Does the Moon Rotate?

[nicho247]

It's absolute.

Hi Chrimony,

I agree, the issue at hand is more along the lines of "does the moon rotate absolutely?" As I have shown (in hypotheticals) above that depending on perspective, there is or isn't rotation relative to the observer.

Specific to your link (wiki), the opening statement is "For the concept of absolute rotation to be scientifically meaningful, it must be measurable."

I think you are onto the issue at hand, however the specific methods noted by the wiki are the following...

1: Mach's principle : I don't think this is applicable, though interesting, we are fully acclimated. A specific measurement?
2: Rotating bucket : Has someone rotated a bucket of water on the moon?
3: Rotating sphere's : Has someone attached an object to the moon with a spring and measured the tension on this spring?
4: Figure of earth : This may work with fluids or gases, but solids? Also, is this even conclusive?
5: Sagnac Experiment : This entire bullet is questionable "Earth will rotate once every rotation of the Earth when using stars as a stationary reference point. Rotation was thus concluded to be absolute rather than relative." This seems relative not absolute. How far away do you have to be before you become an absolute reference point?

Do you have a measurable effect? Please elaborate if so.

Easy. The Moon would not show libration in longitude, as viewed from the Earth, but it does. It's been mentioned several times already, and nobody who argues that the Moon does not rotate has given a satisfactory explanation for it.

Also, from wikipedia regarding libration..."Libration in longitude results from the eccentricity of the Moon's orbit around Earth"

How is this specific to the moon's axial rotation?

Also from wikipedia regarding libartion... "the Moon's rotation sometimes leads and sometimes lags its orbital position."

Couldn't this be confused with the effect of the earth rotating while viewing the moon?

Nick

[nicho247]

This sounds quasi-relativistic. You're overthinking this, friend In this case it is relative to another body in space, not an observer. We're not discussing spacetime. In other words, you're in error.

The Moon rises and sets anyway. You're again overcomplicating this.

Without the Sun for the Earth to orbit then it would not be orbiting the Sun.

The geometric "Einstein's elevator" principle is far-afield and has nothing to do with this topic.

Hi Viscount,

I am a little disappointed. This is more hand-waving than anything.

The Moon would sit in space orbiting nothing, with no visible axial spin. In the case of the Moon today orbiting Earth in "tidal lock", the orbit itself creates the spin. Without the orbit there is no spin.

So....there would be no moon. Is it possible for a body to orbit another body where the axial spin is less than its orbital period? I'm thinking Venus. How slow can the axial rotation be for there to be an orbit? (Just taking your example to the extreme).

What some here are not accepting is that the orbit itself around the Earth moves the Moon around on its axis. The orbit is the actual mechanism of the axial rotation. The orbit itself is a type of spin upon the Moon. In this case it is 1:1.

For example, if you were to close the orbit of the Moon down upon the Earth until the Moon were inside the Earth's body and directly "orbiting" the "core" by becoming the Earth's core (if that were possible), it would appear as if it were spinning around like a top. Therefore the Moon rotates on an axis.

To add, this principle is reciprocal. An axial rotation is also a type of an orbit--the object orbiting itself.

I like this idea, mostly because I was thinking the exact type of example, however I reached a different conclusion. Since the near side of the moon is fixed, if you were to reduce the distance between the earth and the moon and keep all other variables constant, I do not believe the moon would be spinning like a top, but in fact be traveling quickly along the earth, similar to a car or airplane.

In fact, for example, if I am running on the earth, and my speed, size, and distance from the earth were increased, how is this different from the moon? The near-size would be my feet.

Nick

[viscount aero]

This sounds quasi-relativistic. You're overthinking this, friend In this case it is relative to another body in space, not an observer. We're not discussing spacetime. In other words, you're in error.

The Moon rises and sets anyway. You're again overcomplicating this.

Without the Sun for the Earth to orbit then it would not be orbiting the Sun.

The geometric "Einstein's elevator" principle is far-afield and has nothing to do with this topic.

Hi Viscount,

I am a little disappointed. This is more hand-waving than anything.

I addressed your questions.

The Moon would sit in space orbiting nothing, with no visible axial spin. In the case of the Moon today orbiting Earth in "tidal lock", the orbit itself creates the spin. Without the orbit there is no spin.

So....there would be no moon.

There would be no moon? Huh?

My reply was "The Moon would sit in space orbiting nothing, with no visible axial spin." How do you get "no Moon" from that?

Is it possible for a body to orbit another body where the axial spin is less than its orbital period? I'm thinking Venus. How slow can the axial rotation be for there to be an orbit? (Just taking your example to the extreme).

I think you answered your own question

Copied from a post of mine from the previous page:

Rotation axially does not cease just because the body is tidally locked. Axial rotation exists:

• as in the Earth as it spins axially faster each day than its year.
• tidal locking of the Moon as it spins 1:1 with its "year" around the Earth.
• as in Venus as it spins axially slower than its year.

In all cases there is axial rotation. Tidal locking does not cease this activity. It creates a 1:1 relationship of orbit to axial spin.

The orbit = axial rotation

What some here are not accepting is that the orbit itself around the Earth moves the Moon around on its axis. The orbit is the actual mechanism of the axial rotation. The orbit itself is a type of spin upon the Moon. In this case it is 1:1.

For example, if you were to close the orbit of the Moon down upon the Earth until the Moon were inside the Earth's body and directly "orbiting" the "core" by becoming the Earth's core (if that were possible), it would appear as if it were spinning around like a top. Therefore the Moon rotates on an axis.

To add, this principle is reciprocal. An axial rotation is also a type of an orbit--the object orbiting itself.

I like this idea, mostly because I was thinking the exact type of example, however I reached a different conclusion. Since the near side of the moon is fixed, if you were to reduce the distance between the earth and the moon and keep all other variables constant, I do not believe the moon would be spinning like a top, but in fact be traveling quickly along the earth, similar to a car or airplane.

Ok good--we're getting somewhere, bit by bit But perhaps you didn't fully read or understand my post. I concluded with the Moon being inside the Earth itself, in the very center. The Moon at this position would be visibly spinning.

In fact, for example, if I am running on the earth, and my speed, size, and distance from the earth were increased, how is this different from the moon? The near-size would be my feet.

Nick

I don't really understand you. What you stated above doesn't describe what I was explaining.

If the Moon were to spiral into the Earth at each orbit, eventually going inside the Earth to its very center, the "orbit" would become so constrained that it would be visibly spinning (orbiting) "around itself"--which is what an axial rotation is. Does that illustrate what I said more clearly?

[nicho247]

The Moon would sit in space orbiting nothing, with no visible axial spin. In the case of the Moon today orbiting Earth in "tidal lock", the orbit itself creates the spin. Without the orbit there is no spin.

So....there would be no moon.

There would be no moon? Huh?

My reply was "The Moon would sit in space orbiting nothing, with no visible axial spin." How do you get "no Moon" from that?

Hi Viscount,

I apologize for the short response, from a different viewpoint, I can see how you would not read into it as I had implied. An elaboration...from the beginning....

"Can you please help me visualize what the moon would do differently for the axial rotation to be zero?"

Yes. The Moon would sit in space orbiting nothing, with no visible axial spin. In the case of the Moon today orbiting Earth in "tidal lock", the orbit itself creates the spin. Without the orbit there is no spin.

This is relative to the viewpoint from earth, so if the moon is orbiting nothing, from earth, there would be no moon visible to the observer (no moon). It is the conclusion of your answer. If this is not what you had intended, please clarify.

I, in turn, have clarified my question.

"Can you please help me visualize what the moon would do differently for the axial rotation to be zero as seen from earth?"

Is it possible for a body to orbit another body where the axial spin is less than its orbital period? I'm thinking Venus. How slow can the axial rotation be for there to be an orbit? (Just taking your example to the extreme).

I think you answered your own question

Well, the first was more rhetorical, as it is a feasibility test. Concerning the second, any thoughts?

Copied from a post of mine from the previous page:

Rotation axially does not cease just because the body is tidally locked. Axial rotation exists:

• as in the Earth as it spins axially faster each day than its year.
• tidal locking of the Moon as it spins 1:1 with its "year" around the Earth.
• as in Venus as it spins axially slower than its year.

In all cases there is axial rotation. Tidal locking does not cease this activity. It creates a 1:1 relationship of orbit to axial spin.

The orbit = axial rotation

I'll have to go back and read in further detail, as these may have already been addressed. Off-the-cuff, it reads as just because something does not appear to be rotating does not mean it is not rotating. I agree, and this goes the point of relative vs absolute rotation. However, I do not see a differentiation between the two.

Ok good--we're getting somewhere, bit by bit But perhaps you didn't fully read or understand my post. I concluded with the Moon being inside the Earth itself, in the very center. The Moon at this position would be visibly spinning.

I don't think I understand this idea fully, mostly because the lack of description, not the degree of abstraction. Is the center of the moon at the center of the earth? Is the moon's body touching the earths core (like two billiard balls)? Is it still orbiting? Maybe a visualization to help aid your point?

If the Moon were to spiral into the Earth at each orbit, eventually going inside the Earth to its very center, the "orbit" would become so constrained that it would be visibly spinning (orbiting) "around itself"--which is what an axial rotation is. Does that illustrate what I said more clearly?

Unfortunately, no. If you are adamant, please go on.

Nick

[viscount aero]

The Moon would sit in space orbiting nothing, with no visible axial spin. In the case of the Moon today orbiting Earth in "tidal lock", the orbit itself creates the spin. Without the orbit there is no spin.

So....there would be no moon.

There would be no moon? Huh?

My reply was "The Moon would sit in space orbiting nothing, with no visible axial spin." How do you get "no Moon" from that?

Hi Viscount,

I apologize for the short response, from a different viewpoint, I can see how you would not read into it as I had implied. An elaboration...from the beginning....

"Can you please help me visualize what the moon would do differently for the axial rotation to be zero?"

Yes. The Moon would sit in space orbiting nothing, with no visible axial spin. In the case of the Moon today orbiting Earth in "tidal lock", the orbit itself creates the spin. Without the orbit there is no spin.

This is relative to the viewpoint from earth, so if the moon is orbiting nothing, from earth, there would be no moon visible to the observer (no moon). It is the conclusion of your answer. If this is not what you had intended, please clarify.

I, in turn, have clarified my question.

"Can you please help me visualize what the moon would do differently for the axial rotation to be zero as seen from earth?"

Is it possible for a body to orbit another body where the axial spin is less than its orbital period? I'm thinking Venus. How slow can the axial rotation be for there to be an orbit? (Just taking your example to the extreme).

I think you answered your own question

Well, the first was more rhetorical, as it is a feasibility test. Concerning the second, any thoughts?

Copied from a post of mine from the previous page:

Rotation axially does not cease just because the body is tidally locked. Axial rotation exists:

• as in the Earth as it spins axially faster each day than its year.
• tidal locking of the Moon as it spins 1:1 with its "year" around the Earth.
• as in Venus as it spins axially slower than its year.

In all cases there is axial rotation. Tidal locking does not cease this activity. It creates a 1:1 relationship of orbit to axial spin.

The orbit = axial rotation

I'll have to go back and read in further detail, as these may have already been addressed. Off-the-cuff, it reads as just because something does not appear to be rotating does not mean it is not rotating. I agree, and this goes the point of relative vs absolute rotation. However, I do not see a differentiation between the two.

Ok good--we're getting somewhere, bit by bit But perhaps you didn't fully read or understand my post. I concluded with the Moon being inside the Earth itself, in the very center. The Moon at this position would be visibly spinning.

I don't think I understand this idea fully, mostly because the lack of description, not the degree of abstraction. Is the center of the moon at the center of the earth? Is the moon's body touching the earths core (like two billiard balls)? Is it still orbiting? Maybe a visualization to help aid your point?

If the Moon were to spiral into the Earth at each orbit, eventually going inside the Earth to its very center, the "orbit" would become so constrained that it would be visibly spinning (orbiting) "around itself"--which is what an axial rotation is. Does that illustrate what I said more clearly?

Unfortunately, no. If you are adamant, please go on.

Nick

Nick, thanks for your replies. I'll have to do some drawings then. I'll do that soon. You seem to see some of my points but don't see others. The idea is staggeringly simple so I somewhat don't understand why you can't see it. But you're not me. I will draw it

[chrimony]

Chrimony, I agree with you and have agreed with you. But maybe explain for the forum why libration matters and what it is. And why it proves axial rotation. I don't need to invoke libration to prove it but please expound on your position

Is that a joke? Because the problem is I have explained and expounded repeatedly, and then it's ignored and posters like jtb repeat the rigid body analogy without any answer for it. And then somebody new comes on the topic and the discussion starts all over again.

Previous posts:
Sep 30, 2013

Also, if the moon rotated around its own axis, a rotation rate should be able to be discerned when we track the moon across the sky, even if it is just a slight rotation.

We can, via libration. Because the orbit of the moon is elliptical, its orbital velocity speeds up and down, which results in a difference between the moon's orbital velocity and rotation. This is detected as libration in longitude, which means we can see more of the left and right sides, as if it was wobbling slightly back and forth in its orbit.

Oct 05, 2013

If you took the time to understand libration (what finally convinced D_Archer), you would know that we can already perceive this rotation. The moon's rotation is constant, but its orbital velocity around the Earth is not.

Oct 30, 2013

You have ignored that bodies freely rotate in space, so that to maintain the same face to the Earth while orbiting it, the moon must rotate. You have also ignored liberation, which clearly shows that the moon is not always facing "in the same direction" from a stationary Earth point of view.

Oct 30, 2013

Bodies in space rotate freely, unlike a ball on a string. Try and get your ball to show a different face while twirling it around. Yet we have no problems spinning objects in space at arbitrary rates as they orbit. And yet again, libration shows the moon is rotating and not fixed to show the same face to Earth. If you can't answer what causes the libration effect (if not rotation), yet still argue the moon isn't rotating about its axis freely like any other object in space, you are arguing out of willful ignorance.

Nov 01, 2013

Liberation is oscillation, not rotation, due to orbits not being perfect circles.

You haven't given a mechanism to explain the oscillation. Are you claiming that the moon is physically oscillating back and forth? Why does not orbiting in a perfect circle cause the moon to oscillate?

Nov 01, 2013

Chrimony, I can explain rotation but not libration.

Nov 02, 2013

...on the one hand we have Newtonian mechanics, satellites spinning in space as they orbit, and the Earth, Moon, and other planets spinning in their orbits around the Sun, calculated libration effects, and tidal locking, versus... pretty much nothing but busted analogies and "visualizations".

Nov 18, 2013

There is no rod in space connecting the Earth to the Moon. It's gravity and Newtonian mechanics. The Earth orbits around the Sun but it doesn't always show the same face to the Sun. Man-made satellites can spin at any rotation we want. And finally, the Moon does not always show the same face to the Earth, as you can see via libration in longitude . All this has been gone over many times in this thread.

Come up with a model that calculates the libration that we see and matches other orbital mechanics of the solar system, and you can be taken seriously.

Nov 21, 2013

The rod analogy is broken because no matter what motion you put upon the rod, the rigidly attached "moon" will always keep the same position with respect to the rod. This doesn't match what we see with objects in space or something as simple as the bowls and water experiment described in this thread (which you should read instead of repeating the same arguments).

...

(Libration) is not a small anomaly. It is quite significant and any amateur could verify it for themselves by taking pictures of the moon over time. It's the definitive proof which perspective is right. It is the difference between armchair philosophizing and science.

Nov 22, 2013

I think some posters are having a hard time visualizing Libration. This animation demos it very well:
https://www.youtube.com/watch?v=BTlCLgWrws0

Although it is interesting, I would drop the libration issue as it only confuses this topic. It has little to do with the general idea behind the Moon's tidally locked rotation about its axis.

On the contrary, libration is the definitive, quantitative proof that the Moon is indeed rotating and does not always show the same face to the Earth. It is what convinced D_Archer to change his mind and accept that the Moon is rotating. It also isn't that hard to understand. If anything, tidal locking is the more confusing and tangential issue.

But thanks for the video link, it is a good illustration.

Nov 22, 2013

Libration in longitude addresses the claim that the orbit and the rotation are perfectly synchronized to always show the same face to the Earth, as in a fixed rod. Because the orbit of the Moon about the Earth is not a perfect circle, it speeds up and slows down (slower when farther away, faster when closer). However, since the Moon is in fact rotating (spinning) at a constant speed, this causes a desync between the orbital velocity and rotation rate. The apparent wobbling back and forth from the Earth's perspective is an illusion. If you were standing on the Moon you would see the stars circling around you at a fixed rate.

Nov 29, 2013

There's only one constant spin for the Moon. The mistake you are making is that you assume for an object to orbit in space that it already must be spinning.

Dec 05, 2013

Libration in longitude exactly demonstrates that the Moon is not locked in it's orbit as a rigid body would be. It shows that the moon's spin is constant and independent of it's orbital velocity, which changes as it is either farther or closer.

...

The math for the standard model of libration in longitude should be relatively simple to a good approximation. It's a two-body Newtonian gravity problem. If there was something wrong with the math, astronomers would have found it a long time ago.

Aug 29, 2014

So (Tesla) has no explanation for why the bodies would behave as if they are rigidly connected when they are clearly not, and he has no explanation as to why they behave as if they are not rigidly connected as shown by libration in longitude. In the meantime, basic Newtonian mechanics explains it just fine. They are not rigidly connected, and the Moon is rotating.

Aug 29, 2014

Third, even if it were magnetism and not tidal locking keeping the synchronous rotation, it doesn't prevent libration in longitude (mentioned several times in this thread) during the lunar orbit around the Earth. In other words, the face of the Moon that we see from Earth oscillates slightly back and forth based on where the Moon is in its orbit around the Earth.

Aug 30, 2014

Also, keep in mind that there are three types of lunar librations. I have been focusing on libration in longitude because it shows that the Moon's spin is constant, while it's orbital velocity about the Earth is not because the Moon's orbit about the Earth is elliptical and not a perfect circle.

One thing all three librations have in common is that the Moon's face, as viewed from Earth, appears to oscillate. If you were standing on the Moon, however, and watching the fixed stars rotate overhead, there would be no oscillation and hence no axial precession.

[chrimony]

I agree, the issue at hand is more along the lines of "does the moon rotate absolutely?" As I have shown (in hypotheticals) above that depending on perspective, there is or isn't rotation relative to the observer.

Specific to your link (wiki), the opening statement is "For the concept of absolute rotation to be scientifically meaningful, it must be measurable."
(...)
2: Rotating bucket : Has someone rotated a bucket of water on the moon?

The Wikipedia link was a general answer (not specific to the Moon) regarding your general hypothesis that rotation was relative. I'm sure that somebody, at some point in time, has rotated a bucket of water on the Earth or done any number of small-scale experiments that illustrate rotation is absolute. So perhaps you can acknowledge the point that absolute rotation does exist and we can verify it for the Moon.

How is (libration in longitude) specific to the moon's axial rotation?

Describe and calculate the forces and the resulting motions that explain libration in longitude without the Moon rotating on its axis.

Also from wikipedia regarding libartion... "the Moon's rotation sometimes leads and sometimes lags its orbital position."

Couldn't this be confused with the effect of the earth rotating while viewing the moon?

No, because that effect is already accounted for in diurnal libration, described in the mentioned Wikipedia page. It's the difference between a monthly effect (libration in latitude) vs a daily effect (diurnal libration).

[viscount aero]

viscount aero wrote: I think some posters are having a hard time visualizing Libration. This animation demos it very well:
https://www.youtube.com/watch?v=BTlCLgWrws0

Although it is interesting, I would drop the libration issue as it only confuses this topic. It has little to do with the general idea behind the Moon's tidally locked rotation about its axis.


chrimony wrote: On the contrary, libration is the definitive, quantitative proof that the Moon is indeed rotating and does not always show the same face to the Earth. It is what convinced D_Archer to change his mind and accept that the Moon is rotating. It also isn't that hard to understand. If anything, tidal locking is the more confusing and tangential issue.

But thanks for the video link, it is a good illustration.

Chrimony, I do understand libration now. It is a consequence of its changing orbital velocity relative to its axial spin as it orbits. Thank you for clarifying why it is relevant with your long recap. I was initially misunderstanding why it was relevant. I now see it as absolute visual proof of axial spin of the Moon.

[nicho247]

Hi Chrimony,

Thank you for acknowledging my questions and comments. I can see from your reply that this issue has gone around and around, orbiting the issue of rotation.

My argument or point of view is simply while on the earth the moon is not rotating relative to the earth. It may or may not have absolute rotation, I don't know, it does have rotation relative to other bodies like the sun or mars, but not the earth.

Therefore, the title of this thread should be changed to does the moon rotate relative to the earth or does the moon have absolute rotation, as these are two different statements/concepts.

Libration is a new concept for me, as this was not something I had ever heard nor studied my education. I am not as well versed on this concept as others, but am learning.

In this awesome "libration of the moon" youtube video from one of your quotes....

https://www.youtube.com/watch?v=BTlCLgWrws0

The "libration" effects appear to be from it's orbit, not rotation, because it is elliptical. Also, quoting from the submitter of the video "The two horizons don't match because of the libration in longitude, due to the varying orbital speed of the Moon, and in latitude, due to the Moon inclination with respect to its orbit "

The submitter is stated that the libration in longitude is a result in the elliptical orbit, not it's axial rotation. Also, to quote wiki, since you have done so, the bullet on libration in longitude states "Libration in longitude results from the eccentricity of the Moon's orbit around Earth"

Describe and calculate the forces and the resulting motions that explain libration in longitude without the Moon rotating on its axis.

Well, I argue the observable evidence is the moon isn't rotating on it's axis relative to us on earth (evidence is the near-side of the moon). To address the libration in longitude, as the youtube link and wiki imply, if the elliptical orbit of the moon was changed to be circular, the libration in longitude would vanish, since this is stated as the cause. The moon would be appear the same with less "rocking" or "size" differences since the cause has been removed. There would be no change in the perceived near side, since the moon doesn't have axial rotation relative to earth. However, we would still have "Diurnal libration" because the earth is rotating.

Now, for one of my examples...the international space station, ISS, orbits the earth, and has a near side to the earth for simplicity and testing. Limiting our discussion to just orbit, rotation (and possible libration), I argue the moon is not rotating about it's axis relative to earth, also since the ISS orbits earth, and has a near side, the ISS is not rotating about its axis relative to earth.

Do you believe the ISS is rotating about its axis relative to earth?

For a hint, the wiki page does not list axial rotation in its station statistics : http://en.wikipedia.org/wiki/Internatio ... ce_Station

Nick

[chrimony]

My argument or point of view is simply while on the earth the moon is not rotating relative to the earth. It may or may not have absolute rotation, I don't know, it does have rotation relative to other bodies like the sun or mars, but not the earth.

You started with a hypothesis that rotation was relative. I argued that in my previous two posts that it is absolute, and you have not brought a counter to that argument in your most recent post. There may be a philosophical argument about the nature of this principle, but for all practical purposes we know that rotation is testable and linked to the fixed stars.

Libration is a new concept for me, as this was not something I had ever heard nor studied my education. I am not as well versed on this concept as others, but am learning.

I wasn't even aware of it before I came upon this topic and looked into the issue. However, the concept isn't difficult if you understand Newtonian mechanics.

The submitter is stated that the libration in longitude is a result in the elliptical orbit, not it's axial rotation. Also, to quote wiki, since you have done so, the bullet on libration in longitude states "Libration in longitude results from the eccentricity of the Moon's orbit around Earth"

It's a combination of a constant rotation and a varying orbital velocity. You can't explain why the Moon appears to be oscillating back and forth without the rotation.

Describe and calculate the forces and the resulting motions that explain libration in longitude without the Moon rotating on its axis.

Well, I argue the observable evidence is the moon isn't rotating on it's axis relative to us on earth (evidence is the near-side of the moon). To address the libration in longitude, as the youtube link and wiki imply, if the elliptical orbit of the moon was changed to be circular, the libration in longitude would vanish, since this is stated as the cause.

You dodged the question by changing the orbit from elliptical to circular. The point of science is to explain what we see using natural laws. In this case, we have Newtonian mechanics. Describe the actual situation at hand as requested. It's easy to do so with a rotating Moon and a gravitational orbit.

Now, for one of my examples...the international space station, ISS, orbits the earth, and has a near side to the earth for simplicity and testing. Limiting our discussion to just orbit, rotation (and possible libration), I argue the moon is not rotating about it's axis relative to earth, also since the ISS orbits earth, and has a near side, the ISS is not rotating about its axis relative to earth.

Do you believe the ISS is rotating about its axis relative to earth?

I believe this "relative to the earth" is a pointless question of fantasy physics, per the start of my post. It is absolutely rotating.

For a hint, the wiki page does not list axial rotation in its station statistics : http://en.wikipedia.org/wiki/Internatio ... ce_Station

Meaningless. If they wanted to list one, they could.

[Aardwolf]

For a hint, the wiki page does not list axial rotation in its station statistics : http://en.wikipedia.org/wiki/Internatio ... ce_Station

No, but it does mention the control momentum gyroscopes which ensure the station maintains attitude control by effectively rotating it once every orbit.

[nicho247]

You started with a hypothesis that rotation was relative. I argued that in my previous two posts that it is absolute, and you have not brought a counter to that argument in your most recent post. There may be a philosophical argument about the nature of this principle, but for all practical purposes we know that rotation is testable and linked to the fixed stars.

Hi Chrimony,

Correct. I haven't made an opinion about whether the moon has absolute rotation. I have provided a few examples from wikipedia where the notion about absolutes is only meaningful if it can be measured. Providing a measurement "libration" from our frame reference on earth viewing the moon is a relative measurement, not an absolute one. So you cannot use it as conclusive evidence. Also, I have shown your own links regarding libration do not support your statements.

The submitter is stated that the libration in longitude is a result in the elliptical orbit, not it's axial rotation. Also, to quote wiki, since you have done so, the bullet on libration in longitude states "Libration in longitude results from the eccentricity of the Moon's orbit around Earth"

It's a combination of a constant rotation and a varying orbital velocity. You can't explain why the Moon appears to be oscillating back and forth without the rotation.

Your links don't state this. They state "Libration in longitude results from the eccentricity of the Moon's orbit around Earth"

Describe the actual situation at hand as requested.

Your links state the libration in longitude is caused by the elliptical orbit. Changing the axial rotation would have no effect.

I believe this "relative to the earth" is a pointless question of fantasy physics, per the start of my post. It is absolutely rotating.

Sigh, disappointing. Changing the subject to absolute rotation, as requested -

The few from your link (wikipedia), where libration isn't mentioned, I covered in short list where it was clear none of this has been done or is feasible. Once again...."For the concept of absolute rotation to be scientifically meaningful, it must be measurable. In other words, can one decide whether an observed object is rotating or if it is you, the observer that is rotating?"

Has the moon's absolute rotation be measured?

Nick

[viscount aero]

Has the moon's absolute rotation be measured?

Nick

Yes. Go out and look at it. You can see it transit the sky. It is orbiting with the same face to Earth. That means it is rotating, too. The orbit is the rotation.

[chrimony]

Providing a measurement "libration" from our frame reference on earth viewing the moon is a relative measurement, not an absolute one. So you cannot use it as conclusive evidence.

The challenge, which you or nobody else has met, is to describe libration using forces and resulting motions that make sense without the Moon rotating, regardless of the frame of reference.

Also, I have shown your own links regarding libration do not support your statements.

No, you relied on a terse statement without actually understanding what was being displayed in the video. Try these instead:

http://encyclopedia2.thefreedictionary. ... f+the+Moon : "Optical libration in longitude occurs because the moon revolves about the earth nonuniformly while it rotates about its axis at a constant angular velocity."

http://earthsky.org/space/how-much-of-t ... #longitude : " Libration in longitude is the moon’s east-west wobble. This sort of libration is a product of the moon’s elliptical (elongated) orbit. Although the moon’s rotation, or spin, goes at a nearly constant rate, its orbital speed varies, going fastest at perigee (moon’s closest point to Earth) and slowest at apogee (moon’s farthest point from Earth)."

http://www.phy6.org/stargaze/Smoon4.htm : "The rotation rate of the Moon is pretty steady. However, the orbiting motion of the Moon is not steady--at some times it advances faster than average, some times it is slower."

[GaryN]

Teslas explanation:
The Illusion of the Axial Rotation of the Moon.
http://www.teslauniverse.com/nikola-tes ... -illusions