Earth/ Moon synchronisation question

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pyoko

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Seems improbable that the Earth and the Moon are perfectly synchronised. Or am I missing something? (no lewd remarks, please) I'm going to g00gle 'dark side of the moon', but does anyone else have any original answers? <div class="Discussion_UserSignature"> <p> </p><p> </p><p><span style="color:#ff9900" class="Apple-style-span">-pyoko</span> <span style="color:#333333" class="Apple-style-span">the</span> <span style="color:#339966" class="Apple-style-span">duck </span></p><p><span style="color:#339966" class="Apple-style-span"><span style="color:#808080;font-style:italic" class="Apple-style-span">It is by will alone I set my mind in motion.</span></span></p> </div>
 
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doubletruncation

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Are you wondering why the moon always shows the same face to the Earth? The reason is due to tides. Just as the moon raises tides on the Earth, the Earth raises tides on the moon. As a result the moon is slightly elongated. If the moon had a different spin rate than its orbital rate around the Earth (presumably it did in the past) then the bulge would have to move through moon (i.e. the part of the moon that is facing the Earth, and thus closest to the Earth and stretched towards it, would change as the moon spins). There is friction as the bulge moves through the moon and so the bulge cannot move perfectly freely through it - so if the moon's orbital and spin rotation rates are not the same then the bulge will not be perfectly aligned with the Earth (tides on Earth for example don't occur precisely when the moon is crossing the celestial meridian). The result is that if the moon were spinning faster than its orbital period there is a torque between the Earth and the moon that tends to slow down the moon's spin and increase its separation from the Earth. If the moon were spinning slower than its orbital period the torque tends to speed up the moon's spin and decrease its separation from the Earth. So whatever spin rate the moon started with was changed by the tides until its spin rate became equal to its orbital period.<br /><br />This is a fairly general phenomenon, the moon is actually doing the same thing to the Earth (slowing the Earth's spin) and will continue to do so until the same side of the Earth is always facing the moon. However, because the moon is much less massive than the Earth, the Earth has already succeeded in synchronizing the moon whereas the moon hasn't yet synchronized the Earth. Pluto and Charon, on the other hand, are of comparable mass and have succeeded in synchronizing one another. This can also happen in stars - very close binary stars can tidally synchronize each other (usually in this case the result is to speed up the rotation <div class="Discussion_UserSignature"> </div>
 
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Saiph

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I believe another contributing factor is the moon's core is not perfectly uniform, but has a prefferentially heavier hemisphere (facing us) which would have speed up the synchronization mechanisms. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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vogon13

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In all your life of looking upwards at the moon, have you noted even the slightest change in the hemisphere visible to your eye?<br /><br />If you are 25 years old even a consistent drift of 1 kilometer per month (at the equator) would have noticably changed the appearance of the moon in your lifetime.<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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vogon13

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Rocking (libration) as opposed to 'consistent drift' as I mentioned.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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doubletruncation

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<font color="yellow">I believe another contributing factor is the moon's core is not perfectly uniform, but has a prefferentially heavier hemisphere (facing us) which would have speed up the synchronization mechanisms.</font><br /><br />Interesting, are tidal forces responsible for the non-uniformity, or did something else cause it? <div class="Discussion_UserSignature"> </div>
 
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vogon13

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Congenital irregularities in the lunar depths.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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minotast

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<blockquote><font class="small">In reply to:</font><hr /><p><br />In all your life of looking upwards at the moon, have you noted even the slightest change in the hemisphere visible to your eye?<br /><br />If you are 25 years old even a consistent drift of 1 kilometer per month (at the equator) would have noticably changed the appearance of the moon in your lifetime. <p><hr /></p></p></blockquote><br /><br />I am quite sure over ninety-nine percent of all people on this planet have no idea as to what you are talking about in regards to such a statement.<br /><br />In addition, I am quite certain no one could visibly mark out the Moon's surface with just his or her own eyes.<br /><br />Are you superman?
 
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doubletruncation

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<font color="yellow">In addition, I am quite certain no one could visibly mark out the Moon's surface with just his or her own eyes.</font><br /><br />You can easily make out features like the "man in the moon" or the "rabbit in the moon" - have a look especially near the quarter moons, you can easily make out the maria. If you pay attention to it, you'll see that the features that you see are always the same. <div class="Discussion_UserSignature"> </div>
 
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vogon13

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It always looks like Jackie Gleason to me . . . . .<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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vogon13

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All my life, and the angle never changed . . . .<br /><br />{thanks for the memories}<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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vogon13

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This thread is just so . . . . <br /><br />how would you put it?<br /><br /><br /><br />Doncha 'spose somebody, somewhere would have noticed the moon rotating sometime, anytime, before 2006 A.D. ?<br /><br /><br /><br />ROTFLMFAO<br /><br /><br /><br />{ I might suggest again to Administration to reconsider my 'mercy ban' proposal, to prevent the self lobotomized from posting such things so as to embarass themselves for our entertainment. For that kind of thrill, we could just go down to the local nursing home and watch the senile folks soil themselves}<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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doubletruncation

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<img src="/images/icons/smile.gif" /> - you know it kind of reminds me of a person from new york telling me that they had never seen a star before in their life (they were in their 20s). I couldn't believe it, I mean I've seen stars from manhatten many times, sure the light pollution is atrocious but you can easily make out the planets and the brighter stars. I guess it's easy to never look up and notice them if you live at the bottom of a metallic jungle. Similarly, it's always surprising to me when people say that you can't see the moon during the daytime, or that the phases of the moon are caused by clouds (!) or by the Earth blocking the sun - it's easy to never notice it if no one ever points it out even though it's in plain view for so much of a person's life. <div class="Discussion_UserSignature"> </div>
 
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doubletruncation

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<font color="yellow">It always looks like Jackie Gleason to me</font><br /><br />Ever since the woman with the pearl necklace (Tycho as the pearl, Tranquility and Serenity as the bun hairdo, Vaporum as the eye) was pointed out to me, I always see that whenever I look at it. <div class="Discussion_UserSignature"> </div>
 
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CalliArcale

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It is amazing, isn't it, doubletruncation? I think that many myths and misunderstandings about space persist because people just never look at it. They think there's no point (it's too hard to see anything) or that it's too difficult to understand. And both are untrue.<br /><br />Many people, even highly educated engineers, do not realize that you can see satellites with the naked eye.<br /><br />Many people have never seen a sundog, sun halo, or other similar atmospheric effect, even in places where they are common.<br /><br />Many people don't realize that the Sun and Moon appear to have the same angular diameter, though it should be obvious.<br /><br />Many people are unfamiliar with the variety of clouds, thinking there is really only one basic type.<br /><br />Many people have no idea that the Big Dipper is always visible in the northern hemisphere, but many other constellations are not.<br /><br />Many people have never seen the Moon in daylight.<br /><br />Hardly anyone realizes that the lit side of the Moon must always face the Sun, including highly paid artists and special effects wizards, who insert moons into movie shots and do it wrong -- and not just for artistic license, but because they genuinely haven't noticed the effect or realized why it's that way. (This is worth special note, because artists study light and shadow. They really have no excuse for not applying their education to the Moon.)<br /><br />And most people have never seen the aurora.<br /><br />It is really amazing what people don't notice in the sky. Things huge, plainly visible, and seemingly impossible to miss, escape the attention of millions of people every day and night. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>
 
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Saiph

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The lopsided core is, IIRC, due to incomplete differentiation by the time the moon cooled. The moon, being smaller, has a higher surface area to mass ratio, meaning it radiates it's heat away faster (larger percentage per unit time). So the moon solidified before it formed a single uniform core.<br /><br /><br /><br />As for people "not seeing stars, or moon in daylight" I think they have...they just didn't notice. It's just like trying to spot the first star at night, even if people tell you it's right there, it occassonally takes a few minutes, and then viola! you're suprised you ever missed it. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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