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Still Waters

Why Doesn't the Moon Spin?

36 posts in this topic

I would pay to see the dark side of the Moon!

Well the term "dark side" is incorrect to start with. With the exception of a few craters near the poles the sun rises and sets over the whole of the moon, so when we have a new moon on Earth, the side we can not see is actually in daylight (this is because the Moon DOES rotate).

The side we can not see is more correctly called the far side and there are many, many, pictures of it as it has been mapped by Russian, US, European, Japanese, Chinese and Indian spacecrat.

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The phenomenon is called gravitational locking and is brought about over many millions of years by tides. Eventually the earth will also be locked to the moon and keep the same face toward it, so that from the earth the moon will only be visible from one side -- just as the earth is never visible on the moon from the "far side."

The moon does rotate, but one rotation is the same as one revolution about the earth, so that it does not seem to do so from our perspective.

An interesting question is why the far side of the moon looks so different from the side we see. We see the man on the moon -- a surface with some craters but also large flat areas (mare or seas -- although of course that is only their appearance, there being almost no water}. The far side has no mare but instead looks pocketed with nothing but craters.

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The phenomenon is called gravitational locking and is brought about over many millions of years by tides. Eventually the earth will also be locked to the moon and keep the same face toward it, so that from the earth the moon will only be visible from one side -- just as the earth is never visible on the moon from the "far side."

The moon does rotate, but one rotation is the same as one revolution about the earth, so that it does not seem to do so from our perspective.

An interesting question is why the far side of the moon looks so different from the side we see. We see the man on the moon -- a surface with some craters but also large flat areas (mare or seas -- although of course that is only their appearance, there being almost no water}. The far side has no mare but instead looks pocketed with nothing but craters.

This is probable due to most of the impacters hit on the far side.

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Posted (edited)

There are a few maria on the far side of the Moon. There are also several very large impact craters, as large as some of the near side maria. Either the near side is more prone to the sort of mare-producing volcanism that the largest impacts seem to have triggered, or the far side maria were torn up by later impacts. Since the few far side maria seem about as well preserved as those on the near side, the latter possibility appears unlikely.

It has been suggested that mineral sources of radiogenic heat might be more common on the Moon's near side, and that this could explain the tendency to volcanism. If this is so, it counts strongly against the Giant Impact Hypothesis of the origin of the Moon. Such an impact should have distributed radiogenic minerals through all Lunar longitudes.

Edited by bison

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I think I'm beginning to understand now. Thanks Waspie, daniel and others.

Astronomy, obviously, is not one of my strong points.

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I think I'm beginning to understand now. Thanks Waspie, daniel and others.

Did you watch the video I posted? I'm pretty sure that will serve to clarify things for you.

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I think I'm beginning to understand now. Thanks Waspie, daniel and others.

Astronomy, obviously, is not one of my strong points.

It took me awhile too pallidin , Shadowsot's tidal locking link helped. Our solar system is beautiful! *sniffle*

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Did you watch the video I posted? I'm pretty sure that will serve to clarify things for you.

I haven't, but I will. Thank you. :yes:

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I've been asked on a number of occasions recently why the moon always seems to show us the same face -- the lunar nearside. I'm not sure why there's the sudden interest, but it's a very good and valid question, especially as tonight (March 27) is a full moon.

Look at the moon at any time and -- aside from the constantly changing phases that are caused by changing relative positions of the Earth, the moon and sun -- it does indeed show us the same face, constantly. Perhaps surprisingly, it's 'non-rotation' (from our perspective) comes from its interaction with the Earth.

http://news.discover...cked-130327.htm

because it locked with the gravity of earth's rotation

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because it locked with the gravity of earth's rotation

Earths rotation?

The Earths gravity slows down the moons rotation, so that it rotates at the same speed as it revolves around the Earth.

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