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The moon was an ancient, fossilised world.
月球是个古老的化石世界
Its rocks hadn't changed for billions of years.
它的岩石数十亿年来没有改变
Scientists were thrilled.
科学家喜出望外
Basically the surface of the moon kind of froze
基本上来说，月球表面
about roughly 3 billion years ago and preserved
在大约30亿年前结冰
really the first one and a half billion years of its history.
因此保存了月球历史的头15亿年
The moon tells us very much about
月球大大提升了
the early history of the solar system.
我们对太阳系早期历史的了解
It's probably one of the best recorders
可说是太阳系早期历史
of the early history of our solar system.
保存最好的纪录
This ancient fossil was a scientific gold mine.
这个古老化石是科学上的金矿
Because the moon was so well preserved it meant scientists
因为月球保存良好，因此表示科学家
could finally answer the question that had come to obsess them.
终于可以回答萦绕心头多年的问题：
How was the moon formed?
月球是如何形成的？
At the time, there were 2 competing theories.
当时有两派说法
The first was that the moon and the earth
一派主张月球和地球来自相同的星云
were formed at the same time, from the same cloud of dust and gas.
并在同时形成
The other theory was that the moon
另一派则主张
was originally nothing do with the earth,
月球原本与月球毫无瓜葛
but was wandering alone in space until the earth
而是兀自地在太空中漫游
sucked it in with the power of its gravity.
直到被地球的引力吸住为止
But the rocks themselves didn't seem to support either theory.
但月岩让这两派说法不攻自破
They were different enough from rocks on earth
它们和地球上的岩石的差异
to make it unlikely they were all formed at the same time.
让人觉得它们不太可能是同时形成的
But they had enough similarities to make it equally unlikely
但两者间的相似性又让人觉得
that the moon was a completely foreign body.
月球不可能和地球毫无瓜葛
Eventually scientists came up with a new theory
最后科学家终于提出了一个新的理论
that explained these strange rocks.
来解释这些奇特的岩石
It was a brutal tale.
但这是个残酷的故事
It takes us back 4 billion years to
这要从40亿年前说起
when the solar system was a young and volatile place.
当时的太阳系新近形成，动荡不安
There were many planets and asteroids circling the sun.
太阳周围有许多行星和小行星
One of these was a young earth.
其中之一就是年轻的地球
But there was also another young planet, a bit smaller.
但当时还有一个体积比较小的年轻行星
The two were on a collision course.
它眼见就要撞上地球
Eventually they crashed together.
小行星终于撞上了地球
It was the biggest bang the solar system had ever seen.
惊天动地的撞击力道为太阳系中所仅见
The impact was so massive that it spewed out millions of tons
撞击如此猛烈导致数百万顿的
of molten rock and gases.
熔岩和气体喷出
As this debris circled the earth it came together,
这些碎片环绕地球时
forming a separate body our moon.
逐渐凝聚形成一个独立星体，这就是我们的月球
When it first formed the moon was 10 times
月球刚形成时与地球的距离
closer to the earth than it is today.
是现今的十分之一
So it appeared much bigger in the sky
所以看起来不仅大得多
and its gravitational pull was much stronger.
引力也更强
But over time it slowly drifted away from the earth
但随着时间过去，月球和地球渐行渐远
to its present position about a quarter of a million miles away.
直到离地球约25万里远的地方
And there its orbit seemed to have stabilised,
月球的轨道似乎在此处稳定下来
its distance from earth fixed for all time.
月球和地球间的距离就此固定，再也没有任何改变
