1. ## Moon movements.!!!

I was discussing moon rotation with a guy just last week (and invited him here to discuss it)... who is convinced that the moon only revolves around the earth and does not rotate on an internal axis.!!!
For any who might still think the moon does not rotate... below is an animation which shows that the moon rotates one time during one revolution of the earth.!!!

Note:::
The red dot rotates one time around its green dot axis during one revolution of the earth.!!!

Last edited by P Timmy; 2012-Mar-28 at 02:39 AM.

2. This sense that it doesn't rotate is common among people who look at it but don't think about it. I like to point out that someone patient sitting on the Moon at one place will see some particular star in the sky rise, move across the sky, set, and then rise again 27.3 Earth-days later... which says the same thing as your diagram, but sells the idea to a different subset of people.

3. Originally Posted by antoniseb
This sense that it doesn't rotate is common among people who look at it but don't think about it. I like to point out that someone patient sitting on the Moon at one place will see some particular star in the sky rise, move across the sky, set, and then rise again 27.3 Earth-days later... which says the same thing as your diagram, but sells the idea to a different subset of people.
For sure moon rotation is quite the puzzler for some people... and for some people (so far)... I haven't found any solution that sells them the idea... but I find it interesting to try and fun making new animated gifs to support the fact that the moon rotates on an internal axis... plus I've learned new and interesting things along the way.!!!

In the animated gif below... no one disagrees that the object in the center is rotating on its axis... and lets say that the object in the center takes 27.3 days to complete one rotation.!!!

It can also be seen that the object in the center and the object in orbit are interchangeable... so just like our moon... the object in orbit also completes one rotation every 27.3 days... the same length of time it takes to complete one revolution.!!!

Last edited by P Timmy; 2012-Mar-28 at 02:52 AM.

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If it ain't tied down, it will rotate!

Imagine a ball on the end of a string. Most people can imagine the string as gravity and the ball as the moon. If you start spinning where you're standing, the ball flies around in a circle. It orbits, but most would say it does not revolve. They can argue that if it revolved, it would wind up the string around itself, which doesn't happen.

Likewise, can you pick a frame where the moon does not rotate? Maybe one where a spot on the moon faces the same direction as a sunspot. But the sun rotates, so that's no good. How about a point where the stars are pretty much stationary from the moon. But then the galaxy is in rotation, so the moon must still rotate. With motion being relative, and rotational motion being a major headache at that, it's very easy to just stick to your guns and say the moon isn't rotating.

The main point I hold on to is that the moon's period is a special case. If it starts to rotate faster, tidal forces will bring it back to where it is now. If it tries to rotate slower, again tidal forces bring it back. It very well does have a certain equilibrium(resonance) to it, which I do not associate with rotation by itself. It's easy to imagine that tidal foces have slowed the moon's rotation to the point where it can't anymore. It becomes tempting to say the moon doesn't have a day/night because of rotation, but because of its orbit instead. Which is wrong, but alluring.

5. Originally Posted by ShinAce
Imagine a ball on the end of a string. Most people can imagine the string as gravity and the ball as the moon. If you start spinning where you're standing, the ball flies around in a circle.
I performed the ball on a string experiment... and if the ball detaches from the string... the balls angular momentum (due to rotation) is retained and the ball will rotate on its axis as it flies off in a "straight" line... just as the moon would continue to rotate once every 27.3 days (as it orbits the sun) if the earth (and its gravity) suddenly disappeared.!!!

6. I don't think anyone who observes a proper demonstration of the motion denies the fact that the Moon continuously changes the direction it is facing with respect to the fixed stars as it goes around its orbit. Those who deny rotation seem to be hung up on quibbling with words in defining the components of the motion.

7. Originally Posted by Hornblower
I don't think anyone who observes a proper demonstration of the motion denies the fact that the Moon continuously changes the direction it is facing with respect to the fixed stars as it goes around its orbit. Those who deny rotation seem to be hung up on quibbling with words in defining the components of the motion.
That's my impression as well. And people definitely will quibble about it. In a sense it seems equivalent to arguing that for example, the moon doesn't really go around the earth because the earth is moving around the sun and the moon is doing a sort of oscillating movement with regard to the sun, since its orbital speed around the earth is less than the earth's orbital speed around the sun, hence it can never go around the earth. It's fallacious, but it has a certain allure to it.

8. Originally Posted by Hornblower
I don't think anyone who observes a proper demonstration of the motion denies the fact that the Moon continuously changes the direction it is facing with respect to the fixed stars as it goes around its orbit.
Yes that doesn't seem to be an issue.!!!

Those who deny rotation seem to be hung up on quibbling with words in defining the components of the motion.
Maybe some of those people will show up and present their non rotating moon quibbles and then we might come to a meeting of the minds on the issue of whether or not the moon rotates on an internal axis.!!!

The last guy I discussed the issue with claimed that the "hammer" (as in track and field events) doesn't rotate when released because like the moon... it also has no angular momentum.!!!

Below is an animated gif of how he thinks a hammer would fly through the air after being released.!!!

(Refresh to repeat the animation)

Last edited by P Timmy; 2012-Mar-28 at 03:26 AM.

9. There are probably others, but here is an earlier thread where it came up. There are probably others as well.

10. Originally Posted by P Timmy
Yes that doesn't seem to be an issue.!!!

Maybe some of those people will show up and present their non rotating moon quibbles and then we might come to a meeting of the minds on the issue of whether or not the moon rotates on an internal axis.!!!

The last guy I discussed the issue with claimed that the "hammer" (as in track and field events) doesn't rotate when released because like the moon... it also has no angular momentum.!!!

Below is an animated gif of how he thinks a hammer would fly through the air after being released.!!!
(Refresh to repeat the animation)

My bold. It appears that he has a passing acquaintance with physics and is applying it badly, and the animation is crude and simplistic.

While the thrower is swinging the hammer, it is moving much as the Moon does. When it is released, the ball continues to rotate initially, but atmospheric drag on the chain and handle will stop it or at least slow it down. I would be interested in seeing good closeup slow motion video of the action. I have never had a good look at a track meet. My educated guess is that the ball will be oscillating with the chain fluttering like a flag in a breeze.

11. I don't think the wind resistance would have much impact on the angular momentum of the ball at the end of the chain, but that ball is only spinning at roughly one RPS and would only have time to rotate maybe two or three times before hitting the dirt again. It's not like a spinning fastball in baseball where the rotation is obvious at a glance.

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The animation isn't animated for me.

Edit: Never mind, I got it. Straight out from the center, eh?

of years ago in which the poster was adamant about the Moon
either not rotating or rotating only because it is going around in
a circle. The animations showed a rotating geologist's hammer.
I intended to present the animations one at a time and ask the
poster whether the hammer was rotating in each case, but the
thread was closed just after I got started.

I agree with antoniseb that the rotation of the throwing hammer
would hardly be affected by air resistance at all. I'd expect more
like 3 or 4 rotations per second.

-- Jeff, in Minneapolis

13. Originally Posted by Jens
There are probably others, but here is an earlier thread where it came up.

Originally Posted by P Timmy
The last guy I discussed the issue with claimed that the "hammer" (as in track and field events) doesn't rotate when released because like the moon... it also has no angular momentum.!!!

Below is an animated gif of how he thinks a hammer would fly through the air after being released.!!!

(Refresh to repeat the animation)

Originally Posted by Hornblower
...the animation is crude and simplistic.
Well in my defense... ALL my animations are kinda rough :-)
Below is another gif that roughly demonstrates the correct motions of a hammer after its release.!!!

("refresh" to animate gif)

Hornblower
While the thrower is swinging the hammer, it is moving much as the Moon does. When it is released, the ball continues to rotate initially, but atmospheric drag on the chain and handle will stop it or at least slow it down. I would be interested in seeing good closeup slow motion video of the action. I have never had a good look at a track meet. My educated guess is that the ball will be oscillating with the chain fluttering like a flag in a breeze.
The effect isn't as dramatic as you imagined but your educated guess is on target.!!!
Below is the link "the guy" used to support his argument that a hammer does not rotate after it's released... and yet... 30 seconds into the video... the hammer and chain can be seen to rotate after being released... and 1:50 into the video... slow motion shows the hammer and chain still rotating as they fly down the field... but toward the end of its flight the ball does appear to be a bit lower than the handle due to wind resistance having a greater effect on the chain and handle.!!!

Last edited by P Timmy; 2012-Mar-28 at 03:57 AM.

14. Originally Posted by P Timmy
Now try this one:

15. Originally Posted by grapes
Ah yes... that's my friend Ken Dine who started that thread... the guy I recently invited to come here and discuss moon rotation... but since He's already been here and done that... I guess that's why he didn't show up again.!!!

So far I've only read part of his thread but I enjoyed it very much and will finish it as time permits... and as his thread demonstrates... He's a smart guy and He's not just yanking chains... He's sincere about his non-rotating moon beliefs.!!!

16. Originally Posted by P Timmy

Well in my defense... ALL my animations are kinda rough :-)
Below is another gif that roughly demonstrates the correct motions of a hammer after its release.!!!

("refresh" to animate gif)

The effect isn't as dramatic as you imagined but your educated guess is on target.!!!
Below is the link "the guy" used to support his argument that a hammer does not rotate after it's released... and yet... 30 seconds into the video... the hammer and chain can be seen to rotate after being released... and 1:50 into the video... slow motion shows the hammer and chain still rotating as they fly down the field... but toward the end of its flight the ball does appear to be a bit lower than the handle due to wind resistance having a greater effect on the chain and handle.!!!

That Olympic video does appear to show for sure that the ball is indeed rotating and whirling the chain around. I can see now that a lot more time in flight would be needed for the air drag to stop it.

17. Originally Posted by P Timmy
Ah yes... that's my friend Ken Dine who started that thread... the guy I recently invited to come here and discuss moon rotation... but since He's already been here and done that... I guess that's why he didn't show up again.!!!
He's the guy that you mention in the OP, post #1? Interesting.

So far I've only read part of his thread but I enjoyed it very much and will finish it as time permits... and as his thread demonstrates... He's a smart guy and He's not just yanking chains... He's sincere about his non-rotating moon beliefs.!!!
Last edited by grapes; 2012-Mar-28 at 10:06 AM. Reason: Removed discussion of ATM thread

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Lemme say what I never got to say in the thread grapes just
linked to. The first animation of the rotating geological hammer
had the center of rotation at what looked like might be the center
of mass. Each succeeding animation had the center of rotation
farther and farther away from that point. After a few iterations,
the center of rotation moved beyond the end of the handle, the
way it would actually be swung by someone using it. At some
point the nutcase would say the hammer was no longer rotating,
and I would ask whether the rotation suddenly vanished at that
point, or if successive animations depicted progressively less
and less rotation.

-- Jeff, in Minneapolis

19. Originally Posted by P Timmy
The last guy I discussed the issue with claimed that the "hammer" (as in track and field events) doesn't rotate when released because like the moon... it also has no angular momentum.!!!

Below is an animated gif of how he thinks a hammer would fly through the air after being released.!!!

(Refresh to repeat the animation)

Originally Posted by Jeff Root
Straight out from the center, eh?
Yep... but after watching a hammer throw video he did acknowledge there was a wobble motion when the hammer was released... but he explained that the wobble comes from the hammer thrower jerking on the handle as it's being released.!!!

Early on in the discussion (about 5 years ago) I told him about my experiment of attaching a two foot length of string to a tennis ball and then swinging the ball in a circle overhead... and when I released the string the ball rotated as it flew off in a "straight" line... and finally he agreed to perform the experiment but he used a tetherball attached to its eight foot rope... and he reported that the ball did make a jerking motion when he released the rope but it didn't fully rotate and continued on with the rope trailing behind.!!!

I explained to him that I used the smallest string I could find (dental floss) so it would have less effect on the angular momentum of the tennis ball... and that the long rope he used was too much drag for the angular momentum of the tetherball to overcome... but he said that was nonsense.!!!

It's to bad he refused to perform a proper experiment... because he agreed that if the ball rotated when the string was released... that meant it had angular momentum and that the moon also had angular momentum and rotated.!!!

20. When making an analogy between the Moon and a tethered ball, whatever happens in the real world when the tether is released, such as in the hammer throw, is irrelevant to the question about the Moon's rotation, because the Moon is not released. We should be concerned only with what the ball is doing while the tether is being held and swung.

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I think that releasing the ball is intended to show what the ball
had been doing before it was released: rotating. If we are dealing
with the same person-like entity as in the earlier BAUT thread,
then the question is not whether the Moon is rotating, but whether
it can be *shown* that the Moon is rotating. Sort of like trying to
prove that you exist.

-- Jeff, in Minneapolis

22. Originally Posted by Hornblower
When making an analogy between the Moon and a tethered ball, whatever happens in the real world when the tether is released, such as in the hammer throw, is irrelevant to the question about the Moon's rotation, because the Moon is not released. We should be concerned only with what the ball is doing while the tether is being held and swung.
The relevance of the tennis ball experiment is to demonstrate what the moon is doing in the real world.!!!

Because the moon has angular momentum... if the earth suddenly disappeared the moon would be released from its tether of earth's gravity and rotate once every 27.3 days as it orbits the sun... which would be very clear visual proof that an object in synchronous rotation (such as the moon) does have angular momentum and therefore rotates on an internal axis... but since we can't make the earth's gravity disappear to perform such an experiment... we can substitute a tethered tennis ball for the moon and then we can observe that visual evidence.!!!
Last edited by P Timmy; 2012-Mar-30 at 10:06 PM.

23. If the moon is painted on a cylinder wall, the moon need not rotate to keep the same face pointed toward the earth all the time...This allows the sun to rotate about the Earth, too

24. Originally Posted by Jerry
If the moon is painted on a cylinder wall, the moon need not rotate to keep the same face pointed toward the earth all the time...This allows the sun to rotate about the Earth, too
In this scenario, are the sun and moon on different cylinders? Which cylinder moves, the sun cylinder or the moon cylinder?

If you can stand on the "surface" and watch the star fields go by, in regular and repeating progression, the body is rotating. So...which cylinder are the stars on???

25. Originally Posted by Jens
That's my impression as well. And people definitely will quibble about it. In a sense it seems equivalent to arguing that for example, the moon doesn't really go around the earth because the earth is moving around the sun and the moon is doing a sort of oscillating movement with regard to the sun, since its orbital speed around the earth is less than the earth's orbital speed around the sun, hence it can never go around the earth. It's fallacious, but it has a certain allure to it.
That's not really a far out way of looking at the situation and perhaps not fallacious. The Moon is the only planetary satellite whose motion relative to the Sun is continuously concave. It could be said that both the Earth and Moon orbit the Sun while perturbing each other from more perfectly elliptical heliocentric orbits. The way we more commonly consider the situation is also quite acceptable. The latter is the basis of how we analytically (i.e. without numerical integration) calculate the Moon's motion, but the presence of the Sun makes the method immensely complex. Newton complained it gave him headaches.

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Timmy, in your first animation, the Moon is not rotating around its own axial center of rotation wrt the center of revolving (or to any point internal to the circle of revolution of the Moon), but it SEEMS to have its own axial rotation wrt the Sun (or to any point external to the circle of revolution of the Moon). So, in the Earth-Moon system, I clearly sustain that the Moon does not have its own axial rotation movement. I also sustain, that outside of the same Earth-Moon system, the Moon has ONLY an APPARENT, not a REAL own axial rotation movement.

- 1919 - Electrical Experimenter - Nikola Tesla - Famous Scientific Illusions
- 1919 - Electrical Experimenter - Nikola Tesla - Moon's Rotation

I invite everyone who understand what is general relativity, and can analyze the motion of an object in different reference systems, and to expose the arguments for or against those supported by me.

Timmy, in your first animation, the Moon is not rotating around its own axial center of rotation wrt the center of revolving (or to any point internal to the circle of revolution of the Moon)...
Welcome to the group sadang... hopefully you will find the people here willing to hear your arguments and discuss in a respectful manner.
I have to do other things now but I will respond as soon as I can to the issues you raise.

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As I recommended in the other thread, you need to
contact Gerald Kelleher, who often goes by the name
Oriel36. He is the one person you need to discuss
this with. He used to post on sci.astro and I have
seen references to him on the web.

-- Jeff, in Minneapolis

Timmy, in your first animation, the Moon is not rotating around its own axial center of rotation wrt the center of revolving (or to any point internal to the circle of revolution of the Moon), but it SEEMS to have its own axial rotation wrt the Sun (or to any point external to the circle of revolution of the Moon). So, in the Earth-Moon system, I clearly sustain that the Moon does not have its own axial rotation movement. I also sustain, that outside of the same Earth-Moon system, the Moon has ONLY an APPARENT, not a REAL own axial rotation movement.
I'm not quite clear on what you're trying to say, but let me ask you a question. Suppose you hold a bicycle wheel in your hands and make it spin. We all agree it has a rotation, I think. Now, if you put it on the ground and let it go so that it starts moving, is it still rotating around its own center of rotation, or is it no longer rotating?