How come the Moon rotates exactly as fast as it revolves around Earth?

The Moon always shows us only one face, which means that its revolution is synchronized with its rotation. But, 100 000 years ago, was the visible face exactly the same, or is there always a shift which would cause the visible face to slightly change in the long run?

If it is perfectly synchronized, how can it be possible? How small is the probability of such a thing?

11 Answers

  • 10 years ago
    Best Answer

    The moon's rotation is perfectly synchronized. This is because the moon is not exactly a perfect sphere, and is not the same throughout. There is a slight increase in mass on the side facing Earth, and this is attracted to Earth a bit more than the rest of the moon. The Moon used to rotate at a faster rate, but as the extra mass rotated around, there were frictional effects because of tidal deformations caused by the Earth. This friction changed rotational energy into heat, until the moon slowed down enough so that the extra mass was always facing Earth.

    The extra mass is less than 0.03% of the total moon mass, but acting over a few million years, that was enough to synchronize the moon's rotation.

  • 10 years ago

    the moon is tidally locked with the earth... therefor it always shows the same face towards the earth.... as a result of this... sort of as a side effect of being tide ally locked, its revolution is synchronized with its rotation. In the past, the moon spun faster, it has been slowed over thousands of years as a result of the tidal forces. since the mon is not a perfect sphere and its internal composition is not 100 percent even, its a certainty that over time this would happen. the outer or far side of the moon has to sin faster than the inner or near side of the moon... this results in a form of "friction" where energy is lost.

    not only is it possible, the certainty, the probability is 100 percent. Eventually, the earth will be tidally locked with the sun as mercury is. Its an inevitable effect of spinning bodies in orbit around each other.

  • arslan
    Lv 7
    10 years ago

    The moon is tidally locked to the Earth.

    Probability is not to be accounted for, as this phenomena happens because of orbit mechanics.

    If the there is a big mass difference between two bodies, and they are relatively close to Eachother, tidal locking will happen.

    The Earth is 81 times more massive than the moon, and they are only 384,000 km from Each other, tidal locking was bound to happen.

    Pluto and Charon are tidally locked in a similar way.

  • Anonymous
    10 years ago

    The moon is tidally locked with the Earth. That happens when any object orbits close to a larger object - most of the close moons around the other planets are also tidally locked.

    Its not chance, its physics.

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  • 10 years ago

    The moon has a locked synchronis orbit because of the earths gravity. Imagine you have a ball on a string and you spin with it. You and the ball are now locked and you will only see one side of the ball. This happens because you are supplying the force to make it possible. although the moon has no string of course the principles are the same.

  • 10 years ago

    The moon is not a perfect sphere. It has mountains, valleys and craters on it. That means that one side will inevitably be slightly heavier than the other.

    That being so, the earth's gravity will attract the heavier side more than the other, so the heavier side will always turn towards the earth.

    So you see, it is not blind chance, or deliberate design. It is simple necessity that makes it happen.


    Source(s): It was all worked out by Sir Isaac Newton, over 300 years ago!
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    Lv 4
    3 years ago

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  • Adam
    Lv 6
    10 years ago

    A process known as tidal locking is to blame. Probability is irrelevant when the event is caused by orbital mechanics.

  • 10 years ago

    As the others said, tidal locking. It actually happens on most other planets too.

  • 10 years ago

    It's called tidal locking, and is due to the gravitational gradient between two bodies.

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