The moons lack of rotation., page 4

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reply posted on 6-9-2012 @ 08:10 AM by ThreeNF

I'm interested in that the moon and sun have the same apparent size. Maybe we are just living in that time. I understand the moon is moving away from us at a rate of just under 4cm per year. Could life on earth exist without the moon?

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reply posted on 6-9-2012 @ 08:53 AM by CLPrime

Originally posted by PurpleChiten

Originally posted by CLPrime
reply to post by PurpleChiten

It's actually 27.3 days. The Moon's synodic period (the time it takes to complete one phase cycle) is a bit longer because the Earth is, itself, orbiting around the thing that causes those phases.

No, you are incorrect. The sidereal period is 27.3, the synodic period is about 29.5

That's what I said.

The synodic period only matters if you want to make a calendar that includes lunar phases. Since no one seems to be doing that in this thread, it's the sidereal (27.3-day) period that we're dealing with.

reply posted on 6-9-2012 @ 09:03 AM by Sublimecraft

reply to post by CLPrime

oooooh.........ooooh.........but but I was talking tides before and the old 24hr 52min thing - does that count?

Suffice to say - you are both brainiacs.

The witty purple bird and your good self should head over to the debate ring.......I think I'd like to see that one.

(OT: Hows those school kids treating you Shellie?)

reply posted on 6-9-2012 @ 09:34 AM by Soylent Green Is People

Originally posted by ThreeNF
... Could life on earth exist without the moon?

Maybe -- but it probably would be different, and probably not be us.

reply posted on 6-9-2012 @ 12:59 PM by Soylent Green Is People

Originally posted by nine11
What if humans have been living in one long ever lasting continuous day, we just mistake it for thousands of years due to phases of the moon/sun...

I really don't get what you are saying. Time is obviously continuous, and we use the measurement of an "Earth Day" (one rotation of the planet) in order to have some artificial means of keeping track of and measuring that continuous flow of time. However, a "day" is not time itself, but just a measuring device.

Obviously a "day" is measured using a real natural cycle (the rotation of the Earth), BUT in reality you could easily ignore the specific measurement device of what we call a "day", and that would not change the actual amount of time humans have been around (it would just change one of the ways we have of measuring that amount of time).

What you are saying is similar to saying that if it wasn't for the metric system (or feet and inches), then humans might actually be really, really tall.

edit on 9/6/2012 by Soylent Green Is People because: (no reason given)

reply posted on 6-9-2012 @ 07:28 PM by PurpleChiten

Originally posted by Sublimecraft
reply to post by CLPrime

oooooh.........ooooh.........but but I was talking tides before and the old 24hr 52min thing - does that count?

Suffice to say - you are both brainiacs.

The witty purple bird and your good self should head over to the debate ring.......I think I'd like to see that one.

(OT: Hows those school kids treating you Shellie?)

Exactly, calendars were originally based on lunar phases

anyway....
pretty good, worn out though! Be glad when everything hits it's "groove"!!

reply posted on 6-9-2012 @ 07:38 PM by PurpleChiten

Originally posted by CLPrime

Originally posted by PurpleChiten

Originally posted by CLPrime
reply to post by PurpleChiten

It's actually 27.3 days. The Moon's synodic period (the time it takes to complete one phase cycle) is a bit longer because the Earth is, itself, orbiting around the thing that causes those phases.

No, you are incorrect. The sidereal period is 27.3, the synodic period is about 29.5

That's what I said.

The synodic period only matters if you want to make a calendar that includes lunar phases. Since no one seems to be doing that in this thread, it's the sidereal (27.3-day) period that we're dealing with.

That's why you're incorrect

The sidreal only dictates how it travels around the earth, the synodic determines which side of the moon is facing us and that is the purpose of the thread, the moon's apparent lack of rotation.

reply posted on 6-9-2012 @ 07:46 PM by CLPrime

reply to post by PurpleChiten

Nope...that's why you're incorrect. The synodic period is influenced by the position of the Sun relative to the Earth-Moon system. The position of the Sun has nothing to do with which side of the Moon is facing the Earth.

reply posted on 6-9-2012 @ 07:47 PM by PurpleChiten

Originally posted by CLPrime
reply to post by PurpleChiten

Nope...that's why you're incorrect. The synodic period is influenced by the position of the Sun relative to the Earth-Moon system. The position of the Sun has nothing to do with which side of the Moon is facing the Earth.

no, you are mistaken. Take a moment and research it and you'll see where the issue is.

sidreal motion is motion with respect to the stars

edit on 6-9-2012 by PurpleChiten because: (no reason given)

reply posted on 6-9-2012 @ 08:01 PM by CLPrime

reply to post by PurpleChiten

Yes...sidereal motion is motion with respect to the stars. And, for all intents and purposes, the stars are stationary. They provide a stationary reference frame. The Sun is not a stationary reference frame...which is why a lunar orbital period based on the Sun is useless when it comes to describing the Earth-Moon gravitational system (including the tidal lock within that system).

reply posted on 6-9-2012 @ 08:05 PM by PurpleChiten

Originally posted by CLPrime
reply to post by PurpleChiten

Yes...sidereal motion is motion with respect to the stars. And, for all intents and purposes, the stars are stationary. They provide a stationary reference frame. The Sun is not a stationary reference frame...which is why a lunar orbital period based on the Sun is useless when it comes to describing the Earth-Moon gravitational system (including the tidal lock within that system).

I've got papers to grade and plans to write. Keep thinking about it, then ask your professor tomorrow. He'll clarify. You're on the right track but you need to keep going. You have a little misunderstanding concerning the sun, keep looking.

reply posted on 6-9-2012 @ 08:22 PM by CLPrime

reply to post by PurpleChiten

The problem with this debate, of course, is that we're both right. The sidereal rotation period of the Moon is the same as its sidereal orbital period, and its synodic rotation period is the same as its synodic orbital period. The former is relative to the stars and the latter is relative to the Sun...that's the only difference. It doesn't matter which one you go by, as long as you go by the same one for both.

And, by the way, my physics prof would probably not appreciate a call from someone he didn't even know existed 3 years ago when I was last in his class.

reply posted on 6-9-2012 @ 09:01 PM by LightWarrior11

Lol, I feel like I'm reading a debate between sheldon vs sheldon.

Bottom line is, we need another moon. I wonder what the effects would be of earh had two?

reply posted on 7-9-2012 @ 04:44 PM by PurpleChiten

Originally posted by LightWarrior11
Lol, I feel like I'm reading a debate between sheldon vs sheldon.

Maybe... but I'm MUCH better looking!!

reply posted on 7-9-2012 @ 05:14 PM by assspeaker

I have been thinking about this for years.
My logic says the reason the moon keeps the same side facing earth is magnetic forces.
I assume the following are contributing forces: the moon & earths magnetic fields, high iron content on the moon which is not evenly distributed, & a moon with a "heavy side"

To oversimplify, think of the moon as a compass needle that always points at the strongest magnetic source to it, being the earth. This does not absolutly locate the high iron, as it could be on the dark side, being repelled.

The "heavy side" hypothisis can be explained by considering the moon as a ball that is 3/4 foam and 1/4 lead.
Swing this object with the invisable string of gravity, and the heavy side would tend to stay on the outside, away from the swing center. Swing being orbit. Having a heavy side would help keep the spin out.

Seems logical to me.

reply posted on 7-9-2012 @ 05:16 PM by CLPrime

reply to post by assspeaker

If you read the first page of this thread, you'll find the correct answer (posted several times, in fact). And it's not magnetism.

reply posted on 7-9-2012 @ 07:28 PM by assspeaker

Originally posted by CLPrime
reply to post by assspeaker

If you read the first page of this thread, you'll find the correct answer (posted several times, in fact). And it's not magnetism.

I don't know what answer you refer to. (don't play games with me)
I do not agree with tidal lock or gravity as the total cause, and I am prepaired for an intellegent debate.
Gravity is responsible for orbit, and as I said if the moon had a heavy side, gravity, and inertia would both factor.
If you think tidal lock is the answer, please explain the physics to me, as it would not affect the moons lack of rotation in respect to the earth.

Please enlighten me!

reply posted on 7-9-2012 @ 07:45 PM by CLPrime

reply to post by assspeaker

When you have a small mass (like the Moon) orbiting a large mass (like the Earth) at a sufficiently close distance, the gravitational pull of the large mass causes the small mass to bulge in the direction of the large mass.

(On the Earth, the gravity of the Moon causes a bulge in the oceans, which we call tides. The Earth causes the same thing to happen with the Moon.)

The extra gravitational pull that the large mass exerts on this bulge in the small mass causes a torque, the net result of which works against the rotation of the smaller body (i.e., it slows it down).

Eventually, this causes the rotation of the small mass to lock with respect to the large mass. And there you have it: tidal locking.

reply posted on 7-9-2012 @ 07:56 PM by TeslaandLyne

reply to post by youwillneverknow

Its hard to read:
www.scribd.com...

The summary under the title:

" ... the moon contains absolutely no rotational energy, in other words, does not rotate on its axis. "

So no energy of rotation means no rotation.

To the sun that sees all sides of the Moon knows better but obviously we don't.
Seeing all sides of the Moon as the Sun does does not constitute rotation.
ED:
here is another one:
www.scribd.com...

get this:
".. there is not enough energy in the moon to run a delicate watch."

And there is a pile of numbers the science guy can correct if time permits.
(Ed+: that was 1919 where did we get science from Mr. Manierre ?)

edit on 9/7/2012 by TeslaandLyne because: (no reason given)

reply posted on 7-9-2012 @ 07:58 PM by Phage

reply to post by CLPrime

When you have a small mass (like the Moon) orbiting a large mass (like the Earth) at a sufficiently close distance, the gravitational pull of the large mass causes the small mass to bulge in the direction of the large mass.

The bulge actually occurs on two sides of the object; the side near and the side opposite the other body. That's why there are two high tides each day. The reason being the gravity gradient across the diameter of the body. Same result. I just thought I would confuse things by throwing that in there but that double bulge does cause a greater torque than a single one would have.

It should also be noted that it is both bodies which experience the effect. The Earth is still in the process of becoming tidally locked with the Moon.