Why doesn't the moon spin?

This may seem like a really dumb question, but it just popped in my head, so I figured I'd get some answers. Why doesn't the moon spin on its axis?

It just seems odd that nearly every body in the universe spins for one reason or another...except our moon? Is there a scientific answer, or is this one of those things that points to what John Lear has said about the moon essentially being a giant space station of sorts...

OK, enough of my rambling...anyone have any answers for this?

Sure.

It does spin.

It spins once per orbit, so that the same side is always facing the Earth. If it didn't spin at all, it would appear to make one revolution per orbit.

The reason why is called tidal locking. No large body has perfectly uniform density. There are off-center heavy bits here and there. Tidal forces are exerted on these imperfections over time, and the result is that the body will eventually assume a tidally locked state.

There is more than one tidal locking mode. Mercury, for example, is resonantly locked to the Sun at a 3:2 ratio.

Go Google for "tidal locking", there's lots of sites with drawings and lengthy explanations.

[edit on 30-9-2007 by Tom Bedlam]

Have you tried a Google search on this subject ? Wikipedia ?? There are tonnes of websites and articles about this on the internet.

The best place to read about it in IMO is here: www.badastronomy.com...

ok, that makes sense...I guess i just assumed that if it was spinning, we'd actually be able to see it spin, rather than seeing the same side all the time. But I think I understand what you're saying. Thanks for the response!

The wierd thing is...if it wasnt spinning we would see it spin. lol

I have read why the dark side of the moon is never seen on earth for years. All the explanations seem somewhat logical but I still can't wrap my mind around it. Going so far as to take a golf ball and an orange and try to emulate it in theory. It just seems to me if indeed it does rotate...at some point on earth the entire surface areas of moom should at some point become visible. That ? has always blown me away. But I'm no rocket scientist.

Well, the moon does not have a spin cos it should have none. Actually, the difficult question is "What is the origin of the spin in the universe?" . We actually do not know why the galaxies/stars/planets are all rotating and spinning.Of course scientist would never admit they do not know

reply to post by Jaruseleh


Though the moon's orbital period and it's day is about the same, it's not exactly the same because the moon has an eccentricity. Meaning the orbit isn't perfectly circular. This results in something called "libration". Basically the result of libration is such that sometimes you can see more of what's beyond the visible side i.e. the edges of the dark side. It's not much though, just a degree or two extra.

Here's wiki's link on libration:

en.wikipedia.org...

jpm1602: that link should answer some of your confusion as well.

Yes sir Beachcoma, I too have read that very theory, fact etc. It just doesn't get it for me in my craw why such a large area would 'never' be visible. I still just don't get it. Again, far from rocket science material.

reply to post by jpm1602


Way back in the past the moon was spinning faster, but since it's relatively close to Earth, our planet's gravity eventually tugged at the side we see today and so the moon became tidally locked. It spins in the same direction as it orbits the Earth, in more or less the same time it takes to orbit the Earth, with the near side constantly being tugged at.

That's the simplest I can explain it.

The moon does spin as others have explained, but it is also slowly moving away from Earth at a rate of just over an inch per year.

I kind of get that, and I truly want to understand that. I just can't get past the thought that at some point, somewhere on earth we 'should be able to see the entire moon'. I know I'm probably being very dense at what should be an easily understood phenomenon. And believe me, I've spent hours on line trying to educumate myself on this very topic.

It doesn't help when I read articles from the naval observatory such as I did on spaceweather.com two years ago why the coordinates of the moon were suddenly changed/updated with no explanation or follow up. Not to say that means anything I suppose.....

www.astro.virginia.edu...

If this doesnt help I may have to go into great detail. someone save me from going into great detail.

I'll read up Pfiel, thanks for info. Don't strain yourself lol. Who knows, maybe I can get one of them there NASER jobs after this. Just kidding.
Thank you.

I would go with the "the moon doesnt spin because it is a giant observational UFO that was placed here to keep watch on us simple human lifeform" option.

I know it is the most outlandish suggestion, but given the fact that we have seen little of the dark side of the moon and while coupled with the conspiratorial nature of that subject, I think that it doesn spin because "they" dont want it to spin.

Just my 2 cents

I agree Mr. Wahn. Considering your point status you've obviously been around the block a few times. You do not seem to have any fear of the big boy scientists down the street and I truly respect that. I have read a number of your posts and found myself to of like mind on many topics.
Thank you all for the feedback.
Best Regards
John

Ok Pfiel, after viewing aid it all makes perfect sense to me now. Still think it's a spooked out coincidence of a multiple of factors how it is of perfect dimension and distance to perfectly blot sun during eclipses etc etc.
I think it was Sagan who said the irregularities of the moon in our orbit were beyond calculation, but I get it. Thanks man.

I'll hazard a guess and suggest that the reason a planet or moon stops spinning is due to the fact that the strength of gravity varies with distance. The half of the moon that faces us feels a stronger pull towards the earth than the half that's facing away because it's closer. That extra pull keeps the face turning to stay facing the earth since it's pulled more than the face that's turned away. No doubt this face is probably slightly more massive as well than the other face. Thus variations in the mass of the moon probably have an effect as well.

It all comes down to thinking in the third dimension. When earthshine is on earth and moon, the moon just happens to have that face towards us. It's rotational and gravitational drag is just so that when earth is in darkness, the dark side of the moon to us, is in darkness. (Now if I had a really big bloody flashlight...). I know now why pink floyd did a lot of acid. That in itself is quite amazing.

[edit on 30-9-2007 by jpm1602]