Does the Moon Rotate?

[Armand]

I think it is safe to say that the Moon does rotate relative to the Sun.

The question is: Why does the Moon not rotate relative to the Earth? or put another way

What keeps the Moon in synchronous rotation with the Earth?



Is it just a coincidence that the Moon's axial rotation precisely matches its orbital cycle around the Earth?




It's almost as if the Moon was tethered to the Earth by some invisible cord...



Which is exactly what I think is happening... I believe the Moon's surface (either the Dark or Light Side) is magnetically tethered to the Earth's magnetic field, and that it is that magnetic link which keeps the Light Side of the Moon constantly facing the Earth (and the Dark Side constantly facing away).

Back in the 60's I was very interested in the US Space Program. I remember reading one particular report from the Apollo 11 Astronauts where, during their orbital swing around the Dark Side of the Moon, something seemed to grab the Command Module and shake it. They said it felt like they had hit a pot hole in the road - 60 miles above the surface of the Moon...

Subsequent mapping of the Moon indicates that there is a magnetic anomaly on the Dark Side of the Moon.



I believe that it is that magnetic anomaly on the Moon (possibly the result of a large meteor collision) that magnetically locks the Moon in synchronous rotation with the Earth...

Of course, I suppose it could be a coincidence - the orbital cycle and axial rotation just happen to synch up...

[viscount aero]

Of course, I suppose it could be a coincidence - the orbital cycle and axial rotation just happen to synch up...

Yes you are correct, coincidence or not. There is a 1:1 relationship there.

[chrimony]

I think it is safe to say that the Moon does rotate relative to the Sun.

It's also safe to say the Moon does rotate relative to the distance stars and galaxies, which is the classical definition to know whether something is rotating or not.

What keeps the Moon in synchronous rotation with the Earth?

As has already been mentioned in this very long thread, tidal locking.

It's almost as if the Moon was tethered to the Earth by some invisible cord...

Which is exactly what I think is happening... I believe the Moon's surface (either the Dark or Light Side) is magnetically tethered to the Earth's magnetic field, and that it is that magnetic link which keeps the Light Side of the Moon constantly facing the Earth (and the Dark Side constantly facing away).

First off, it's the far side and near side. There is no fixed light side or dark side. Second, it's not just the Earth's moon that exhibits synchronous rotation with its host planet, as other moons in the solar system exhibit the same behavior. 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.

[viscount aero]

I think it is safe to say that the Moon does rotate relative to the Sun.

It's also safe to say the Moon does rotate relative to the distance stars and galaxies, which is the classical definition to know whether something is rotating or not.

What keeps the Moon in synchronous rotation with the Earth?

As has already been mentioned in this very long thread, tidal locking.

It's almost as if the Moon was tethered to the Earth by some invisible cord...

Which is exactly what I think is happening... I believe the Moon's surface (either the Dark or Light Side) is magnetically tethered to the Earth's magnetic field, and that it is that magnetic link which keeps the Light Side of the Moon constantly facing the Earth (and the Dark Side constantly facing away).

First off, it's the far side and near side. There is no fixed light side or dark side. Second, it's not just the Earth's moon that exhibits synchronous rotation with its host planet, as other moons in the solar system exhibit the same behavior. 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.

I must agree with chrimony.

Even if the Moon were glued down to a lazy susan, like jtb's horse idea, it would still axially rotate. But that is only a diagramatic example. There is libration which proves it is not actually fixed to a celestial lazy susan.

Although it is being ignored constantly, the spiral example that I explained in prior posts proves that there is axial rotation. 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.

I know that jtb will never accept this but this post is for other readers who want more clarification. And read chrimony's posts about it.

[D_Archer]

The moon rotates around the earth, i think we can all agree on that (in a limited sense since motion proper is helical).

The moon however does not rotate about its own axis.

Imagine the moon is locked in stone, it can not move, now this stone rotates around the earth. The moon will always show the same face to the earth but will never rotate around its own axis since it is 'locked in' stone. However it is possible to imagine a moon axis and locking the axis to the perceivers position, the moon is then rotating around it with one full rotation, but this "axial rotation" is an illusion.

Mainstream "tidal locking" is flawed and does not explain the orbit of the moon, so we need something better.

Regards,
Daniel

[Sparky]

Do not most things spin?

[Armand]

If there is a force that tethers/links/locks the Moon's surface to the Earth, it must be invisible...

Magnetic, Electric, Gravitational or Other (Hyper-Dimensional)... Take your pick...

My bet is on magnetic...

[viscount aero]

The moon rotates around the earth, i think we can all agree on that (in a limited sense since motion proper is helical).

The moon however does not rotate about its own axis.

Imagine the moon is locked in stone, it can not move, now this stone rotates around the earth. The moon will always show the same face to the earth but will never rotate around its own axis since it is 'locked in' stone. However it is possible to imagine a moon axis and locking the axis to the perceivers position, the moon is then rotating around it with one full rotation, but this "axial rotation" is an illusion.

Mainstream "tidal locking" is flawed and does not explain the orbit of the moon, so we need something better.

Regards,
Daniel

No because then the stone that the Moon is locked in will rotate about its axis. You just replaced one object for another.

[viscount aero]

This is for chrimony:

As you have imparted the phenomenon of the Moons libration, would this be, too, part and parcel to the Moon's precession of its axis?

[chrimony]

This is for chrimony:

As you have imparted the phenomenon of the Moons libration, would this be, too, part and parcel to the Moon's precession of its axis?

As far as I can tell from searching, the Moon does not have precession about it's axis of rotation. In other words, it doesn't wobble like the Earth does. Do you have a reference that says otherwise? I also think we discussed this question earlier, and the answer was that libration is not axial precession.

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.

[viscount aero]

This is for chrimony:

As you have imparted the phenomenon of the Moons libration, would this be, too, part and parcel to the Moon's precession of its axis?

As far as I can tell from searching, the Moon does not have precession about it's axis of rotation. In other words, it doesn't wobble like the Earth does. Do you have a reference that says otherwise? I also think we discussed this question earlier, and the answer was that libration is not axial precession.

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.

Ok excellent, thank you

[nicho247]

Hi All -

After watching the majority of the EU 2014 conference videos on YouTube, I have discovered this forum and have been reading it for about 3 months now. I have found this thread to be particularly enticing since you can at least visualize the topic at hand, so much so, this comment will be the first on this forum.

Focusing on visualizations, I figure, the rotation of a body is really a matter of perspective, relative to the observer.

From earth, viewing the moon, the moon does not appear to rotate (the near side face is fixed) and others argue it does and simply the axial rotation is equal to it's orbital period (providing the illusion of no axial rotation). Without the sun and the stars for reference, viewing the moon (assuming you can see it), it would rise and set. This would imply orbit, but how would you determine it has axial rotation?

From the moon, viewing the earth, the earth does appear to rotate because the axial rotation is 365x greater than the orbital period. Again, without the sun and the stars for reference, viewing the earth (assuming you can see it), it would sit fixed in the sky, spinning. This would imply axial rotation, but how would you determine it has an orbit?

Without external references (external to earth and moon), this is analogous to the difference between gravity and going up in an elevator.

After some thought, I figured there has to be a website which has our solar system modeled. After about 5 minutes of using google, I found one, there may be more, and I have no affiliation here.

http://www.solarsystemscope.com/

The website appears to have the orbits correct, and the rotation of bodies correct, but scale appears to be wrong (planet size and distance between orbits). I am no astrologer either. A cool feature is that you can hit play and watch the modeled system act, change the rate of time, and even go in reverse. It was interesting to see Venus barely spin, while Jupiter is really really fast. Going back to the moon, you can watch it orbit the earth, and the earth orbit the sun. You can pick any reference you want, outside the bleachers, from the sun, from the earth, or from the moon.

It appears to me the moon does not rotate only while on the moon or earth (relative to the moon and earth), and any reference point outside of these systems, the moon will appear to rotate about it's axis. Axial rotation appears to be a relative attribute.

For those who argue the moon does have axial rotation (rotate) relative to the earth, can you please help me visualize what the moon would do differently for the axial rotation to be zero?

I hope this can carry the discussion further.

[chrimony]

It appears to me the moon does not rotate only while on the moon or earth (relative to the moon and earth), and any reference point outside of these systems, the moon will appear to rotate about it's axis. Axial rotation appears to be a relative attribute.

It's absolute.

For those who argue the moon does have axial rotation (rotate) relative to the earth, can you please help me visualize what the moon would do differently for the axial rotation to be zero?

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.

[viscount aero]

It appears to me the moon does not rotate only while on the moon or earth (relative to the moon and earth), and any reference point outside of these systems, the moon will appear to rotate about it's axis. Axial rotation appears to be a relative attribute.

It's absolute.

For those who argue the moon does have axial rotation (rotate) relative to the earth, can you please help me visualize what the moon would do differently for the axial rotation to be zero?

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.

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

[viscount aero]

Hi All -

After watching the majority of the EU 2014 conference videos on YouTube, I have discovered this forum and have been reading it for about 3 months now. I have found this thread to be particularly enticing since you can at least visualize the topic at hand, so much so, this comment will be the first on this forum.

Focusing on visualizations, I figure, the rotation of a body is really a matter of perspective, relative to the observer.

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.

From earth, viewing the moon, the moon does not appear to rotate (the near side face is fixed) and others argue it does and simply the axial rotation is equal to it's orbital period (providing the illusion of no axial rotation). Without the sun and the stars for reference, viewing the moon (assuming you can see it), it would rise and set. This would imply orbit, but how would you determine it has axial rotation?

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

From the moon, viewing the earth, the earth does appear to rotate because the axial rotation is 365x greater than the orbital period. Again, without the sun and the stars for reference, viewing the earth (assuming you can see it), it would sit fixed in the sky, spinning. This would imply axial rotation, but how would you determine it has an orbit?

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

Without external references (external to earth and moon), this is analogous to the difference between gravity and going up in an elevator.

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

After some thought, I figured there has to be a website which has our solar system modeled. After about 5 minutes of using google, I found one, there may be more, and I have no affiliation here.

http://www.solarsystemscope.com/

The website appears to have the orbits correct, and the rotation of bodies correct, but scale appears to be wrong (planet size and distance between orbits). I am no astrologer either. A cool feature is that you can hit play and watch the modeled system act, change the rate of time, and even go in reverse. It was interesting to see Venus barely spin, while Jupiter is really really fast. Going back to the moon, you can watch it orbit the earth, and the earth orbit the sun. You can pick any reference you want, outside the bleachers, from the sun, from the earth, or from the moon.

It appears to me the moon does not rotate only while on the moon or earth (relative to the moon and earth), and any reference point outside of these systems, the moon will appear to rotate about it's axis. Axial rotation appears to be a relative attribute.

For those who argue the moon does have axial rotation (rotate) relative to the earth, can you please help me visualize what the moon would do differently for the axial rotation to be zero?

I hope this can carry the discussion further.

That's a cool website and I bookmarked it.

To this: "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.

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.