Are you certain that the heavy side of the moon faces Earth? Another theory holds that the heavy side is perhaps the far-side of the moon.

I think that is an inaccurate analogy since the Earth's gravity would have raised an actual moving wave in the moon's surface that would have traveled around the moon's circumference while the moon still rotated, just as the moon today raises a (small) tide in the Earth's land surface. So, tidal braking would occur continuously, no matter which side of the moon was facing the Earth at the moment.

If your beach ball moon were revolving in a circle around an exterior axis, then centrifugal force may swing the lop-sided beach-ball (w/ a magnet on its side) to face away from its center-point axis of spin with the magnet facing outward.

I doubt if magnetism is even a good analogy for gravity since the attraction between the Earth & moon may better be exemplified as traveling in curved space.

Even if the heavy-side of the moon does face inward as a result of gravity pulling more on that side, even so, the pull of gravity isn't so much as to keep the near-side always facing Earth since the moon in fact spends more time each orbit facing its empty focus – even Newton remarked on that fact:

"But because the lunar day, arising from its uniform revolution about its axis, is menstrual, that is, equal to the time of its periodic revolution in its orbit, hence the same face of the moon will be always nearly turned to the upper focus of its orbit; but, as the situation of that focus requires, will deviate a little to one side and to the other from the earth in the lower focus; and this is the libration in longitude ..."

(Sir Isaac Newton's Mathematical Principles of Natural Philosophy – Page 423)

In each anomalistic month the moon spends more time facing its empty focus since its orbital velocity is less when heading to and away from apogee. Libration is mostly optical in nature with very little actual physical wobble by the moon.

I realize it is the conventional "wisdom" that the moon still rotates around its polar axis (one time per each orbit), but this nonsense has been contested for as long as it has been claimed. For example, see Johannes Von Gumpach's 1856 "The Moon's Rotation on her Axis."

There are generally two arguments (in various forms) that are used to support the claim the moon still has polar axial rotation.

PROOF #1 – if you stand on the moon the star field would swirl around you. However, see EXAMPLES #1 & #2 (below) since that would happen whether the moon rotated around its internal polar axis, or instead just made a progressive 360˚ turn around an exterior axis (the barycenter) each orbit.

PROOF #2 – put a quarter and a penny on a table and then have the penny orbit the quarter, and you’ll be forced to “rotate” the penny to keep it facing the quarter.

A corollary to PROOF #2 is the “zero-rotating” moon. E.g., (as this argument goes) put your finger firmly on the penny and orbit it around the quarter, and this time the penny will face in one direction the entire orbit – hence, ZERO ROTATION!

Well, in fact, a so-called “Zero-rotation” astronomical body still does have some polar axial spin left, it’s just spinning down from the retrograde direction like this (as viewed from the sidereal perspective):

4 - 3 - 2 - 1 - 0 - 1

Venus is spinning down that way and is currently rotating a tad faster than zero. NOTE that when an astronomical body spins down from the retrograde direction it would have TWO 1:1 spin rates on either side of the zero 0:1 rate. The “God’s Eye” sidereal perspective obviously has its quirks.

This would be easier to grok if you try this simple demonstration of "SPIN" using a can of tuna – your body would represent the Earth and a can of tuna would be the moon. You need to actually get off your arse and do this for these spatial relationships to actually sink in - don't worry, it only takes a minute to do.

EXAMPLE #1 -- Place a can of tuna in your outstretched right palm, and with your left hand rotate the tuna-can both counter-clockwise (CCW) and clockwise (CW) - clearly, when you do that the tuna-can is rotating around its center of mass (CM) and its label would face (in turn) all four walls in the room.

EXAMPLE #2 -- Place a can of tuna in your outstretched right palm, then turn your entire body 360˚ CCW - clearly, when you do that the can is now revolving around your body's center of mass (CM) and its label would again face (in turn) all four walls in the room.

EXAMPLE #3 -- Next, with the can of tuna in your outstretched right palm, turn your body CCW 360˚ again and give the can a single CCW 360˚ spin around its CM – that can (moon) would have TWO *apparent* rotations from the sidereal perspective (a 2:1 rate).

EXAMPLE #4 -- Next, with the can of tuna in your outstretched right palm again, turn your body CCW 360˚ again, and with your left hand try to keep the can's label pointed to one wall – to do so, you will be forced to rotate the can CW 360˚ as you spin your body 360˚ CCW - i.e., the tuna can (moon) would have zero sidereal rotation (0:1). Venus is fairly close to doing that right now.

Amazingly, many websites falsely (and incredulously) claim that EXAMPLE #4's "zero-rotation" moon is proof that our moon must rotate, when clearly, the tuna can in EXAMPLE #4 is both revolving 360˚ around an exterior axis (your body) at the same time the tuna can is rotating 360˚ around its CM.

SIMPLY, from the sidereal perspective, these two counter-spinning 360˚ circular motions cancel each other out. Yet, a moon with that spin rate would continue to slow from 0:1 to finally stop at 1:1 since a so-called zero-rotation moon would still be subjected to tidal braking friction while at a 0:1 sidereal spin rate.

FROM A SIDERAL PERSPECTIVE, a *counter-clockwise*
orbiting and *counter-clockwise* polar-axis rotating astronomical body
spins down like this (starting with a random 5 polar rotations):

6 - 5 - 4 - 3 - 2 - 1

From the same SIDERAL PERSPECTIVE, a *counter-clockwise* orbiting
and *clockwise* polar-axis rotating astronomical body INSTEAD spins down
like this (starting with the same random 5 polar rotations) - with TWO 1:1 spin rates:

4 - 3 - 2 - 1 - 0 - 1

Yet, from the CENTER-POINT PERSPECTIVE, a *counter-clockwise*
orbiting and *clockwise* polar-axis rotating astronomical body INSTEAD
spins down from either direction like this (starting with the same random 5 polar rotations):

5 - 4 - 3 - 2 - 1 - 0

Finally, as you did in EXAMPLE #2, turn your body CCW and don't rotate the can either way – i.e., just let the can's label stare you in the face as you spin your body, just like our moon's face stares down at us – that would be the classic 1:1 spin rate of a despun moon. I.e., a moon with zero polar axial rotations left!

TODAY, our despun moon ONLY orbits the Earth and DOES NOT rotate around
its own polar axis in the process!

There's an old saying, "The Earth *revolves* around the sun as it *rotates* around its polar axis." Our Earth has two spin axes, and our despun moon has one spin axis left, which is around the earth-moon barycenter.

If your proof is wrong, then you should re-examine your beliefs.

Ken

Of course the moon is rotating around its own axis. Its rotation just matches its orbital motion around the Earth. The equivalent of what happens with a tidelocked satellite orbiting a planet is what you describe in Example 2 - you may not be rotating the tuna can around its own axis but it's still rotating to keep its face toward you.

Better still, use a screwdriver (or a pen) instead of a can of tuna. Place the pen in the palm of your hand with the long axis pointing towards you (you should have a convenient dent in your palm that lines up with your arm that you can rest it in too). And do this so that your body is in front of a distant doorway or something (so if you look at it from above, you'll see palm-body-doorway). So right now, the pen points towards your body and the distant door.

Now rotate yourself 90 degrees - the long axis still points toward you, right? But it's not pointing toward the doorway anymore, it's at 90 degrees to that. That's what the moon is doing. Someone standing at the doorway though would see the moon rotate by 90 degrees (which is what you'd see if you were standing in the direction of the sun looking at the earth-moon system).

If the pen wasn't rotating around its own axis then it'd point in the same direction no matter, so if you rotated 90 degrees then should still be pointing toward the door... but it doesn't. If that's what was really happening to the moon then you'd see all the sides of the moon from Earth - but we don't see that.

Greetings, kdine.

The conventional wisdom is correct. The Moon rotates with a
period essentially equal to its period of revolution about the Earth.

The location of the axis of rotation is irrelevant. Nomatter where
you think the axis is located, the Moon is rotating.

Wrong. You are using your left hand to prevent the rotation
that your right hand would cause if the can were allowed to rest
in your right hand as you rotate. In your example #4 the can is
revolving about your body, but not rotating.

Instead of trying to prevent the rotation with your left hand, have
a second person hold the can on the palm of your right hand while
you rotate. That may make it more obvious to you that the can
is not rotating.

Also, when you said "incredulously", you meant "incredibly".

-- Jeff, in Minneapolis

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"I find astronomy very interesting, but I wouldn't if I thought we
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kdine,

All your voluminous display of mental gymnastics is doing here is demonstrating a disagreement with the vocabulary most of us use in describing the Moon's compound motion.

I think our poster grav once held the same opinion, hopefully he'll come around

Hi – you didn’t say where to look, so in the “spinning moon” thread I did find this (and I agree with Grav’s comment):

That reference to another thread led me to this one, while it may not be the same one you referred to, it had some interesting comments – poor Steffani got double-teamed as you guys threw all the usual nonsense at her:

---snip---
84323-moon – Post #2:
The coin would ONLY be *REVOLVING* around an exterior axis in that example!

84323-moon – Post #9:
Once again, you would ONLY be *revolving* around an exterior axis in that example! If Steffani both walked around the lamp as she did pirouettes, then Steffani would have two spin axes, just as the Earth has two spin axes.

84323-moon – Post #10:
Hmmm? Seems to be a variation of the failed 'penny around the quarter' argument.

84323-moon – Post #15 – Poor Steffanie responds to all this misinformation:
At this point it appears that poor Steffani is the only one who understands that words have meanings (“revolve” and “rotate”), but unfortunately, she didn’t realize she’d fallen down into the rabbit hole where words mean what you guys say they do.

I realize that "rotation" is often used as a synonym for "revolution" by many people, but traditionally, “rotation” is around an interior axis while “revolution” is around an exterior axis.

The double-teaming continues:

84323-moon – Post #22:
See my EXAMPLES #1 & #2 above – clearly, progressive motion around an exterior axis (i.e., revolution), and rotation around an interior axis, would BOTH result in the relative movement of the window.

I’ve always loved this next one – this is the classic Porsche example where, by way of explaining moon rotation, you are asked to imagine driving a Porsche in ever smaller circles AROUND AN EXTERIOR POINT until the Porsche is finally spinning on its internal axis (don’t try this one with a Ford):

84323-moon – Post #25 (as a newbie here I can’t post URLs yet, so fill in the rest):
Ya, and if I placed a can of tuna on my head as I spun around, then the can would also be “Rotating” around its center of mass instead of *revolving* around an exterior axis – a really dumb example!

Actually, this exact same argument was adequately rebutted by Joahannes Von Gumpach way back in 1856:

---snip---
"§76. Of a similar nature is an illustration, which makes a
man, sideways again ("as the man in the Moon does") walk
round a chalk-spot, marked on the floor, and gradually get closer
to it, until he finds himself moving upon the spot itself. Assuming that
he will be admitted, in the last instance, to turn round
himself: the author of this illustration thereupon imagines to
have settled the question, in consequence of his having demonstrated
to evidence the perfect identity of rotatory and progressive motion;
or, he triumphantly asks, “should anyone perchance be able to explain,
at what particular distance from the spot, rotatory motion can be
said to commence?” FN-67

"The explanation demanded by him is easily given. Rotation begins at no
distance whatever from " the spot," i. e. from its axis the author having,
by the truly Jesuitical gradatim-process, converted the centre of revolution
into an axis of rotation; but only can take place upon the spot itself, i.e.
upon the axis of rotation.

"So long as the man continued walking round the chalk-spot, he was
walking around the spot - the moment he occupied its
very place, he could though, if he choose, he might, upon the
spot and by an independent act, turn about himself - no longer
turn round the spot, as the Moon could no longer turn round
the Earth from the moment she had trodden her underfoot.

"A gradual transition from progressive into rotatory motion, under
the circumstances of the case, is simply an impossibility, with-
out the man being transformed into the chalk-spot; or, speaking
of the Moon and the Earth, without the former being metamorphosed
into the latter."

(The Moon's Rotation On Her Axis, Von Gumpach – pgs 75 - 77)


Of course, if you can’t explain something, then do as Tim does next and claim that moon rotation is so mystical only an astronomer can understand it:

84323-moon – Post #26:

Ya, a few of the smarter teachers refused to buy the nonsense you were trying to sell them – GOOD FOR THEM!

Von Gumpach had something to day about that line of argumentation too:

---snip---
"§15. Goethe remarked of his own countrymen, that they
certainly understood the art how to render themselves unintelligible. We
fear that remark applies not to us Germans alone.

"Confused ideas are ever expressed in confused language; and a confused
mode of expression is always the sign of confused ideas. If we cannot make
ourselves intelligible to others, let us rest assured, that we are neither
intelligible to ourselves nor master of our subject ; and that the obscurity
in which we imagine that subject to be involved, is but the reflexion of our
own want of understanding.

"What can be more simple and easy of comprehension than rotatory motion, properly defined?"

(The Moon's Rotation On Her Axis, Von Gumpach – pg 30)

NO, the Earth has 365.25 polar axial *rotations* per year, and one (1) 360˚ *revolution* per year, and together there are 366.25 *apparent* sidereal rotations per year. I.e., the Earth has 365.25 *rotations* around an internal axis and one (1) 360˚ *revolution* around an exterior axis (the earth-moon barycenter.)

Over time the Sun & Moon can both slow the Earth's rotation (tidal braking), but I think in the sense you meant it, you're correct.

kdine,

Please get in touch with Gerald Kelleher (Oriel36) and convince
him of your ideas. Then get back to us. Good luck.

-- Jeff, in Minneapolis

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"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

How long does it take the Earth to make a single rotation?

Are you aware that the path of the moon around the sun is almost a circle--at no point is the path concave away from the sun. It is not a series of loops, it is not even a series of waves with peaks and troughs. Each motion can be analyzed from a lot of different points of view.

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If we would have a ball of yarn (very strong stuff) at the centre of the Sun and tie one end to a point at the equator of the moon, magically make the Earth gaseous so that the yarn can pass through it unimpeded, what happens to the ball in the centre of the sun? It unwinds, while it winds up around the equator of the moon. This would not happen if the moon would only revolve, keeping the same face towards the Sun all the time. The moon is revolving around the Earth and rotating around its own central axis. Otherwise, we would not be able to get the moon face shaking no in the heavens over one month. There is a nice movie showing the moon shake no, but I cannot find it at the moment.

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
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“A good scientist has freed himself of concepts and keeps his mind open to what is”
道德經, 二十七 (dào dé jīng, 27)

I would rather convince Steffani since she seemed to have come here with an open mind about it, and then was fed the silly "penny around the quarter" and the Porsche example for her troubles.


Since many websites erroneously claim that libration is caused by lunar rotation, libration often goes hand in hand with this discussion.

Does everyone agree that longitudinal libration is caused when the moon is facing its empty focus during each orbit and NOT caused by lunar polar axial rotation?

I saw in another thread here where one of the posters explained libration as a racecar going around an oval track with the observer standing in the center, but closer to one of the turns than the other, and from that vantage point you would tend to see the rear of the car when it was moving away from you, and the front as it traveled back in your direction.

I think that was a good analogy, and no one disputed that poster, so I assume we're all on the same page there?

If so, the only issue would be as to whether, or not, a race car running around the track is also *rotating* around its CM each lap.

I contend that a racecar traveling an oval track is ONLY *turning* around an exterior axis. I realize that after going in a 180˚half-lap the racecar will then be pointing in the oposite direction, but that is the result of a progressive turn around an exterior axis, just as the moon orbits around an exterior barycenter.

ORRERY

Have you ever seen an Earth-moon orrery? I've seen many, and there has NEVER been an orrery ever built that required gearing to *rotate* the moon-model around its internal axis.

I have a picture (and website) for an orrery that is so complex that it even moves its lunar nodes in an 18 year cycle, but that orrery's model-moon lacks any gearing to *rotate* it.

I can't imagine having so much free time to actually build an orrery, but people have been building orreries for centuries, and they NEVER rotate their model-moons – just no need to do so!

Now, if Gerald Kelleher (or anyone else) can demonstrate an orrery with a rotating moon that keeps the same face pointed to the Earth, then I'll be impressed!!!

Ken

I doubt if many would agree that.
The idea that a synchronous rotator always keeps the same face to the empty focus of its elliptical orbit is an approximation, which becomes less useful as the orbit becomes more elliptical, or as we require greater accuracy. It turns out that an object in an elliptical orbit sweeps out roughly equal angles around the empty focus while sweeping out equal areas around the gravitational focus in equal time periods. So a synchronous rotator keeps one face more or less aimed at the empty focus of its orbit. Emphasis on more or less.

(The "equal angles at the empty focus" approximation sits in the background of Ptolemy's equant theory of planetary motion, which is explained in mathematical detail here. It was successful for as long as we dealt with low eccentricities and limited measurement accuracy.)

Grant Hutchison

kdine,

There is no one on BAUT who can explain rotation like Gerald Kelleher,
and probably no one except you who can appreciate his explanations.
I urge you to find him and discuss your ideas with him. I believe he is
located in Australia. He was active in the Usenet sci.astro newsgroup
under the name Oriel36.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

From which reference point? I would say that the important frame of reference would be solar since a sidereal reference is often not very relevant and only tends to confuse people. E.g., due to sidereal confusion, about 75% of all websites are also confused about the length of day on Venus (as I recall, Venus has nearly 2 days per orbit.)

As for the Earth, even a 24-hour solar day can vary a tad due the Earth's elliptical orbit around the sun.

As a newbie I can't post URLs yet, but Johannes Von Gumpach was well aware of that back in 1856 and he has a moon-path diagram in his book consistent with what you're describing. Remind me later after a few more posts and I can post his diagram.

It's actually surprising how sophisticated they were about all this way back in 1856.

E.g., I was rather surprised that Von Gumpach even touched upon tidal braking. He never actually referred to it as "tidal braking" since that term was coined much later (perhaps by William Darwin), but he seemed aware of the process.

I also have some interesting "Letters to the Editor" from 1856, written to the Cambridge Times, which still publishes. What set off a round of "Letters to the Editor" back in 1856 was an article concerning an English 'Inspector of Schools', Sir Jelinger Symons – who was astonished by the moon rotation lunacy then being taught in English schools – and that generated quite a few impassioned responses to the Times, both pro & con.

I could post those 1856 letters here – their writing styles are somewhat archaic, but even so, the letters are clear enough and pretty much the same thing you'd hear on the topic today. So, not much has changed over the years, except silly examples like the Porsche analogy had to be updated – e.g., a lot of their analogies in 1856 instead used wagon wheels.


The history if this lunar rotation nonsense is rather interesting to see how it evolved and gained traction. I would say Sir William Herschel was one of the first to lay it out there. Newton was vague on the subject. Grant (GRANT, ROB., F.R.A.S., History of Physical Astronomy. London, 1852, 8vo.) eventually put Herschel's nonsense in his authoritative text, which sealed the deal.

Later, after the internet came into existence, bad ideas spread like weeds with a simple CC&P.

Ken

I'd asked this question in the thread in which your OP appears, before I merged the other two posts, but it is apparent what your answer is, and that you are aware of the difference in opinion between you and the mainstream. There are a lot of reasons for preferring the mainstream point of view.

The earth's sidereal rotation takes about 23hr 56min. There are some very small or very long wobbles, and a tiny bit of long-term slowing down, but the rate of that rotation is fairly constant.

That's not true of the "24 hour day"--I just checked Skymap and from my point of view, the sun took 24hr and 31sec to appear at the meridian on Dec 21 and Dec 22, whereas it will take 23hr 59min 42sec between Mar 21 and Mar 22. We'd have a lot of geophysical problems if the earth's rotation were really that inconstant.

We can do that experimentally with a can of tune too. Fix one end of the yarn at some fixed exterior point and the other end of the yarn to the tuna-can. Then, hold the tuna-can in your outstretched palm and spin the can and your body 360˚ around – hold the can a tad higher than your head so as to not interfere with it. If you do that, then the yarn will wrap around the tuna-can WITHOUT any rotation around its CM in your palm.

You are simply being confused by compound motions. The Earth revolves around the sun, but our moon both revolves around the sun as it revolves around the Earth.

I've seen those time-lapsed created movies many times before, but the moon is not physically shaking (much), so most of what you're seeing is instead optical illusions cause by the moon's elliptical orbit.

There are many illusions in astronomy, such as the outer planets reversing direction and gravity lensing, so what you THINK you see is not necessarily the reality.

Ken

Methinks you are the one who does not understand compound motions. With repsect to that center the can of tuna is rotating, even though your hand "does not move". Any civilization living on the surface of the tuna can will see a whole 360 degree panorama of the room you are standing in. It really gets confusing when 1 revolution and 1 rotation have the same period.

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道德經, 二十七 (dào dé jīng, 27)

Naturally one of the tests to see whether the moon is rotating is looking at the coriolis force. At the moment I have not found any papers discussing this, but I will keep looking.

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
He who is good at counting, uses no counting tools
“A good scientist has freed himself of concepts and keeps his mind open to what is”
道德經, 二十七 (dào dé jīng, 27)

As far as I'm concerned, this is the important thing. Do we agree that the star field would swirl around you on the moon? Anything beyond that is just a question of how terms are defined. AFAIK, if you are an inhabitant of the moon and you see the stars moving around you, then you are rotating. But if somebody wants to say revolving, I don't have a problem with that either. It's kind of like arguing over whether plants "eat" nutrients. Well, technically they use osmosis to draw them in, so it's not really "eating," which perhaps requires a digestive tract. But for certain purposes it's not wrong to say that. The main point to understand is that even though we see the same side of the moon at all times, an inhabitant of the moon would still see the stars spinning overhead.

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The best thought experiment I've encountered that shows that the Moon does indeed rotate is this:

Imagine that the Moon rotates once every 24 hours. There is no such thing as a far side, and at full Moon you can just about see every single part of its surface over the course of an entire night.

Now slow the rotation by half. You thus have roughly 14 lunar days per month, instead of 28. Is the Moon still rotating?

Now continue slowing it. At one quarter the original rotation rate, we have about seven lunar days per month. At one fourteenth, there are two lunar days per month. Is the Moon still rotating?

Now slow it to one twenty-eighth of its original value. That's 1/28 - a non-zero number. As in the Moon is still rotating. But now we have our own real world situation in which the Moon presents the same face to us (neglecting libration) as it orbits around us.

You can keep going, though. Slow it down to 1/56th of the rate at the start of this example. You now have one lunar day per two orbits. You once again get to see the entire surface over time, as it shows different hemispheres at the same point in alternate orbits. And yet, it rotates.

You can keep slowing it down to an arbitrarily small ratio of the original rotation rate, but the only case in which is presents one face continuously to us is when the non-zero rotation matches the orbital period.

You can then imagine stopping the rotation completely. Will it suddenly start only showing one face to us again, or will it show us every side over a complete orbital period?

The moon revolution is closer to 27 days than 28

Imagine the moon were set, with many tons of superglue, into the rim of a wheel whose hub was at the barycentre. throughout the revolution of the wheel, the moon would remain still in relation to the rim it's set in.

So the moon doesn't 'rotate on it's own axis', it 'revolves' around the barycentres axis, at the same rate it orbits it.

Therefore the moon revolves, but does not spin or rotate on it's own axis.

It does both. It does rotate about its own axis, but the axis moves in a circle.

Take a meter stick and hold it straight down, then rapidly bring it up horizontal. It rotates about its end, near your hands, obviously. But the center of it describes a circle, and the stick rotates about that as well--if you let it go as soon as it is horizontal, the center flies straight up, and the stick continues to rotate about it.

Hmmm, maybe I should try that first.

Mind you don't poke your observing eye out.
Seems to me the net effect is that it doesn't spin on it's own axis. There is redundancy in your description.

In fact it wobbles backwards and forwards in librations. If it was spinning, how would it stop and go the other way?

Your vector addition is faulty.

No, your vector addition is faulty.

The Moon is spinning and it does not stop and go the other way.

The Moon rotates at a constant rate, but orbits the Earth at a
varying speed, due to the varying distance. So a feature near
the center of the Moon's face is to the east of center when the
Moon is approaching apogee, and to the west of center when it
is approaching perigee.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

I bow to your superior knowledge. Please could you explain how my thought experiment fails so I can understand better. Are the vectors relative to a certain frame of reference?
Thanks

I'm confused. What about the phases of the Moon? Aren't they consistent with the rotation of the Moon relative to the Sun, roughly every month?

It rotates so slowly, there may be no data available.
The pseudoforces are, of course, key to this argument. Although we may not yet have been able to measure them on the Moon, they do have readily measurable effects on other synchronous moons, particularly those close to the Roche limit. Simple tidal distortion produces an equilibrium shape that is a prolate spheroid, with a long axis (aligned radially) and two short axes of equal length. Add the synchronous rotation, however, and the equilibrium shape is triaxial: short polar axis, long radial axis, and an intermediate axis at right angles to these. And we observe the latter, rather than the former.

Another way to think about the rotational pseudoforces is to realize that the residuals look the same no matter where we place our rotation axis. So we can imagine the moon rotating around an external axis at the centre of its orbit, or we can decompose the motion into a uniform revolution and a superimposed rotation around an axis in the centre of the moon. The pseudoforces sum out exactly the same way.

(Tusenfem, I realize you know all this already. My comments are general.)

Grant Hutchison