了解宇宙是如何运行的（2010）

How the Universe Works S01E07

Part 2 April 18, 2021, 7:57 p.m.

科学家已知道恒星从何而来
Scientists understood
where stars come from
但不知行星如何从气体和尘埃形成
but not how planets grow
from the disk of gas and dust.
国际太空站上一次偶然事件
The answer was discovered by accident
解开了这一谜团
aboard the International Space Station.
航♥天♥员佩蒂特用糖和盐
Astronaut Don Pettit was experimenting
with grains of sugar and salt
在太空的无重状态做实验
in the weightlessness of space.
洛夫正在地面指挥中心观察
Stanley Love was watching
from Mission Control...
当佩蒂特无意中发现…
when Pettit stumbled onto the process
宇宙尘埃形成行星的过程
of how planets form from cosmic dust.
其中一个佩的周六早上科研项目
Well, one of Don's...
Saturday-morning science projects
要用到我们储存饮料的袋子
was to take the bags
that we store drinks in
他将像盐和糖等其它东西放进袋子
and he put other stuff in
it, like salt and sugar,
其中一个袋子只放了咖啡粉
and there was one bag that he
just left the coffee powder in.
然后给袋子充气
Then he inflated the bags,
由于袋子里有粒子
and with these particles in them,
发觉粒子立即聚成一团
noticed that the particles
would just clump up immediately.
形成了积尘
They make a little dust bunny.
我们观察了一段时间
We'll be spending some
time watching that.
我说: 佩蒂特, 这太不可思议了
I said, "Don, this is incredible!"
你解决了困扰行星科学40年的问题
"You've just solved a 40-year-old
problem in planetary science!"
佩蒂特解开了一个重大谜团
Astronaut Pettit had
discovered something big.
在太空的零引力里面
!n the zero gravity of space,
尘埃粒子不会四散悬浮
particles of dust don't float apart,
而是会聚集成一团
they clump together.
宇宙尘埃就是这样形成行星的
This is how mighty planets
are made from cosmic dust.
尘埃粒子会碰撞并粘连在一起
The dust particles would
collide and stick and grow
形成更大的尘粒
into ever larger dust particles
接着形成岩块, 最终会形成巨石
and eventually rocks
and eventually boulders.
巨石越大, 引力就越强
The bigger the boulder,
the more gravity it has.
它开始吞噬周边的一切
It begins to eat up everything around it
从而越长越大
and grows bigger.
巨石变得更大, 更重
It becomes larger, heavier,
吞噬的岩块也越来越大
and consumes bigger and bigger rocks.
最后有些巨石变成了行星
Eventually, some of these
rocks grow into planets.
这是太阳系在46亿年前发生的事
This is what happened in our
solar system 4.6 billion years ago.
有100个年轻行星绕着新太阳运行
There were about a hundred young
planets all orbiting the new sun.
碰撞是不可避免的
Collisions were inevitable.
所有太阳系在初时都很狂暴
At the beginning, solar
systems are violent.
我们的太阳系也不例外
Ours was no different.
它最初约有100个小行星
It began with about
100 small, new planets.
那么100个小行星如何发展成为…
So how did it go from 100 small planets
今天的八大行星呢?
to the eight major planets of today?
从研究其它太阳系进化找到了答案
We got the answer by studying the
evolution of other solar systems.
我们看到太阳系诞生时期的行星
We see solar systems forming planets...
突然
and all of a sudden,
它们周围出现这些巨大圆盘
they had these giant disks around them.
这些圆盘一定由巨大碰撞产生
Those disks must be
from huge collisions.
若其它行星系中的行星会相互撞击
If planets are smashing
together in other systems,
那么我们的太阳系也会如此
they probably smashed
together in our own.
我们现在知道所有太阳系
We now know that all
solar systems do this
在稳定之前都会这样
before they settle down.
这是它们形成的方式
It's the way they're built.
今天看到的整齐有序的太阳系
The nice, neat, orderly
solar system that we see today
并非一直如此
has not always been the case.
在早期, 即是在行星开始形成后
In the early days, a few
million years, basically,
的数百万年间
after the planets started forming,
有几十个, 甚至数百个早期行星
there were dozens, maybe even
hundreds of these young planets
在太阳系周围流窜
that were bouncing
around the solar system.
它们相互碰撞
They would smash into each other.
有时会聚集起来成为更大的行星
Sometimes they would collect
and get to be bigger planets.
有时会将彼此撞成碎片
Sometimes they would smash each
other and turn into little bits.
在新生的太阳系中
There was heavy traffic
in the new solar system,
大大小小的物体穿梭往来
objects of all sizes.
难免会发生碰撞
They were bound to collide.
一些行星变得巨大, 碰撞也更剧烈
Some of the planets grew larger,
and so did the collisions.
想象一下那会是怎样一番景象
I like to try to imagine
what it would have been like
若站在早期地球上抬头仰望夜空
to actually stand on the early
Earth and look up into the night sky.
肯定会大异其趣
Things would have looked different.
行星♥相♥互撞击
Planet hit planet.
只有最大的才能幸存
Only the largest survive.
其余的难免粉身碎骨
The rest are smashed to pieces.
某个庞然大物撞击早期水星
Something very large struck
the young planet Mercury.
将水星外壳撞落, 只剩下铁质内核
It blew the crust off and
left behind just the iron core.
早期地球也未能幸免
And the young planet Earth
did not escape either.
一个行星大小的物体撞着地球
A planet-sized object slammed
into the Earth off-centre
将一大块外壳撞碎
and blew a huge amount of
the Earths crust into space.
碎片绕着地球运行
The debris circled around the Earth...
最后聚集在一起形成月球
and eventually coalesced
to become the moon.
这场撞车大赛持续了五亿年之久
This demolition derby
raged for 500 million years.
现在的火星, 地球, 水星和金星
What we see now, Mars and
Earth and Mercury and Venus,
这些内太阳系行星都是幸存者
these planets in the inner solar
system, they're the survivors.
它们在这些巨大撞击中生存了下来
They're the ones who lived
through these giant impacts.
幼年行星的碎片就形成小行星带
Debris from smashed infant planets
ended up in the asteroid belt,
如同一个行星废料堆积场
a junkyard of rocky,
leftover planet parts.
大多数大型撞击发生在内太阳系
Most of the big impacts happened
in the inner solar system.
但是外行星中的天王星也受到撞击
But one of the outer planets, Uranus,
was also hit and knocked on its side.
这是个谜, 因为外行星…
A mystery, since the outer planets
主要由气体构成
formed mostly from gas
避开了内太阳系的剧烈撞击
and largely escaped the violence
of the inner solar system.
这些岩石内核形成
These rocky cores formed.
气体聚集在内核周围
The gas accumulated around them.
这个过程发生得很快
This process actually
happened very rapidly.
只用了大约一百万年
In astronomical terms, in
only about a million years.
那就是我们今天看到的巨行星
And those are the giant
planets we see today.
在气体巨行星木星和土星之外
Beyond the gas giants,
Jupiter and Saturn,
是天王星和海王星
are Uranus and Neptune.
后两者由气体和冰构成
These two are made of gas and ice.
它们之外是柯伊伯带
And beyond them lies the Kuiper Belt,
是沿轨道运行的冰封岩石和矮行星
a band of orbiting icy
rocks and dwarf planets.
曾经被当作第九大行星的冥王星
We used to think that one
Kuiper Belt object, Pluto,
其实是柯伊伯带天体
was the ninth planet.
冥王星其实是一颗矮行星