了解宇宙是如何运行的（2010）

How the Universe Works S01E03

Part 3 April 18, 2021, 7:56 p.m.

and it's being eaten by the
super massive black hole.
黑洞吃的时候有时会吃得太快
When black holes eat, they
sometimes eat too fast...
把晚餐以纯能量束的形态吐出来
and spit their dinner back out
into space in beams of pure energy.
那就是类星体
It's called a quasar.
科学见到类星体从星系爆发出来
When scientists see a quasar
blasting from a galaxy,
就知道那星系有一个超级黑洞
they know it has a
super massive black hole.
我们的银河系又怎样?
But what about our galaxy?
这里没有类星体
There's no quasar here.
意思是没超级黑洞吗?
Does that mean there's no
super massive black hole?
安德烈姬斯跟她的队员
Andrea Ghez and her team have spent
这15年来一直在找答案
the last 15 years trying to find out.
在银河中心发现超级黑洞的关键
So the key to discovering a super massive
black hole at the centre of our Milky Way
是观察恒星怎样移♥动♥
is to watch how the stars move.
恒星移♥动♥是因为引力
The stars move because of the gravity,
像行星环绕太阳运转
just like the planets orbiting the sun.
可是最接近银河中心的恒星
But the stars closest to
the centre of the galaxy
被一团尘埃云遮盖
are hidden by clouds of dust
姬斯用在夏威夷的巨型凯克望远镜
So Ghez used the giant
Keck telescope in Hawaii
看穿那团尘埃云
to look through the clouds.
她见到一个古怪且残酷的地方
What she saw was a
strange and brutal place.
在银河系中心, 一切都变得更极端
Everything is more extreme
at the centre of our galaxy.
对象移♥动♥得极快
Things move really fast
恒星高速刷过对方
and stars are gonna be
whizzing by one another.
风很大, 很狂暴
It's windy. It's violent.
跟银河系里面的其它地方很不同
It's unlike any place
else in our galaxy.
姬斯跟队员拍摄绕中心运转的恒星
Ghez and her team began to take pictures
of a few stars orbiting near the centre.
目的是制♥作♥影片观察在中♥央♥的恒星
The task has been to make a
movie of the stars at the centre.
要很有耐性, 因为拍了一幅照片
And--so you have to be patient
because you take a picture
然后拍另一张, 才能见到它移♥动♥
and then you, you take another
one and you see it move.
恒星的照片揭露令人讶异的事实
The pictures of the orbiting
stars revealed something amazing.
它们在以时速几百万英里移♥动♥
They were moving at several
million miles an hour.
我们拍第二幅照片的时候
When we had the second picture,
也是这实验最刺♥激♥的时刻
was the most exciting
point in this experiment
因为我们清楚见到恒星高速移♥动♥
because it was clear to us that
these stars were moving so fast
表示有超级黑洞的假设是正确的
that the super massive black
hole hypothesis had to be right.
事实如此
And it was right.
姬斯跟队员追踪恒星的活动
Ghez and her team tracked
the movement of the stars
指出它们在环绕甚么运转
and pinpointed what they were orbiting.
只有一件对象有足够的力量
There's only one thing powerful enough
把巨大的恒星这样抛出去
to sling big stars around like that
那就是超级黑洞
a super massive black hole.
超级黑洞的引力令恒星运转
It's the gravity of the super massive
black hole that makes these stars orbit.
那弧度确实地证明了
So the curvature was the definitive
proof of a super massive black hole
在银河系中心有超级黑洞
at the centre of our galaxy.
银河系中心的黑洞非常巨大
The black hole at the centre
of the Milky Way is gigantic,
阔1500万英里
15 million miles across.
那么地球有危险吗?
So is Earth in any danger?
我们绝对没有危险
We are in absolutely no
danger of being sucked
不会被那超级黑洞吸进去
into our siper massive black hole.
因为太遥远了
It's simply too far away.
地球跟在银河系中心的超级黑洞
In fact, the Earth is 25,000 light-years
away from the siper massive black hole
距离2万5000光年
at the centre of the Milky Way.
相等于好几兆英里
That's many trillions of miles.
地球暂时安全
The Earth is safe for now.
超级黑洞可能是巨大引力的来源
Super massive black hole maybe the
source of huge amounts of gravity
却不足以把星系拉在一起
but they don't have enough
power to hold galaxies together.
根据物理定律, 星系应该会飞开
In fact, according to the laws
of physics, galaxies fly apart.
为甚么不会这样?
So why don't they?
因为宇宙里有…
Because there's something out there
力量比超级黑洞强大的东西
even more powerful than a
super massive black hole.
它不能被看见, 也不能探测
It can't be seen and it's
virtually impossible to detect
那是暗物质, 无处不在
Its called dark matter,
and it's everywhere.
天文学家知道了超级黑洞
Astronomers have figured out
that super massive black holes
存在于星系中♥央♥, 把恒星高速拉动
live at the heart of galaxies and
pull stars at incredible speeds.
不过力量不足以束缚所有恒星
But they're not strong enough
形成一个巨大的星系
to hold all the stars in
a gigantic galaxy together.
那么是甚么把它们拉在一起?
So, what does hold them together?
那一直是个谜
It was a mystery
直至一位我行我素的科学家
until a maverick scientist
came up with the idea
想到有我们不知道的东西在运作中
that something unknown was at work.
20世纪30年代
Back in the 1930's,
瑞士天文学家弗里茨兹威基
Swiss astronomer, Fritz Zwicky, wondered
想知道星系怎会聚集成群
why galaxies stayed together in groups.
他计算出星系产生的引力并不足够
By his calculations, they
didn't generate enough gravity
所以它们应该飞开
so they should fly away from each other.
于是他说:
And so he said,
我知道它们没有飞散
Well, I know that they
haven't flown apart.
我见到它们聚集成这整齐的形状
I see them all gathered
together in this nice collection.
所以一定有东西把它们拉在一起
Therefore something must
be holding them in place.
不过我们的引力不够强
But our own gravity was
just not strong enough.
所以他得出结论
And so he concluded
that it must be something
那一定是没有人探测到或想过的…
which nobody had detected
before, nobody had thought about,
他称之为暗物质
and he gave it this name, dark matter.
那是天才的想法
And this was really a stroke of genius.
弗里茨兹威基的思想走快了几十年
Fritz Zwicky was decades
ahead of his time.
所以他激怒了天文学界
And that's why he grated on
the astronomical community.
不过他是对的
But, you know, he was right.
若是他说的暗物质令星系形成群体
If what Zwicky called dark matter
held galaxies together in groups,
或也是暗物质把个别星系拉在一起
perhaps, it also holds
individual galaxies together.
为找答案, 科学家用计算机仿真星系
To find out, scientists built
virtual galaxies in computers
还模拟了恒星和引力
with virtual stars arid virtual gravity.
我们在模拟实验中令很多粒子运转
We did a simulation where we
put a lot of particles in orbit..
形成一个扁平的圆盘
in a flat disk...
像我们的银河系那样
which was just like the
picture of our galaxy.
我们预料会见到一个有秩序的星系
And we expected to find that
we get a perfectly good galaxy.
期待看它是不是螺旋形状
We were looking to see if
it has a spiral or whatnot
结果却发现它每次都散开
But we found that it always came apart.
银河系的引力不足以把它拉在一起
There just wasn't enough gravity
in the galaxy to hold it together.
奥斯迪卡于是加入模拟暗物质引力
So Ostriker then added extra
gravity from virtual dark matter.
那是很自然的尝试, 结果问题解决
It seemed like a natural thing
to try and it solved the problem.
那就是答案
It fixed it.
暗物质的引力把星系拉在一起
Gravity from dark matter