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# Does the moon rotate (Spin)?

Thomas

1
Fri 28 Jun, 2013 07:48 am
@mark noble,
mark noble wrote:
IT is YOU who fail to understand that your diagram SUPPORTS what I'm saying.

No it does not. The moon rotates around the Earth in both diagrams. That's not the issue. The issue, and the difference, is that in the left diagram, it also rotates around its own axis, whereas in the right diagram it does not. It is the diagram where the moon does rotate around its own axis that observers on Earth always see the same side of it.
mark noble

1
Fri 28 Jun, 2013 07:50 am
@Thomas,
Again - It is you who err.
mark noble

1
Fri 28 Jun, 2013 07:54 am
@Thomas,
Draw a line from earth's axis through moon ... Now learn 'Moon no rotate', diagram 1
Thomas

2
Fri 28 Jun, 2013 07:55 am
@mark noble,
Suppose the Earth was not there in diagrams 1 and 2. Suppose there's an object nailed to the Moon's surface. In what diagram would this object "feel" a greater centrifugal force?
Thomas

2
Fri 28 Jun, 2013 07:59 am
@mark noble,
Irrelevant, because the center of the Earth is not the reference point for the Moon's rotation around its own axis. The center of the Moon is.
mark noble

1
Fri 28 Jun, 2013 08:11 am
@Thomas,
If the Earth wasn't there, the moon would not have an object to revolve around.
Have you bothered to draw a line through the moon yet, or are you just going headlong into convincing me I'm ignorant on merit's sake?

If the moon was a big bus, Driver facing Earth, ALWAYS, at what point does that bus revolve around ITSELF?.......... NEVER. It cant.
It is like my fist, at the end of my arm (Hand is FIXED at wrist) - It cannot rotate, in and of itself, else it falls off.
timur

1
Fri 28 Jun, 2013 08:16 am
Quote:
A surprising number of people are very insistent that the moon does not rotate.

Not only the Moon rotates but over time, slightly more than half (about 59%) of the Moon's surface is seen from Earth due to libration.
0 Replies

maxdancona

1
Fri 28 Jun, 2013 08:16 am
@mark noble,
So Mark,

In the second diagram you would say that the moon is spinning about its own axis?

We all get your point drawing a line between Earth and Moon, and none of us has a problem with that. That fact is irrelevant to the fact that it is rotating around its axis. A ball attached to a string you spin around your head is rotating about its own axis. A ball attached to a solid rod you spin around your head is still rotating around its own axis.

I think you problem is that you don't understand the definition of the word "spin". So answer my question. Is the moon in the second diagram spinning?
mark noble

1
Fri 28 Jun, 2013 08:27 am
@Thomas,
The moon does Not rotate on its axis - Its only direction is forward.
If you add solar-orbit into the diagram you will see that the (diagramatic cyclic impression is far from accurate). Moon's orbit around Earth is eliptical, not circular.... And its solar-orbit is arch-loop-arch-loop.
0 Replies

Thomas

1
Fri 28 Jun, 2013 08:28 am
@mark noble,
mark noble wrote:
If the Earth wasn't there, the moon would not have an object to revolve around.

Rotation isn't relative to objects, rotation is relative to points. Sometimes there are objects where the points are, sometimes there aren't. It doesn't affect the nature of the motion.

mark noble wrote:
Have you bothered to draw a line through the moon yet, or are you just going headlong into convincing me I'm ignorant on merit's sake?

Neither. I haven't bothered to draw that line because it's irrelevant. And while it happens to be true that you're ignorant of the relevant physics, I'm not all that interested in pointing it out. It's not personal, it's business. My business is to point out the relevant arguments and the valid conclusions to anyone who will listen to them. Whether that includes you is your choice.

mark noble wrote:
If the moon was a big bus, Driver facing Earth, ALWAYS, at what point does that bus revolve around ITSELF?..........

Always. The Bus's would always rotate around the Earth and itself.

mark noble wrote:
It is like my fist, at the end of my arm

It is like that. If you sit on a carousel and stretch out your fist inward, towards the axis of the carousel, your fist will rotate around the center of the carousel, and itself --- at the same angular speed.

mark noble wrote:
(Hand is FIXED at wrist) - It cannot rotate, in and of itself, else it falls off.

It can rotate if the force rotating it exceeds the force attaching it to your arm. While that's certainly unpleasant, it's perfectly possible.
mark noble

1
Fri 28 Jun, 2013 08:36 am
@maxdancona,
'so mark'? Get off your high-horse fella.

'My problem is'?

If I hold a cup, by its handle, clasped tightly, and rotate, arm outstretched, never allowing it to change face.

Is the cup rotating around its OWN axis??
NO - It is always Forward - NEVER revolving in/of ITSELF.
mark noble

1
Fri 28 Jun, 2013 08:40 am
@Thomas,
So, is my fist rotating in/of itself?
maxdancona

1
Fri 28 Jun, 2013 08:57 am
@mark noble,
Try this Mark,

Take a tennis ball on a string and spin it around your head. Then release it. It will fly off in a straight line. Now see if the string (continues) rotating around the ball, or if it remains pointing back towards you (answer as the ball has angular momentum it will continue rotating about its axis after you release it).

You could do the same experiment with a ball attached to a rod (hint: the rod will continue rotating around the ball).
mark noble

1
Fri 28 Jun, 2013 09:09 am
@maxdancona,
I don't disagree with your ball/rod theory, but the release would create that spin, for it was spinning around MY axis at the point of release.
If I did the same, applying moon's solar-orbit - the cyclic motion would be highly erratic.
But, at this point in time, the moon is not detached from earth, it is attached.

Now, using your (Hammer-throwing) scenario - Do you class the ball (hammer) as rotating on its own axis...it's OWN axis?
maxdancona

1
Fri 28 Jun, 2013 09:14 am
@mark noble,
How does the release create the spin? You are going through a lot of mental gymnastics to avoid the fact that the ball is spinning all the time.

If the earth were suddenly "detached" (i.e. the centripetal force of gravity instantly disappeared) the moon would go off in a tangent, but it would (still) be spinning.

I am not using a shotput scenario. It is more of a hammer throw. And yes, when the hammer is being spun around the atheletes head, it is most definitely spinning about its own axis. And the instant it is released, you can clearly see this.
mark noble

1
Fri 28 Jun, 2013 09:23 am
@maxdancona,
It says 'hammer'.
You are insane if you think the hammer is spinning around ITSELF!
It is clearly BEING spun around the thrower, but it is attached to a CHAIN!
The chain does NOT allow the hammer to revolve (spin) 360` per cycle. It is physically impossible.

Fil Albuquerque

1
Fri 28 Jun, 2013 09:24 am
Yes the Moon rotates on its own axis very "slowly"...for some people this might turn out confusing...the thing is the rotation of the Moon on its axis coincides with its 24H 1 year around the Earth...
maxdancona

1
Fri 28 Jun, 2013 09:25 am
@mark noble,
So an instant after the hammer leaves the thrower's hand (at this point is is going in a straight line) do you think the hammer is spinning about its axis?

Why or why not?
mark noble

1
Fri 28 Jun, 2013 09:31 am
@Fil Albuquerque,
Moon takes approx 28 days to orbit earth Fil, and a year to orbit the sun.
1 day (24 earth hrs)
Moon 1 day (approx 670 earth hrs.
0 Replies

mark noble

1
Fri 28 Jun, 2013 09:49 am
@maxdancona,
Would you class the hammer to be in comparative equality to the javelin or are you relying on your (Spin) theory bearing more weight?

It is the weight/hammer/moon having greater mass than the chain/stick that carries its tail as its motion determines. The sudden tug that is imposed upon the stick/chain/tail upon release will propel said stick/tail/chain in an equal direction to that it was propelled from at the time of its release.

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