Paging Tom Kaye, mr astronomy himself...

[warpfeedmod]

I was reading this article:

Did the moons far side once face the earth?

And not being very versed in astronomy, this threw me off:

The far side of the moon never faces us, because the moon rotates once for every orbit it makes of the Earth. Yet an analysis of impact craters shows the far side may once have pointed our way.

Huh wait so the moon rotates but always keeps a side facing us?

So I did some more searching and came across this:

Link

Which has this comment:

The Moon rotates at just the right speed so that it always keeps one face pointed toward the Earth, which seems like a pretty big coincidence, doesn't it?

Now I understand that the earth spins as it orbits the sun, and the moon apparently spins as it orbits us, but that spinning motion is so in sync due to gravity that the moon always has a side that faces away from us?

Is there some sort of animation or something to explain this because I can't figure it out..

[Hexis]

From the wiki page:

The Moon is in synchronous rotation, meaning that it keeps the same face turned toward the Earth at all times. This synchronous rotation is only true on average because the Moon's orbit has a definite eccentricity. As a result, the angular velocity of the Moon varies as it moves around the Earth, and is hence not always equal to the Moon's rotational velocity. When the Moon is at its perigee, its rotation is slower than its orbital motion, and this allows us to see up to eight degrees of longitude of its eastern (right) far side. Conversely, when the Moon reaches its apogee, its rotation is faster than its orbital motion and this reveals eight degrees of longitude of its western (left) far side. This is referred to as longitudinal libration.

http://en.wikipedia.org/wiki/Orbit_of_the_Moon

[MoeMag]

Hexis is right about why we can see appx 8% of the "far side of the moon" due to longitudinal libration, and yet another 1% from parallax.

However the reason behind why we never see the far side of the moon is called tidal locking.

http://en.wikipedia.org/wiki/Tidal_locking

[tribalman]

Now I understand that the earth spins as it orbits the sun, and the moon apparently spins as it orbits us, but that spinning motion is so in sync due to gravity that the moon always has a side that faces away from us?

Is there some sort of animation or something to explain this because I can't figure it out..

ok, this is totally simple but i think it is an effective way to demonstrate this. you will need a friend to do this. one person will be the earth, the other the moon. just for reference, have the person who is portraying the moon start north of the "earth" while facing south. now the moon is going to walk to the east while still facing you. when they reach east of you they have revolved around earth AND have rotated also, because they are now looking west. if they were to continue to where they would be south of the earth they would now be facing north. regardless of the state of the revolution around the earth, the person portraying the earth would only see the front part of the person who is the moon.

if the moon had a stationary rotation, one where we would see certain parts of the moon depending on state of the revolution this would be different. in the 2 person scenario "moon" starts north of "earth" facing south again, except this time they must always face south. the moon then walks to the east, the earth would now see the right shoulder profile of the person as the moon. if the moon continues walking south the earth would now see back of the moon.

the earth's rotation is independent of the moon's.

[Army]

Huh wait so the moon rotates but always keeps a side facing us?

Now I understand that the earth spins as it orbits the sun, and the moon apparently spins as it orbits us, but that spinning motion is so in sync due to gravity that the moon always has a side that faces away from us?

Is there some sort of animation or something to explain this because I can't figure it out..

Think of a tether-ball. The ring that holds the rope to the ball (moon) is always facing the pole (Earth).

The ball still spins, just in a large continuous arc that happens to be around the pole. With us being the pole, we only see that side of the ball.

[TeamBob]

awsome

awsome. I didnt know that, and i completly get it

[malJohann]

I've heard a theory that suggest the Earth being a foreign planet to this system, that it once passed Mars so closely that it "stole" the whole atmosphere from Mars due to its greater gravitational forces, and that Mars ripped a piece from the Earth which we now call the Moon. This would also explain why we only ever see one face of the Moon.

It would also explain why there are pyramids on Mars, because there once was an advanced civilisation that lived there. They then relocated to the Earth during all this, obviously with space flight, since I doubt millions of people would have survived being sucked from Mars, then space flight and free fall on to the face of the Earth by their own accord with only the clothes on their backs, not to mention how turbulent things would have been, but anyway.

[tribalman]

I've heard a theory that suggest the Earth being a foreign planet to this system, that it once passed Mars so closely that it "stole" the whole atmosphere from Mars due to its greater gravitational forces, and that Mars ripped a piece from the Earth which we now call the Moon. This would also explain why we only ever see one face of the Moon.

It would also explain why there are pyramids on Mars, because there once was an advanced civilisation that lived there. They then relocated to the Earth during all this, obviously with space flight, since I doubt millions of people would have survived being sucked from Mars, then space flight and free fall on to the face of the Earth by their own accord with only the clothes on their backs, not to mention how turbulent things would have been, but anyway.

wow, interesting to say the least. that wouldn't be possible. if the earth passed that close to mars to pull atmosphere it would would rip more than the atmosphere. if it could pull mass away to create our moon it would actually rip mars apart. also, the location of earth is key that it isn't from outside of Sol's system. Solar systems are very similar to atoms, there is a core and revolving around the center are planets or in the case of atoms, electrons. in both scenarios they are revolving at certain distances. that is actually how they found the asteroid belt between jupiter and mars. it is called the Titius-Bode Law. this belt was created by mars and jupiter ripping apart planetoids with their gravity. if these 2 planets can rip apart a mass from far away distances then earth would completely destroy everything about mars, not just still an atmosphere and a bit of it's rock.

plus during our manned study of the moon we found that there are rocks that are also found on earth, giving the theory that the moon is from Earth or at least part from Earth.