Try this:
Get yourself 2 coins, a large one and a small one. The large one is the Earth, the small one is the Moon. Rest them flat on a table top.
Now, with the Earth held still, move the Moon around the Earth in a circle to simulate the Moon's orbit around the Earth, with the "Heads" side of the coin facing upwards so you can see it.
When the Moon is above the Earth, would a person looking from the Earth's surface towards the Moon see the top or bottom of the "head" on the Moon?
The conventional wisdom is (amazingly) that the moon rotates on its polar axis one time per orbit. HOWEVER, that is simply not true, because due to tidal braking, the moon no longer rotates around its internal polar axis at all. The moon's polar rotation ground to a halt billions of years ago, so today the moon just *orbits* around the Earth-moon common-mass barycenter, which is a point located within the Earth.
The *apparent* rotation of the moon from the sidereal perspective (and your above example is from the sidereal perspective) ONLY shows a 360 degree turn as the moon orbits, which is not a true polar rotation. E.g., if you had a sidereal perspective of the Earth orbiting the sun, then you would count 366.25 rotations per year instead of 365.25, which is our Earth's 365.25 polar rotations plus one (1) 360 degree orbit.
What happens when the Moon has moved to the other side of the Earth?
The moon will then have *turned* halfway around as a result of its orbit, so as viewed from the stars (the sidereal perspective), the moon would point in the opposite direction. HOWEVER, the axis for that turn would be the Earth-moon barycenter located within the Earth and NOT a rotation around our moon's internal polar axis!
If the moon BOTH orbited and rotated around its polar axis (two axes at the same time), then you would see all sides of the moon. The Earth has two axes, its polar axial spin as well as its orbit around the Earth-sun-moon barycenter. The moon has only ONE (1) relevant spin axis as the moon orbits (revolves) around its barycenter.
Now, in fact you know that we always see the same side of the real Moon.
Yes, we do ...BECAUSE, the moon lost all of its polar axial spins billions of years ago!!
Using the coins, how can you make sure that the "head" on the Moon coin always faces the same way, as seen from the Earth?
Are you referring to a so-called "zero-rotation" moon as shown in this graphic -- NOTE, I don't have enough posts yet to post URLs, so you need to add the http part to this URL (don't add www):
community-2.webtv.net/kdine5/Lunacy/scrapbookFiles/mailedD1.gif
If that so-called "zero-rotation" moon is what you mean, then that moon actually has one clockwise polar rotation per each counter-clockwise orbit.
When viewed from a sidereal perspective, all counter-clockwise orbiting bodies that are either tidally locked, or rotating on their polar axis counter-clockwise, *appear* to have one (1) extra polar rotation, which in fact is its orbit and not a true polar rotation. Thus, the Earth has a 366.25:1 spin ratio, and the moon has a 1:1 spin ratio - BUT, the Earth still has only 365.25 polar rotations per year (366.25 - 1 = 365.25), and the moon has zero polar rotations per orbit (1 - 1 = 0).
Conversely, from the same sidereal perspective, all counter-clockwise orbiting bodies that are spinning down from the clockwise direction will *appear* to have one (-1) less polar rotation from the sidereal perspective than they actually have.
Think about it - at one time our moon did have polar axial rotation, but billions of years ago tidal braking quickly ground the moon's polar rotations to a halt ... and normally, when you lose all of something you end up with ZERO, not one!
What confuses this issue is the claim that a sidereal perspective shows some sort of absolute truth (i.e., God's eye!) But, there are no absolute reference frames, and it's easy to prove that the sidereal perspective has obvious problems.
E.g., from the sidereal perspective a counter-clockwise orbiting body spinning down from the clockwise direction will not only have a 0:1 spin rate when that theoretical moon actually still has one polar rotation left as it orbits around its larger planet, but also, a moon spinning down from that clockwise direction will have TWO (2) 1:1 spin rates!!!!
Don't believe it? It's true, and rather easy to prove!
Let's try your table top experiment again, but instead of orbiting a coin around the center-point, instead take an orange (or any other round object) and draw a happy-face on one side, and draw an X on the opposite side.
Place the orange in the 6 o'clock position with the X facing you, and then push the orange in the counter-clockwise position to 3 o'clock as you spin the orange around its polar axis one time – when you land at 3 o'clock the happy-face should again be facing the center-point and you should have counted the X one time.
Proceed in this same fashion to 12 o'clock, then 9 o'clock, then back to the starting point at 6 o'clock.
In that single orbit the orange's happy face will have faced inwards four (4) times, and you will have counted the X five (5) times! No matter how many polar rotations you make per each orbit, you will ALWAYS count the X one more time ... and, that extra X count is caused by the 360 degree orbit, NOT a polar rotation!
Try the same experiment with the same counter-clockwise orbit, but rotate the orange clockwise this time, and you'll then count the X one (-1) time LESS than than the orange's actual polar rotations - thus, the so-called zero-rotating moon is actually a counter-clockwise orbiting moon spinning down from the clockwise direction. Amazingly, counter-clockwise moon spinning down from the clockwise direction that still has 2 polar rotations left will have a 2nd 1:1 sidereal spin ratio, the same 1:1 it will have when it finally spins down.
So much for the absolute truth of the sidereal perspective!!!
Thus, despite appearing to not spin from the sidereal perspective (0:1), that zero-rotation moon is actually spinning clockwise around its polar axis one time per orbit (0 + 1 = 1):
Likewise, this tidally-locked moon with a 1:1 (sidereal) spin rate is often incorrectly cited as a one (1) rotation moon:
community-2.webtv.net/kdine5/Lunacy/scrapbookFiles/mailedD0.gif
But, the only spin you're seeing these 1-rotation models make is the moon's 360 degree orbit around an exterior axis (its barycenter.)
The moon ONLY *orbits* around its Earth-moon barycenter! The Earth both *revolves* around the sun and *rotates* around its polar axis. The Earth also wobbles around the Earth-moon barycenter.
I realize that most websites have this wrong - likely, this rotation nonsense is being taught in Astronomy 101 courses and most people don't think too deeply about it and just accept it.
The Earth was once known to be flat, too!
:shrug:
Ken
And now the big question: do you think the Moon rotates now, or not?