill a galaxy.
这是宇宙犯罪现场调查
It's a cosmic crime scene investigation.
是最可恶的谋杀吗？
Is it murder most foul?
还是只是寿终正寝？
Or is it death by natural causes?
嫌疑犯排好了队
The suspects are lined up.
审讯正在进行中
The interrogation is underway.
我们的宇宙再次向我们抛出了一道
It's another example of this big universe of ours
我们现在必须要解决的谜题
throwing puzzles at us that now we have to solve.
是什么正在杀死银河系？
What is killing the Milky Way?
宇宙是如何运行的
第六季第六集银河系之死
地球
Earth.
我们的家
Our home.
只是1000亿个行星中的一个
Just one of 100 billion planets
行星们围绕着4000亿个恒星运行
orbiting 400 billion stars
这些恒星构成了一个巨大的螺旋星系……
that make up an immense galactic spiral...
银河系
the Milky Way.
星系是恒星形成的地方
Galaxies are where stars form,
当然，行星也是围绕着恒星形成的
and, of course, planets form around stars,
所以地球的故事
so the story of the Earth,
你的故事，以及太阳系的故事
of yourself, of the solar system
都与星系的故事有关
has everything to do with the story of the galaxies.
银河系的故事开始于136亿年前
The story of the Milky Way begins 13.6 billion years ago,
即宇宙大爆♥炸♥之后
just after the big bang.
这是一个没有行星和恒星的时期……
It's a time when there are no planets and no stars...
只是一团巨大的炽热氢气云
Just a vast, lumpy soup of superheated hydrogen gas.
在数百万年的时间里，温度逐渐下降
Over millions of years, the temperature drops,
引力将这些团块压缩到一起
and gravity compresses the lumps down, until eventually
直到氢分子最终引爆核聚变并点燃一颗恒星
the hydrogen molecules fuse and ignite a star.
随着时间的推移，数十亿颗恒星迸发诞生了
In time, billions of stars burst into life.
银河系开始成形
And the Milky Way begins to take shape.
你可以把星系想象成人类
You can think of a galaxy as sort of like a human being.
当你年轻的时候，处于青春期
When you're young and in your adolescent stage,
你充满生机和活力
you're vibrant and active.
这是一个以疯狂的方式形成恒星的年轻星系
That's a young galaxy forming stars in a crazy way,
它甚至还没有完全成形
and it's not even fully formed yet.
在某一时刻，星系会步入中年
At a certain point, galaxy reaches middle age,
而中年星系实际上就是它定形的样子……
and a middle-aged galaxy really is what it's going to be...
星系都有独特的形状……
It has its shape...
但长♥期♥下去，星系会停止形成恒星
But in the long run, a galaxy will stop forming stars,
最终，就像我们人类都会死亡一样，我们的星系也会死亡
and eventually, just like we all die, our galaxy will die.
那么，银河系现在处于生命的哪个阶段呢？
So, at what stage of life is the Milky Way?
它是一个健康活泼的小家伙
Is it a healthy, active youngster,
还是要即将走向死亡？
or is it heading for its deathbed?
科学家可以通过每个星系的颜色来确定
Scientists can determine each galaxy's stage of life
它的生命阶段
by its color.
所以，我们看到宇宙中不同颜色的星系
So, we see different colors of galaxies in the universe.
我们看到有偏蓝色的星系
We see galaxies that are tinted blue
也有偏红色的星系
and galaxies that are tinted red.
当我们看到一个偏蓝色的星系时，它往往是一个年轻的星系
When we see a blue galaxy, that tends to be a younger galaxy
充满了新形成的明亮、炽热的恒星
full of bright, hot, newly formed stars.
当我们看到一个偏红色的星系时
When we see a redder galaxy,
它往往是一个更暗、更老的星系
that tends to be a dimmer, older galaxy
并且不会再形成新的恒星
that isn't forming new stars in the present moment.
星系中所有的恒星都很古老，越老越红
All its stars are aged and older and redder,
所以整个星系呈现出不同的色调
and so the entire galaxy casts a different hue.
那么，我们的星系是什么颜色呢？
So, what color is our galaxy?
这是一个简单的问题，但是很难得到答案
It's a simple question, but the answer is hard to come by,
即便是我们已经观察银河系
even though we've been looking at the Milky Way
有几千年了
for thousands of years.
“银河系”这个术语很古老
The term "Milky Way" is ancient.
这要追溯到古代，天黑的时候
It goes back to a time when in the dark sky,
那时人们已经注意到有一条光带
people noticed there was this light band
从地平线一头延伸到另一头
that actually went from horizon to horizon,
而这条光带
and that band turned out
是由成千上万颗星星组成的
to be made of thousands and thousands of stars
它太远了，我们无法看到星系的整体
actually too far away to see individually.
我们花了很长时间
But it took us a long time to realize
才意识到银河系的形状和规模
what the shape and the scale of the Milky Way galaxy is.
令人惊奇的是，我们其实对我们自己的家园星系
The amazing thing to think about is that we actually don't know
并不十分了解
our home galaxy very well at all.
我们生活在这个由气体和尘埃组成的圆盘的中间
We actually live in the middle of this disk of gas and dust,
这实际上掩盖了银河系的“庐山真面”
and that obscures our view of the larger Milky Way.
使用可见光，我们甚至看不到中心
Using visible light, we can't even see to the center,
更不用说银河系的另一边了
let alone the other side of the Milky Way galaxy.
解决办法是使用一种
The solution is to use a form of light
能穿透气体和尘埃的光……
that passes through the gas and dust...
红外线
Infrared.
这是斯隆数字巡天望远镜
This is the Sloan digital sky survey telescope
位于新墨西哥州阿帕奇点天文台
at the Apache point observatory in new Mexico.
它利用红外线绘制星系地图
It's mapping the galaxy using infrared
给科学家们提供了前所未有的视角
and giving scientists unprecedented insights.
高感度红外线观测技术
The first sensitive infrared observations really weren't done
直到15年前才完成
till the last 15 years,
每一种新技术都是了解宇宙的新的窗口
and each of these new windows on the universe
教会了我们不同的东西
teach us different things.
在过去的15年里
In the last 15 years,
斯隆研究了超过2.5亿颗恒星
Sloan has surveyed more than 250 million stars,
通过分♥析♥它们的光来计算出银河系的颜色
analyzing their light to work out the color of the Milky Way.
科学家们所看到的让他们非常震惊
And what scientists saw shocked them.
直到最近，我们还一直认为银河系是
Until very recently, we thought the Milky Way
一个年轻、健康的星系
was a young, healthy galaxy,
但现在有证据表明
but now there's evidence
我们可能正在进入死亡之路
that we may be entering the pathway to death.
斯隆望远镜显示，我们星系的恒星产量
The Sloan telescope reveals that star production in our galaxy
正在不断下降
is falling through the floor.
银河系正在死去
The Milky Way is dying.
当它停止形成新的恒星时
And when it stops forming new stars,
它的时间也就结束了
its time will be up.
矛盾的是，我们的星系的容器中
Paradoxically, our galaxy still has
仍然有形成恒星的气体，所以它应该是健康的
star-forming gas in the tank, so it should be healthy,
但有什么东西正在杀死它
but something is killing it off.
银河系是一个美妙的圆盘
So, the Milky Way galaxy is this wonderful disk
里面充满了丰富的氢气，还有很多稠密的尘埃云
filled with rich hydrogen gas, lots of dense dust clouds.
它拥有恒星形成所需的一切
It has everything you need there for star formation,
但它似乎在减速，甚至停止
but it seems to be slowing down and even turning off,
现在，我们还不知道罪魁祸首是什么
and right now, we don't really understand what the culprit is.
随着星系杀手逍遥法外，科学家们开始了宇宙历史上
最大的谋杀案调查。当你在探索一个问题时，科学中
的一切，都有点像犯罪现场，证据就摆在你面前……
我们得找出是谁干的。我们在宇宙中的家园正在消亡……
不是地球，而是我们的银河系
数十亿年来，银河系一直在制♥造♥恒星
The milky way has been producing stars for billions of years,
但是我们自己的恒星太阳究竟有多少岁呢？
But just how old is our own star? The Sun.
它是我们银河系中一颗相对较新的恒星吗？
Is it a relatively new star in our Galaxy?
而我们的太阳在银河系已经大约有45亿年了
And our own sun about 4.5 billion years ago in the milky way Galaxy,
我们并不是迄今为止最古老的恒星
and we are not the oldest star by far.
然而，不幸的是，我们实际上
And yet, tragically, we actually seem to be
似乎是银河系中最后一代新恒星之一
one of the last generations of new stars in the Milky Way.
目前的预测表明，在大约40亿年内
Current projections suggest that in about 4 billion years,
恒星的形成可能已经全部停止
star formation may have ceased all together,
这在宇宙的生命周期中
which is almost just a blink of an eye
几乎只是一眨眼的时间
in the life cycle of the universe.
为了找出原因，科学家们展开了一项调查
To find out why, scientists launch an investigation.
最关键的问题是什么？
The most crucial question?
银河系是如何消亡的？
How is the milky way dying?
要消灭一个星系，你必须摆脱冷的气体
To kill a galaxy, you have to get rid of the cold gas,
因为恒星是由冷气体形成的
because that's what stars form from.