了解宇宙是如何运行的（2010）

How the Universe Works S01E06

Part 1 April 18, 2021, 7:57 p.m.

过去我们所认识的行星
It used to be the only
planets we knew about
只限于围绕我们太阳系内的那几个
were the ones that orbit our sun.
现在才发现
But now we've discovered
另有岩质行星与气态行星
rocky worlds and gas giants
围绕其它恒星运转
orbiting other stars.
它们各有奇妙身世
They tell an amazing story.
这些行星的初生历史肯定动荡不宁
The early history of these planets
would have been very, very violent
各处行星的诞生方法如出一辙
Planets are made
everywhere in the same way.
由恒星诞生所遗下的尘与瓦砾聚成
They form from the dust and debris
left over from the birth of stars.
既然形成方法相同
So if they're all made the same way,
何以又面貌各异?
what makes them all so different?
解读宇宙
How the Universe Works
第1季第6集：行星
Planets
宇宙间有许许多多的银河系
The universe is full of galaxies,
气体云
gas clouds,
恒星
stars,
原来还有许多行星
and planets, as it turns out.
我们的太阳系有八颗行星
Our solar system has eight planets.
但与银河系内整个行星大家族相比
But we now know they're a tiny group,
实在是小巫见大巫
compared to the huge cosmic family
of planets across the galaxy.
这是科学史上一个异乎寻常的时刻
It's an extraordinary
moment in scientific history
我们确知外面还有别的行星系
to know, for sure, that there are
other planetary systems out there.
极其普遍
They're very common.
我们银河系里有二千亿颗恒星
And out of the 200 billion
stars in our Milky Way galaxy,
肯定也有数百亿颗的行星
there are surely dozens of
billions of planets out there.
2009年
In 2009,
太空总署发射开普勒太空望远镜
NASA launched the Kepler space telescope
升空六年, 寻找系外行星
on a six-year mission to find
new planets orbiting other stars.
迄今发现了四百多颗
So far, astronomers have found over 400.
好些是翻腾不息的庞大气团
Some are colossal balls of churning gas,
体积五倍于木星
five times the size of Jupiter.
别的是比地球大许多倍的岩质行星
Others are huge, rocky worlds
many times larger than Earth.
好些的轨道飘忽无定
Some follow wild, erratic orbits,
因贴近恒星而燃烧起来
so close to a star they're burning up.
有一点再明白没有
One thing is clear,
没有两颗行星是一模一样的
no two planets are the same.
每一颗都是独一无二
Each is one of a kind.
但新发现的行星遥远而难以探究
But most of these new planets
are far away and hard to study.
我们对行星运作的了解
Most of what we know
about how planets work
主要来自我们太阳系内的八颗行星
comes from the eight
that orbit our own star.
我们的系内行星分为两大类:
Our own planets come in two main types.
内太阳系的四颗岩质行星:
There are four rocky planets
in the inner solar system:
水星
Mercury.
金星
Venus.
地球
Earth.
还有火星
And Mars.
另有是外太阳系的四颗气态行星:
And in the outer solar system,
there are four giant gas planets:
木星
Jupiter.
土星
Saturn.
天王星
Uranus.
还有海王星
And Neptune.
八颗行星面貌各异, 大不相同
Each of the eight planets is
distinct and very different.
行星的特性早在46亿年前
Their unique personalities began to
form at the birth of our solar system,
太阳系诞生之际已然形成
4.6 billion years ago.
太阳燃烧, 留下一团巨大气尘云
When the sun ignited, it left
behind a huge cloud of gas and dust.
岩质行星与气态行星合共八颗行星
All eight planets, the inner
rocky and the outer gas planets
都是来自这一团宇宙残余物质
came from this cloud of cosmic debris.
太阳系的行星无不脱胎自同一物质
The planets in ocr solar system
are all made from the same stuff.
脱胎自同一团气尘云
They're made from the
same cloud of gas and dust,
却在不同的环境下合成
but they formed under
very different conditions.
部分在邻近太阳的高温地区形成
Some of them formed in close to
the sun, where it was much hotter,
部分在远离太阳的低温地区形成
some much farther away,
where it was much colder.
因为环境迥异
And because the conditions
were so different,
形成的结果也各不相同
the end result, the product of their
formation, was, was different as well.
依我看法, 太阳系的开始
So you start the solar
system, in my view,
源自同一团的硅酸盐、水蒸汽
with a pretty homogeneous mix
of silicates and water vapour
大量氢气与甲烷与别的元素
and hydrogen, lots of hydrogen,
and methane and other elements.
尘云里的元素好比做蛋糕的材料
These elements in the dust cloud
are like ingredients in a cake.
用相同材料能烘成不同的蛋糕
They cook differently,
取决于材料的配搭与炉温的高低
depending on the combination of the
ingredients and the temperature of the oven.
就像做蛋糕, 把材料混和
And just like with the cake,
you'd mix the ingredients.
送入炉里烤烘, 受热而变质
And then you'd put it in the oven
and bake it, and it would change.
太阳系里也是同一原理
And so this is kind of what
happened in the solar system.
每个行星的受热情况不同
Overall, the planet cooks
in a slightly different way,
视乎距离太阳的远近
depending on how close it is to the sun.
距离相近, 热力高
Close in, where it's hot,
太阳会烧掉气体和水分
the sun burns off gases
and boils away water.
唯有高温下仍能保留固态的物质
Only materials that stay
solid at high temperatures,
诸如金属和岩石
like metals and rock,
才得以保留
can survive,
是以接近太阳的行星都是岩质行星
which is why only rocky
planets form close to the sua
远离太阳热力的地方
Move farther away from
the heat of the sun,
就换成另一种行星炮制法
and you get different
kinds of planets cooking.
不过究竟会形成哪一类行星
But it's the ingredients in the cloud
还要看云团里有甚么材料而定
that determine precisely what
kinds of planets will form.
这要看形成太阳系的是哪种星云
Well, depending on the type of
cloud a solar system forms in,
有些太阳系根本没有岩质行星
you could have solar systems
that don't have rocky planets
正是缺乏形成地球这类行星的物质
because it was just too poor in the
materials to build something like the Earth,
结果只会形成更多气态巨行星
and instead you could end
up with more gas giants
反而一颗岩质行星也没有
and, and no rocky planets at al
要有岩质行星
If you want rocky planets,
先要有一团满是金属和岩石的星云
you need a cloud full
of metals and rock.
下一步, 降温
Next step, turn the heat down.
温度下降时, 内里沸点高的元素
As it cools down, some of the elements
in there that have a high boiling point
开始凝成固体
start to condense out as solids.
于是形成许多微小的矿粒
And you can get these very tiny
little mineral grains forming.
这些小矿粒是孕育岩质行星的种子
These tiny mineral grains are
the seeds of a new rocky planet
假以时日, 小矿粒聚合
Over time, they start to stick together.
一个尘分子与另一个尘分子
You have one dust molecule
and another dust molecule,
基本上就是撞在一起
and they would basically
slam into each other,
形成一个稍大一级的尘分子
and become one slightly
bigger dust molecule.
它们吸收越来越多的分子
And they would pick up
more and more and more.
这个步骤名叫吸积