Why does the Moon always show the same face to the Earth?

[greyl]

Good question, eh?

http://www.badastronomy.com/bad/misc/tides.html

[laruemtt]

1. the other side's not as photogenic? n/t

[emanymton]

2. ID Tells Me The Moon Is Cheese. The Flying Spaghetti God Likes

pizza with cheese.

[WildClarySage]

9. Parmesan and/or Romano, naturally.

[clydefrand]

3. The moons face on 1 side, its backside on the other, and

it doesn't believe in 'mooning' people.

[zbdent]

10. Okay, that made me laugh.

:rofl:

[Dead_Parrot]

4. It wants to keep an eye on Bush. nt

[mntleo2]

5. Seriously...

The moon does not rotate on its axis.

Which brings us to our political "moonies" who love to fraternize with the self ascribed messiah that owns the Washington Times. Like the moon, they do not rotate ~ but boy are they spinning!

:evilgrin:

Cat In Seattle

[ChairmanAgnostic]

6. bravo!

but the real reason is that 6,000 years ago, this big god hand scooped out the moon and tied it with an invisible god-string to someplace in the Pacific basin. Then, the hand rested.

[greyl]

7. ?

You are joking when you say the moon doesn't rotate, right?

[DRoseDARs]

8. Erm, the moon does rotate on its axis. Exactly one revolution per orbit.

Go here for better information than I could provide:
http://www.nineplanets.org/luna.html

snip

The gravitational forces between the Earth and the Moon cause some interesting effects. The most obvious is the tides. The Moon's gravitational attraction is stronger on the side of the Earth nearest to the Moon and weaker on the opposite side. Since the Earth, and particularly the oceans, is not perfectly rigid it is stretched out along the line toward the Moon. From our perspective on the Earth's surface we see two small bulges, one in the direction of the Moon and one directly opposite. The effect is much stronger in the ocean water than in the solid crust so the water bulges are higher. And because the Earth rotates much faster than the Moon moves in its orbit, the bulges move around the Earth about once a day giving two high tides per day. (This is a greatly simplified model; actual tides, especially near the coasts, are much more complicated.)

But the Earth is not completely fluid, either. The Earth's rotation carries the Earth's bulges slightly ahead of the point directly beneath the Moon. This means that the force between the Earth and the Moon is not exactly along the line between their centers producing a torque on the Earth and an accelerating force on the Moon. This causes a net transfer of rotational energy from the Earth to the Moon, slowing down the Earth's rotation by about 1.5 milliseconds/century and raising the Moon into a higher orbit by about 3.8 centimeters per year. (The opposite effect happens to satellites with unusual orbits such as Phobos and Triton).

The asymmetric nature of this gravitational interaction is also responsible for the fact that the Moon rotates synchronously, i.e. it is locked in phase with its orbit so that the same side is always facing toward the Earth. Just as the Earth's rotation is now being slowed by the Moon's influence so in the distant past the Moon's rotation was slowed by the action of the Earth, but in that case the effect was much stronger. When the Moon's rotation rate was slowed to match its orbital period (such that the bulge always faced toward the Earth) there was no longer an off-center torque on the Moon and a stable situation was achieved. The same thing has happened to most of the other satellites in the solar system. Eventually, the Earth's rotation will be slowed to match the Moon's period, too, as is the case with Pluto and Charon.

Actually, the Moon appears to wobble a bit (due to its slightly non-circular orbit) so that a few degrees of the far side can be seen from time to time, but the majority of the far side (left) was completely unknown until the Soviet spacecraft Luna 3 photographed it in 1959. (Note: there is no "dark side" of the Moon; all parts of the Moon get sunlight half the time (except for a few deep craters near the poles). Some uses of the term "dark side" in the past may have referred to the far side as "dark" in the sense of "unknown" (eg "darkest Africa") but even that meaning is no longer valid today!)

snip

[Tesha]

11. Au contraire! The moon *DOES* rotate on its axis!

Once rotation per revolution, so the sam face always faces the Earth.

The commonly-accepted theory is that tidal forces eventually forced
the moon into the "rotation lock" with the Earth (roughly, the heavy
side of the moon faces us).

Tesha

[mntleo2]

13. "Seriously"

That was a bad subject line, sorry. However, I was "serious" about the Moonie times' habit of spinning pap like it is a top. I HATE that paper, that Tony Blankley or whatever his name is, as well as the fact that so-called devout "Christian" elected officials when they showed up at its owner's announcement that he was indeed the messiah. Whaaaaa???? Actually if his name is "BLANK-ley", this is a good description of that wingnut and his rag, lol!

Cat In Seattle

[soothsayer]

12. You gotta' try the coin trick to demonstrate it

To see how this works, put two coins on a
table, a large one to represent the Earth, and a small one to
represent the Moon. Choose a particular place on the edge of the
"Moon" as a reference point. Now, move the Moon around the Earth in a
circle, but be careful to always keep the spot you picked pointed at
the Earth (this is analogous to the Moon always keeping the same face
pointed at the Earth). You should notice that as you do this, you
have to slowly rotate the Moon as it circles the Earth. By the time
the Moon coin goes once around the Earth coin, you should have had to
rotate the Moon exactly once.

[greyl]

14. Oranges are used in the article.

Using your coin method the demo is shinier - that's always nice.

[soothsayer]

15. lol!

[WindRavenX]

16. it's tidal locked with us

nt

[greyl]

17. No, that's not why.

As stated in the article in the op:

Since Earth's gravity is much stronger than the Moon's, the tides from the Earth on the Moon are much stronger than the Moon's tides on the Earth. The Moon has tidal bulges just like the Earth, and so it too was slowed by the Earth's pull on its nearer bulge. Eventually, the Moon's rotation was locked so that it took the same time to spin once on its axis as it takes to go around the Earth. This is why we always see the same face of the Moon! And this happened to the Moon before the Earth because the Earth's tides are so much stronger.

Iow, the Moon's tidal was always "locked" with us. How could it not be?
It's the Moon's rotation that has become locked with us.

[WindRavenX]

18. That's what I meant

I was in a hurry and didn't get the time to elaborate :hi:

[greyl]

19. My drive-bys have bitten me in the ass, too. :) nt

[Salviati]

31. As as aside...

that's precicely what tidally locked means, that the rotational period is the same as the orbital period. This takes place with all orbiting bodies capable of deformation (namely everything) due to tidal forces...

[Esra Star]

20. In my considered opinion, the moon has a magnetic component,

that is it has a magnetic north and south pole.
The Earth also has a magnetic component.
So it only makes sense that they would affect each other.
At this time the moon has stopped spinning and presents the same face to the earth, It is true that is still rocking a little bit but
this will eventually fade. The slowing of the Earth's rotation can also be attributed to this.
The above is just my opinion.

[greyl]

21. What were you considering when you reached that false conclusion?

The question is answered in the OP as far as I know. ;)

edit: To be clear, the Moon doesn't have magnetic poles.

[Esra Star]

23. are you saying that there is no magnetically affected material in the moon

.. I understood that the make up of the moon is
approximately the same as the earth.

[rman]

24. Gravitational effects are much stronger

then magnetic effects.

[Esra Star]

25. Gravitational effects keep the moon in it's relatively stable orbit.

What I am saying is that the orientation is due to
a response to the magnetic field of the earth.
As if the moon is a giant compass needle.

[rman]

26. The mass of the moon is distributed unequally

Which causes the effect of gravity to be stronger on one side then on the other side of the moon. This is a well established fact in astronomy, so there's no need to speculate.
But maybe you know something that astronomers don't know.

[Esra Star]

27. I am not aware of any unequal moon mass distribution......

Can you point to any site that quantifies this?

[rman]

28. google for "moon orbit tidal lock"

[LunaSea]

29. Google "Mascon"

short for "Mass Concentration"

[Esra Star]

30. Thank you rman & lunarsea

I am still processing the information.
It is also interesting to note that "mass concentration" caused the
problem with landing the Apollo 11 lem.
That was a pretty close run thing. Lucky Neil (Ice cold) Armstrong
was manually landing or it could have been in that crater.

[Ouabache]

22. I am pretty sure it has to do with the aliens on the dark side of it

I read that on the internet somewhere.