行星（2019）

几乎所有的行星都是沿自转轴
Almost all the planets spin on their axis in the same
以逆时针方向旋转
anticlockwise direction.
但出于一些我们尚未完全理解的原因
But, for reasons we don't yet fully understand,
金星和天王星都是以反方自转的
Venus and Uranus spin on their axes in the opposite direction.
天王星更是让人感到好奇
And Uranus is even more curious.
整颗星球都倒向一侧
The entire planet is on its side.
我们尚不确切了解为什么天王星以这种方式自转
It's not known for certain why Uranus spins in this way.
不过有可能是在
But it seems likely that, at some point,
遥远过去的某个时刻 它被另一个地球大小
probably in the distant past, it was hit by another planet,
甚至更大的行星撞了一下
possibly the size of Earth or even larger,
把它给撞倒了 而现代计算机
which knocked the planet over, and, indeed, modern computer
模拟结果也显示 如果行星本身发生这种情况
simulations suggest that when you do that to a planet,
它所有的卫星也会随之变化 最终这个行星
all the moons follow, and you end up with the planet
和它的卫星系统 甚至包括它的行星环
and its system of moons, and now its rings,
都是横躺着沿螺旋线环绕太阳运转的
sort of corkscrewing around the Sun on its side.
“旅行者”2号♥到达了人类探访过的距离最遥远的行星
Voyager had taken us to the most distant planets we had ever visited.
而现在 这台空间探测器和它将邂逅的下一个天体之间
And, now, an almost unthinkable distance of 1.6 billion kilometres
相隔着几乎难以想象的 距离达16亿公里的
of icy cold space lay between the spacecraft
冰冷宇宙空间
and its next encounter.
太阳系的规模之大是无法想象的
The size and scale of the solar system is impossible to imagine.
但如果把所有东西按比例缩小 就变得比较形象了
But, when we scale everything down, then it becomes easier to visualise.
太阳直径140万公里
The Sun is 1.4 million kilometres in diameter.
但如果用它的直径除以6亿
But scale that down by a factor of around 600 million,
它大概就是那盏灯那么大了
and it becomes the size of that light.
那么地球 火星和其它岩质行星
And the Earth, Mars and the rocky planets
按比例来说大约只有这么大
are about that big on this scale.
它们之间的距离则更加令人惊叹
And the distances are, I think, even more remarkable.
离太阳最近的水星
So, Mercury, the closest planet to the Sun,
就要一直往那边去 直到海边
would be all the way over there by the sea.
水星
这里就是水星的轨道
So, this would be where Mercury orbits.
相当于水星距离太阳96米
And Mercury is 96 metres away.
它的直径还不到一厘米
It's about just under a centimetre in diameter.
下一个行星金星就在那边
And the next planet, Venus, is somewhere over there.
水星 金星
从太阳出发飞行大约180米会经过金星
We'd fly past Venus about 180 metres away from the Sun.
然后继续向远处的地球进发
And then head onwards and outwards towards the Earth.
在地球的轨道这里 我们可以切身体会到
Here, at the Earth's orbit, the true scale of our fragility
地球
人类是多么脆弱 多么孤独
and isolation becomes apparent.
太阳在那里 有250米远 后面是遥远银河系
The Sun there, 250 metres away with the twinkling stars
闪烁的星星 地球的直径
of the galaxy beyond, and here's the Earth.
是两厘米
Two centimetres across.
人类的全部历史就在这卵石大小的地方上演
On that pebble, all of human history play out.
在大约380米处我们经过了火星
At around 380 metres, we pass by Mars,
这是最后一个岩质行星 然后继续深入黑暗空间
the last of the rocky planets, and then onwards into the darkness.
水星 金星 地球 火星
渡过海湾 我们将到达
Crossing the harbour takes us to the fringes
外太阳系的边缘地带
of the outer solar system.
行星之间的距离和行星的体积
And, now, the distances and the sizes
水星 金星 地球 火星
变得越来越大
are beginning to get really big.
木星是太阳系最大的行星
Jupiter, the largest planet in the solar system,
直径是地球的10倍还多 太阳在那里
is over ten times the diameter of our Earth, and there's the Sun,
木星
横跨海湾1.3公里
1.3km across the harbour.
走过几乎两倍于太阳到木星的距离之后
At almost twice the distance from the Sun to Jupiter,
我们到达了土星
we reach Saturn.
土星 木星
在这个比例下是2.4公里
2.4km on our scale.
接下来我们要真正进入太阳系的昏暗地带了
And we really are now entering the twilight of the solar system.
这里的亮度和地球的清晨或傍晚时分差不多
Light levels are like early morning or late evening here on Earth,
不过我们还是能够看到夜空中的土星
but we can still see Saturn in the night sky,
因为这颗行星和它的行星环高度反光
because the planet and its rings are highly reflective.
经过了所有岩质行星 经过了木星和土星
As far again as all the rocky planets, and Jupiter and Saturn,
我们到达了天王星
we reach Uranus.
天王星
要远离太阳30亿公里 我们开始充分体会到
3 billion kilometres from the Sun, and we begin to fully appreciate
“旅行者”2号♥究竟走了多么远
the distances Voyager had travelled...
这是一趟到达太阳系最远端的旅程
..on its journey to the farthest reaches of the solar system.
旅程的终点是海王星 一个直径大约
Journey's end, Neptune, a ball of gas about
7.5厘米的气态星球
7.5 centimetres across.
在我们这个比例下它距离太阳7.4公里
7.4km away from the Sun on this scale.
海王星
我们依然还在这个岛上 在雷克雅未克的海湾
And we are still down there on the island in Reykjavik harbour.
小到肉眼看不见的蚂蚁在这颗卵石表面上爬来爬去
Little, microscopic ants crawling around on the surface of a pebble.
尽管用了12年之久 “旅行者”2号♥最终还是
It had taken 12 years, but Voyager had finally crossed
还是成功跨越了从地球到最遥远行星系统之间的
the great expanse of space between Earth and the most
广阔宇宙空间
distant planetary system.
海王星 距离太阳45亿公里
海王星
Neptune.
其质量是地球的17倍 甚至超过了天王星的质量
17 times the mass of the Earth, and even more massive than Uranus.
不过与它的姐妹行星形成对比的是 海王星的大气层
But, in contrast to its sister planet, Neptune's atmosphere
有着猛烈的气象活动
is bursting with activity.
我们发现这是一颗存在极端天气的行星
What we found was a planet of extreme weather,
高空的大风让白色的甲烷云团翻涌而起 风速超过了
where high altitude winds whip white methane clouds around at speeds
每小时2000公里
of over 2,000km/h.
这是整个太阳系风速最快的
Those are the highest wind speeds anywhere in the solar system.
南半球 大黑斑
“旅行者”2号♥看到了一个大黑斑
And Voyager saw a great, dark spot,
跟木星的大红斑有些相似
not unlike Jupiter's great, red spot.
这个风暴系统有地球大小 但当我们在四五年后
A storm system the size of Earth, that, when we looked only four
再观察时 发现它已经消失了
or five years later, we found had vanished.
多年以来 我们在海王星上观察到了
But, over the years, we've observed more storms raging
更多的风暴
over the planet.
这是行星探测领域的几大不解之谜之一
It's one of the great mysteries of planetary exploration,
为什么一个行星距离太阳如此遥远
why a planet so far from the Sun, with so little energy falling
大气层从太阳获得的能量如此之少 却会存在太阳系中
into its atmosphere from sunlight, can have the most extreme winds
最猛烈的强风
in the solar system.
“旅行者”2号♥还发现另一件令人困惑的事
And Voyager made yet another puzzling discovery.
平均气温 零下214摄氏度
尽管距离太阳更远 海王星却比天王星温度要高
Although further from the Sun, the planet is warmer than Uranus.
这些额外的能量来源至今仍是一个谜
The source of this extra heat remains a mystery.
出于某种原因 海王星散发的热量
But, for some reason, Neptune emits over two and a half times
是它从太阳接收热量的两倍半还多
the heat it receives from the Sun.
这种来自内部的热量或许解释了猛烈风暴的成因
And this internal heat helps to explain the ferocious storms.
在热量从行星核心一路向外散发到
As the heat makes its way from the core of the planet
宇宙空间的过程中
and out into space...
整个大气层被搅动
..it churns up the entire atmosphere...
形成了不同于太阳系其它地方的大风
..creating winds unlike anything seen elsewhere in the solar system.
风速如此之快 很可能是因为
The probable reason that wind speeds can be so high
像海王星这样的行星没有坚硬的表面
is because there's no solid surface on a planet like Neptune.
各种奇怪液体在下面流淌 各种气体在上面飘
It's exotic liquids further down, and gases further up.
但没有岩质的表面
But there's no rocky surface.
那里没有高山和大♥陆♥来阻断
There are no mountains and continents to break up the flow
大气中气体的流动 所以行星上的风暴
of atmospheric gases, and, so, the winds can just whip
达到了超音速的速度
around the planet at supersonic speeds.
“旅行者”2号♥在太阳系的这场宏大之旅就要结束了
Voyager 2 had almost completed its grand tour of the solar system.
不过它在进行孤独的
But before it began its lonely journey
星际旅行之前
out into interstellar space...
还有最后一个世界要探访
..it had one, last world to visit.
海卫一 海王星14颗卫星中最大的一颗
海卫一 一颗巨大的卫星 表面覆盖着冻结的固态氮
Triton, a vast moon covered in a sheen of frozen nitrogen.
我们本以为这个世界寂静无声
We expected it to be a silent, still world,
但“旅行者”2号♥带来了最后一个惊喜
but Voyager was in for one, last surprise.
当“旅行者”2号♥到达时
But, when Voyager arrived,
我们发现这个冰冻世界上存在地质活动
we saw geological activity on that frozen world.
我们看到喷涌向太空的间歇泉 高度达8公里
We saw geysers erupting up into space 8km high,
裹挟着沿顺风方向 绵延100公里的深色物质
and then carrying dark material 100km downwind.
现在我们发现 理解喷发形成过程的关键在于
Now, the key to understanding what process caused those eruptions
喷发的间歇泉大都集中在海卫一表面
was that we noticed that the geysers tended to erupt on a place
一个有微弱阳光照射的地方
on Triton's surface below the faint Sun,
尽管太阳远在数十亿公里之外
even though it's so many billions of miles away.
这个过程中 阳光照射在一层薄薄的氮冰上
What's happening is the sunlight is falling on the thin layer
穿透冰层 然后使一层深色的 位于地表之下一米的
of nitrogen ice, going through, and heating up a layer of darker
物质温度变高
particles a metre below the surface.
仅仅4摄氏度的温度