Most of us appreciate the beauty of a full Moon sedately² moving across our night skies.

我们中的大多数人都会因满月静静地从我们的夜空滑过而产生美的感觉。

The Moon seems unchanging, as if for eons it has been there, controlling the tides, going through its phases every month and inspiring poets and lovers.

月球看起来似乎不曾改变，就像千万年来它一直就在那里那样，掌控着地球的潮水涨落，经历着自身的一月一次的阴晴圆缺和激发诗人和情人们的灵感与情思。

It might surprise you to know that in the past, things were much different, and they are still changing.

可能你会惊奇，当你得知，在过去，情况是非常不同的，并且“不同”仍在加剧。

A billion years ago, our relationship with the Moon was quite different.

10亿年前，我们与月球的关系完全不同。

For one thing, the Moon was much closer and therefore appeared much larger: and we saw the entire Moon, not just one face as we do now.

首先，月球近得多，因此看起来更大，并且我们能看到月球的全貌，而不是像现在，仅仅看到一面。

It took the Moon only twenty days to circle the Earth, and Earth's day was only eighteen hours long.

月球绕行地球一周只需二十天，地球的一天也只有十八小时长。

Massive tides, over a kilometer in height, would ebb³ and flow every few hours.

每几个小时，超过一千米高的大规模潮汐就发生一次。

From the beginning though, things were changing, as the Moon's orbit was getting larger.

一开始，事情就在发生变化，月球的轨道在越变越大。

Every year, the Moon moves about four centimeters (about 1.6 inches,) farther out into space, away from Earth.

每一年，月球都会深入太空，远离地球约4厘米（约1.6英寸）。

Right now, the Moon's rotation⁴ rate, and the time it takes to orbit Earth are the same.

现在，月球的自转速度与绕地球公转速度是一样的。

Is this all just some cosmic coincidence?

难道这一切只是宇宙巧合吗？

Would it surprise you to know that at one time, Earth didn't even have a moon?

当你得知，曾几何时，地球甚至还不曾拥有月亮，你是否会感到惊奇？

Where then, did our nearest neighbor in space come from, and what will the future bring? To answer these questions we must go very far back into time.

那么，我们这个最近的邻居来自何方，未来又将怎样？为了回答这些问题，我们必须回到遥远的过去。

黑暗面月球

Four and a half billion years ago the Earth was about sixty percent formed, though it did have a differentiated⁵ core, crust and mantle⁶.

45亿年前，地球大约只有现在百分之六十，尽管它确有能够区分的地核，地壳和地幔。

In these primal⁷ skies, there was no Moon.

在原始的天空里，没有月亮。

It was a very violent time in the Solar System with other planets forming from clumps⁸ of gas, dust and rock and impacts among these bodies were the norm.

这是一段变化剧烈的时间，在太阳系里，气团，尘埃和岩石遵循一定的规则相互影响变化形成其他的行星。

Orbits were not the sedate¹, orderly system they are today.

轨道还不是今天那样静止、有序的系统。

One planet, about the size of Mars, probably had an orbit which crosses Earth's, and eventually a collision occurred.

一个大小与火星相当，轨道可能与地球轨道交叉的行星，最终与地球发生了碰撞。

The impacting planet made a hard, but glancing blow off Earth at just the right angle.

撞击行星以一个恰当的角度硬生生地几乎是一瞬间地砸向了地球。

It almost bounced off Earth, but was consumed instead.

它几乎弹起，但最终为地球所吞噬。

But the blow sent shock waves across Earth, spewing gas and debris⁹ into space, giving Earth, for a very short time, a ring around it.

但是，撞击产生的冲击波穿透了地球，导致它向太空喷出了环绕自己的气体和碎片，但这种情况持续的时间很短。

The debris around Earth began to condense into clumps and quite rapidly, a blink in cosmic time, formed a large glowing ball: our primal Moon.

那些围绕地球的碎片开始迅速地凝结，依宇宙时间的标准，就在瞬间形成了一个大灼热球：即我们的原始月球。

The Moon would have looked about ten times larger than it does today, and the Earth was changed forever.

那个月球看起来比今天的要大约10倍，地球也就从此改变了。

This story, about the birth of the Moon, is still a theory, one among several attempting to explain the source of our satellite.

这个关于月球诞生的故事，还只是几个试图解释我们这个卫星来源的理论中的一个。

Currently, this is the most widely accepted of the theories.

目前，这是接受度最高的理论。

Since that cosmic collision, the Earth and Moon have both have an effect on each other, and will continue to have an affect far into the future. Since the Earth is so much more massive than the Moon, the Earth has had the larger effect.

宇宙撞击之后，地球和月球相互影响对方，并且这种影响将持续到久远的将来。由于地球比月球大很多，所以地球施加的影响更大。