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mclarek
User ID: 971744
05/20/2010 01:09 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would
Actually, for the "doesn't rotate" crowd, the question should be "What heavenly bodies *DO* rotate about an axis, and why?

Clare said that applied to bodies "not having an orbit", but she included Earth as falling under that definition. Whoops!
Quoting: Menow 935048

The Earth rotates about its axis ... because if it were fixed relative to the Sun (and the Sun is fixed relative to us and spins, so you could use it as your example) ...

IT WOULD STILL BE MOVING AS A BODY AROUND ITS CENTRE.

Eliminate the forward movement (rotation path) of its axis relative to the fixed point of the Earth, and NO SPIN OF ITSELF OCCURS with the Moon.

Can we get this point?
Anonymous Coward
User ID: 558013
United States
05/20/2010 01:21 PM
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Idiotic.

A spin on an axis is defined relative to fixed points. If one is travelling (with one's axis moving forward) in a CIRCLE, the inside of the circle has a fixed centre point (the axis of the Earth) and the outside of the circle has a fixed point, say, the Sun.

For the rotation to be ABOUT ITS OWN AXIS, the total body (Moon) must show all faces to fixed points on all sides of it, whether its axis is moving relative to them or not.

Quoting: mclarek 971744

The moon DOES this. For all observers anywhere EXCEPT on the earth, they see all sides of the moon as it rotates. For an observer on the sun, they see all sides of the moon. For an observer on Mars, they see all sides of the moon. For an observer on Jupiter, they see all sides of the moon. For an observer anywhere in the univers EXCEPT on the surface of the earth, they see all sides of the moon as it rotates.
Setheory
User ID: 869850
United States
05/20/2010 01:22 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would
Actually, for the "doesn't rotate" crowd, the question should be "What heavenly bodies *DO* rotate about an axis, and why?

Clare said that applied to bodies "not having an orbit", but she included Earth as falling under that definition. Whoops!

The Earth rotates about its axis ... because if it were fixed relative to the Sun (and the Sun is fixed relative to us and spins, so you could use it as your example) ...

IT WOULD STILL BE MOVING AS A BODY AROUND ITS CENTRE.

Eliminate the forward movement (rotation path) of its axis relative to the fixed point of the Earth, and NO SPIN OF ITSELF OCCURS with the Moon.

Can we get this point?
Quoting: mclarek 971744

Clare did you follow along with the thought experiment above? What about Menow’s question about removing the earth? It has been explained in many ways on this thread.

Wiki answers explains it this way:

I do admit tidal locking can make this difficult to understand, but you have been provided with the tools to aid in this.
Anonymous Coward
User ID: 558013
United States
05/20/2010 01:22 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would
Actually, for the "doesn't rotate" crowd, the question should be "What heavenly bodies *DO* rotate about an axis, and why?

Clare said that applied to bodies "not having an orbit", but she included Earth as falling under that definition. Whoops!

The Earth rotates about its axis ... because if it were fixed relative to the Sun (and the Sun is fixed relative to us and spins, so you could use it as your example) ...

IT WOULD STILL BE MOVING AS A BODY AROUND ITS CENTRE.

Eliminate the forward movement (rotation path) of its axis relative to the fixed point of the Earth, and NO SPIN OF ITSELF OCCURS with the Moon.

Can we get this point?
Quoting: mclarek 971744

The earth does not rotate around it's center. It rotates around the barycenter of the earth/moon system, as shown in the animation posted earlier.
Anonymous Coward
User ID: 558013
United States
05/20/2010 01:25 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would disagree that it is rotating and rotating on its own axis.

Now, let's slowly start the moon orbiting the earth and settling into once every 29 days while still rotating every 20 hours. Is it still rotating?

Now, let the rotation speed slow down over time to where it is rotating every 20 days. Is it still rotating?

It's rotation speed then slows further until it is tidally locked to its orbital period of 29 days. Is it still rotating?

If you say not, then when did it stop?
Quoting: Anonymous Coward 558013

mclarek
User ID: 971744
05/20/2010 01:30 PM
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Perhaps our Canadian friend couldn't stand all the factual
data and gave up trying to throw philosophy at us in hopes
that we'd give up reality in favor of sophistry.

OK - a legitimate question.

I pick up a beach ball, and hold it out away from my chest. I then turn around 360 degrees.

Did the beach ball just "rotate" ... on its "own" axis???

Nothing in your example is operating in free space. There is no actual "axis" to talk about in your example.

Uhhmm, how is "TIDAL LOCK" any different than a "zetard" holding a beach ball?

In tidal locking, both bodies are in free space and free to rotate on their own...there is no "string" or physical structure between them...only an attractive force. Weak tidal forces gradually adjust the speed of rotation of the smaller body to match the orbital period.
Quoting: Anonymous Coward 558013

YIIIIKKES!

You are confusing classical mechanics with relativity insights. I will try to blend the two to show you what EACH gives us as insights.

All is relative; relative to a fixed point (counting one or the other as fixed) then

a) both may be fixed. These are AXES of each.
b) one may be seen as "moving", or count the other as "moving".
c) when the movement is circular of one body, the centre point of the circle is considered fixed. (An outside point may also be fixed.)
d) as such, the circle around it in movement is a PATH, *relatively* speaking.
e) this relative path (or fixity, if there is no relative movement at all), relative to the other chosen fixed point (in this case the centre of the circle and an arbitrary grid of "xyz" from that) will determine relative orientation.
f) if the body on the relative path maintains its own axial grid (face, back, sides), relative to the direction of its path, which remains relative to the fixed point, no matter where the path goes (circle, stop, right angle -- even up and down, as long as it's a forward-moving turn, still relative to the path) ...
g) and if the body turns according to the path (itself defined by the fixed points) and does not turn its own body's face relative to the path's determinable direction, it has not spun; the PATH has changed.

Imagine a train: the train turns with the tracks; a spinning train moving forward is a different thing.

Can we understand this now?

The path being where the body's own axis is moving along, relative to fixed points, and inside a circular path is an even-distanced fixed point, called the orbital axis.

ANY FIXED POINT inside the circle of a circular path will see one face if the body on the path is not changing on its own axis relative to the path's forward movement.

ANY FIXED POINT outside the circle of a circular path will see different faces of the body on the path. This is actually an illusion relative to the outside fixed point.
mclarek
User ID: 971744
05/20/2010 01:42 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would disagree that it is rotating and rotating on its own axis.

Now, let's slowly start the moon orbiting the earth and settling into once every 29 days while still rotating every 20 hours. Is it still rotating?

Now, let the rotation speed slow down over time to where it is rotating every 20 days. Is it still rotating?

It's rotation speed then slows further until it is tidally locked to its orbital period of 29 days. Is it still rotating?

If you say not, then when did it stop?

Quoting: Anonymous Coward 558013

What about your own thought experiment did you not understand? Or better: what about the points re. Nancy did you not understand?

She didn't understand the Moon has an orbital path whose speed is not determined solely by the Earth, hence it is a true orbit, not a fixed satellite.

Second, she understood better than you guys that it does not orbit on its OWN AXIS (relative to its path). Its axis changes direction of the whole, along a path relative to other things. But its body, in turning around its circle always faces its next forward motion; it does NOT show different faces along its circle relative to the circle. This is viewable inside the circle (e.g., from Earth) but outside the circle, if the Earth were not in the way, the circular total movement would be visible without moving to see it, if you were far back enough.

Inside the circle of rotation, you cannot get "far enough back" to see the whole circle without turning.

Only when ALL IMAGINAL FIXED POINTS (inside the circle or outside, or on one side or other of a non-circular path) could see all sides of an object on a path, that that path is SPINNNG ON ITS OWN AXIS.

This is easiest understood from a point above.

The moving diagram shows it from above: the Earth is stopped, to help you know it is a fixed point relative to the movement they want to show of the Moon. The Sun (not shown) is the axis (line of sight and light) demonstrated by the pink dot and "North" on the map -- not real North, since we are above North looking down.

So, the Earth is a fixed point and the Sun, in this picture.

From inside the Moon's circle (with earth in it) the relatively moving Moon is always facing its directional path, and shows a side half to the fixed points in the circle.

And to us, above, it shows the top half.

Outside the circle, from the Sun, say, different halves of the sphere show and we from the top can see it's a circular movement.

SO, the Moon ORBITS relative to the Earth, spinning around the EARTH'S axis, which is fixed relative to it. The rest of the Earth can be spinning but the centre point is not.

Our diagram stops the whole, so you can see the Earth as if fixed, too. It helps, so you know there's an imaginal circle not moving in your mind, to compare the Moon's path to.

Have a good day.
mclarek
User ID: 971744
05/20/2010 01:44 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would
Actually, for the "doesn't rotate" crowd, the question should be "What heavenly bodies *DO* rotate about an axis, and why?

Clare said that applied to bodies "not having an orbit", but she included Earth as falling under that definition. Whoops!

The Earth rotates about its axis ... because if it were fixed relative to the Sun (and the Sun is fixed relative to us and spins, so you could use it as your example) ...

IT WOULD STILL BE MOVING AS A BODY AROUND ITS CENTRE.

Eliminate the forward movement (rotation path) of its axis relative to the fixed point of the Earth, and NO SPIN OF ITSELF OCCURS with the Moon.

Can we get this point?

The earth does not rotate around it's center. It rotates around the barycenter of the earth/moon system, as shown in the animation posted earlier.
Quoting: Anonymous Coward 558013

Geeeeez.

The Earth of its OWN, definitional physical self is rotating around its own centre.

The Earth and Moon are (in reality) a system, but they are also PART of the SOLAR SYSTEM, and so on.

So let's stick with, the Earth moves relative to its own axis.

It's also on a path around the Sun.

THE EARTH IS SPINNING RELATIVE TO THAT PATH DIRECTION.

The Moon is not spinning, relative to its own path direction around the Earth.

Clare
Anonymous Coward
User ID: 558013
United States
05/20/2010 01:47 PM
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Clare, why are you avoiding addressing the historic Chandler Wobble data?

I had all of 1/2 hour yest. on my computer and got as far as the Moon nonsense stuff.

Re. The Chandler Wobble -- I told the person to re-post it. I don't know what page it's on.

I was going to ask again for the post. Do you know what page it's on?

Got so bogged down, obviously, with the other posts the other day and no time yest.

Love to see it ...
Thanks!
Clare
Quoting: mclarek 971744

Here is the quote from 10 pages back:

"Clare, you do realize, don't you, that the 2005 anomaly in the Chandler wobble is only one of several in the historic record. An even larger one occured in 1920 when the phase of the wobble changed by 180 degrees and earlier in 1850 as well. Was px around in 1850 and 1920 as well?"

Anonymous Coward
User ID: 558013
United States
05/20/2010 01:52 PM
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YIIIIKKES!

You are confusing classical mechanics with relativity insights. I will try to blend the two to show you what EACH gives us as insights.

Quoting: mclarek 971744

Your use of the term "relativity" is laughable. Where did you get your education of relativity...from the back of a cereal box?

All is relative; relative to a fixed point (counting one or the other as fixed) then

a) both may be fixed. These are AXES of each.
b) one may be seen as "moving", or count the other as "moving".
c) when the movement is circular of one body, the centre point of the circle is considered fixed. (An outside point may also be fixed.)
d) as such, the circle around it in movement is a PATH, *relatively* speaking.
e) this relative path (or fixity, if there is no relative movement at all), relative to the other chosen fixed point (in this case the centre of the circle and an arbitrary grid of "xyz" from that) will determine relative orientation.
f) if the body on the relative path maintains its own axial grid (face, back, sides), relative to the direction of its path, which remains relative to the fixed point, no matter where the path goes (circle, stop, right angle -- even up and down, as long as it's a forward-moving turn, still relative to the path) ...
g) and if the body turns according to the path (itself defined by the fixed points) and does not turn its own body's face relative to the path's determinable direction, it has not spun; the PATH has changed.

Imagine a train: the train turns with the tracks; a spinning train moving forward is a different thing.

Can we understand this now?
Quoting: mclarek 971744

I understand that you are arm-waving and havn't the first clue about which you speak.
Anonymous Coward
User ID: 558013
United States
05/20/2010 01:53 PM
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THE EARTH IS SPINNING RELATIVE TO THAT PATH DIRECTION.

The Moon is not spinning, relative to its own path direction around the Earth.

Clare
Quoting: mclarek 971744

What, in your opinion, is the difference, other than the rate of rotation of the moon?
mclarek
User ID: 971744
05/20/2010 01:55 PM
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Maybe 'Clare' has joined Elle and Volar at Camp ZetaFail!

It's interesting how she made such a big deal of the 2005 "anomaly" in the Chandler Wobble, but then steadfastly evaded the subject when historical data was provided showing that the same "anomaly" had occured twice decades before.
Quoting: Anonymous Coward 558013

No, it's interesting how I requested someone to re-post it because CLEARLY I am more charitable than most of you and actually listen to what people are saying as best I can with kindness and usually show this in my cheerful attempts to "be everywhere and answer all I can".

To discount THIS EVIDENCE OF MY CHARACTER right before your eyes indicates YOU steadfastly evade reality on this issue.

If you would please re-post the data, or tell me where to find it in this long thread, I would still appreciate it very much.

I have shown that I would love to see real information --- and real scientific full understanding, which includes philosophically knowing how you know things, so we can all be on the same page and test our thoughts according to standards.

As to putting my name in quotation marks, you clearly have a small-hearted sense of reality. My manner has been open and though as many of you would like to make fun of my point about "possible realities", there are also "likelihoods". Given my open manner, it is not LIKELY that my name is not Clare, especially since I sign my posts, which NO-ONE else does.

Stop being such shits.

Let's get down to a real discussion.

Now, where are the Chandler data?

Thank you.
Clare
or "Moi" --- which someone went so far as to suggest I was using an alibi! What idiocy. It's being FUN and CUTE and that's been mostly my manner so why not try to end cheerful! You (so many of you, and sorry to those who are not) cynical people.

P.S. This "Zeta fail" crap is also ridiculous. And that I cannot take a day to myself to work and go for a walk is silly. ... Do you (the general pop. here) ever join in POSITIVE ENTHUSIASM instead of covert aggression about the topic, or aggressive enthusiasm? Yikes.
Menow
User ID: 935048
United States
05/20/2010 01:56 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would disagree that it is rotating and rotating on its own axis.

Now, let's slowly start the moon orbiting the earth and settling into once every 29 days while still rotating every 20 hours. Is it still rotating?

Now, let the rotation speed slow down over time to where it is rotating every 20 days. Is it still rotating?

It's rotation speed then slows further until it is tidally locked to its orbital period of 29 days. Is it still rotating?

If you say not, then when did it stop?

Well done, that is an effective thought experiment.

Here is an interesting question: What heavenly bodies do not rotate about an axis?

Actually, for the "doesn't rotate" crowd, the question should be "What heavenly bodies *DO* rotate about an axis, and why?

Clare said that applied to bodies "not having an orbit", but she included Earth as falling under that definition. Whoops!

Idiotic.
Quoting: mclarek 971744

Excuse me? You didn't say that your term for bodies spinning on their own axis meant that they were "not having an orbit", and using Earth as an example of such an object?

A spin on an axis is defined relative to fixed points.
Quoting: mclarek 971744

Fascinating! Tell me more.

If one is travelling (with one's axis moving forward) in a CIRCLE,
Quoting: mclarek 971744

BZZT! Why would it matter if one was moving in a 'circle'? By the way, the Moon is not moving in a 'circle' at all. You're flailing, here.

the inside of the circle has a fixed centre point (the axis of the Earth) and the outside of the circle has a fixed point, say, the Sun.
Quoting: mclarek 971744

Sorry, but the Moon does not revolve around Earth's axis, nor in a 'circle'. Neither are Earth's axis, nor the Sun "fixed points".

For the rotation to be ABOUT ITS OWN AXIS, the total body (Moon) must show all faces to fixed points on all sides of it, whether its axis is moving relative to them or not.
Quoting: mclarek 971744

What you are struggling to suggest, is that if any body is in any other state of motion, it cannot be rotating "on its axis". You tried to say that before by implying that Earth rotates at a certain "spot". It does not. I guess you abandoned that poorly-thought-through stance, without notice, like you abandon every other 'explanation' you come up with when it is shot down.

In circular motion, all points on the inside of the circle will not see all sides of a fixed axis (non-spin) with forward momentum object, whereas any fixed point on the outside (Sun) will.
Quoting: mclarek 971744

You are simply making up this "rule" to fit your conclusion. There is no such "rule".

Now, your diagram was intended to show what parts of the Moon would get sunlight and it fixed the Earth's spin (and forward momentum rotation) to show the issue.
Quoting: mclarek 971744

No, Dr P's animation had nothing to do with sunlight, if that is to what you refer.

But in fact, the "around its own axis" that you are claiming, is technically an optical illusion (relativity) as seen from objects outside the circle it describes with its momentum.
Quoting: mclarek 971744

More made-up "rules". And you attempt to invoke relativity? Really? Heh.

The 'circle' you keep invoking has NOTHING to do with whether an object is rotating. They are two separated and independant motions. One exists OBLIVIOUS to the other.

RELATIVE TO ITS PATH (in this case a circle, but it could be no path or it could be a straight line or a zig-zag) the Moon has not shown a new face.
Quoting: mclarek 971744

Sorry? You lost me. I don't see where you demonstrated any such thing. Apparently you a moving the point of observation, now, but I can't be sure.

Therefore it is not spinning on its own axis. It has forward momentum and its AXIS circles ABOUT its original directional orientation, which in this case is a fixed circular point.

Can we all understand the difference now?
Quoting: mclarek 971744

Again, you are attempting to state something about other motion affecting rotation. It does not.

If the Moon were fixed and the Sun went around it, it would still get the light change and we could still represent it with the red dot that moves.
Quoting: mclarek 971744

Is that what you think is happening? The Sun orbiting the Moon?

That red dot that moves is RELATIVE MOVEMENT OF ONE AXIS OF ONE OR THE OTHER BODY, n an axial PATH. It is not spin of the body relative to its path. At any given point on its path, it faces forward relative to its path, not spinning.

Einstein and far lesser lights would not be impressed here ... Geeeez.

:)
Quoting: mclarek 971744

I'm sure you can find any number of people who will be impressed with your 'explanation'. Try the ning.

Why do you refuse to acknowledge any of the thought exercises offered by others, yet expect everyone to wade through your dense ramblings?

One more time: What motions would the Moon exibit if Earth suddenly went missing? Would it be spinning "on its axis" or not? If not, why not? I so, when did it start, and why?
Anonymous Coward
User ID: 558013
United States
05/20/2010 01:56 PM
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What about your own thought experiment did you not understand? Or better: what about the points re. Nancy did you not understand?

She didn't understand the Moon has an orbital path whose speed is not determined solely by the Earth, hence it is a true orbit, not a fixed satellite.

Second, she understood better than you guys that it does not orbit on its OWN AXIS (relative to its path). Its axis changes direction of the whole, along a path relative to other things. But its body, in turning around its circle always faces its next forward motion; it does NOT show different faces along its circle relative to the circle. This is viewable inside the circle (e.g., from Earth) but outside the circle, if the Earth were not in the way, the circular total movement would be visible without moving to see it, if you were far back enough.

Inside the circle of rotation, you cannot get "far enough back" to see the whole circle without turning.

Only when ALL IMAGINAL FIXED POINTS (inside the circle or outside, or on one side or other of a non-circular path) could see all sides of an object on a path, that that path is SPINNNG ON ITS OWN AXIS.

This is easiest understood from a point above.

The moving diagram shows it from above: the Earth is stopped, to help you know it is a fixed point relative to the movement they want to show of the Moon. The Sun (not shown) is the axis (line of sight and light) demonstrated by the pink dot and "North" on the map -- not real North, since we are above North looking down.

So, the Earth is a fixed point and the Sun, in this picture.

From inside the Moon's circle (with earth in it) the relatively moving Moon is always facing its directional path, and shows a side half to the fixed points in the circle.

And to us, above, it shows the top half.

Outside the circle, from the Sun, say, different halves of the sphere show and we from the top can see it's a circular movement.

SO, the Moon ORBITS relative to the Earth, spinning around the EARTH'S axis, which is fixed relative to it. The rest of the Earth can be spinning but the centre point is not.

Our diagram stops the whole, so you can see the Earth as if fixed, too. It helps, so you know there's an imaginal circle not moving in your mind, to compare the Moon's path to.

Have a good day.
Quoting: mclarek 971744

Funny how you make up your own definitions. Sorry, but reality doesn't work like that. Perhaps you should go back to your silly "philosophical" mumbo-jumbo.
Anonymous Coward
User ID: 558013
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05/20/2010 02:00 PM
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Clare, answer me one question, please. If you stood at the north pole of the moon and looked straight up, what would the distant stars appear to do?
Setheory
User ID: 869850
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05/20/2010 02:02 PM
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I think everyone agrees that the moon is tidally locked so the same side is always facing the earth. However, this also means that it rotates once per lunar cycle. In other words one revolution around the earth = one rotation on its axis. If the moon didn’t rotate, then every part of the moon would face the earth at one point or another during a month.
Menow
User ID: 935048
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05/20/2010 02:03 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would
Actually, for the "doesn't rotate" crowd, the question should be "What heavenly bodies *DO* rotate about an axis, and why?

Clare said that applied to bodies "not having an orbit", but she included Earth as falling under that definition. Whoops!

The Earth rotates about its axis
Quoting: mclarek 971744

No, you said a self-spinning body is one "not having an orbit".

... because if it were fixed relative to the Sun (and the Sun is fixed relative to us and spins, so you could use it as your example) ...

IT WOULD STILL BE MOVING AS A BODY AROUND ITS CENTRE.
Quoting: mclarek 971744

Gobbldygook. Nothing you just said is different when applied to the Moon.

Eliminate the forward movement (rotation path) of its axis relative to the fixed point of the Earth, and NO SPIN OF ITSELF OCCURS with the Moon.
Quoting: mclarek 971744

Nonsense. If you stopped the Moon from orbiting Earth and held it suspended in space, we would then see all sides of it once a month.

Can we get this point?
Quoting: mclarek 971744

See above. Your analogy fell apart. Time to change it again.
mclarek
User ID: 971744
05/20/2010 02:03 PM
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THE EARTH IS SPINNING RELATIVE TO THAT PATH DIRECTION.

The Moon is not spinning, relative to its own path direction around the Earth.

Clare

What, in your opinion, is the difference, other than the rate of rotation of the moon?
Quoting: Anonymous Coward 558013

In my opinion?!

Let me explain again -- okay? I don't mind. :(

If the moon showed different faces TO ITS PATH as it moved .(Its path is itself defined by fixed points on either side ... which could THEMSELVES be moving relative to something ELSE, of course.)

The mountains are fixed in relation to the train tracks. A pond is fixed in relation to train tracks. This is true whether the tracks are in a circle or not.

Now if a choo-choo train is SPINNING relative to its tracks, as it moves forward (which as relativity indicates, is a movement only definable relative to the fixed points of the mountains and pond and so on) ...

The train will show different faces to ALL fixed points around its relative movement. Even when they are inside a circle described by its path.

I should add, however, that the fixed points and the fixity of the path (round or not), can all together be moving as well ... as mountains, ponds, and train tracks move on the SPINNING AND ORBITING EARTH INSIDE A GALAXY AND WHO KNOWS WHAT ELSE.

All are relative positions. And movement/paths are relative: to points which, relative to them are fixed. But one could also say one is ON the train and the "fixed points" of the Earth are "moving".

However, the movement or perceived movement of each side of the fixed-with-moving system will be calculable.

And from overhead, one can see what's going on.

Clare
Menow
User ID: 935048
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05/20/2010 02:06 PM
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Perhaps our Canadian friend couldn't stand all the factual
data and gave up trying to throw philosophy at us in hopes
that we'd give up reality in favor of sophistry.

OK - a legitimate question.

I pick up a beach ball, and hold it out away from my chest. I then turn around 360 degrees.

Did the beach ball just "rotate" ... on its "own" axis???

Nothing in your example is operating in free space. There is no actual "axis" to talk about in your example.

Uhhmm, how is "TIDAL LOCK" any different than a "zetard" holding a beach ball?

In tidal locking, both bodies are in free space and free to rotate on their own...there is no "string" or physical structure between them...only an attractive force. Weak tidal forces gradually adjust the speed of rotation of the smaller body to match the orbital period.

YIIIIKKES!

You are confusing classical mechanics with relativity insights. I will try to blend the two to show you what EACH gives us as insights.

All is relative; relative to a fixed point (counting one or the other as fixed) then
(snip)
Quoting: mclarek 971744

Then we may as well conclude that the Sun orbits Earth because it SEEMS to from our relative perspective.
Anonymous Coward
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05/20/2010 02:09 PM
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And from overhead, one can see what's going on.

Clare
Quoting: mclarek 971744

Yes, that the moon is rotating on its own axis every 29 days.
Returner
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05/20/2010 02:09 PM
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Clare's an idiot.

Or Volar Rebooted. My money is on the latter -- this is the same shit he pulled, sung in a different voice.

How's that Meade, VolarClare? Still hiding under the couch?
Setheory
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05/20/2010 02:11 PM
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Clare:

This may illustrate what we are talking about better than the gif provided.

Does this help?
mclarek
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05/20/2010 02:13 PM
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Another way to think about it. Let's say that the moon is not orbiting the earth, but is somehow hanging in space stationary at some distance from the earth, and it's rotating at some high rate...say once every 20 hours. We would see all sides of it every time it revolved and someone standing on its north pole would see the sky appear to be rotating around it. I don't think anyone would
Actually, for the "doesn't rotate" crowd, the question should be "What heavenly bodies *DO* rotate about an axis, and why?

Clare said that applied to bodies "not having an orbit", but she included Earth as falling under that definition. Whoops!

The Earth rotates about its axis

No, you said a self-spinning body is one "not having an orbit".

... because if it were fixed relative to the Sun (and the Sun is fixed relative to us and spins, so you could use it as your example) ...

IT WOULD STILL BE MOVING AS A BODY AROUND ITS CENTRE.

Gobbldygook. Nothing you just said is different when applied to the Moon.

Eliminate the forward movement (rotation path) of its axis relative to the fixed point of the Earth, and NO SPIN OF ITSELF OCCURS with the Moon.

Nonsense. If you stopped the Moon from orbiting Earth and held it suspended in space, we would then see all sides of it once a month.

Can we get this point?

See above. Your analogy fell apart. Time to change it again.
Quoting: Menow 935048

HOLY SHIT YOU MAKE YOURSELF DUMB! I HATE TO SAY IT BUT YOUR EGO IS SO BIG YOU CANNOT SEE.

Okay, Me-now. Honestly ... let's try again. Can you ever be wrong and admit it?

If you stopped the Earth from moving, and the Earth were fixed, which is what we're talking about, the Moon would not show all its sides.

There are 2 movements going on in this system: the Earth's rotation about its own axis AND the Moon's rotation about the Earth's axis, at different rates, by the way.

But the MOON IS NOT SPINNING!

Second, if you DID suspend the Moon, the point would be fixed and in fact we'd leave it behind as we, with our spin about ourself, moved on on our forward, orbital path (a dual motion).

The Moon has no such dual motion of spin and orbital forward momentum on the circular path.

This is why DrPostman's diagram showed it from the top, with the Earth stopped. But move about that circle, or move the Earth about (as it truly does, on a SPIN on its AXIS), and still see that anywhere YOU/THE EARTH goes -- relativity -- within the circle, or to stop the Earth as in the image, anywhere the MOON goes if you are fixed as in this image ... You cannot see the back of the Moon.

DUUUH.

That's why they stopped the Earth, but you could move the Earth in its circular self-spin and stop the Moon and ... NOPE! Same face of the Moon.

AS LONG AS THE EARTH DOESN'T MOVE ITS AXIS OUT OF THE CIRCLE.

At that point, like the Sun, it would "see" all sides of the Moon as the Moon goes around its forward path.

If the Moon were spinning on its axis as it moved forward on its spin around the Earth's axis, the Sun would "see" (or shed light on) the faces of the Moon more quickly than the mere orbit currently does.

Are we there yet, about relative movements?
Setheory
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05/20/2010 02:14 PM
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Then we may as well conclude that the Sun orbits Earth because it SEEMS to from our relative perspective.
Quoting: Menow 935048

Or if we were standing on Venus, we would conclude that the Earth does not spin.
Menow
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05/20/2010 02:16 PM
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YIIIIKKES!

Quoting: mclarek 971744

A spacecraft approaches our area from outside the Solar System. It intends to land on the Moon. The occupants have allowed for the Moon's orbital velocity of both the earth-orbit and the Sun-orbit components and other various motions EXCEPT for Lunar rotation. Does it have to allow for any additonal lateral motion of the Lunar surface due to Lunar rotation? Why not?
Anonymous Coward
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05/20/2010 02:18 PM
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DUUUH.

Quoting: mclarek 971744

Now clare is sounding just like Nancy.
mclarek
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05/20/2010 02:20 PM
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Clare:

This may illustrate what we are talking about better than the gif provided.

Does this help?
Quoting: Setheory 869850

This claims it moves about its axis. Which it does, ON A PATH. It does not SPIN on its axis as it moves.

No, it has MOVED in a CIRCLE so it ends up (if you collapsed the movement) seeing all faces from a fixed point outside the circle of the path.

And no, it does not roll this way and that, so it has an axis which it moves forward with.

As it completes the circle it has "moved about its axis" but not in the normal meaning of this expression, to mean SPIN on its axis relative to the PATH which takes it forward, in a total circle of its axis.

YIIIKES.

It must present different faces to its PATH as it goes forward or backward or left or right or circular ... to be SPINNING on its axis.

This site is pointing out that if you count the total movement it is accurate to say that it moved on its path using ONLY ONE AXIS, and that total forward movement adds up to having circled on its axis, which can be represented as the total movement around the axis (if the source is made clear, that it is not relative to the path but the path collapsed into the diagram).

What the issue REALLY is is that when you indicate the "movement around the axis" you are actually diagramming the PATH moves and the way other things (outside the circle) will see the path.

NO ONE EVER SEES THE DARK SIDE OF THE MOON.

If this were a straight-line path, we would never see part of the dark side either.

It is not spinning relative to its path.
Anonymous Coward
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05/20/2010 02:21 PM
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If you stopped the Earth from moving, and the Earth were fixed, which is what we're talking about, the Moon would not show all its sides.

Quoting: mclarek 971744

That's NOT what he asked. Again, if the moon were to suddenly stop orbiting the earth and stayed over one location on the earth, what would we see and why?

There are 2 movements going on in this system: the Earth's rotation about its own axis AND the Moon's rotation about the Earth's axis, at different rates, by the way.

But the MOON IS NOT SPINNING!

Second, if you DID suspend the Moon, the point would be fixed and in fact we'd leave it behind as we, with our spin about ourself, moved on on our forward, orbital path (a dual motion).

The Moon has no such dual motion of spin and orbital forward momentum on the circular path.
Quoting: mclarek 971744

Yes, it does. All motions are independent and can and are analyzed as such, as I explained in an earlier post. The rotation of the moon ON ITS AXIS is superimposed onto it's orbital motion around the earth. That is a simple fact and no amount of arm-waving by you can change that.

If the Moon were spinning on its axis as it moved forward on its spin around the Earth's axis, the Sun would "see" (or shed light on) the faces of the Moon more quickly than the mere orbit currently does.

Quoting: mclarek 971744

It DOES. That is why the sidereal period of the moon is 27.32 days while the synodic period is 29.53 days.

Menow
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05/20/2010 02:22 PM
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What about your own thought experiment did you not understand? Or better: what about the points re. Nancy did you not understand?
Quoting: mclarek 971744

So, you refuse to address ANY of the thought experiments?

She didn't understand the Moon has an orbital path whose speed is not determined solely by the Earth, hence it is a true orbit, not a fixed satellite.
Quoting: mclarek 971744

Pure gobbldygook and nonsense.

Nancy went on and on at sci.astro about how Newton didn't truly explain the Lunar orbit. She certainly understood that it *IS* an orbit!
Anonymous Coward
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05/20/2010 02:24 PM
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