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为什么我们只能看到月亮的一面 – 译学馆
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Tidal Locking | Why Do We Only See One Side of the Moon?

1959年 苏联的月球三号航天器传回一些
In 1959, the Soviet spacecraft Luna 3 beamed back
地球人类从未见过的照片 即月球的背侧
images of something Earthlings had never before seen: the far side of the moon.
我们总看到月球的同一侧 是因为
We always see the same old side of the moon because the moon
rotates exactly once on its axis each time it orbits Earth.
如果月球静止不动 那在它绕地公转的过程中
If it weren’t spinning at all, we’d get at least one
360 degree view of its surface with each lap.
如果其为两倍转速 我们就能在月球公转时
If it were spinning twice as fast, we’d also see the moon’s
无死角 多次观察月球表面
entire surface more than once per orbit.
然而 我们的月球运动——就像太阳系中其他的卫星
But instead, our moon’s motions – like the spin and orbit of most other moons in
our solar system – are, remarkably, in perfect sync.
This wasn’t always the case: our best guess is that our own moon formed due to a massive
小行星冲撞 而月球初始自转和极快的十小时公转几乎
asteroid impact, and its initial spin and dizzying 10-hour orbit were almost certainly
not in sync with each other – though we don’t know which was faster.
在如此接近的距离里 地球的重力使得月球变成椭圆形
At such close range, Earth’s gravity deformed the moon into a slight oval, with one of its
bulges facing Earth.
由于月球自转和公转不同步 其表面突起很快甩出公轨
Those bulges quickly swung out of alignment, thanks to the moon’s asynchronous spin and
orbit, but Earth’s gravity continually squeezed them back again.
What’s more, this gravitational tugging would have influenced the moon’s rotation
如果月球自转比公转快 地球为对抗月球其他方向的自转
rate: if it was spinning more than once per orbit, earth would pull at a slight angle
会用引力牵拉调整它的公轨 减缓自转 如果月球
against the moon’s direction of rotation, slowing its spin; if the moon was spinning
自转比公转慢 地球为加快月球自转会另寻办法
less than once per orbit, Earth would have pulled the other way, speeding its rotation.
无论哪种情况 都需要花费近千年的时间来调整月球
Whatever the case, it took just 1000 years for the Earth’s pull to adjust the moon’s
自转 直至月球自转和公转同步为止
spin enough that one rotation of the moon corresponded to one trip around the earth,
也就锁定月球背侧 永远背对我们
leaving one side forever locked facing away.
最终我们不止能看到月球一侧 是因为月球
We do end up seeing slightly more than that one side, because the moon’s elliptical
公轨呈椭圆形 其赤道面和轨道面微微倾斜的存在
orbit gives us peeks beyond its average eastern and western horizons, and its tilted axis
形成“月球时间” 这能看到更多的月球北面或南极
causes “moon-seasons” revealing more of the lunar north or south poles.
但这只增加了9%的观测 仍有41%不能从地球上看到
But those glimpses only add up to an extra 9%, leaving 41% of the moon hidden from earth.
月球三号卫星已能让我们观测月球其余面貌了 然而
Satellites, starting with Luna 3, have allowed us to map the rest, but it’s safe to say
我们还是说 地球和月球只有一面之缘
that our relationship with the moon is still pretty one-sided.



地球与月球之间说不清的故事 为什么我们看不到月球的背面 原来是这样