为啥地球需要自转？月球也同样？ - 未名空间MITBBS历史存档

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为啥地球需要自转？月球也同样？

为啥地球需要自转？月球也同样？# GeoSpace - 地球与空间科学

l*G2007-05-14 07:05

1 楼

弱弱的问大伙, 月球自转的周期＝月球公转的周期=24.84 hours，因此我们永远只看
到月亮的同一边，为什么它们相等呢？
还有，地球的自转和公转周期为何就不一样？
还有，为啥要自转呢？有公转不就行了吗？
月亮是地球的卫星，它有自转我不知到原因，那么我们送上天的人工卫星也必须自
转么？
legolasGG

H*o2007-05-14 07:05

2 楼

100000个为什么

【在 l*******G 的大作中提到】

: 弱弱的问大伙, 月球自转的周期＝月球公转的周期=24.84 hours，因此我们永远只看
: 到月亮的同一边，为什么它们相等呢？
: 还有，地球的自转和公转周期为何就不一样？
: 还有，为啥要自转呢？有公转不就行了吗？
: 月亮是地球的卫星，它有自转我不知到原因，那么我们送上天的人工卫星也必须自
: 转么？
: legolasGG
:

O*r2007-05-14 07:05

3 楼

初条件是怎样，太空摩擦力又小，现在就是怎样乐。
至于INITIAL CONDITION，那是神学的范畴，我们MORTAL无法参悟。举个例子，万有引
力是平方反比关系。那就有人要问，为什么不是1.99998次方反比呢？1.99998次方反比
世界也会存在罢，只是各种现象不一样而已。在我看来SCIENCE无法回答这个问题。

w*a2007-05-14 07:05

4 楼

due to tidal effect, the earth's spin period is same as that of the moon.
even you perturb the system such that they have difference rotation periods,
after some time, they will match with each other.

【在 l*******G 的大作中提到】

w*a2007-05-14 07:05

5 楼

that we are ignorant doesn't mean there is no answer.

【在 O*********r 的大作中提到】

: 初条件是怎样，太空摩擦力又小，现在就是怎样乐。
: 至于INITIAL CONDITION，那是神学的范畴，我们MORTAL无法参悟。举个例子，万有引
: 力是平方反比关系。那就有人要问，为什么不是1.99998次方反比呢？1.99998次方反比
: 世界也会存在罢，只是各种现象不一样而已。在我看来SCIENCE无法回答这个问题。

O*r2007-05-14 07:05

6 楼

Sorry, my fault. It's tidal locking.

periods,

【在 w**a 的大作中提到】

: due to tidal effect, the earth's spin period is same as that of the moon.
: even you perturb the system such that they have difference rotation periods,
: after some time, they will match with each other.

l*G2007-05-14 07:05

7 楼

I kind of understand that tidal lock caused the moon self spin period becomes the same as moon revolution around earth.
But for planets that don't have water/atmosphere, so no water/atmos tides, why do they still have self-spinning. This could be very deep question,, very interesting.
lego

w*a2007-05-14 07:05

8 楼

it can be 'solid tide' due to gravitational pull.
for example, in Earth's early history,
the moon is closer to the Earth. The solid tide could be as high as tens of
meters.

becomes the same as moon revolution around earth.
tides, why do they still have self-spinning. This could be very deep
question,, very interesting.

【在 l*******G 的大作中提到】

:
: I kind of understand that tidal lock caused the moon self spin period becomes the same as moon revolution around earth.
: But for planets that don't have water/atmosphere, so no water/atmos tides, why do they still have self-spinning. This could be very deep question,, very interesting.
: lego