行星（2019）

美国国家航♥空♥航♥天♥局“信使”号♥水星探测器发射升空
Lift off of Messenger on Nasa's mission to Mercury.
水 星
金 星
火 星
木 星
土 星
天 王 星
海 王 星
行星 第4集
在温暖的内太阳系之外
Beyond the warm worlds of the inner Solar System...
在气态巨型星木星之外
beyond the gas giant Jupiter...
在远离太阳的寒冷空间里
in the freezing regions far beyond the Sun...
土星运行其中
lies Saturn...
这颗行星因拥有近30万公里宽的固态冰质行星环
a planet made unique, thanks to a nearly 300,000km-wide ring
而显得极为独特
of frozen water.
这里的数万亿块冰在引力的作用下
Here, trillions of pieces of ice have been sculpted by gravitational
被塑造成了太阳系中最令人赞叹的奇观之一
forces into some of the Solar System's most stunning vistas.
地球上的水有多种形态 海洋 云雾
Here on Earth, water takes many forms - oceans and clouds
和河流 而结晶态的冰
and rivers, but it's in its crystalline form, ice,
却是最美丽的一种
that it's at its most beautiful.
这里的冰成为地球上的一道景色 但在土星所处的太阳系外层
Here, ice just adorns the landscape, but in the Outer Solar System,
冰的储量极为丰富
where Saturn lives, ice is so abundant that, well,
以至于成为了基础的构造材料
it's become a building material.
在太阳系中没有比土星的冰环
Now, there's no more beautiful sight in the Solar System than
更美丽的景象了
the ice rings of Saturn.
它就像是上帝把雪片轻轻撒在了引力场上
It's almost as if a god had taken snowflakes and sprinkled them
让我们观赏 但如此精致的景象
over a gravitational field, so we could see it, but how could
怎么会是如此简单的事物创造的呢
something so intricate be sculpted out of something so simple?
其实 科学一贯都是如此
Well, as is always the case in science,
现象中蕴含着真理之美
the true beauty lies in the story.
土星是太阳系中一颗经历过
Saturn is a planet that has undergone some of the most
剧烈转变的行星
radical transformations in the Solar System.
它经历过毁灭
A planet that has seen destruction...
经历过创世
and creation.
这颗行星上存在众多隐秘的世界
A planet that harbours hidden worlds...
那里或许
where, just perhaps,
可能存在着生命的
there may exist a second home
第二个家园
for life.
太阳系远端的生命 土星
设想一下 一颗表面无处立足的星球
Imagine a place with no surface to stand.
那里只有无尽的气体
Just an endless atmosphere.
土星 距离太阳14亿公里
与地球相比 土星实在太特别了
Compared to Earth, Saturn is so alien
人们很难想象二者是以相同的物质
that it's hard to imagine how it could have grown
形成的
from the same ingredients.
但如果回到足够久远的过去
But go far enough back in time
土星则看上去与地球惊人的相似
and Saturn would appear to be surprisingly familiar.
46亿年前
土星诞生之初 是一个由岩石和冰构成的小世界
Saturn began life as tiny worlds of rock and ice...
它在太空中无序地翻滚着
tumbling chaotically through space.
和地球 火星 金星和水星一样
Just like Earth, Mars, Venus and Mercury,
土星也开始了融合 聚集 生长的过程
they began to merge and clump together and grow.
但与太阳系内层的行星不同
But unlike the planets of the inner Solar System, Saturn was
土星是在我们称之为雪线的太阳系外缘形成的
forming on the other side of a boundary we call the Snow Line...
那里距离太阳过于遥远 十分寒冷
a place where the Sun is so distant and it's so cold,
水只能以固态形式存在
water exists only in its frozen, solid state.
数以万亿计的冰晶颗粒就像岩石一样
Out here, trillions of particles of ice behave just like rock,
为行星的形成提供了不计其数的额外材料
providing huge amounts of extra planetary building material.
在引力的作用下 大量的冰和岩石相互碰撞
Under the force of gravity, this abundant ice and rock collided
结合在了一起
and combined...
这使得年轻的土星变得越来越大
helping the young Saturn to grow into a giant.
关于太阳系中行星的形成过程 人们对其中的细节
The details of how the planets formed in the Solar System is
还不完全了解 这是科学研究的前沿课题
not fully understood. It's cutting-edge scientific research.
因为那毕竟是在45亿年前发生的事
We're talking about events that happened over 4.5 billion years ago,
不过很可能的是 土星曾经是一个由岩石和冰构成的世界
but it seems likely that Saturn was once a world of rock and ice,
其质量可能是地球的10倍到20倍 也许在你的梦境里
perhaps ten or even 20 times the mass of the Earth and it's almost
能想象出自己站立在土星上的类似情景
possible, in your dreams, to imagine standing on its surface.
但是由于它巨大的质量
But because of its immense mass and its place
和在太阳系中所处的位置 土星的这种岩冰形态并没有持续多久
in the Solar System, Saturn didn't remain a rocky, icy world for long.
随着时间的推移 土星变成了一颗截然不同的行星
As it grew older, Saturn became a radically different kind of planet.
在新的行星形成的区域里
In the region in which the young world was forming, there was
不仅有冰和岩石 还有大量的气体
more than just ice and rock - there were large amounts of gas.
土星的大气层开始成形
And Saturn began to gain an atmosphere...
但其规模远不是地球的大气层能比拟的
but on a scale unlike anything we experience here on Earth.
只有从太空中看去 你才会真正意识到
It's not until you see the Earth's atmosphere from space that
地球的大气层是多么薄
you appreciate just how thin it really is.
地球 大气层厚度100公里
太阳系内层的其它行星
And it's a similar story for the other
情况也基本相似
worlds of the inner Solar System.
火星 大气层厚度80公里
金星 大气层厚度120公里
尽管厚度较薄 这些行星的大气层
Despite being relatively thin, these atmospheres can exert
却能够对行星的地表施加强大的作用力
powerful forces on the planetary surfaces beneath.
在地球上 只要用一个密闭容器 你就能看到
On Earth, you can see the effects of an atmosphere with nothing
大气压力的威力
more than a sealed container.
人们很容易忽略大气层的重量
It's easy to forget that the atmosphere has a weight.
我们头顶上方有一根大约100公里长的空气柱
There's a column of air stretching up 100km above my head.
其中有大量的气体分子 它们会产生压力
That's a lot of molecules and it exerts a pressure.
通过这个瓶子的变化 我们就能见识到大气的压力了
You really see it if you look at what happens to this bottle.
我们把瓶子灌满了山顶海拔3000米处的
We've filled it with air from the top of the mountain, which is
空气
about 3,000 metres.
相较于海平面而言
Now, up there, the atmosphere is about 25% less dense
那里的大气密度要低25%
than it is down there at sea level.
所以当我们下降时 瓶外的大气压就会增大
So, as we descend, the atmospheric pressure outside is increasing
而瓶内的气压等同于
and the pressure in here is just what it
山顶的情况 所以我们可以直观的看到
was at the top of the mountain and so, you see visually that
大气压力的作用 瓶子被压扁了
force in action and that is squashing the bottle.
这就是物理效果
Physics in action!
很厉害吧
It's brilliant, isn't it?
仅仅几百米落差的大气压就能压扁一个瓶子
While just a few hundred metres of atmosphere can crush a bottle...
如果大气层足够大的话 就能改变整个星球的面貌
if an atmosphere gets big enough, it can transform an entire planet.
46亿年前
在土星诞生后的几百万年里
Within just a few million years of its birth...
它依靠聚集岩石和冰 尽可能地变大
Saturn had grown as large as it could, from rock and ice alone.
现在它转向了另一种物质材料
And now, it turned to another building material -
太阳形成时残留下来的氢气和氦气
the hydrogen and helium gas left over from the formation of the Sun.
这两种气体质量太轻 太阳系内层
This gas would have been too light for the smaller
体积较小的行星无法束缚它们
worlds of the inner Solar System to hold on to.
但土星的巨大质量所形成的强大引力
But Saturn's great mass created gravitational forces powerful
却足以让它们聚拢过来
enough to draw it in.
数以万亿吨♥计的氢气和氦气
Trillions upon trillions of tonnes of hydrogen
开始包裹在这颗行星的表面
and helium gas began to envelope the planet.
随着新大气层的增长
And as this new atmosphere grew,
它也改变了下方的行星地表
it transformed the surface below.
气体重量所产生的巨大压力使得岩石和冰的温度急剧上升
Enormous pressures, created by the weight of this gas, heated rock
这颗行星开始放出光芒
and ice so much, they began to glow.
当土星成年时 其表面的压力达到了
As Saturn matured, the pressure at the surface rose
地球大气压力的1000万倍
to ten million times the atmospheric pressure on Earth.
在如此大的压力下
Under those kind of pressures,
物质的表现也变得怪异起来
matter behaves in extremely strange ways.
地表的概念已经毫无意义了
The very idea of a surface becomes meaningless and Saturn was
土星从一颗寒冷的
transformed from an icy,
岩石行星 变成了完全另类的行星
rocky world into a completely different class of planet -
气态巨行星
a gas giant.
土星变得极其巨大
Saturn was now so big,
可以容纳近5000颗相当于地球大小的星球
it could contain nearly 5,000 Earth-size worlds.
但这颗巨大的原始行星与我们现在所看到的土星
But this vast, wild protoplanet was totally unlike the Saturn
全然不同
we see today.
要了解土星是如何形成的
To discover how that world emerged,
我们就必须发射探测器近距离地观察它
we had to send spacecraft to meet it close up.
点火成功 泰坦四号♥运载火箭升空 它搭载了
We have ignition and we have liftoff of the Titan Centaur carrying
两个“旅行者”号♥探测器中的第一个
the first of two Voyager spacecraft to extend Man's senses
“旅行者”号♥ 1977年
人类的触角将前所未有地伸向太阳系的深处
farther into the Solar System than ever before.
65000个独♥立♥部件
造价 8.65亿美元
返回报告显示两部大功率火箭发动机运转良好
Reports coming back indicate those twin large solid motors are
每部发动机能产生120万磅的推力
functioning perfectly, producing 1.2 million pounds of thrust each.
“旅行者”2号♥ 前往土星的时间 4年
返回的导航数据表明航向完全正确