Talk:Moon/Archive 6

Moon and earth gravity
I'd like to point out that the moon and earth move around each other, they both share a gravitational pull 1,000 miles below the earth, meaning the earth has three centres of gravity, the sun its own axis and this. --Game overman (talk) 19:04, 9 January 2008 (UTC)


 * What you probably intended to say with the first statement you made is that the moon and the earth rotate around the centre of gravity of the moon/earth system, which is below the earth's surface. As for the earth having three centres of gravity, I'm not exactly sure what you mean.  Maybe something along the lines that the earth has a centre of gravity on its own, the moon/earth system has a centre of gravity, and the sun/moon/earth system also has a centre of gravity? --Slashme (talk) 13:01, 10 January 2008 (UTC)

The Moon's Movement Away From The Earth
I'd like a little more information with regard to this statement: The Moon will continue to move slowly away from the Earth until the tidal effects between the two are no longer of significance, whereupon the Moon's orbit will stabilise.

I take it that means that once the Moon's orbit stablizes, the Moon will not move further away from Earth. Also, have scientists determined how long it will be when this happens? —Preceding unsigned comment added by 157.174.221.169 (talk) 19:14, August 28, 2007 (UTC)

Moon The Only Natural Satellite!
Cruithne, discovered in 1986, is another natural satellite and is a temporary moon of the earth which may become a permanent moon. So to say that the moon is the only natural satellite of the earth is false, especially since scientists believe there are more temporary moons than just Cruithne. I haven't changed the article in reference to this, but it does need to be changed.

Here is a quote from Space.com (http://www.space.com/scienceastronomy/solarsystem/second_moon_991029.html):

"Earth has a second moon, of sorts, and could have many others, according to three astronomers who did calculations to describe orbital motions at gravitational balance points in space that temporarily pull asteroids into bizarre orbits near our planet.

The 3-mile-wide (5-km) satellite, which takes 770 years to complete a horseshoe-shaped orbit around Earth, is called Cruithne and will remain in a suspended state around Earth for at least 5,000 years."

There is some debate as to whether it can be classified as a moon, though the term "temporary moon" seems to satisfy everyone. However, it is indeed a natural satellite and is referrenced as such in the quote above.


 * That could mean satellite of the sun, or it could just be grasping for a term to refer to something that's hard to categorise. Wikipedia has a page on it 3753 Cruithne. Looking at the orbit simulations I wouldn't count it as a satellite of the Earth but that's just me. The type of object is on Wikipedia page Quasi-satellite. CaspianM 14:55, 1 November 2006 (UTC)


 * POVdeRursus: The scientists mentioned speak rubbish, by my account - a satellite is a non-star astronomical body orbiting a planet. A moon, by my subjective POV, is a huge satellite. Now to be precize about orbiting a planet, this means (my subjective POV again) that the gravitational force from the planet by far supersedes the gravitational force from the sun as applied upon the satellite. The chaotic and dysfunctional process of the professional astronomers as regards to the definition of planet, clearly demonstrates to us that they're not prepared with the necessary linguistic insight to make definitions about anything - yet. That was not meant to prove anything, except to say that "IMHO Cruithne isn't a satellite to Earth", and maybe we should be a little cautious of listening to how astronomers speak (and besides, I got the chance to make a small revenge to the astronomers for producing crap-definitions, heheehhehee!!!) Rursus 15:48, 15 November 2006 (UTC)
 * By your standards, we would not have a Moon. The Sun pulls the Moon harder than we do.Saros136 15:56, 15 November 2006 (UTC)
 * By Jove, You're right!

OK, then I've ever thought that the Moon was a little weak in performing it's role - so then we'll demote Moon to being a planet. ;-) Rursus 16:20, 15 November 2006 (UTC)
 * the moon/earth is a double planetary system. no other moon so affects its planet —Preceding unsigned comment added by 69.125.110.223 (talk) 17:11, August 30, 2007 (UTC)

Are there other co-orbitals, and are the ones listed correct? In the article it says "Three other near-Earth asteroids (NEAs), (54509) 2000 PH5, (85770) 1998 UP1 and 2002 AA29, which exist in orbits similar to Cruithne's, have since been discovered." In a book I have it claims that there are 7 indentified, Cruithne, 2000 PH5, 2000 WN10, 2002 AA29, 2003 YN107 and 2004 GU9. (Strangely the book only names 6?). I don't want to add this info, as I know very little about the subject, and the book is not a serious science reference, so could somebody 'in the know' check these details? 213.48.1.131 19:35, 2 January 2007 (UTC)

Suggestion: Why not change the opening sentence to, "The Moon is the largest of several natural satellites that orbit the Earth". This neither supports or opposes the idea that the Earth has more than one moon. I'd do it myself, but I'm newly registered, and the page is protected, presumably because people keep changing the definition to "The act of flashing one's buttocks to another person or group of persons".


 * Co-orbitals do not orbit the Earth. Saros136 08:49, 6 January 2007 (UTC)

I've tried to make changes to reflect this, however it gets reverted straight back (well within 12 hours) - any reasons why?Rufty 10:42, 5 March 2007 (UTC)]

A couple of points.
 * 1.This article is not titled "The various moons, natural and artificial satellites and sundry orbiting debris of every size and shape of Earth and other planets". It is titled "The Moon". You know, the one we see just about every night? The heavenly body also called Luna? It's amazing that people can write thousands of words without pausing to consider whether they are simply arguing about the definition of a word. In this case, the confusion arises because the term "moon" is both a common noun (when it refers generally to natural orbitting satellites) and a proper noun (when it is used as the name of our very own moon, the biggest one we have).


 * 2. If pedantry were compulsory, Wikipedia would have articles the size of an entire library on "Chewing gum". And the article would consist of so much hair-splitting and concern for exhaustively documenting the most insignificant counterexamples that no one would bother reading any of it, and if they did, they would hardly be wiser for it. I imagine that if some people were asked to write something on dogs, the sub-heading on "legs" would inform us that dogs had anywhere from 0 to 7 legs, with a mean of 3.81987, although some experts have disputed the exact figure. Given that if you define "a moon of Earth" as properly referring to any of our natural satellites, then every grain of interstellar dust in orbit is a moon, and thus must be dealth with here. No thank you. I know this is unfair to the peanut-shaped and sized Belllabonga moon, but I'm only interested in reading about Luna here. That's why your stuff is taken off as soon as you put it on there. It's boring. Why don't you start a New Encyclopedia called Inconsequentia. Myles325a 12:24, 8 April 2007 (UTC)


 * With respect, I think this is moot. What is or is not a satellite/moon is defined by the IAU, this matter has been settled.  Winning an argument on Wikipedia does not mean winning in the real world.   I was not particularly happy about the outcome of the Pluto controversy, but I grudgingly accept it because the IAU is the final arbiter in such matters. PrivateWiddle 19:45, 14 May 2007 (UTC)


 * It used to be two, but it has changed over the last couple of yeras. CorleoneSerpicoMontana 15:42, 28 May 2007 (UTC)

My understanding (and wikipedia backs me up here :-)) went that "A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made." in fact the IAU (http://www.iau.org/fileadmin/content/news/iau0601/iau0601_Q_A.doc) says "an object in orbit around the planet is called a “satellite”". So regardless of what anyone here wants to think Cruithne is by that definition a satellite of the Earth. Like Pluto is no longer a planet, Cruithne is a Satellite of the earth and therefore deserves mention here. I thought Wikipedia cared most about facts/official definitions? Rufty 16:33, 4 July 2007 (UTC)
 * Wikipedia does care about facts and official definitions. If you can get the IAU to officially state that Earth has two moons, one of them being Cruithne, then it will go in the article. Otherwise, there can be only one... --Ckatz chat spy  18:16, 4 July 2007 (UTC)

If the formal definition states that the asteroids under question are satelites, then the line "The moon is earth's only natural satelite" is technically a lie. Warren from calgary 13:44, 5 July 2007 (UTC)

There are 6 other NEA's that are orbiting earth. Adding Luna makes 7. The natural satellite statement is false, these other 6 are natural satellites. Their status as moons are questioned however. We haven't quite got a definition as to what makes a moon, and isn't top of the list. Getting a good solid ground for a definition of a moon could help us decide. So we could end up having something like what happened with Pluto. Cruithne has a strange "horse-shoe" orbit, which is one of the reasons why scientists would say it's not a moon. —Preceding unsigned comment added by Jamiepgs (talk • contribs)


 * Getting definitions of these things is not easy as they have arisen over history and new discoveries are showing there are no black and white boundaries. The new definition of planet caused uproar and is still not widely accepted. The Moon is accepted as our only natural satellite as it is the only one we could see for millennia and it is known its presence affects the earth. I would be interested to see what variety of definitions for "moon" people come up with but I would support keeping the statement that the moon is the earth's only natural satellite as to all intents and purposes it is true. Sophia  11:51, 15 July 2007 (UTC)

No amount of discussion, citation, or consensus will turn any of these bodies into the Moon. I suggest that further debate about Cruithne et al. be directed to Talk:Solar system. When the issue is resolved, the incidental sentence about the singularity of the Moon can be corrected - if necessary. Sheffield Steel talkersstalkers 19:39, 28 August 2007 (UTC)

Moon and colour
There are occasions where the moon is tinted a red colour due to the light passing through the atmosphere of the earth. However, the article makes no mention of it (it's not a lunar eclipse, as it happened less than two hours ago as I post this) and the moon is not in the Earth's shadow. Does this have a name? i think it should be included in the article.--Tiberius47 11:13, 2 February 2007 (UTC)


 * The "Copper Moon" is actually a lunar eclipse where the earth stands between the moon and the sun . The earth's atmosphere causes some light from the sun to bend and fall on the moon which is why the moon is not totally dark and also what gives it the colour. I'll check the article and add missing details. Sophia  21:13, 12 February 2007 (UTC)


 * I think he's talking about when the moon is near the horizon and looks red or orange.thx1138 03:06, 13 February 2007 (UTC)

This occurs where the light reflected from the Moon has to pass through more atmospheric dust due to the shallower angle, and this causes the amount whereby the light is refracted to be greater, therefore in turn the light is changed to longer wavelengths. The same happens to the Sun. As for a name, God knows. Let's call it perihorizontal discoloration. Kris 22:30, 2 March 2007 (UTC)

Moon in the day
I'm just wondering if there is a technical term for when the moon is visible during the day. - Jigsy 16:02, 1 March 2007 (UTC)
 * Is there a technical term for the Moon visible at night, or when it's not visible (either obscured or below the horizon)?? I'm not sure. If not, there should be. Kris 22:22, 2 March 2007 (UTC)

The moon in the day is the new moon Roo  7 April

The moon in the day is not the new moon (notice how it doesn't go from full to "new" as night sets in? Just saying) John jarrell 22:55, 11 May 2007 (UTC)

intro
From the intro - 'The related adjective for the Moon is lunar (from the Latin root), but this is not found in combination with words using the prefix seleno- or suffix -selene (from the Greek deity Selene).' this is awkward - needs re-writing but I can't think of a good way to do it... sbandrews 00:15, 11 March 2007 (UTC)


 * I've had a go:


 * "The related adjective for the Moon is lunar (from the Latin root), however this is never found in combination. The preferred combining form is -selen- (from the Greek deity Selene), appearing as a prefix (seleno-, as in selenography) or suffix (-selene, as in aposelene)." Kris 09:43, 11 March 2007 (UTC)


 * better, thanks, the combination bit is still awkward - its probably not *entirely* obvious that we wouldn't say 'lunar selenography' (or 'lunography'!) but this seems a matter for an article on English grammer rather than an intro on the Moon...


 * "The related adjective for the Moon is lunar (from the Latin root) and words can also be combined with -selen- (from the Greek deity Selene), appearing as a prefix (seleno-, as in selenography) or suffix (-selene, as in aposelene)." sbandrews 11:54, 11 March 2007 (UTC)

It's misleading to say that "lunar" is never found in combination; if the adjective "selenic" applied to the Moon rather than to selenium, it would not be used in combination either. The article needs to distinguish between the related adjective and the related combining form. (In any case, the would-be combining form "luna-" is used in some Moon-related words, such as "lunatic", even though this is not an astronomical term.)

I think sbandrews' suggestion should therefore be modified to:

"The related adjective for the Moon is lunar (from the Latin root). However, the combining form is -selen- ... " &mdash; Paul G 10:10, 20 March 2007 (UTC)

Political viewpoint?
There's a section in the exploration that says

What was the next big step depends on the political viewpoint: in the US (and the western world in general) the landing of the first humans on the Moon in 1969 is seen as the culmination of the space race.

As opposed to what? The article doesn't expand on other political viewpoints (for instance the Eastern world viewpoint). It just expands and explains the US (Western world) Viewpoint. —Preceding unsigned comment added by 68.205.70.254 (talk)


 * Taken care of. Nick Mks 10:43, 3 April 2007 (UTC)

FA push
It seems to me that the people who made this article to what it is today (a fine piece of work just short of FA status) have lost their interest a bit after GA was achieved. I'd like to give it a try to give this one the final FA push it needs, starting later today. Any help is welcome of course. Nick Mks 10:48, 3 April 2007 (UTC)
 * On second thoughts, I don't see anything that I personally want to see improved. It also seems that all comments from the previous peer review have been taken care of. Let's just do it and address problems along the way. I'm nominating! Nick Mks 17:43, 3 April 2007 (UTC)

Yes, it's good. But good is the enemy of great. There are changes that need to be made, issues which require clarification. For example, the article displays instances of the widespread practice of employing technical terms without attendant definition or explanation. When such occurs, it is often manifest material has been lifted from some academic journal with little effort made to assimilate it to the needs of Wikipedians. Further, some material is improperly positioned, and has the misfit look characteristic of afterthoughts, or sops to the completists. The stuff on angular momentum should be given a sturdier, non-technical foundation. This is an area where there is some current interest due to the moon’s recession entailing a supposed consequence for some religious beliefs on the creation of the world. It would be timely to provide clarification of the extant data pertinent to this, not in a disputative or belligerent way, but in recognition that many are searching for pertinent information. But I don’t want to carp. It’s good, damn good. Myles325a 13:02, 8 April 2007 (UTC)


 * Allow me to respond to two of your quotes:
 * This is an area where there is some current interest due to the moon’s recession entailing a supposed consequence for some religious beliefs on the creation of the world. I'm sorry, but I'm not getting into that. My experience (outside of Wikipedia) has shown that this is totally useless and sometimes outright dangerous.
 * Oh, I think it is nit-picky to make such a pointed discrimination between "dark" and "far" side of the Moon. For all practical purposes the two are the same. That's a common misunderstanding, and exactly what the article tries to sort out. The far side is the side we never see from Earth, the dark side is the side that is not illuminated. So only when it is full Moon the two are equivalent. During new Moon, we see the near side (as always), which is then the dark side. Nick Mks 13:23, 8 April 2007 (UTC)

Oh. Yes, I withdrew my dark vs far comment almost as soon as I had written it. My typing finger slipped. (chortle). On point 2, don't get me wrong. I'm not saying get into this controversy. In my own case, I had often in years past, wondered WHY the Moon was moving away from the Earth. And the answer "Angular Momentum" didn't do it for me, because I couldn't see how the Earth slowing down on its axis could somehow cause the Moon to go further away. How was such a force transmitted, I pondered. Now, I believe I have it figured out, sort of. It has to do with the braking effect of the tides on the other body, but it is not AUTOMATIC that a slow down in the Earth's rotation is transmitted to the Moon. You could have the Earth slow down and not affect the Moon's orbit at all. This is important, if only for the reason that people who are interested in the Moon, will be interested in whether it is moving away from us, whether we are going to lose it, or if it will come back. And why. I think these are fair enough concerns. And if the YEC crowd happen to have a stake in it, it has nothing to do with Wikipedia. I don't think we should antagonise them, but I'm damned if I'm going to start avoiding issues because it conflicts with their medieval views. I have inserted one sentene to do with the Moon's recession. When I get more data, I will add it. In addition, I have made quite a few, mainly cosmetic and stylistic changes to the content. Hope you like it (well, most of it) Myles325a 16:59, 8 April 2007 (UTC)
 * Yes, absolutely, thanks for your input. As for angular momentum stuff is concerned, this is actually my speciality (but then for binary stars in stead of the Earth-Moon system). I do not feel at ease writing this down for a general audience though since it actually is quite mathematical, so feel free to give your view and I'll see if it's scientifically correct. Nick Mks 17:44, 8 April 2007 (UTC)
 * On second thoughts, are you sure that the system will ever be totally synchronous and stable? I know the lecture notes say so, but I always heard it would take longer to achieve that than the lifetime of the Sun. Nick Mks 17:54, 8 April 2007 (UTC)

Well, even so, it would still stop recessing in principle. Of course, this phenomenon (of combined angular momentum of planet and moon leading to the moon always facing the planet) is not unique to us. Mercury was thought to always face the sun, but maybe there's been some revision on that recently. OTOH, there are other moons that always face host planet. And not all of them are going to get eaten up by the dying sun. (Friend of mine told me his science teacher had told class that moon always facing Earth was one of those Great Coincidences like the sizes and distances of the Moon and Sun making perfect eclipses possible. One too many moon coincidence, huh?) I read that Moon would stop moving further out, and by that time, tides on Earth would be insignificant. Then, Moon would start moving back via gravitational radiation, but it would take untold billions of years before it would theoretically hit Earth. Makes sense to me. Will research it. BTW, was interested to read in article that Sun's tidal effect on us is half that of Moon's. I didn't think it would be even this much. I wonder if there are any calculations as to what the tides would be like if the Moon wasn't there. I suppose that with today's computers, it shouldn't be that hard to model. Myles325a 20:11, 8 April 2007 (UTC)

Many thanks to all for their comments and input! Nick Mks 07:05, 12 April 2007 (UTC)

Observations
This section included an image labelled "Moon reddened because of physical phenomena." I couldn't tell just what this phenomena was, and the image caption wasn't telling. Could someone clarify the matter? Until then, I've removed the image from the article. mdf 19:14, 4 April 2007 (UTC)


 * Maybe we better just drop it. It's not bad, but not a featured picture either... We could also drop the caption alone. I could write an entire paragraph on the atmospheric phenomena causing this, but that's got nothing to do with the Moon. Nick Mks 19:53, 4 April 2007 (UTC)


 * Image quality is not an issue, just the description of what the image is supposedly of. If someone specifically identifies the "physical phenomena", I have no objection to its re-introduction into the article.  mdf 19:58, 4 April 2007 (UTC)


 * Yeah, I understand. How about just atmospheric phenomena? Nick Mks 20:01, 4 April 2007 (UTC)


 * Even that may be a bit vague, but it's certainly better than nothing. The person who knows best is probably the author of the image, User:Valdezlopez.  I've left him a note.  mdf 20:12, 4 April 2007 (UTC)

Under the heading of Observation is "The highest altitude of the Moon on a day varies and has nearly the same limits as the Sun. It also depends on season and lunar phase with the full moon being highest in winter." is this for the Northern Hemisphere, is this article written for Northern readers? —Preceding unsigned comment added by 220.233.208.191 (talk)


 * This statement is correct for both hemispheres, i.e. full Moon is highest in local winter. Nick Mks 13:36, 5 April 2007 (UTC)

I see the image of the Moon I removed yesterday has returned with a caption "lunar eclipse". Thank you, User:Valdezlopez. However, it pains me to make a few observations here. (a) the geometry of the shadow is wrong for an eclipse of the Moon. Compare the shape of the shadow with the animation currently at Lunar eclipse. (b) The red color of an eclipse is going to be on the inside of the curvature, and there is a noticeable gradient in color and intensity, features apparently absent in this image. And, most alarming of all, there was no lunar eclipse in 2006 May (see http://en.wikipedia.org/wiki/List_of_lunar_eclipses). mdf 20:53, 5 April 2007 (UTC)


 * I'll also note that according to the EXIF data within the image, it was collected at 2006-05-20T03:18:38. At that time, the Moon was almost exactly at third quarter.  And indeed, but for the red color, this looks for all the world like a picuture of the Moon at third quarter, not in eclipse.  mdf 20:57, 5 April 2007 (UTC)


 * I hadn't noticed that it had returned yet. Indeed, the caption is impossible. It think we better remove it, since the last talk at the FA is that there are too many pics. Nick Mks 16:39, 6 April 2007 (UTC)

Selenography
This word is currently moribund, if it was ever used at all in the way Wikipedia is currently using it. As I mentioned at the selenography talk page, it's arguably a neologism. I'd love to be bold and just change it to "lunar geography", if only to be consistent with "lunar geology" (used in-article). But one suspects resistance. mdf 19:27, 4 April 2007 (UTC)


 * If you know this, it's your call. I'm just the astrophysicist here, before yesterday I hadn't even heard the word. Nick Mks 19:54, 4 April 2007 (UTC)


 * I've been trying to find a "real" use of the word in the manner Wikipedia is doing, but have mainly drawn a blank. People use it, but not the "important people" (so to speak).  Most of the good stuff on the subject is found by searching for "lunar geography".  Hopefully, I'll be surprised.  Just today, for example, I came across "selenophysics" for the first time (see http://www.iers.org/documents/publications/tn/tn34/tn34.pdf).  I initially thought it was just some guy trying to be cute with "lunar geophysics" (~650 hits at google), but others have been using the word in the same way (~40 hits).  mdf 20:26, 4 April 2007 (UTC)


 * Selenography was always understood to be the study of the physical features of the surface when I was studying many years ago. As for it being a neologism I would refer you to this library entry

Our Satellite: a Selenography Author: D'ORSAN, Dr. A. Le Vengeur Contributor: DE MORGAN, Augustus Mark : DE MORGAN Reference : 1824 (October 11,1862), 460 - at

http://www.soi.city.ac.uk/~asp/v2/titles/tget.cgi?1824.html@OurSatellite:aSelenography

Sorry about the length of the link but I could not use tinyurl for some reason. I think 1824 counts as not new, and I'm sure the phrase pre-dates that book by a good way. Its a shame people like to change lovely old words for no particular reason. PrivateWiddle 20:03, 14 May 2007 (UTC)

Moon News
One of the major benefits of wikipedia over other encyclopedias is the option for being current, and providing news - a place to revisit for updates. One of the most newsworthy items through the centuries has been the eclipses of the sun and moon. This news should be included in this site - based on relevance and interest:

Next Eclipse:

 * 28 Aug 2007 - Total Lunar Eclipse

A total lunar eclipse will be visible over the Americas, the Pacific, eastern Asia, and Australasia.

(Saros 128, umbral mag. 1.481, max. eclipse 10:37 UT total: 09:52:00 UT to 11:22:45 UT)

Next Solar Eclipse:

 * 11 Sep 2007 - Partial Solar Eclipse

A partial eclipse will be visible over southern South America, and parts of Antarctica.

(Saros 154, umbral mag. 0.749, max. eclipse 12:31 UT partial: 10:25:45 UT to 14:36:33 UT)

Next Total Solar Eclipse:

 * 1 Aug 2008 - Total Solar Eclipse

The track -- 237 km wide at maximum -- begins in north Canada, passes near the North Pole, and into northern Russia. It then runs south-east into China. It is visible as a partial eclipse in Britain, though will not be dramatic. The maximum duration is 2 minutes 27 seconds, and the path width at maximum is 237 kilometers.

(Saros 126, umbral mag. 1.039, max. eclipse 10:21 UT total: 09:21:07 UT to 11:21:28 UT)

citations: http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2007.html and for being user friendly http://www.hermit.org/eclipse/

Roo 7 April
 * Yeah, well, good point but a list like the one you added is not acceptable in a FA. I'll see to it. Nick Mks 12:16, 7 April 2007 (UTC)

Exploration suggestions
I think an important and interesting fact to place in the second intro paragraph would be how many people have landed/set foot on the moon, to date; I don't know where that figure is given, if it is anywhere on Wikipedia. That the six Apollo missions have been the only manned missions to the moon should also be given more prominence; I don't think Project Apollo states that clearly either. Cheers, Postdlf 22:07, 8 April 2007 (UTC)
 * Feel free to amend. Nick Mks 14:50, 9 April 2007 (UTC)

I took the liberty of removing a statement stating that the section of the article detailing the moon landings is based on "assumption" and "hard evidence suggests they were staged". The vast majority of the scientific community accepts the landings as fact. If someone wishes to pass off statements to the contrary as valid scientific discussion, perhaps it belongs in its own section "Controversy about the Apollo landings" or something to that effect- with actual citations to scientific evidence rather than a generalized, uncited vague statement such as the one that was here. I personally won't waste my time on starting such a section, however... spiffmedic 10:21, 2 June 2007 (EDT)

There is no conclusive evidence that any human being has ever set foot on the Moon. These sorts of myths and urban legends have no place in an encyclopedic article. 84.50.77.116 08:18, 28 August 2007 (UTC)

moon earth angular momentum and Moon's recession
Ok tell me if I’m way off the scent here but this is what how I’ve been thinking on this.

1.The Moon causes tides on Earth, and this big bump of seawater wants to stay facing the moon but is moved all the time to the West becoz of the Earth’s rotation on its axis. This “deforms” the Earth’s mass from an almost perfect sphere into one whose mass is slightly asymmetrical.
 * Almost. There is also a bulge on the side of the Earth facing away from the Moon. This is a result of the combination of the fact that this water is less attracted than the Earth itself and the (virtual) centrifugal force. This is the reason that you have high tide twice a day, not once. Nick Mks 18:33, 11 April 2007 (UTC)

2.The moon "feels” this asymmetry as if the Earth is slightly ahead of where it actually is, and this acts as a slingshot, making the Moon move faster.

3.The rate the Moon should be moving is governed by Newton’s Celestial Mechanics, which specify the orbit height of a Moon type - object as based on the masses of the objects and the speed at which the Moon was initially traveling.

4.The Moon moves faster than it should be based on these Laws, and is therefore kicked up continually into higher orbits. The Moon is actually spiraling upward.
 * (2) through (4) may be a bit plastic, but I guess it's a good way of visualising something that is actually quite abstract. Nick Mks 18:33, 11 April 2007 (UTC)

5.The Earth is losing angular momentum as a result of the friction of the tides which causes water to crash into continents. This is slowing the Earth down, and thus making the tides less energetic over time. In turn, this means that the “slingshot” factor in 2 above becomes weaker, and the Moon’s recession rate will slow down.
 * Correct. Nick Mks 18:33, 11 April 2007 (UTC)

6.This means that if you set up an electricity station working on tidal power, you are not only slowing the Earth down, you are slowing the Moon’s rate of recession down.
 * Correct. Nick Mks 18:33, 11 April 2007 (UTC)
 * Yes,


 * Myles here. Now that I've slept on it, I've got a question on this. Yes, you are slowing the Earth down if you generate electricity from the tides, but now I think that the Earth would have slowed down just as much even if that tidal plant had never been built. Reason: The tidal surge you used would have been stopped by friction anyway. You just exchanged one source of friction for another, and as this is a simple diversion, then there has been no change to the status quo. Correct? Myles325a 08:00, 12 April 2007 (UTC)
 * Of course. However, I'm not an engineer, but I can imagine power plants intentionally create more friction than you would normally have from water against water. Nick Mks 08:33, 12 April 2007 (UTC)


 * Myles here.Sure, but does the TOTAL friction the tide water encounters change, according to the terrain it traverses, or is it spread out for longer. Look at 3 scenarios: 1. the tide runs into a massive sea wall which stops it dead, 2. the tide runs on to a marshy plain like near the Everglades, or 3. there is a whole coastline of tidal generators. The 3 options take different times to stop the tide, but I am now thinking that the total work done by the tide must be the same. If that is true, we are not robbing the Earth of anything it would not have lost already. --Myles325a 23:16, 12 April 2007 (UTC)
 * Yes, eventually, when synchronisation is achieved, the total amout of energy lost will be the same, it will just go faster. But on a human timescale, this seems to be more. Nick Mks 09:12, 13 April 2007 (UTC)
 * Myles here. You mean the synchronization when the Earth faces the Moon all the time? Will that ever happen? And would that mean the Earth's day then would be about a month long? My question was really if EACH INDIVIDUAL TIDE expends the same energy regardless of whether it is stopped suddenly or flows out over a marsh? After all, in each scenario, each drop of water is brought to a full stop, it's just that if you have a sea wall that stop is sudden. --Myles325a 05:50, 14 April 2007 (UTC)
 * Yes, eventually this would happen. However, as I've said, I don't think the solar system will survive long enough for that. And yes, a month would be equal to a day then (but none of them would last the number of seconds it does now). I'm unsure about the friction thing, but since the water always goes the same way (it does not stop and turn back) I do believe it's possible to lose more energy than it does naturally. Nick Mks 18:33, 14 April 2007 (UTC)

7.As well as this, as the Moon moves away, the tidal effects will become less pronounced anyway because such effects depend not only on the gravitational strength of the Moon but the differential of its effect. In other words, if the Moon’s gravitational attraction were to be spread more evenly over the Earth’s surface, then the tidal effects would become weaker. That is, presumably why the Sun’s tidal effects are so weak. The Sun is much more massive than the Moon, but its gravity effects are less focused on any particular area on Earth. As the Moon moves away from us, its tidal effects will also become less focused and thefore less intense.
 * Well, quite close. Gravity is a force that declines with R², so if you're twice as far, you have four times less attraction. I don't see though how this relates to spreading the force evenly over the surface (which obviously always is the case). Nick Mks 18:33, 11 April 2007 (UTC)

8.The Moon faces the Earth because over time, the Earth’s tidal effects on the Moon caused the Moon to slow down and come into synch with the Earth, by similar mechanism as in all above. Many satellites in Solar System are similarly affected.
 * Correct. This is not yet total synchronisation though. This also requires the revolving period to be equal to the rotation period of the other body. So eventually you'll have 1 day = 1 month. Once Earth synchronises with the Sun as well, you'll have 1 day = 1 month = 1 year. However, you'd need many times the expected lifetime of the universe for that, while we only have five billion years left. Nick Mks 18:33, 11 April 2007 (UTC)

9.Becoz the Moon now always faces us, Earth senses that the Moon is correctly positioned, whereas the Moon senses that the Earth is slightly ahead of where it really is. Had the Moon still been rotating on its axis at its original speed, the rate of the Moon’s recession would now be higher. Moon’s recession rate decreased as its orbit around Earth as its “day” came into synch with its “year”. That is, the duration of one spin on its axis became the same as the duration of one round on it orbit.
 * I'm not so sure about this. The facts are correct, but I don't see why a faster rotating (rigid) Moon would recess faster. Nick Mks 18:33, 11 April 2007 (UTC)

10.The whole business of the “conservation of angular momentum” as the reason why the Moon is moving away is confused and misleading. If the Earth and Moon had been perfect spheres of an inelastic substance, then there would BE NO TRANSFER of angular momentum. In such a scenario, you could rev up the Earth’s rotation on its axis to a million per hour, and it would have no affect on the Moon. The whole mechanism is caused by the tides, nothing more or less. It is the deformation of the material changing their centers of gravity that give rise to the effect. This last is what I really want some feedback on. I had always wandered how it was possible for the Moon to somehow sense that the Earth was slowing down, and adjust itself accordingly in order for the equations governing “preservation of angular momentum” to work out.
 * Correct. The reason is that in a system of perfect spheres of an inelastic substance you would need an external force to rev up the Earth’s rotation on its axis to a million per hour. There, you have an external source (or drain) of angular momentum, so it's no longer conserved in the Earth-Moon system. Nick Mks 18:33, 11 April 2007 (UTC)

Myles325a 14:18, 11 April 2007 (UTC)
 * Now this is all good and well, but what of this do you want to put in the article? I do find the current content on this pretty good, it's informative and yet understandable. Nick Mks 18:33, 11 April 2007 (UTC)

Thanks a lot for that, Nick. It mainly confirms what I had kinda nutted out. It means that the Moon's recession will stop, or at least asymptotically approach a limit, and it should be possible to calculate when that should happen. So we've saved the Moon, and I've managed to use the word "asymptotically" for the first time. Yippee! You're right, it probably doesn't belong in this article, but it does belong somewhere. Perhaps I should donate it to Conservapedia? They seem to have some problems with Moon recession. Also see my new comment on point 6 above. Myles325a 07:53, 12 April 2007 (UTC)
 * I'm afraid that would get you a lifetime block over there. I'm not so sure whether we saved the Moon, the timescales involved here are enormous. It's quite possible that the Moon is already lost by then (theoretically, Earth's gravitational field extends to infinity, but at some point the noise from other bodies gets larger). Nick Mks 08:33, 12 April 2007 (UTC)

11. Myles back. Some ideas I've had in my head. Impact events on the moon should have been affected by change in moon's spin over time. Far side impacts should be more numerous because near side impacts have to pass the gauntlet of Earth which would clean up a lot of them, and send some into orbit. Thus, stat survey of dispersion of impacts on Earth should give indication of when Moon’s orbit synchronized with its rotation, thus giving insight into age. Same idea for statistical survey of “leading edge” impacts, as the leading edge has changed over time. Do you think that any of these could bear fruit? (oh and see another comment on point 6 above0 Myles325a 05:50, 14 April 2007 (UTC)

The Moon's interaction with Earth acts only in the disipation of Moon's energy, so Moon must fall down into our Earth (because of a simpe gravitational force). Moon can go up in speed only by introducing other forces into this system (not terrestrial, and Sun is guilty for that if this is true). So in this article is written a pure nonsense.

Another nonsense is that Moon always faces Earth because of interaction between them. In fact, we are lucky that Sun and Moon have similar spatial angles which are guilty for such Moon's behaviour (as well as eclipses) —Preceding unsigned comment added by 82.21.144.216 (talk)
 * I'm not sure what exactly you are trying to say, but you seem to indicate that you believe the Sun to be the reason for Moon recession and synchronisation. I can assure you that this is not the case. Nick Mks 18:57, 17 April 2007 (UTC)


 * "The Moon's interaction with Earth acts only in the disipation of Moon's energy" - this is not true. The Earth/Moon interaction causes a transfer of angular momentum and energy from the Earth to the Moon.  "Moon can go up in speed only by introducing other forces into this system" is therefore not true.


 * "Another nonsense is that Moon always faces Earth because of interaction between them" - this is not nonsense, it's the real reason. "we are lucky that Sun and Moon have similar spatial angles which are guilty for such Moon's behaviour" - no, the Moon would show the same face to Earth even in the absence of the Sun.  There are other instances of tidal locking in the solar system where the Sun and the moon in question do not have similar angular diameters as seen from the planet (see Tidal_locking). Occultations 14:47, 18 April 2007 (UTC)

I think the second paragraph of the article on the moon is incorrect on the issue of the moon's recession. It states:

"The energy dissipated in generating tides is directly responsible for the reduction in potential energy in the Moon-Earth orbit around the barycentre, resulting in a 3.8 cm yearly increase in the distance between the two bodies"

The recession of the moon away from the earth increases the gravitational potential energy of the system. This increase in GPE is offset by a decrease in the rotational energy of the earth. Gordion 10:32, 21 August 2007 (UTC)


 * I made a note of this point on the 11th of June. Besselfunctions 04:11, 28 August 2007 (UTC)


 * I agree that the statement about potential energy decrease is wrong. I think the confusion stems from the counterintuitive notion that an increase in distance between two masses means an increase in gravitational potential energy. However, the statement did not specify the type of energy described as potential. Also, the author/authors may have meant to say "decrease in kinetic energy." Either way, I think the statement needs subtle rewording.--146.145.125.131 17:47, 28 August 2007 (UTC)


 * I haven't read through this entire section (sorry, too busy!) But I have worked out a considerably longer explanation that I think doesn't fly in the face of the physics.  I was going to put it in then realised I hadn't incorporated the recessionary figure of 3.6 cm / [time unit].  I'm not going back to rework it, but here's my contribution if anyone else would like to.
 * Rotational energy is converted to heat by the frictional effects of the tides. This energy radiates away from the system.  The result of this is that the kinetic energy of rotation is decreased, making the orbital period longer.  Paradoxically, to balance the lower centripetal force of the slower rotation, the earth-moon distance increases, raising the potential energy.  The net effects are thus: loss of energy from the system through radiated heat; lower kinetic energy through slower movement around the barycentre, but increased potential energy through greater earth-moon separation.

King Hildebrand 18:53, 29 August 2007 (UTC)

Eternal light
From images taken by the Clementine mission, it appears that four mountainous regions on the rim of the 73-km-wide Peary crater at the Moon's north pole remain illuminated for the entire lunar day, at least during the hemisphere's summer season. These peaks of eternal light are possible because of the Moon's extremely small axial tilt to the ecliptic plane. The text above contains an inconsistency. For the peaks to be illuminated for the entire day during summer, a large axial tilt is not prohibitive. Compare earth: large axial tilt and midnight sun. What an extremely small axial tilt might enable however, are peaks that are illuminated during the entire lunar year. Also luna orbits very close to the ecliptic, so the eternally lit areas would have to be very horizontal. Shinobu 15:48, 14 April 2007 (UTC)
 * Good point. I looked it up and it should be really eternal (except during eclipses). Nick Mks 18:38, 14 April 2007 (UTC)

Earth's New Temporary Moon
Someone with experience at editing pages should add this. It is the only known natural moon besides 'the Moon'. It's identified as "6R10DB9" see. See also and. An article from Sky & Telescope --Daveonwiki 18:00, 19 April 2007 (UTC)
 * Cool, but not appropriate in this article I'd say. Nick Mks 18:53, 19 April 2007 (UTC)

Only celestial body orbited...
The first sentence of the second parargraph states that the Moon is the only celestial body that humans have orbited except for the Earth. What about the Sun? The centre of the Milky Way? -- Rmrfstar 23:08, 19 April 2007 (UTC)
 * Hm, can't say that you're wrong. Any suggestions on how to rephrase? Nick Mks 09:15, 21 April 2007 (UTC)
 * Well I don't think it's that significant of a fact. I'd take it out and leave that it's the only celestial body that we've landed on. -- Rmrfstar 12:43, 21 April 2007 (UTC)
 * or add "in spacecraft". I assume it's there to make it explicit that although probes have been to other planets, men have not. Sophia  13:48, 21 April 2007 (UTC)
 * Yes, but while you are orbiting the Earth in a spacecraft, you're also orbiting the Sun in your spacecraft. So that doesn't really solve the problem. I guess I'll take it out. Nick Mks 14:47, 21 April 2007 (UTC)

Direction of orbit
The article implies, but does not state directly, which way the Moon orbits the Earth - anticlockwise, as viewed looking down on the North Pole of the Earth, same as the Earth itself rotates. It might be better to state this explicitly.148.197.5.19 09:22, 20 April 2007 (UTC)
 * Why not, go ahead. Nick Mks 09:16, 21 April 2007 (UTC)

Limb?
What is a limb of the Moon? I saw the word used in Lohrmann (crater) and it is in this article too, but not explained. Thanks. Itsmejudith 11:39, 23 April 2007 (UTC)


 * See limb for the answer. Urhixidur 14:43, 24 April 2007 (UTC)


 * Thanks very much for your answer and for making the link in the article. If I've got it right the limb is the great circle that divides the near side from the far side. I don't quite see how the term would relate to other celestial bodies, unless it is always defined by their positions relative to Earth. A bit more clarification in the relevant articles might be called for. Itsmejudith 15:01, 24 April 2007 (UTC)


 * As a common amateur astronomer I have always understood it to mean the visible/apparent edge of the Moon and those areas close to it. This has more currency because the Moon presents the same face to us all the time so you can simply say that such and such a feature is on the southern limb. PrivateWiddle 18:45, 14 May 2007 (UTC)

70.68.70.186 15:13, 4 July 2007 (UTC) I saw a 3/4 full Moon on July 4th from the northern hemisphere at 6:00 AM, with the sun a little above the horizon. But the lit surface of the Moon does not point at the sun; it's as if the sun ought to be much higher in the sky. How can that be?

Correct, or badly written?
"allow a total of about 59 per cent of the lunar surface to be visible from Earth at one time or another"

As it currently reads, this would mean that you can see 59 percent of the moon at any given instant. Is this correct or should it have been written as; "allow a total of about 59 percent of the lunar surface to be viewed from Earth."

I skimmed through the article looking for shape descriptions other then oblateness, as this wouldn't change the maximum permissible view at a single instant, but didn't find anything.

--Charlesburg 03:30, 26 April 2007 (UTC)


 * Your rephrased interpretation is correct, however I don't see the problem. I think the at one time or another does the trick. Nick Mks 17:16, 26 April 2007 (UTC)

So at any given point in time I can look at the moon and see 59 percent of the surface even though it's a slightly squashed sphere and that should be impossible? I went and read the NASA article quoted, it has indeed been misquoted. You can not instantaneously see 59 percent of the moon as the quoted sentence reads, the original quote is "Because of libration, about 59 percent of the lunar surface is visible from Earth.".

I would suggest either correcting the sentence to the original quote, or modifying it to remove time.

Charlesburg 01:44, 1 May 2007 (UTC)


 * Yes, but the sentence in the article does say at one time or another and not at any given time. I really don't see the problem, but if you want to change the wording, go ahead... Nick Mks 09:16, 1 May 2007 (UTC)