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Old 3rd September 2015, 06:51 PM   #1
Ken Dine
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Synchronous Rotation

Mod Info The first ten posts were split from Continuation Part 18 AK/RS, where they were off-topic.
Posted By:Agatha


Edited by Agatha:  Edited to remove political discussion, off topic to the original thread and this new split one.


One last OT concerns your hero, the actual Nikola Tesla (who I have quoted many times myself).

Over the last few hundred years there's been an ongoing debate as to whether our moon has synchronous rotation, or not.

Synchronous rotation lunatics claim that our moon shows one face towards Earth each orbit because our moon rotates 360º around its polar axis in perfect synchronization with our moon's 360º orbit around Earth.

Synchronous rotation lunatics claim that if our moon didn't have these two synchronized 360º spins, that our moon would instead face in one direction as it orbited Earth, as explained here:



Image from this page:

http://www-istp.gsfc.nasa.gov/stargaze/Smoon.htm

Lunar synchronous rotation theory left poor Nikola sputtering, and in later life he spent a lot of his time arguing against synchronous rotation theory:

http://www.teslauniverse.com/nikola-...moons-rotation

Nikola Tesla was correct since our moon lost all of its polar axial rotation billions of years ago due to tidal braking friction, but unfortunately, Nikola's arguments attacking synchronous rotation theory could have been better.

As for the above graphic which claims that an astronomical body without polar axial rotation would point in one direction as it orbited its primary, that moon in that graphic would actually have one 360º clockwise polar axial rotation as it orbited its primary 360º in the opposite counter-clockwise – two 360º spins in opposite directions, around two different axes, from the sidereal (outside) perspective, they merely APPEAR to cancel each other out ...it's as simple as that.

While the above graphic implies that such a thing is impossible, retrograde rotating Venus is currently being spun down to that exact same 'APPARENT" zero spin rate.

It's funny what different people choose to believe (and how they justify their beliefs), whether it's about Amanda, our moon, or even Hillary.

Last edited by Agatha; 6th September 2015 at 05:20 AM.
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Old 3rd September 2015, 09:08 PM   #2
Numbers
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Originally Posted by Ken Dine View Post
....

Nikola Tesla was correct since our moon lost all of its polar axial rotation billions of years ago due to tidal braking friction, but unfortunately, Nikola's arguments attacking synchronous rotation theory could have been better.

....

It's funny what different people choose to believe (and how they justify their beliefs), whether it's about Amanda, our moon, or even Hillary.
Apparently Nikola Tesla did not have access to Wikipedia:

"Tidal locking (or captured rotation) is when one side of an astronomical body always face another. It is also called synchronous rotation. The classic example is the Moon: the same side of the Moon always faces the Earth.

A tidally locked body takes {approximately} just as long to rotate around its own axis as it does to revolve around its partner. This makes one hemisphere constantly face the partner body. Usually, at any given time only the satellite is tidally locked around the larger body. If the two bodies are similar in mass, and their distance apart is small, the tidal force will lock each to the other. This is the case between Pluto and Charon.

If the Moon were not spinning at all, it would alternately show its near and far sides to Earth, while moving around Earth in orbit."

Source: https://simple.wikipedia.org/wiki/Tidal_locking

Edited by Agatha:  Removed off topic material

Last edited by Agatha; 6th September 2015 at 05:21 AM.
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Old 3rd September 2015, 10:38 PM   #3
Ken Dine
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Originally Posted by Numbers View Post
Apparently Nikola Tesla did not have access to Wikipedia:

"Tidal locking (or captured rotation) is when one side of an astronomical body always face another. It is also called synchronous rotation. The classic example is the Moon: the same side of the Moon always faces the Earth.

A tidally locked body takes {approximately} just as long to rotate around its own axis as it does to revolve around its partner. This makes one hemisphere constantly face the partner body. Usually, at any given time only the satellite is tidally locked around the larger body. If the two bodies are similar in mass, and their distance apart is small, the tidal force will lock each to the other. This is the case between Pluto and Charon.

If the Moon were not spinning at all, it would alternately show its near and far sides to Earth, while moving around Earth in orbit."

Source: https://simple.wikipedia.org/wiki/Tidal_locking

Thanks for playing!


Nikola Tesla didn't have access to Wikipedia, which probably explains why Tesla had used his common sense instead of reading and memorizing utter nonsense!

Which was the point of my 'Lunacy' posting, and it does apply to the Amanda Knox case since people often believe what they read without thinking very deeply about the topic under discussion.

By citing Wikipedia you are making an argument from authority, and if you wanted to make a better argument from authority than by using Wikipedia, then why not use the NASA page I had posted?

IN FACT, nearly 100% of websites spout synchronous theory nonsense, so it MUST be true, RIGHT?

Or, is it?

They've been making orrerys (Earth-moon-sun models) for hundreds of years, so do you see the moon in this child's orrery actually spinning 360º around its metal support spindle as it keeps one face pointing inwards at the faux Earth?



So, why doesn't the faux moon in that orrery model require amy gearing to spin its moon around its metal support spindle in order to keep one face pointing inwards?

The real Nikola Tesla felt that synchronous theory was utter nonsense, and so do I. Not sure what our NG's faux Tesla poster thinks about the real Tesla's lunar position?

In astronomy, ‘ROTATION’ is a 360˚ spin about an interior polar axis, and ‘REVOLUTION' is a 360˚ spin about an external axis, such as our moon's orbit around our Earth-moon barycenter (which is the center of their combined mass).

‘ROTATION’ and ‘REVOLUTION’ would be easier for you to understand if you actually try doing what I call my tuna can experiments to see how two different 360˚ circular motions act in concert, as viewed from both the center-point perspective as compared to the outside sidereal perspective since these two perspectives (ALWAYS differ by one observed rotation).

Don't worry, this only takes a few minutes to do, and when you're done, then hopefully you'll understand the issue better:


‘ROTATION’ and ‘REVOLUTION’ would be easier for you to understand if you actually try doing the tuna can experiments (or use any round object) to see how these two different 360˚ circular motions act in concert.

Your body would represent the Earth and the can of tuna in your outstretched palm would represent the moon. You need to actually get up and do this for these spatial relationships to actually sink in –– don't worry, it only takes a minute to do.

EXPERIMENT #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. Now that you understand what it means for an object to rotate around its own center mass (CM), let’s proceed.

EXPERIMENT #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, but it does that with no need to reach out with your free hand to spin the can around its center mass (your body will now be the can’s exterior spin axis).

EXPERIMENT #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). Have a friend observe (from the sidereal perspective) and count, and they will see the label twice, while you in the center only see the can’s label once.

Clearly, your friend would count two (one more turn than you) since your friend will see the can make one 360˚ orbit (around an exterior axis) and one 360˚ spin around the can's center mass, and two 360˚ spins = 2 spins from the sidereal perspective.

EXPERIMENT #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 360˚ CW as you spin your body 360˚ CCW - i.e., the tuna can (moon) would have zero sidereal rotations (0:1).

Venus is fairly close to doing that right now.
—/--

Two 360˚ turns, one around an internal axis, and the 2nd turn around an external axis in the opposite direction, they will cancel each other out. It’s as simple as that.

BTW ~ each year from the (theoretical) sidereal perspective, our Earth appears to spin 366.25 times even though we only have 365.25 solar days.

From the sidereal perspective, the Earth’s 360˚ annual CCW orbit adds one (1) apparent turn to our 365.25 CCW polar axial rotations.

The sidereal perspective can be confusing since it always differs from the center-point perspective by one (1) 360˚ apparent rotation.



Originally Posted by Numbers View Post
Wikipedia also has an article on Amanda Knox which begins with the accurate statement:

"Amanda Marie Knox (born July 9, 1987) is an American woman who spent almost four years in an Italian prison accused of the 2007 murder of Meredith Kercher, one of the women who shared her apartment, before being definitively acquitted by the Supreme Court of Cassation."

https://en.wikipedia.org/wiki/Amanda_Knox

Note that: 1. This Wikipedia article has been previously full of inaccuracies, in the view of many; it still contains some questionable and unsourced statements; 2. There is no Wikipedia article on Raffaele Sollecito.

There are gross inaccuracies all around us, which is why you sometimes should use your noodle instead of blindly believing utter nonsense that you may read.
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Old 3rd September 2015, 11:33 PM   #4
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Originally Posted by Ken Dine View Post
Thanks for playing!


Nikola Tesla didn't have access to Wikipedia, which probably explains why Tesla had used his common sense instead of reading and memorizing utter nonsense!

Which was the point of my 'Lunacy' posting, and it does apply to the Amanda Knox case since people often believe what they read without thinking very deeply about the topic under discussion.

By citing Wikipedia you are making an argument from authority, and if you wanted to make a better argument from authority than by using Wikipedia, then why not use the NASA page I had posted?
....
To view this analogy from another perspective, persons who argue that Amanda Knox and Raffaele Sollecito were guilty often base their views on a failure to objectively examine the evidence and lack of evidence in the case, and adopt complicated and physically impossible explanations rather than the simplest one that accounts for all the evidence and lack of evidence.

Similarly, those who do oppose the concept of "tidal locking" may be substituting a convoluted explanation for a simple one, while possibly shifting the reference frame.

There was no credible evidence of Amanda or Raffaele in the murder room or in contact with Meredith or her clothes, no sign of a clean-up, and it is impossible in any practical way to selectively eliminate DNA or even fingerprints at a crime scene. Nor was there any transfer of blood to Amanda or Raffaele or to their clothing. The simple explanation for this state of evidence is that neither Amanda nor Raffaele were present in the room during the murder of Meredith Kercher. Indeed, there is no evidence to contradict their assertion that they were together at Raffaele's apartment at the relevant time.

In terms of tidal locking or captured rotation, which is observed in a number of satellites (and which is not relevant to Venus), it is simplest to consider it as the gravitational forcing of the alignment of the satellite so that one hemisphere of the satellite always faces the primary body. Just as the gravitational field of the moon and of the sun raise tides on the oceans of the earth and differentially tug on earth's rocky (solid and liquid) body, the gravitational field of a primary (a very massive body), such as the earth, has effects on a satellite, such as the moon.

Last edited by Numbers; 3rd September 2015 at 11:41 PM.
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Old 5th September 2015, 10:36 AM   #5
Ken Dine
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Originally Posted by Ken Dine View Post

Nikola Tesla didn't have access to Wikipedia, which probably explains why Tesla had used his common sense instead of reading and memorizing utter nonsense!

Which was the point of my 'Lunacy' posting, and it does apply to the Amanda Knox case since people often believe what they read without thinking very deeply about the topic under discussion.

By citing Wikipedia you are making an argument from authority, and if you wanted to make a better argument from authority than by using Wikipedia, then why not use the NASA page I had posted?

IN FACT, nearly 100% of websites spout synchronous theory nonsense, so it MUST be true, RIGHT?

Or, is it?

Originally Posted by Numbers View Post
To view this analogy from another perspective, persons who argue that Amanda Knox and Raffaele Sollecito were guilty often base their views on a failure to objectively examine the evidence and lack of evidence in the case, and adopt complicated and physically impossible explanations rather than the simplest one that accounts for all the evidence and lack of evidence.

EXACTLY! We’re all sitting here waiting for the final report, and discussing bleach and lamps ad nauseum while we wait is a total waste of time.

What can be more relevant to this case is discussing why people believe what they believe, especially when the evidence contradicts their beliefs.

Originally Posted by Numbers View Post
Similarly, those who do oppose the concept of "tidal locking" may be substituting a convoluted explanation for a simple one, while possibly shifting the reference frame.

I don’t recall saying "tidal locking (just "tidal braking”), so it appears you know something about this – GOOD!

However, I do NOT oppose either "tidal braking” or “tidal locking” (which is the end result of "tidal braking”).

It was Charles Darwin’s son, George Darwin, who primarily proposed the concept of "tidal braking” as the process which slows moons (and planets) until they’ve been fully despun and “tidally locked,” and I fully accept that concept as being scientifically sound. I merely disagree with the perspective that some people use to count ‘APPARENT’ moon and planetary rotations.

The sidereal perspective has its practical uses, such as aiming telescopes, but the sidereal perspective also confuses many people since it doesn't reflect reality.

I fully realize that I’m bucking a traditional viewpoint of astronomy (as Nikola Tesla did before me), but we’re supposed to be SKEPTICS here who can rationally look at the evidence.

Originally Posted by Numbers View Post
There was no credible evidence of Amanda or Raffaele in the murder room or in contact with Meredith or her clothes, no sign of a clean-up, and it is impossible in any practical way to selectively eliminate DNA or even fingerprints at a crime scene. Nor was there any transfer of blood to Amanda or Raffaele or to their clothing. The simple explanation for this state of evidence is that neither Amanda nor Raffaele were present in the room during the murder of Meredith Kercher. Indeed, there is no evidence to contradict their assertion that they were together at Raffaele's apartment at the relevant time.

EXACTLY! And likewise, there is also no evidence which supports synchronous rotation theory, but there is ample evidence which disproves that theory.

Originally Posted by Numbers View Post
In terms of tidal locking or captured rotation, which is observed in a number of satellites (and which is not relevant to Venus), it is simplest to consider it as the gravitational forcing of the alignment of the satellite so that one hemisphere of the satellite always faces the primary body. Just as the gravitational field of the moon and of the sun raise tides on the oceans of the earth and differentially tug on earth's rocky (solid and liquid) body, the gravitational field of a primary (a very massive body), such as the earth, has effects on a satellite, such as the moon.

Mostly true, but to be precise, there are over 200 moons in our solar system (plus a few planets) that are tidally locked to the primaries they orbit around.

However, why do you say say that tidal locking is not relevant to Venus? Granted, that Venus is primarily being despun by its thick atmosphere rubbing against its mountainous terrain (Venus' is 90 times thicker than Earth’s atmosphere); nevertheless, since our sun does exert its gravity on Venus, our sun's gravity is also exerting some tidal braking forces on Venus.

Maybe you mean that Venus just isn't fully tidally locked yet? TRUE, but Venus is quickly heading that way and Venus will be the next body in our system to become tidally locked.

In any event, gravity isn’t like a tractor beam that can force our moon to keep facing Earth. Rather, our moon once had rotation (inertia) around its polar axis, but Earth’s gravity had raised tides on the moon, which caused friction that slowly bled off that stored rotational energy, and now it’s all gone, and it was a very slow process. Despite being a slow process, once an astronomical body’s rotational energy is finally gone, it’s gone for good.

Since energy can't be destroyed, as Earth's gravity despun our moon, the lost energy of the moon's former polar axial rotation was merely converted by pushing the moon farther away from Earth, which is another form of stored energy. Some of the moon's lost rotational inertia was also converted to heat in the process of being despun.

If you’re interested in this topic in more detail, then click on the spoiler:

That Earth’s gravity isn’t like a tractor beam pulling our moon’s nearside towards us can be proved by the fact that the center-point of our moon’s nearside faces away from Earth each orbit more than it faces directly at Earth, which is called Longitudinal Librations.

Half of astronomy websites explain 'Longitudinal Librations’ as resulting from the mismatch between our moon’s orbital speed (slower as the moon heads towards its apogee, or farthest point away from us as it pulls against Earth’s gravity), and they claim that since the moon’s last remaining polar axial rotation spins at a steady rate, that these differences causes 'Longitudinal Librations’ as our moon travels around apogee, and then again around perigee, the fastest portion of our moon’s orbit (fastest portion of the orbit because Earth’s gravity is pulling the moon towards its perigee).

PROBLEM: the websites which which claim that mismatch between our moon’s orbital speed and rotation rate at apogee & perigee, are WRONG since maximum 'Longitudinal Librations’ actually occur midway BETWEEN apogee & perigee instead of at apogee & perigee – Oooops!

Other websites correctly say that our moon’s actual maximum 'Longitudinal Librations’ do occur midway BETWEEN apogee & perigee instead of ‘AT' apogee & perigee, but those sites never say why that happens at the midway point, probably because it isn’t consistent with synchronous rotation theory, so they just don’t even try to explain it.

I can easily explain why maximum 'Longitudinal Librations’ occur midway BETWEEN apogee & perigee using a fully despun moon as the model –– our fully despun moon is merely facing the empty focus of its eliptical orbit, twice each orbit, which is around midway between apogee & perigee:




Mercury, a planet, has already been tidally locked to our sun. Of course, due to Mercury’s eccentric orbit, Mercury makes a little half-flip each aorbit as it rounds its apogee, which gives Mercury a 3:2 rotation rate (using astronomer jargon).

While no longer considered to be a planet, Pluto is tidally locked with its large moon, Charon.

Our moon is in the process of tidally braking Earth – e.g., 400 million years ago, Earth rotated every 23 hours (using today’s hours).

In addition to Venus, in our solar system about 10% of our astronomical bodies (which almost always have a CCW orbit) either have, or once had, a retrograde CW polar axial rotation.

We don’t know which direction our CCW revolving moon spun down from (w/ either CW or CCW rotation), but no matter which direction our moon spun down from, from our center-point direction, our moon spun down to ZERO!

4 ~ 3 ~ 2 ~ 1 ~ 0

However, from the sidereal perspective astronomers claim our moon spun down to ONE (1) remaining polar axial rotation:

4 ~ 3 ~ 2 ~ 1

So, what happened to the ZERO?

As retrograde Venus proves, the ZERO is still there.

Venus currently has 1.92 CW (retrograde) polar axial rotations left, so from the sidereal perspective Venus is spinning down like this:

4 ~ 3 ~ 2 ~ 1 ~ 0~ 1

In short, at 1.92 CW current rotations Venus has already passed thru its first 1:1 spin rate, and is now heading to a zero spin rate (0:1) before being fully despun at a 2nd and final 1:1 spin rate.

There’s your ZERO! If you don’t believe it, then work it out with a can of tuna.



BTW –– not only do half of astronomy sites conflict as to the timing of our moon’s maximum 'Longitudinal Librations’, astronomy sites are also in conflict (again about evenly) as to the length of a Venusian day.

Venus has 1.92 CW polar axial rotations left (thus 1.92 solar days), but from the sidereal perspective Venus ‘APPEARS’ to have .92 polar axial rotations (since center-point and sidereal always differ by one), so many websites incorrectly claim that a Venusian day is shorter than a Venusian year, which is clearly wrong.

Whether the timing of our moon’s 'Longitudinal Librations’ or the conflicting opinions about how many days Venus has each orbit, it should give pause to any skeptic that astronomers can’t seem to agree on these basic things concerning Earth’s two closest neighbors.

I would be happy to post the URLs to these reputable astronomy sites with their conflicting opinions about Venus’ length of day, and the timing of our moon’s 'Longitudinal Librations’. These conflicts are real!
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Old 5th September 2015, 06:44 PM   #6
whoanellie
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Originally Posted by Ken Dine View Post
Thanks for playing!


Nikola Tesla didn't have access to Wikipedia, which probably explains why Tesla had used his common sense instead of reading and memorizing utter nonsense!

Which was the point of my 'Lunacy' posting, and it does apply to the Amanda Knox case since people often believe what they read without thinking very deeply about the topic under discussion.

By citing Wikipedia you are making an argument from authority, and if you wanted to make a better argument from authority than by using Wikipedia, then why not use the NASA page I had posted?

IN FACT, nearly 100% of websites spout synchronous theory nonsense, so it MUST be true, RIGHT?

Or, is it?

They've been making orrerys (Earth-moon-sun models) for hundreds of years, so do you see the moon in this child's orrery actually spinning 360º around its metal support spindle as it keeps one face pointing inwards at the faux Earth?

http://i.imgur.com/g8zua5s.jpg

So, why doesn't the faux moon in that orrery model require amy gearing to spin its moon around its metal support spindle in order to keep one face pointing inwards?

The real Nikola Tesla felt that synchronous theory was utter nonsense, and so do I. Not sure what our NG's faux Tesla poster thinks about the real Tesla's lunar position?

In astronomy, ‘ROTATION’ is a 360˚ spin about an interior polar axis, and ‘REVOLUTION' is a 360˚ spin about an external axis, such as our moon's orbit around our Earth-moon barycenter (which is the center of their combined mass).

‘ROTATION’ and ‘REVOLUTION’ would be easier for you to understand if you actually try doing what I call my tuna can experiments to see how two different 360˚ circular motions act in concert, as viewed from both the center-point perspective as compared to the outside sidereal perspective since these two perspectives (ALWAYS differ by one observed rotation).

Don't worry, this only takes a few minutes to do, and when you're done, then hopefully you'll understand the issue better:


‘ROTATION’ and ‘REVOLUTION’ would be easier for you to understand if you actually try doing the tuna can experiments (or use any round object) to see how these two different 360˚ circular motions act in concert.

Your body would represent the Earth and the can of tuna in your outstretched palm would represent the moon. You need to actually get up and do this for these spatial relationships to actually sink in –– don't worry, it only takes a minute to do.

EXPERIMENT #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. Now that you understand what it means for an object to rotate around its own center mass (CM), let’s proceed.

EXPERIMENT #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, but it does that with no need to reach out with your free hand to spin the can around its center mass (your body will now be the can’s exterior spin axis).

EXPERIMENT #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). Have a friend observe (from the sidereal perspective) and count, and they will see the label twice, while you in the center only see the can’s label once.

Clearly, your friend would count two (one more turn than you) since your friend will see the can make one 360˚ orbit (around an exterior axis) and one 360˚ spin around the can's center mass, and two 360˚ spins = 2 spins from the sidereal perspective.

EXPERIMENT #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 360˚ CW as you spin your body 360˚ CCW - i.e., the tuna can (moon) would have zero sidereal rotations (0:1).

Venus is fairly close to doing that right now.
—/--

Two 360˚ turns, one around an internal axis, and the 2nd turn around an external axis in the opposite direction, they will cancel each other out. It’s as simple as that.

BTW ~ each year from the (theoretical) sidereal perspective, our Earth appears to spin 366.25 times even though we only have 365.25 solar days.

From the sidereal perspective, the Earth’s 360˚ annual CCW orbit adds one (1) apparent turn to our 365.25 CCW polar axial rotations.

The sidereal perspective can be confusing since it always differs from the center-point perspective by one (1) 360˚ apparent rotation.






There are gross inaccuracies all around us, which is why you sometimes should use your noodle instead of blindly believing utter nonsense that you may read.
Ken,
At the risk of following you down another off-topic rabbit hole and noting that I may be completely missing your point, but you seem to be arguing that the moon does not undergo a synchronous rotation as it revolves around the earth. I am not an astronomer but here is what the folks at NASA have to say
http://saturn.jpl.nasa.gov/files/Syn...s_Rotation.pdf

By the way, in none of your models is the tuna can "revolving" around the person holding it. Do you realize that?

Your last sentence is spot on.
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Old 5th September 2015, 08:21 PM   #7
Numbers
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Originally Posted by whoanellie View Post
Ken,
At the risk of following you down another off-topic rabbit hole and noting that I may be completely missing your point, but you seem to be arguing that the moon does not undergo a synchronous rotation as it revolves around the earth. I am not an astronomer but here is what the folks at NASA have to say
http://saturn.jpl.nasa.gov/files/Syn...s_Rotation.pdf

By the way, in none of your models is the tuna can "revolving" around the person holding it. Do you realize that?

Your last sentence is spot on.
One may also look at:
http://www.badastronomy.com/bad/misc/moon_spin.html
http://www.badastronomy.com/bad/misc/tides.html

It is important to keep the "frame of reference" in mind, and to be consistent about it, to understand this issue.

To an "outside observer" positioned above (or below) the earth-moon system, who maintains a coordinate system aligned with the "fixed stars" (meaning those which do not apparently measurably move relative to each other over several years, in terms of gross angular measurement), the moon will be seen to rotate with a period equal, to a very high degree of approximation, to one period of its revolution about the earth.

However, with respect to a line joining the centers of the earth and moon, there is no rotation of the moon. That is a different "frame of reference". (ETA: This line rotates around the center of the earth, with respect to the "fixed stars", with a period equal to the moon's period of revolution.)

There's an analogy to the Knox - Sollecito case, and to criminal justice, in the "frame of reference" of presumption of innocence v. presumption of guilt.

In the usual common-law system, the accused are presumed to be innocent, meaning that the State has the responsibility of proving them guilty. Thus, any forensic test performed by the State must be shown to be performed and interpreted in a credible manner. For example, the collection, testing, and interpretation must have met accepted scientific standards, and the State must show that contamination or inappropriate methods have not produced false inculpatory results.

In the Italian judicial system, the procedural law requires that a conviction may only be pronounced if the accused's guilt is established by proof beyond a reasonable doubt (CPP Art. 533, para. 1), and that the existence of a fact cannot be inferred from circumstantial evidence unless such evidence is "serious, precise and consistent" (CPP Art. 192, para. 2). However, in the Knox - Sollecito case, some of the judges, such as Massei, Chieffi, and Nencini reversed the presumption of innocence into a presumption of guilt, for example, by requiring that contamination be proven by the defendant, rather than freedom from contamination be established by the State. Furthermore, the State was allowed to present forensic DNA data without establishing its essentially validity or credibility. Thus, the "frame of reference" (presumption of which side must establish proof) was reversed by those courts.

Last edited by Numbers; 5th September 2015 at 10:07 PM.
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Old 5th September 2015, 11:22 PM   #8
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Originally Posted by Ken Dine View Post
EXACTLY! We’re all sitting here waiting for the final report, and discussing bleach and lamps ad nauseum while we wait is a total waste of time.

What can be more relevant to this case is discussing why people believe what they believe, especially when the evidence contradicts their beliefs.




I don’t recall saying "tidal locking (just "tidal braking”), so it appears you know something about this – GOOD!

However, I do NOT oppose either "tidal braking” or “tidal locking” (which is the end result of "tidal braking”).

It was Charles Darwin’s son, George Darwin, who primarily proposed the concept of "tidal braking” as the process which slows moons (and planets) until they’ve been fully despun and “tidally locked,” and I fully accept that concept as being scientifically sound. I merely disagree with the perspective that some people use to count ‘APPARENT’ moon and planetary rotations.

The sidereal perspective has its practical uses, such as aiming telescopes, but the sidereal perspective also confuses many people since it doesn't reflect reality.

I fully realize that I’m bucking a traditional viewpoint of astronomy (as Nikola Tesla did before me), but we’re supposed to be SKEPTICS here who can rationally look at the evidence.




EXACTLY! And likewise, there is also no evidence which supports synchronous rotation theory, but there is ample evidence which disproves that theory.




Mostly true, but to be precise, there are over 200 moons in our solar system (plus a few planets) that are tidally locked to the primaries they orbit around.

However, why do you say say that tidal locking is not relevant to Venus? Granted, that Venus is primarily being despun by its thick atmosphere rubbing against its mountainous terrain (Venus' is 90 times thicker than Earth’s atmosphere); nevertheless, since our sun does exert its gravity on Venus, our sun's gravity is also exerting some tidal braking forces on Venus.

Maybe you mean that Venus just isn't fully tidally locked yet? TRUE, but Venus is quickly heading that way and Venus will be the next body in our system to become tidally locked.

In any event, gravity isn’t like a tractor beam that can force our moon to keep facing Earth. Rather, our moon once had rotation (inertia) around its polar axis, but Earth’s gravity had raised tides on the moon, which caused friction that slowly bled off that stored rotational energy, and now it’s all gone, and it was a very slow process. Despite being a slow process, once an astronomical body’s rotational energy is finally gone, it’s gone for good.

Since energy can't be destroyed, as Earth's gravity despun our moon, the lost energy of the moon's former polar axial rotation was merely converted by pushing the moon farther away from Earth, which is another form of stored energy. Some of the moon's lost rotational inertia was also converted to heat in the process of being despun.

If you’re interested in this topic in more detail, then click on the spoiler:

That Earth’s gravity isn’t like a tractor beam pulling our moon’s nearside towards us can be proved by the fact that the center-point of our moon’s nearside faces away from Earth each orbit more than it faces directly at Earth, which is called Longitudinal Librations.

Half of astronomy websites explain 'Longitudinal Librations’ as resulting from the mismatch between our moon’s orbital speed (slower as the moon heads towards its apogee, or farthest point away from us as it pulls against Earth’s gravity), and they claim that since the moon’s last remaining polar axial rotation spins at a steady rate, that these differences causes 'Longitudinal Librations’ as our moon travels around apogee, and then again around perigee, the fastest portion of our moon’s orbit (fastest portion of the orbit because Earth’s gravity is pulling the moon towards its perigee).

PROBLEM: the websites which which claim that mismatch between our moon’s orbital speed and rotation rate at apogee & perigee, are WRONG since maximum 'Longitudinal Librations’ actually occur midway BETWEEN apogee & perigee instead of at apogee & perigee – Oooops!

Other websites correctly say that our moon’s actual maximum 'Longitudinal Librations’ do occur midway BETWEEN apogee & perigee instead of ‘AT' apogee & perigee, but those sites never say why that happens at the midway point, probably because it isn’t consistent with synchronous rotation theory, so they just don’t even try to explain it.

I can easily explain why maximum 'Longitudinal Librations’ occur midway BETWEEN apogee & perigee using a fully despun moon as the model –– our fully despun moon is merely facing the empty focus of its eliptical orbit, twice each orbit, which is around midway between apogee & perigee:

http://i.imgur.com/T6SgHYb.png


Mercury, a planet, has already been tidally locked to our sun. Of course, due to Mercury’s eccentric orbit, Mercury makes a little half-flip each aorbit as it rounds its apogee, which gives Mercury a 3:2 rotation rate (using astronomer jargon).

While no longer considered to be a planet, Pluto is tidally locked with its large moon, Charon.

Our moon is in the process of tidally braking Earth – e.g., 400 million years ago, Earth rotated every 23 hours (using today’s hours).

In addition to Venus, in our solar system about 10% of our astronomical bodies (which almost always have a CCW orbit) either have, or once had, a retrograde CW polar axial rotation.

We don’t know which direction our CCW revolving moon spun down from (w/ either CW or CCW rotation), but no matter which direction our moon spun down from, from our center-point direction, our moon spun down to ZERO!

4 ~ 3 ~ 2 ~ 1 ~ 0

However, from the sidereal perspective astronomers claim our moon spun down to ONE (1) remaining polar axial rotation:

4 ~ 3 ~ 2 ~ 1

So, what happened to the ZERO?

As retrograde Venus proves, the ZERO is still there.

Venus currently has 1.92 CW (retrograde) polar axial rotations left, so from the sidereal perspective Venus is spinning down like this:

4 ~ 3 ~ 2 ~ 1 ~ 0~ 1

In short, at 1.92 CW current rotations Venus has already passed thru its first 1:1 spin rate, and is now heading to a zero spin rate (0:1) before being fully despun at a 2nd and final 1:1 spin rate.

There’s your ZERO! If you don’t believe it, then work it out with a can of tuna.



BTW –– not only do half of astronomy sites conflict as to the timing of our moon’s maximum 'Longitudinal Librations’, astronomy sites are also in conflict (again about evenly) as to the length of a Venusian day.

Venus has 1.92 CW polar axial rotations left (thus 1.92 solar days), but from the sidereal perspective Venus ‘APPEARS’ to have .92 polar axial rotations (since center-point and sidereal always differ by one), so many websites incorrectly claim that a Venusian day is shorter than a Venusian year, which is clearly wrong.

Whether the timing of our moon’s 'Longitudinal Librations’ or the conflicting opinions about how many days Venus has each orbit, it should give pause to any skeptic that astronomers can’t seem to agree on these basic things concerning Earth’s two closest neighbors.

I would be happy to post the URLs to these reputable astronomy sites with their conflicting opinions about Venus’ length of day, and the timing of our moon’s 'Longitudinal Librations’. These conflicts are real!
The problem here is the frame of reference. Inertia, needs to be considered against the universe. So imagine you are standing on the moons surface, would the stars move? In particular if you set a camera with a long exposure would you see the circular streaks as the stars rotated round the axis of the moon? Look at that star on the horizon, does it move? The moon still rotates on its axis, it has not lost all rotational energy, the spin on the moon's axis is synchronised so the same face faces the earth, but that is not true for the universe as a whole.
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Old 5th September 2015, 11:56 PM   #9
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This is a gif I made for the last person I found that didn't understand that the moon rotated....
Attached Images
File Type: gif MoonAnim3.gif (37.3 KB, 323 views)
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Old 6th September 2015, 12:07 AM   #10
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Originally Posted by PhantomWolf View Post
This is a gif I made for the last person I found that didn't understand that the moon rotated....
It is ironic that the dark side of the moon is bright, and the bright side dark.
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Old 6th September 2015, 09:23 AM   #11
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Originally Posted by Samson View Post
It is ironic that the dark side of the moon is bright, and the bright side dark.
Of course, the issue of irony disappears since the two lunar hemispheres are accurately called "far side" and "near side". One hemisphere - the near side - continually faces earth. Both lunar hemispheres are illuminated in turn as the moon rotates/revolves about the earth.

On the issue of librations, those result largely from the elliptical orbit of the moon around the earth. Other contributors are the angle of the line through the lunar poles (the polar axis) to the plane of its orbit around earth, and the fact that the moon is viewed from the surface of the earth, not the center.

BTW, for those who don't think the moon rotates, how can it have poles and a polar axis if it did not?

ETA: If the moon were not rotating with respect to the fixed stars (or the cosmic microwave background, if one prefers), then it would be rotating with respect to the earth, about the moon's axis of rotation (polar axis).

Last edited by Numbers; 6th September 2015 at 11:01 AM. Reason: ETA, including italicized add to define polar axis
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Old 6th September 2015, 12:05 PM   #12
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To misquote and mis-paraphrase Theodore Sturgeon, "Why so little syzygy?", in this thread?

Dedicated to all those who believe that the Earth rotates on its axis once every 24 hours.
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Old 6th September 2015, 12:23 PM   #13
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I think I saw a question about this on a test once. A test where spatial orientation was a factor in scoring. If you could imagine how something looked from different angles, times and reference points, you scored higher.

It was called an IQ test.
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Old 6th September 2015, 06:12 PM   #14
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Originally Posted by Numbers View Post
Of course, the issue of irony disappears since the two lunar hemispheres are accurately called "far side" and "near side". One hemisphere - the near side - continually faces earth. Both lunar hemispheres are illuminated in turn as the moon rotates/revolves about the earth.

On the issue of librations, those result largely from the elliptical orbit of the moon around the earth. Other contributors are the angle of the line through the lunar poles (the polar axis) to the plane of its orbit around earth, and the fact that the moon is viewed from the surface of the earth, not the center.

BTW, for those who don't think the moon rotates, how can it have poles and a polar axis if it did not?

ETA: If the moon were not rotating with respect to the fixed stars (or the cosmic microwave background, if one prefers), then it would be rotating with respect to the earth, about the moon's axis of rotation (polar axis).
My point was that the far side has no mari or seas. It is featureless and shines more brightly than our side. I think this is because tidal locking happened early, and meant our side of the moon got the asteroid blasts that missed earth as they were attracted and swung by.
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Old 6th September 2015, 06:30 PM   #15
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Of course, in a reference frame attached to the earth (and rotating with it), the earth does not rotate. It's all the rest of the universe that swings around the earth approximately once every 24 hours.
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Old 6th September 2015, 06:40 PM   #16
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Originally Posted by Numbers View Post
Of course, in a reference frame attached to the earth (and rotating with it), the earth does not rotate. It's all the rest of the universe that swings around the earth approximately once every 24 hours.
No. The Earth rotates on its axis in 23 hours 56 minutes and 9 seconds.
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Old 6th September 2015, 07:08 PM   #17
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Originally Posted by Gord_in_Toronto View Post
No. The Earth rotates on its axis in 23 hours 56 minutes and 9 seconds.

Whose siderial on?
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Old 6th September 2015, 07:45 PM   #18
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Originally Posted by Ken Dine View Post
http://i.imgur.com/g8zua5s.jpg

So, why doesn't the faux moon in that orrery model require amy gearing to spin its moon around its metal support spindle in order to keep one face pointing inwards?
Why would it need to spin around the spindle, the spindle itself is spinning.
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Old 6th September 2015, 08:37 PM   #19
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Originally Posted by Gord_in_Toronto View Post
No. The Earth rotates on its axis in 23 hours 56 minutes and 9 seconds.
Thanks for the correction.

In a frame of reference fixed to the earth, and rotating with the earth, the rest of the universe revolves* around the earth in approximately 23 hours 56 minutes and 9 seconds.

(That period of revolution holds true for the present era.)

* Some may prefer to say: appears to revolve
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Old 6th September 2015, 08:41 PM   #20
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Originally Posted by phunk View Post
Why would it need to spin around the spindle, the spindle itself is spinning.
The spindle is in effect the line (that is, a parallel to the line) from earth center to moon center; the moon does not rotate with respect to the frame of reference determined by this line because the moon is tidally locked to the earth.

The frame of reference could be more completely defined as the plane of the moon's orbit and the plane through the line joining the centers and passing through the axis of rotation of the moon (where that axis is determined in the fixed-stars frame of reference.) In the orrey model, the plane through the line joining the centers is perpendicular to the orbital plane.

Last edited by Numbers; 6th September 2015 at 08:48 PM.
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Old 6th September 2015, 09:12 PM   #21
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Originally Posted by Numbers View Post
Thanks for the correction.

In a frame of reference fixed to the earth, and rotating with the earth, the rest of the universe revolves* around the earth in approximately 23 hours 56 minutes and 9 seconds.

(That period of revolution holds true for the present era.)

* Some may prefer to say: appears to revolve
I think the universe revolves round Mars every 24 hours, 39 minutes, and 35.244 seconds.
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Old 6th September 2015, 11:00 PM   #22
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Originally Posted by Planigale View Post
The problem here is the frame of reference.

Astronomer Steve Smyers explains why the center-point and sidereal perspectives always differ by one (1):

Quote:


We now see that our "Earth" makes one complete rotation with respect to the Sun, as the white half faces the Sun at the right, and the dark at the left-most part of the orbit. The year now is one solar day long, but two sidereal days long! It is easy now to see how this will generalize to more days.

There will always be one more sidereal rotation than solar rotation. If there are 365 solar days in the solar year, then there will be 366 sidereal days in the solar year. Thus, the solar day must be (366/365) x sidereal day!

http://www.aoc.nrao.edu/~smyers/cour...avigation.html

As astronomer Steven Smyers also explains on his above website, from the sidereal perspective our Earth has 366.25 (apparent) rotations per year, while from the center-point perspective of our sun, our Earth has 365.25 polar axial rotations per year (i.e., solar days).

The math is simple, subtract one (-1) from Earth’s 366.25 (apparent) SIDEREAL polar axial rotations per year and that will give you Earth’s actual polar axial rotations (DAYS) per year:

366.25 - 1 = 365.25 actual polar axial rotations per year.

Subtract one (-1) from our moon’s single (apparent) polar axial rotation per month (every 29.5 days), and that will give you the moon’s actual polar axial rotations per month:

1 - 1 = 0 actual polar axial rotations per month.

The math is grade-school simple, and it proves that our moon has ZERO polar axial rotations left!

Originally Posted by Planigale View Post
Inertia, needs to be considered against the universe.

An astronomical body either has spin inertia around its center-mass (i.e., polar axis), or it doesn’t.

You can widen the perspective to include the Earth-moon’s orbit around our sun (which also has its own inertia), and you can also consider our solar system’s inertia around our galaxy’s center, ad nauseum, but what we’re considering here is whether a fully despun moon still retains 1 polar axial rotation per orbit, or does it instead have ZERO polar axial rotation per orbit?

Originally Posted by Planigale View Post
So imagine you are standing on the moons surface, would the stars move?

YES, but in his class-notes astronomer Steven Smyers explains why that would happen without any polar axial rotation after a body has been despun, such as he explains here using the Earth as his example:

Quote:
Sidereal and Solar Days:

I would like to demonstrate that even if the Earth were locked facing the Sun so that it was always the same solar time, that the celestial sphere, and thus the distant stars, would be seen to rotate once during the year.

Shown below is a rough diagram illustrating two differently colored hemispheres of the Earth locked facing the Sun. Note that the dark colored half rotates once relative to our point-of-view of the stars.



http://www.aoc.nrao.edu/~smyers/cour...avigation.html

Compare the above graphic to this one again which depicts an astronomical body which clearly still has some polar axial rotations left:




Originally Posted by Planigale View Post
In particular if you set a camera with a long exposure would you see the circular streaks as the stars rotated round the axis of the moon?

The main spin inertia that would cause the stars to move while standing upon the moon, that would be the inertia of the moon’s 360˚ orbital revolution around Earth.

Clearly, Earth has both polar axial rotations (365.25 / orbit), as well as orbital velocity around our sun, as explained above. Our moon only has its 360˚ orbital revolution left.

Everyone agrees (at least I do) that our moon has been despun (likely billions of years ago) by tidal braking forces, as explained by Charles Darwin’s son, George Darwin.

The issue here is whether a fully despun moon still retains one last 360˚polar axial rotation, or not?

I maintain that today our fully despun moon ONLY retains its 360˚ orbit around the Earth, and I can prove it!

Originally Posted by Planigale View Post
Look at that star on the horizon, does it move?

Are you asking whether the stars appear to move from our perspective while standing upon Earth’s surface? If so, then YES!

However, from Earth’s perspective the stars appear to primarily move in our sky due to Earth’s polar axial rotation, as well as to a lesser degree by Earth’s orbit around the sun, and to an even lesser degree as our entire solar system also moves in relation to the background stars.

When looking at our moon at night from Earth, our moon appears to rise in the East and set in our West, thus appearing to travel in a clockwise (CW) direction (when looking down on Earth’s North pole). However, our moon is actually orbiting in the opposite CCW direction around Earth!

Our moon only APPEARS to be going CW (east to west) in its orbit since Earth’s CCW polar axial rotation is faster (24 hours) than the moon’s 29.5 day CCW orbit around us.

What you think you see does not always reflect reality.

Originally Posted by Planigale View Post
The moon still rotates on its axis, it has not lost all rotational energy, the spin on the moon's axis is synchronised so the same face faces the earth, but that is not true for the universe as a whole.

You have baldly claimed something, but you still need to prove it! Which force would cause such a perfect synchronization, GOD?

INDEED, instead of attempting to explain this amazing coincidence of effects early astronomers often just chalked it up as further evidence of a Supreme Intelligence – as astronomer Robert Grant explained back in 1852:

Quote:
“It is natural enough, indeed, to suppose that
the illustrious author of the Principia {Newton} did
not feel any anxiety to repudiate the original equality
of the motions of rotation and revolution a relation
which, although perhaps difficult to explain by the
doctrine of chances,
becomes very
interesting and suggestive when it is considered
as the result of Supreme Intelligence
.


GRANT, History of Physical Astronomy. London, 1852, pp 72 – 76, at p. 75.

Hallelujah!

As intelligent skeptics, let’s discuss whether your synchronous rotation beliefs are valid, and to do that, we need to discuss our moon’s Longitudinal Librations, because if our moon’s Longitudinal Librations are NOT consistent with synchronous rotation theory, then it means that YOU should honestly reexamine synchronous rotation theory, as any good skeptic should do when faced with inconsistencies.

So then, using synchronous theory as your model, what exactly causes our moon’s (supposedly) single remaining 360˚ polar axial rotation to be in nearly perfect sync with its 360˚ revolution around Earth?

To be clear, the center-point of our moon’s NEAR-SIDE does NOT always point directly at Earth, so the sync (if any) isn’t perfect, which is why we have longitudinal librations of our moon where the moon seemingly shakes its head back and forth (the moon’s apparent nodding up & down are called latitudinal librations).

Most astronomy sites, in conformance with synchronous rotation theory, claim that longitudinal librations are caused by the disparity between our moon’s steady polar axial rotation coupled with our moon’s varying orbital speeds.

All astronomical bodies have elliptical orbits (basically, an oval) with the primary they orbit around occupying one focus of the ellipse, and the far turn’s elliptical radius has an ‘Empty Focus’, thus, as our moon pulls away against Earth’s gravity to reach its farthest point away from us (apogee), our moon travels at its slowest orbital velocity around apogee.

Conversely, after the moon rounds its apogee, then Earth’s gravity pulls the moon back towards its perigee (its closest approach to Earth), so our moon then travels at fastest around perigee.

After our moon travels around perigee and starts heading back towards its apogee again, the entire process repeats (albeit, no two orbits are exactly the same). Everyone agrees that this is what causes our moon’s varying orbital velocity.

What we disagree on is the cause of longitudinal librations!

Whether you know it or not, YOU claim Longitudinal Librations are caused by an imbalance between varying orbital speed and our moon's steady polar axial rotation.

I claim that our fully despun moon moon is instead merely facing its empty focus twice each orbit, and that our moon's varying orbital speed has nothing to do with it since longitudinal librations are caused by the changing geometric viewing angles of an observer here on Earth, as shown in this graphic:



To determine who is correct, let’s first review Wikipedia’s explanation (which is clearly wrong but consistent with many websites):

Quote:
The Moon is in synchronous rotation, meaning that it keeps the same face toward Earth at all times. This synchronous rotation is only true on average, because the Moon's orbit has a definite eccentricity. As a result, the angular velocity of the Moon varies as it orbits Earth and hence is not always equal to the Moon's rotational velocity. When the Moon is at its perigee, its rotation is slower than its orbital motion, and this allows us to see up to eight degrees of longitude of its eastern (right) far side.

Conversely, when the Moon reaches its apogee, its rotation is faster than its orbital motion and this reveals eight degrees of longitude of its western (left) far side
. This is referred to as longitudinal libration.

https://en.wikipedia.org/wiki/Orbit_...Moon#Libration

While Wikipedia’s explanation is clearly wrong, nevertheless, it does reflect the views of many websites on the subject, such as this one from a UK site:


ii) Longitudinal libration

Longitudinal libration, by Greg Smye-Rumbsy

The Moon moves in an elliptical orbit around the Earth. As a result it does not move at a constant speed (this is Kepler's second law)

However the Moon rotates at a constant speed. When it is moving faster in its orbit, this allows observers on Earth to see around the trailing edge of the Moon. When it is moving slowly it is possible to see around the Moon's leading edge.

http://www.rmg.co.uk/gcse-astronomy/...#39;s-movement



The above citation claims that “ ...the Moon rotates at a constant speed. When it is moving faster in its orbit, this allows observers on Earth to see around the trailing edge of the Moon. When it is moving slowly it is possible to see around the Moon's leading edge.

That UK site is utterly wrong since our moon’s maximum Longitudinal Librations happen midway between apogee and perigee, with no Longitudinal Librations precisely at apogee and perigee.

If synchronous rotation theory were correct, then you’d indeed expect maximum librations during the slowest (@ apogee) and fastest (@ perigee) portions of our moon’s orbit, but that simply is not when maximum librations happen!

This site is basically correct since it states maximum librations are a result of the moon’s eccentric (elliptical) orbit:

Quote:
"You may have noticed while examining the pictures above that the two images of the Moon differ not only in size, but in the position of features on the disc of the Moon. This might seem puzzling in light of the frequently-stated assertion “the Moon always keeps the same face toward the Earth”. But this generalisation is not strictly true; in fact, the combination of the eccentricity and inclination of the Moon's orbit causes the Moon, as seen from the Earth, to nod up and down and left and right.

These apparent motions, the lunar librations, allow us to observe, over a period of time, more than 59% of the Moon's surface from the Earth, albeit with the terrain in the libration zones near the edge of the visible disc, only very obliquely.”


https://www.fourmilab.ch/earthview/moon_ap_per.html

Here’s another one, and while this site correctly states that maximum librations don’t coincide with apogee or perigee it has other problems:
At perigee or apogee, there is NO libration of longitude.”.
While correct about the timing of longitudinal librations, that site incorrectly states that the moon’s changing orbital velocity is involved in longitudinal librations (it’s not), and it also incorrectly identifies the proper limb that is revealed one week before, and one week after apogee (they have the correct lunar limbs reversed):

Quote:
"Libration of longitude, the Moon's east-west wobble, is a product of the Moon's elliptical (elongated) orbit. Although the Moon's rotation is nearly constant, its orbital speed various, going fastest at perigee (Moon's closest approach to Earth) and slowest at apogee (Moon's farthest point from Earth).

"At perigee or apogee, there is NO libration of longitude. Maximum librations are seen about one week AFTER perigee and one week AFTER apogee, revealing (depending upon the month) up to 8 degrees of longitude on the Moon's far side.

Following perigee, the Moon's rotation can't keep pace with its orbit, so a slice of the Moon's back side slips into view along the Moon's east (or right) limb; following apogee, the Moon's rotation surges ahead of its orbit, causing a sliver of the Moon's back side to appear along the west (or left) limb.”

http://www.idialstars.com/luli.htm

Here’s another site that correctly states that maximum libration doesn’t coincide with apogee and perigee, and even though it mentions synchronous rotation, it has a graphic that shows where maximum libration occurs (at midpoint between perigee and apogee), which is NOT consistent with synchronous rotation theory:

Quote:
"Libration of the Moon –– the apparent periodic pendulum-like oscillations of the moon at its center, as a result of which the spots on the lunar disk seen by an observer on the earth appear to shift slightly first in one direction and then in the other. Optical (geometric) libration and physical libration are distinguished.

"Optical libration in longitude occurs because the moon revolves about the earth nonuniformly while it rotates about its axis at a constant angular velocity. Figure 1 depicts an elliptic lunar orbit;

"Figure 1. Libration in longitude



"T is the Earth (at the focus of the ellipse). When the moon is at position A (perigee), let some point a on its surface be visible at the center of the disk. After a quarter of a month, the moon will be at point B and will have turned about its axis one-fourth of a revolution, that is, 90°. The point a observed from the earth will no longer be visible at the center of the disk but will have shifted to the east. At position C (apogee), the point a again coincides with the center of the disk. At the end of the third quarter, the point a will lie to the west of the center at position D. The largest libration in longitude is 7°45″.”

http://encyclopedia2.thefreedictiona...on+of+the+Moon
Click on the spoiler to review several other websites which likewise rely on lunar polar axial rotation to explain longitudinal librations, as well as WRONGLY claiming that maximum librations coincide with apogee and perigee:

"On average, the Moon is tidally locked to the Earth’s surface. But its actual orbit is elliptical, it moves closer and then more distant from the Earth.

"When the Moon is at its closest point [perigee], it’s rotation is slower than its orbital speed, so we see an additional 8 degrees on its eastern side. And then when the Moon is at the most distant point, the rotation is faster than its orbital speed, so we can see 8 degrees on the Western side.”


http://www.universetoday.com/19699/d...e-moon-rotate/[/quote]


KEN: Another site with bad info:

Quote:
"Lunar libration

"In addition to its orbit around the Earth, the Moon rotates around its axis at a constant speed. Like all celestial objects with elliptical orbits, the Moon's speed varies on its path around the Earth - it speeds up when it is at its perigee, and slows down when it is at the apogee. This means that at its perigee, the Moon's orbital speed is faster than its rotational speed.

"This causes lunar libration, a slow rocking back and forth of the Moon. This allows an observer on Earth to see slightly different portions of the Moon’s surface at different times. About 58% of the Moon's surface is visible from Earth, though at any given time, you can only see 50% of the Moon.”

http://www.timeanddate.com/astronomy...ee-apogee.html

KEN: Another site with bad info:

Quote:
"Does the Moon Wobble?

"The Moon doesn't really wobble, but we do see more than 50% of the surface over time. The Moon's orbit is not a perfect circle, but is actually an ellipse. That means that when it is closer to the Earth it orbits a little faster; when it is farther out it orbits a little slower.

The rate of rotation of the Moon itself is constant, though, so when the Moon moves at a different speed in its orbit, it is effectively changing the rotation rate relative to the Earth. Sometimes we see a little bit past one edge, and sometimes a little past the other (this is in the East-West direction). This effect is called "libration." As a result we're able to see roughly 59% of the lunar surface over time.”

http://www.digipro.com/Trials/moon.html

KEN: Another site with bad info:

Quote:
"Libration of Longitude is like the Moon “shaking its head no,” and it results from the Moon’s elliptical orbit. The reason why the Moon keeps the same face toward Earth is because it rotates once per revolution. But whereas its rotation speed remains constant, its orbital velocity changes. The Moon orbits the fastest when closest to Earth, and slowest when furthest away. This causes the Moon’s rotation to lag behind its revolution after it reaches perigee, its closest approach to Earth, and we see a few degrees further to lunar east. Then, two weeks later, the opposite happens; the Moon’s revolution lags behind its rotation after it reaches apogee, its furthest distance from Earth. This gives us a peek of a few degrees to lunar west.”///

https://petersoncello.wordpress.com/...-october-2010/



If you disagree that maximum longitudinal librations occur midway between apogee & perigee, then here is Nasa’s Longitudinal Libration Calculator to prove it:

https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4236

To make sense of it, look at the “Sub-Earth E” reading as it changes from around zero degrees at apogee & perigee in this screen-cap:



To slightly over 5° midway between apogee & Perigee, as show here (max libration can only be slightly above 7°):



If you’re going to successfully argue Synchronous Rotation theory, then you will need to logically explain why maximum longitudinal librations occur midway between apogee & perigee!

If you can logically explain that, then you’ll be the first person to do it!

If your synchronous rotation theory does NOT match all of the observable data about our moon, then it may be time to review your theory!
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Old 6th September 2015, 11:32 PM   #23
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Originally Posted by Gord_in_Toronto View Post
No. The Earth rotates on its axis in 23 hours 56 minutes and 9 seconds.

From the sidereal (OUTSIDE) perspective, since you must aggregate 360˚ polar axial rotations (if any) with a body's single 360˚ orbit around its primary, Earth does have 366.25 'APPARENT' polar axial rotations per orbit, and each of those 366 'APPARENT' polar axial rotations does indeed work out to about 23 hours 56 minutes and 9 seconds each.

Nevertheless, Earth only has 365.25 actual polar axial rotations per orbit (24 hours each), so that 366th 'APPARENT' polar axial rotation is of course not a true polar axial rotation, it's just Earth's 360˚ orbit around the sun.

This intelligently written 1864 letter by an English astronomer mentions your 23 hours 56 minutes 366th rotation, so they've known about the absurdities inherent in the sidereal perspective for quite awhile.

As this 1864 letter also proves, this synchronous rotation controversy is not new (I particularly like his explanation #5 below):

Quote:
THE MOON CONTROVERSY,

TO THE EDITOR OF THE ASTRONOMICAL REGISTER.

"Sir,—On reviewing the whole controversy respecting the moon's
rotation, or non-rotation, on her own axis, it will be observed that
mathematicians are ranged on one aide, and practical mechanics and
engineers on the other, and that theory is at variance with practice.

"Mathematicians have adopted a quasi definition of rotation, which
leads to innumerable absurdities, e.g. that every atom of a spinning-
top rotates on its own axis, that the ball on St. Paul's cathedral
rotates on its own axis once in 23h, 56m
, etc, etc..


"They use the terms of "rotation" and "rotation on its own axis" as though
they were synonymous in meaning, quite overlooking the distinction
between axial and radial rotation.
It would surely be quite possible
for them to be more concise in the use of language without calling in
question any single mathematical deduction or truth of any sort or
kind. It would be better to understand the term "rotation" in the
sense used by mechanics, engineers, and men of plain common sense.

"It is really astonishing how one writer after another, like Mr. Bird
in the last No. of the Register, can persuade themselves that "turning
round" necessarily involves "rotation," either axial or radial.

"Before closing the correspondence on this most interesting subject
it may be as well to notice Sir John Herschel's illustration of axial
rotation. He "plants a staff in the ground, and, grasping it in both
hands, walks round it, keeping as close to it as possible, with his face
always turned towards it, "when the unmistakable sensation of
giddiness effectually satisfies him of the fact that he has rotated on his
own axis!"

"Mr. Bertram Mifford, of Cheltenham, in a letter addressed
to the Practical Mechanics' Journal, Dec. 1, 1859, thus effectually dis¬
posed of this most transparent fallacy by the following arguments;—

"1. Because giddiness may be produced in various other ways, by
looking over a precipice, etc.

"2. Because (mechanically speaking) no man can walk round his
own axis in any way, much less turn upon it when holding on to any
fixed object, which must be external to his body. He may walk his
axis round any object he pleases, but he cannot in any sense walk
round his own axis.

"3. Because a man holding by a stick and revolving round it turns
on the axis of the stick and not on his own axis, the axis of the stick
in this case becoming the common axis of both man and stick.

"4. The alteration of the relative position of the objects round him is
no proof that the man has turned on his own axis, he has merely
dragged his axis after him, and has not turned upon it.

"5. "Keeping as close to it as possible" is certainly the nearest
approach to turning on his own axis, but until he is impaled on the
stick and turned on it he does not revolve (mechanically speaking) on
his own axis.

"Fearing to trespass at too great a length on your space,
I have the honour to be, very faithfully yours,

"Buckland: Nov. 12, 1864. ACADEMICUS."

John G-Wolbach Library, Harvard-Smithsonian Center for Aslrophysics • Provided by the NASA Aslrophysics—

The above letter (starting on page 19) and other pro & con letters on the issue can be found here:

http://articles.adsabs.harvard.edu//...00034.000.html
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Old 6th September 2015, 11:36 PM   #24
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Originally Posted by phunk View Post
Why would it need to spin around the spindle, the spindle itself is spinning.

PRECISELY MY POINT!!!

The metal spindle's axis is the center of the Earth with zero polar axial spins by the faux moon around that supporting metal spindle, which proves synchronous rotation theory is a pile of bunk.

Thank you for being observant!

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Old 6th September 2015, 11:42 PM   #25
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Originally Posted by Ken Dine View Post
http://i.imgur.com/g8zua5s.jpg




PRECISELY MY POINT!!!

The metal spindle's axis is the center of the Earth with zero polar axial spins by the faux moon around that supporting metal spindle, which proves synchronous rotation theory is a pile of bunk.

Thank you for being observant!
Then why, in your opinion, is the moon showing the same face to the earth all the time, if not for synchronous rotation?
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Old 6th September 2015, 11:44 PM   #26
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Am I the only person who thinks this "issue" is just people trying to confuse themselves for the simple pleasure of it?

I honestly don't see the controversy, which is a bummer for me since I enjoy arguing about stupid things.
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Old 7th September 2015, 12:13 AM   #27
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Originally Posted by erwinl View Post
Then why, in your opinion, is the moon showing the same face to the earth all the time, if not for synchronous rotation?

As I've explained above, our moon was fully despun billions of years ago, so today our moon is left with a single 360˚ orbit around Earth approximately every 29.5 days.

Think of a racetrack. As the cars race 360˚ around the track the people in the stands (in the sidereal outside perspective) will see both sides of each car as they complete a lap.

However, people in the infield will only see the left doors of each car (unless they spin out around their center-mass).

Where is the spin axes of these race cars?

Their turn axes would be in the infield!

Are the cars spinning 360˚ around their center-mass each lap, or are they instead merely turning around their center-mass each lap?

This would be easier to grok if you try this simple demonstration of "SPIN" using a can of tuna (or any round object), which I like to call my Tuna Can Experiments - don't worry, it only takes a minute to do!

Your body would represent the Earth and a can of tuna in your outstretched hand would represent the moon. You really need to actually get off your arse and do this for these spatial relationships to actually sink in!

Quote:
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.

Now that you understand what it means for an object to rotate around its own center-mass, let's proceed.

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.

This is what our moon does.

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). Have a friend in the outside (sidereal) perspective count, and they will count two (2) rotations while you in the center will only count one (1) rotation.

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 A zero sidereal rotation RATE (0:1).

Venus is fairly close to doing that right now.

In EXAMPLE #4, 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.

Venus is currently spinning down that way from the CW direction and is now rotating a tad faster than zero (.92 from the sidereal perspective, but 1.92 CW rotations left from the center-point perspective).

NOTE that when an astronomical body spins down from the retrograde CW direction it will 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!
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Old 7th September 2015, 12:20 AM   #28
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Originally Posted by Ken Dine View Post
As I've explained above, our moon was fully despun billions of years ago, so today our moon is left with a single 360˚ orbit around Earth approximately every 29.5 days.

Think of a racetrack. As the cars race 360˚ around the track the people in the stands (in the sidereal outside perspective) will see both sides of each car as they complete a lap.

However, people in the infield will only see the left doors of each car (unless they spin out around their center-mass).

Where is the spin axes of these race cars?

Their turn axes would be in the infield!

Are the cars spinning 360˚ around their center-mass each lap, or are they instead merely turning around their center-mass each lap?

This would be easier to grok if you try this simple demonstration of "SPIN" using a can of tuna (or any round object), which I like to call my Tuna Can Experiments - don't worry, it only takes a minute to do!

Your body would represent the Earth and a can of tuna in your outstretched hand would represent the moon. You really need to actually get off your arse and do this for these spatial relationships to actually sink in!




In EXAMPLE #4, 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.

Venus is currently spinning down that way from the CW direction and is now rotating a tad faster than zero (.92 from the sidereal perspective, but 1.92 CW rotations left from the center-point perspective).

NOTE that when an astronomical body spins down from the retrograde CW direction it will 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!
Those are a lot of words where you prove that the Moon spins around its axis once every revolution around the Earth. As do the racing cars around the track.

Now. Having proved that by you and agreeing with current knowledge, what is the problem exactly?
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Old 7th September 2015, 12:32 AM   #29
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Originally Posted by marplots View Post
Am I the only person who thinks this "issue" is just people trying to confuse themselves for the simple pleasure of it?

I honestly don't see the controversy, which is a bummer for me since I enjoy arguing about stupid things.

Well, you're in good company since that's basically what they said about Galileo Galilei's heliocentrism model:

Quote:
During the Late Middle Ages, Bishop Nicole Oresme discussed the possibility that the Earth rotated on its axis, while Cardinal Nicholas of Cusa in his Learned Ignorance asked whether there was any reason to assert that the Sun (or any other point) was the center of the universe.

In parallel to a mystical definition of God, Cusa wrote that "Thus the fabric of the world (machina mundi) will quasi have its center everywhere and circumference nowhere.

Nicholas of Cusa, De docta ignorantia, 2.12, p. 103, cited in Koyré (1957), p. 17.

In the end, it's probably much easier to just teach the kiddies that the Earth is flat, so why waste time teaching them the truth, which can be complicated and probably not make them a dime extra on the assembly line.

Just show the kiddies the Lunatics' Penny around the Quarter parlor trick and call it good (can you spot why this proof is bogus?):

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Old 7th September 2015, 12:44 AM   #30
marplots
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Originally Posted by Ken Dine View Post

In the end, it's probably much easier to just teach the kiddies that the Earth is flat, so why waste time teaching them the truth, which can be complicated and probably not make them a dime extra on the assembly line.

Just show the kiddies the Lunatics' Penny around the Quarter parlor trick and call it good (can you spot why this proof is bogus?):

https://planetarium.madison.k12.wi.u...tationani2.gif
Um, as far as I can tell, there's no difference between the two descriptions except the insistence on one particular way of saying it is better than the other.

Is there some consequential difference I'm missing?
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Old 7th September 2015, 12:48 AM   #31
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Originally Posted by erwinl View Post
Those are a lot of words where you prove that the Moon spins around its axis once every revolution around the Earth. As do the racing cars around the track.

I was actually arguing the opposite. Oh, well?

Originally Posted by erwinl View Post
Now. Having proved that by you and agreeing with current knowledge, what is the problem exactly?

Let's try it again.

Our moon has two (2) potential spin axes, (#1) its polar axis (if any); and/or (#2) its orbital axis around the combined mass of the Earth-moon system (called a barycenter).

The issue here is, does our moon have both spin axes left (as our Earth does), or does our fully despun moon today retain only its 360º orbital revolution around Earth?

How many spin axes do you see that our moon now has today?

I only see #2 above, which is our moon's orbital axis around the combined mass of the Earth-moon system (which is a point about 1,000 km below Earth's surface).
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Old 7th September 2015, 12:52 AM   #32
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Originally Posted by marplots View Post
Um, as far as I can tell, there's no difference between the two descriptions except the insistence on one particular way of saying it is better than the other.

Which two descriptions are you referring to?

Originally Posted by marplots View Post
Is there some consequential difference I'm missing?

I'm confused as to why you're confused? Can you elaborate some about your particular dilemma?
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Old 7th September 2015, 01:01 AM   #33
marplots
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Originally Posted by Ken Dine View Post
Let's try it again.

Our moon has two (2) potential spin axes, (#1) its polar axis (if any); and/or (#2) its orbital axis around the combined mass of the Earth-moon system (called a barycenter).

The issue here is, does our moon have both spin axes left (as our Earth does), or does our fully despun moon today retain only its 360º orbital revolution around Earth?

How many spin axes do you see that our moon now has today?
What's the difference? The testable difference in some set of data? Would, for example, the measured centrifugal force on the moon be different?

Last edited by marplots; 7th September 2015 at 01:03 AM.
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Old 7th September 2015, 01:03 AM   #34
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Originally Posted by Ken Dine View Post
I was actually arguing the opposite. Oh, well?




Let's try it again.

Our moon has two (2) potential spin axes, (#1) its polar axis (if any); and/or (#2) its orbital axis around the combined mass of the Earth-moon system (called a barycenter).

The issue here is, does our moon have both spin axes left (as our Earth does), or does our fully despun moon today retain only its 360º orbital revolution around Earth?

How many spin axes do you see that our moon now has today?

I only see #2 above, which is our moon's orbital axis around the combined mass of the Earth-moon system (which is a point about 1,000 km below Earth's surface).
No.

The moon has one spin axis. Through the Moon polar axis to be exact.
It revolves around the Earth-Moon barycenter though. That is not spinning.
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Old 7th September 2015, 01:15 AM   #35
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Originally Posted by Ken Dine View Post
Astronomer Steve Smyers explains why the center-point and sidereal perspectives always differ by one (1):




As astronomer Steven Smyers also explains on his above website, from the sidereal perspective our Earth has 366.25 (apparent) rotations per year, while from the center-point perspective of our sun, our Earth has 365.25 polar axial rotations per year (i.e., solar days).

The math is simple, subtract one (-1) from Earth’s 366.25 (apparent) SIDEREAL polar axial rotations per year and that will give you Earth’s actual polar axial rotations (DAYS) per year:

366.25 - 1 = 365.25 actual polar axial rotations per year.

Subtract one (-1) from our moon’s single (apparent) polar axial rotation per month (every 29.5 days), and that will give you the moon’s actual polar axial rotations per month:

1 - 1 = 0 actual polar axial rotations per month.

The math is grade-school simple, and it proves that our moon has ZERO polar axial rotations left!




An astronomical body either has spin inertia around its center-mass (i.e., polar axis), or it doesn’t.

You can widen the perspective to include the Earth-moon’s orbit around our sun (which also has its own inertia), and you can also consider our solar system’s inertia around our galaxy’s center, ad nauseum, but what we’re considering here is whether a fully despun moon still retains 1 polar axial rotation per orbit, or does it instead have ZERO polar axial rotation per orbit?




YES, but in his class-notes astronomer Steven Smyers explains why that would happen without any polar axial rotation after a body has been despun, such as he explains here using the Earth as his example:




Compare the above graphic to this one again which depicts an astronomical body which clearly still has some polar axial rotations left:


http://www.aoc.nrao.edu/~smyers/cour...01/L5-sid3.gif




The main spin inertia that would cause the stars to move while standing upon the moon, that would be the inertia of the moon’s 360˚ orbital revolution around Earth.

Clearly, Earth has both polar axial rotations (365.25 / orbit), as well as orbital velocity around our sun, as explained above. Our moon only has its 360˚ orbital revolution left.

Everyone agrees (at least I do) that our moon has been despun (likely billions of years ago) by tidal braking forces, as explained by Charles Darwin’s son, George Darwin.

The issue here is whether a fully despun moon still retains one last 360˚polar axial rotation, or not?

I maintain that today our fully despun moon ONLY retains its 360˚ orbit around the Earth, and I can prove it!




Are you asking whether the stars appear to move from our perspective while standing upon Earth’s surface? If so, then YES!

However, from Earth’s perspective the stars appear to primarily move in our sky due to Earth’s polar axial rotation, as well as to a lesser degree by Earth’s orbit around the sun, and to an even lesser degree as our entire solar system also moves in relation to the background stars.

When looking at our moon at night from Earth, our moon appears to rise in the East and set in our West, thus appearing to travel in a clockwise (CW) direction (when looking down on Earth’s North pole). However, our moon is actually orbiting in the opposite CCW direction around Earth!

Our moon only APPEARS to be going CW (east to west) in its orbit since Earth’s CCW polar axial rotation is faster (24 hours) than the moon’s 29.5 day CCW orbit around us.

What you think you see does not always reflect reality.




You have baldly claimed something, but you still need to prove it! Which force would cause such a perfect synchronization, GOD?

INDEED, instead of attempting to explain this amazing coincidence of effects early astronomers often just chalked it up as further evidence of a Supreme Intelligence – as astronomer Robert Grant explained back in 1852:




Hallelujah!

As intelligent skeptics, let’s discuss whether your synchronous rotation beliefs are valid, and to do that, we need to discuss our moon’s Longitudinal Librations, because if our moon’s Longitudinal Librations are NOT consistent with synchronous rotation theory, then it means that YOU should honestly reexamine synchronous rotation theory, as any good skeptic should do when faced with inconsistencies.

So then, using synchronous theory as your model, what exactly causes our moon’s (supposedly) single remaining 360˚ polar axial rotation to be in nearly perfect sync with its 360˚ revolution around Earth?

To be clear, the center-point of our moon’s NEAR-SIDE does NOT always point directly at Earth, so the sync (if any) isn’t perfect, which is why we have longitudinal librations of our moon where the moon seemingly shakes its head back and forth (the moon’s apparent nodding up & down are called latitudinal librations).

Most astronomy sites, in conformance with synchronous rotation theory, claim that longitudinal librations are caused by the disparity between our moon’s steady polar axial rotation coupled with our moon’s varying orbital speeds.

All astronomical bodies have elliptical orbits (basically, an oval) with the primary they orbit around occupying one focus of the ellipse, and the far turn’s elliptical radius has an ‘Empty Focus’, thus, as our moon pulls away against Earth’s gravity to reach its farthest point away from us (apogee), our moon travels at its slowest orbital velocity around apogee.

Conversely, after the moon rounds its apogee, then Earth’s gravity pulls the moon back towards its perigee (its closest approach to Earth), so our moon then travels at fastest around perigee.

After our moon travels around perigee and starts heading back towards its apogee again, the entire process repeats (albeit, no two orbits are exactly the same). Everyone agrees that this is what causes our moon’s varying orbital velocity.

What we disagree on is the cause of longitudinal librations!

Whether you know it or not, YOU claim Longitudinal Librations are caused by an imbalance between varying orbital speed and our moon's steady polar axial rotation.

I claim that our fully despun moon moon is instead merely facing its empty focus twice each orbit, and that our moon's varying orbital speed has nothing to do with it since longitudinal librations are caused by the changing geometric viewing angles of an observer here on Earth, as shown in this graphic:

http://i.imgur.com/T6SgHYb.png

To determine who is correct, let’s first review Wikipedia’s explanation (which is clearly wrong but consistent with many websites):




While Wikipedia’s explanation is clearly wrong, nevertheless, it does reflect the views of many websites on the subject, such as this one from a UK site:


ii) Longitudinal libration

Longitudinal libration, by Greg Smye-Rumbsy

The Moon moves in an elliptical orbit around the Earth. As a result it does not move at a constant speed (this is Kepler's second law)

However the Moon rotates at a constant speed. When it is moving faster in its orbit, this allows observers on Earth to see around the trailing edge of the Moon. When it is moving slowly it is possible to see around the Moon's leading edge.

http://www.rmg.co.uk/gcse-astronomy/...#39;s-movement



The above citation claims that “ ...the Moon rotates at a constant speed. When it is moving faster in its orbit, this allows observers on Earth to see around the trailing edge of the Moon. When it is moving slowly it is possible to see around the Moon's leading edge.

That UK site is utterly wrong since our moon’s maximum Longitudinal Librations happen midway between apogee and perigee, with no Longitudinal Librations precisely at apogee and perigee.

If synchronous rotation theory were correct, then you’d indeed expect maximum librations during the slowest (@ apogee) and fastest (@ perigee) portions of our moon’s orbit, but that simply is not when maximum librations happen!

This site is basically correct since it states maximum librations are a result of the moon’s eccentric (elliptical) orbit:




Here’s another one, and while this site correctly states that maximum librations don’t coincide with apogee or perigee it has other problems:
At perigee or apogee, there is NO libration of longitude.”.
While correct about the timing of longitudinal librations, that site incorrectly states that the moon’s changing orbital velocity is involved in longitudinal librations (it’s not), and it also incorrectly identifies the proper limb that is revealed one week before, and one week after apogee (they have the correct lunar limbs reversed):




Here’s another site that correctly states that maximum libration doesn’t coincide with apogee and perigee, and even though it mentions synchronous rotation, it has a graphic that shows where maximum libration occurs (at midpoint between perigee and apogee), which is NOT consistent with synchronous rotation theory:



Click on the spoiler to review several other websites which likewise rely on lunar polar axial rotation to explain longitudinal librations, as well as WRONGLY claiming that maximum librations coincide with apogee and perigee:

"On average, the Moon is tidally locked to the Earth’s surface. But its actual orbit is elliptical, it moves closer and then more distant from the Earth.

"When the Moon is at its closest point [perigee], it’s rotation is slower than its orbital speed, so we see an additional 8 degrees on its eastern side. And then when the Moon is at the most distant point, the rotation is faster than its orbital speed, so we can see 8 degrees on the Western side.”


http://www.universetoday.com/19699/d...e-moon-rotate/



KEN: Another site with bad info:




KEN: Another site with bad info:




KEN: Another site with bad info:





If you disagree that maximum longitudinal librations occur midway between apogee & perigee, then here is Nasa’s Longitudinal Libration Calculator to prove it:

https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4236

To make sense of it, look at the “Sub-Earth E” reading as it changes from around zero degrees at apogee & perigee in this screen-cap:

http://i.imgur.com/ljh0AfH.png

To slightly over 5° midway between apogee & Perigee, as show here (max libration can only be slightly above 7°):

http://i.imgur.com/xh3V5hE.png

If you’re going to successfully argue Synchronous Rotation theory, then you will need to logically explain why maximum longitudinal librations occur midway between apogee & perigee!

If you can logically explain that, then you’ll be the first person to do it!

If your synchronous rotation theory does NOT match all of the observable data about our moon, then it may be time to review your theory![/quote]

I have no problems with longitudinal libration being due to the variation in speed of the moon taking an elliptical orbit vs the constant axial spin. This would give maximal libration between apogee and perigee. To put it simply, At the nearest point of its orbit to earth the moon moves fastest, so there is an increasing discrepancy between synchrony. This reaches its maximum at the midpoint of the orbit, then as the moon approaches its furthest point orbital speed slows and the axial rotation catches up until discrepancy is zero at the furthest point.

bolded my response as otherwise it is hard to separate from yours because I didn't format properly first time!

Last edited by Planigale; 7th September 2015 at 01:23 AM.
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Old 7th September 2015, 01:34 AM   #36
Ken Dine
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Originally Posted by PhantomWolf View Post
This is a gif I made for the last person I found that didn't understand that the moon rotated….


How is your graphic any different than this Penny-around-the-Quarter parlor trick graphic:



Take the penny and then scotch-tape it to the top of the faux moon in this child’s orrery, and then crank that orrery around as long as you like:




Do you really see that penny (and faux moon) rotating around their center-mass, or are they just REVOLVING around the faux Earth?

Think about it!

BTW - the Penny-around-the-Quarter parlor trick is often what the Lunatics use to beguile and convince people that our moon has synchronous rotation, from this site:

https://planetarium.madison.k12.wi.u.../moonfaq.htm#1

After they place the penny and quarter on the table they tell the sucker to keep Lincoln's head pointing at the quarter as they move the penny CCW around the quarter, which requires the sucker to manually turn the penny to keep it pointing inwards at the quarter.

After that, they then tell the sucker to place their finger firmly on the penny and move the penny around the quarter, and the penny will of course point in one direction, as shown in this graphic:



The trick is a basic misdirection to take the sucker's mind off of what that supposedly zero-rotating penny is actually doing, which is turning 360˚ once around its center-mass in the CW direction as it revolves around the quarter (Earth) 360˚ in the opposite CCW direction, and two 360˚ spins around two different axes in opposite directions merely cancel each other out.

Of course, it’s easier to do the Penny-around-the-Quarter parlor trick while sitting at a table. Nevertheless, place the quarter on your kitchen floor, then firmly place your finger on the penny as you spin around on your knees over the quarter, and this time the penny will remain pointing at the quarter with no need to manually turn the penny.

While the table may be more comfortable than getting down on the kitchen floor to do the Penny-around-the-Quarter parlor trick, that’s not how science works!

The Penny-around-the-Quarter demonstration is clearly a parlor trick!

Thanks for sharing, but you didn't prove a thing with your graphic.

Try doing my four Tuna-Can Experiments and this will all make more sense to you. Seriously, it may sound silly, but it works!
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Old 7th September 2015, 01:43 AM   #37
Planigale
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Originally Posted by Ken Dine View Post
As I've explained above, our moon was fully despun billions of years ago, so today our moon is left with a single 360˚ orbit around Earth approximately every 29.5 days.

Think of a racetrack. As the cars race 360˚ around the track the people in the stands (in the sidereal outside perspective) will see both sides of each car as they complete a lap.

However, people in the infield will only see the left doors of each car (unless they spin out around their center-mass).

Where is the spin axes of these race cars?

Their turn axes would be in the infield!

Are the cars spinning 360˚ around their center-mass each lap, or are they instead merely turning around their center-mass each lap?

This would be easier to grok if you try this simple demonstration of "SPIN" using a can of tuna (or any round object), which I like to call my Tuna Can Experiments - don't worry, it only takes a minute to do!

Your body would represent the Earth and a can of tuna in your outstretched hand would represent the moon. You really need to actually get off your arse and do this for these spatial relationships to actually sink in!




In EXAMPLE #4, 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.

Venus is currently spinning down that way from the CW direction and is now rotating a tad faster than zero (.92 from the sidereal perspective, but 1.92 CW rotations left from the center-point perspective).

NOTE that when an astronomical body spins down from the retrograde CW direction it will 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!
The problem with the tuna can is it not free to rotate in your hand. What you need is it suspended on a thread that it is free to rotate on (preferably with some device to measure torsion). So I would say get a length of wood then suspend by a thread a significant mass. As you rotate say clockwise, the mass will appear to you to rotate counterclockwise and the part facing you moves. The mass is keeping itself fixed in relation to the universe. Alternatively one could argue in a closed system it develops a contrawise rotation to maintain its angular momentum as zero against the angular momentum of its orbit.

ETA
This is a version of Foucault's pendulum.

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Old 7th September 2015, 01:48 AM   #38
Ken Dine
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Originally Posted by Planigale View Post
I have no problems with longitudinal libration being due to the variation in speed of the moon taking an elliptical orbit vs the constant axial spin. This would give maximal libration between apogee and perigee.

Other than your wishful thinking, how so?

Can you find even one astronomy site which supports your contention that Synchronous Rotation theory is consistent with maximum librations occurring midway between apogee and perigee?

If so, you're a better googler than I am.

Originally Posted by Planigale View Post
To put it simply, At the nearest point of its orbit to earth the moon moves fastest, so there is an increasing discrepancy between synchrony. This reaches its maximum at the midpoint of the orbit, then as the moon approaches its furthest point orbital speed slows and the axial rotation catches up until discrepancy is zero at the furthest point.[/b]

Can you explain the mystical forces which would do such a thing? Perhaps, the hand of GOD?

Have you tried doing the 4 Tuna-Can Experiments yet? Any can will work, but I prefer a tuna can since you can eat the experiment on crackers when you're done.

Originally Posted by Planigale View Post
bolded my response as otherwise it is hard to separate from yours because I didn't format properly first time!

Merely hit the Edit button, and try, try again!
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Old 7th September 2015, 02:30 AM   #39
Ken Dine
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Originally Posted by Planigale View Post
The problem with the tuna can is it not free to rotate in your hand.

The can doesn't need to be free-spinning to grok this 2-body problem. Indeed, a free-spinning contraption would muck up the experiment.

Think of gravity as a curvature of space-time caused by mass, the more the mass, the greater the distortion of space-time (Earth’s mass is 81 times greater than our moon’s mass):



Our moon is hurtling thru space in seemingly a straight path, just as these bicycles turn on a steep track while the rider essentially steers straight ahead:



Earth’s mass has distorted space-time trapping our moon in Earth’s gravity well. In short, our moon is not free to go swing freely around, so your analogy has no direct bearing.

Originally Posted by Planigale View Post
What you need is it suspended on a thread that it is free to rotate on (preferably with some device to measure torsion). So I would say get a length of wood then suspend by a thread a significant mass. As you rotate say clockwise, the mass will appear to you to rotate counterclockwise and the part facing you moves. The mass is keeping itself fixed in relation to the universe. Alternatively one could argue in a closed system it develops a contrawise rotation to maintain its angular momentum as zero against the angular momentum of its orbit.

ETA
This is a version of Foucault's pendulum.

A Foucault pendulum only works on Earth and would have zero relationship to a body in orbit, which is essentially falling towards Earth, but an object in orbit (if it is to remain in orbit) has enough velocity to keep missing Earth.

Our moon is essentially trapped in Earth's gravity well, just as the Earth-moon system is trapped within our Sun's gravity well.
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Old 7th September 2015, 04:55 AM   #40
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Consider a square room with four walls -- A, B, C and D.

Put a chair in the middle of the room.

With your back to wall A face the chair.

Walk in quarter circle while continuing to face the chair so that your back is toward wall B. Continue another quarter circle so your back is toward wall C. Note that, at this point you are now not just facing the chair, you are now facing wall A.

Initially you had your back to wall A, now you are facing it. You must have rotated a half revolution.

Continue walking while continuing to face the chair. After walking completely around the chair and your back once again is toward wall A, you will have rotated one full revolution.

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