Talk:Supermoon

Cleanup

Someone please help this article. I don't even know where to begin, short of deleting everything after the first couple of sentences.

What is this, amateur hour?? --67.188.134.94 (talk) 23:53, 11 March 2011 (UTC)

Agree, this article is really awful. I do believe deleting everything after the first couple of sentences would improve it. Those sentences might need some work too. Darkest tree (talk) 01:46, 12 March 2011 (UTC)

I've flagged this on Wikipedia:Fringe_theories/Noticeboard#Astrology_and_the_Japanese_earthquake, as this article will be getting a lot of pageviews at the moment, judging by the way spurious connections with the Japanese earthquake are being bandied around the less thoughtful corners of the internet, including major tabloid newspapers. 82.46.43.33 (talk) 02:19, 12 March 2011 (UTC)

Thanks for that (I noticed the post and will watch this article). Johnuniq (talk) 04:09, 12 March 2011 (UTC)

Tautology

"...at 90 percent or more of its closest perigee"... The moon is always at 90 percent or more of its closest perigee, since perigee by definition means it never gets any closer than this. In fact, it is always at 100 percent or more of its closest perigee. 95.149.140.214 (talk) 17:24, 12 March 2011 (UTC)

Perhaps it meant to say ".9 or more of its greatest inward deviation from average distance"? —Tamfang (talk) 17:09, 13 March 2011 (UTC)

Maybe, but if the people creating this content don't understand mathematics, it's not our job to try to translate their nonsense. HiLo48 (talk) 21:17, 13 March 2011 (UTC)

Jessiessica (talk · contribs) corrected it to "90% or less of average distance" (which would imply eccentricity ≥0.1), but sourced the definition to Nolle's site which says "90% or greater of its mean closest approach to Earth (perigee)". Not good enough! —Tamfang (talk) 08:49, 14 March 2011 (UTC)

Sorry, Nolle's definition was ambiguously worded, making it difficult to understand. I changed it to "90% or greater", but if you can think of a more correct way to state this fact you are welcome to edit it. It is necessary to include this aspect of the definition however as it needs to be made clear that a supermoon is not merely any perigee. By the way, I realise in one of my edit description I mistakingly wrote "a supermoon is not merely an apogee". I of course meant perigee. - Jessiessica (talk · contribs)

I'm good at improving language but I can't work with nothing. Nolle's definition (which your last revision restores) is nonsense. The Earth-Moon distance never gets anywhere near as small as 9/10 of its average, so that can't be it either. —Tamfang (talk) 18:25, 14 March 2011 (UTC)

Whether it is nonsense is a distinct question from if that is what Nolle meant. JoshuaZ (talk) 03:30, 15 March 2011 (UTC)

Let me just pop in here to apologize for causing the entire 90% ruckus with my vague and ill-defined usage. I was so caught up in axing the boatload of astrology and disaster nonsense from the article that "at 90 percent or more of its closest perigee" must have sounded great to me at the time. Sorry all around... Darkest tree (talk) 03:46, 19 March 2011 (UTC)

There is nothing unclear about "within 90% of its closest approach". 75.69.114.89 (talk) 02:02, 20 March 2011 (UTC)

OK, I'll play dumb. It's a bit unclear to me. If, say, its closest approach is 100,000 km (I know it's not), is 90,000 within that? HiLo48 (talk) 02:09, 20 March 2011 (UTC)

"within 90% of its closest approach" to me means "the distance between the earth and the moon is at or above 90% of (whatever the closest approach is)". Unless the exact distance of the closest approach is for some reason impossible to accurately measure, I see nothing wrong with the wording. 75.69.114.89 (talk) 02:46, 20 March 2011 (UTC)

See Nolle's definition he emailed me below starting with "Look at it this way..." and you will see why there is such confusion. He implies the 90% is actually in reference to "mean perigee distance" rather than the closest perigee distance. The original definition never made this distinction. He then goes on to confusingly state that it's a time (rather than a distance) parameter.- Jessiessica (talk · contribs)

Maybe he's gone senile. 75.69.114.89 (talk) 02:59, 20 March 2011 (UTC)

timing

lol. I'm curious, did this article just suddenly appear after the 9.0 Earthquake in Japan, is this another ex post facto prophecy come true? WHY DIDN'T YOU LISTEN?!98.165.15.98 (talk) 13:47, 13 March 2011 (UTC)

The article was created at 21:11, 11 March 2011. [1]. Any fool can make 'predictions' this way. It is also possible to predict that (a) people will keep on producing such nonsense, and (b) other people will believe it. Sad, but true. AndyTheGrump (talk) 14:48, 13 March 2011 (UTC)

Interestingly, I saw an article three or four days before the earthquake (In the Post or the BBC news feed, I forget which), which talked about the supermoon and that astrologer's prediction that it would cause horrid devastation of numerous types. They had some geologist poopooing it as pseudoscience, and of course it is pseudoscience, but you know what they say - even a broken clock is right twice a day. coincidence is always highly salient, but neither of those implies causation. --Ludwigs2 09:13, 14 March 2011 (UTC)

P.s. - I just glanced through the article, and is it just me, or is most of the 'Link to natural disasters' pure OR? I think we could reduce that whole section to a single line "Links between supermoons and natural disasters such as earthquakes have been speculated, but the moon's impact on such events is generally dismissed by geologists as trivial or nonexistent." what do you think? --Ludwigs2 09:19, 14 March 2011 (UTC)

Sounds good to me - I don't think the 'generally' is really necessary though, unless someone can find a geologist who actually believes this bullpoop. AndyTheGrump (talk) 18:08, 14 March 2011 (UTC)

I disagree. The main reason why people are showing any interest in supermoons at all is due to the pseudoscientific arguments made by astrologers who are arguing that it may (of has already) influence natural disasters. A link between natural disasters and supermoons is one of the main arguments made by Richard Holle, the inventer of the term (and the hype) and so is central to the discussion of supermoons. As such, it is important to explain the empiricism surrounding such a claim. However the part about the Indian ocean tsunami can be removed if necessary. - Jessiessica (talk · contribs)

• <sarcasm alert>Wait - ...article was created at 21:11, 11 March 2011... 21:11 11/11? I suppose you "scientists" will try to tell me that is merely coincidence? OMG, conspiracy!!!!1111111eleventyone! Hehehehe. They don't call it 'lunacy' for nothing :-) only having a bit of fun; no offence intended. I'm off to make a tin foil hat  Chzz  ►  17:55, 20 March 2011 (UTC)

fraction mystery

... at or near (within 90% of) its closest approach ...

Okay, what does "within 90%" mean? In ordinary usage, if the closest approach is N, "within 90% of N" means not less than 0.1×N and not more than 1.9×N — which would include the entire orbit of the Moon with plenty of room to spare.

... when the moon is at 100% or greater mean perigee.

This can be made into a useful definition, if we merely read it backward: a syzygy when the Earth-Moon distance is less than mean perigee. —Tamfang (talk) 00:52, 15 March 2011 (UTC)

I have emailed Richard Holle and asked him to modify his article with a less ambiguously worded definition of supermoons. Strange that in an article where he stated "When I see people misrepresenting the idea, not really understanding it at all, I feel impelled - not compelled - to try and set the record straight. Words mean things, after all . . ." he still failed to provide a meaningful definition - Jessiessica (talk · contribs)

Here is Nolle's response:

“ Look at it this way: if 100% is as close as two bodies can get (mean perigee distance), then 90% is enough to qualify. Practically speaking, it’s a time parameter: if perigee and syzygy happen at exactly the same moment, then you’ve got your 100%. This rarely happens. Generally speaking, if the separation of these two events is more than about 12 hours, there’s no SuperMoon. The software I was using made this the most effective search algorithm.

Mean perigee distance is exactly that: the mean between the extremes. If you’ll look at the annual apogee/perigee tables at my website, this becomes readily apparent: some perigees are much closer than others.

”

— Preceding unsigned comment added by Jessiessica (talk • contribs) 03:57, 15 March 2011 (UTC)

Can you parse that? Because I'm not at all sure what he's trying to say. JoshuaZ (talk) 04:01, 15 March 2011 (UTC)

Me neither. I was hoping some more informed people might have a better idea what he means, but I'll have a crack at it. I think it might make better sense if you reverse the numbers so one could say: "...defined as a new or full moon that occurs when the moon is within 10% of its minimum distance from the Earth.", however I don't even know where to begin with that talk of it being a "time parameter". Any insights? - Jessiessica (talk · contribs)

Because the eccentricity is less than 6%, the moon is "within 10% of its minimum distance" most of the time.

The phrase "time parameter" suggests to me that the elusive criterion is one-tenth of a month (or a demi-month?) between perigee and syzygy. —Tamfang (talk) 07:02, 15 March 2011 (UTC)

Argh. 90% of what is enough to qualify? The distance never gets as low as 0.9× mean perigee. —Tamfang (talk) 07:03, 15 March 2011 (UTC)

Nolle wrote to me that he meant 90% of the difference between extreme apogee and extreme perigee. —Tamfang (talk) 06:09, 16 March 2011 (UTC)

So the phrasing I'd use is: when the Earth-Moon distance is in the lowest tenth of its range. —Tamfang (talk) 06:25, 19 March 2011 (UTC)

There is nothing unclear about "within 90% of its closest approach". This means when it is at least 90% as close as it ever gets. It is perplexing to me how anyone could misunderstand this. 75.69.114.89 (talk) 02:06, 20 March 2011 (UTC)

It is undeniably perplexing that Nolle seems to switch back and forth between the 90% being a distance and a time parameter. - Jessiessica (talk · contribs)

Here is what Nolle has to say about the confusion over the definition of a supermoon taken from a modified form of http://www.astropro.com/features/articles/supermoon/:

“ ...I’ve had questions from people who claim that my definition of SuperMoon is nonsensical because "the Earth-Moon distance is *always* "90% or greater of its mean closest approach"...(Seriously, so many of these critics are really only interested in criticizing - which they do without first bothering to know what they're talking about. But that's just the way skeptics are.) ”

Included is a long, not particularly concise explaination of his supermoon definition which you can see at the bottom of the page at the link.

All I have to say to Mr Nolle is don't blame the skeptics/critics for your sloppy use of ambigiously worded terminology. You should have provided a clear, concise definition from the outset rather than waiting 30 years to clear up any confusion. - Jessiessica (talk · contribs)

The name: Supermoon or Super Moon?

I noticed today NASA, in their video blog ScienceCast, write the name of Super Moon instead of the one word name Supermoon. Is there a reason why the article is written as one word (Supermoon)? It doesn't seem to me it should be written as one word, rather two words seem natural...

ScienceCasts: Super Moon

Thanks, -- Joel M.Chat ✐ 15:40, 18 March 2011 (UTC)

Given that the name is from astrology, not astronomy, there is unlikely to be an 'official' name at all - it comes down to which is used more often in the sources we have. 'Supermoon' certainly seems to be used quite a few. AndyTheGrump (talk) 16:09, 18 March 2011 (UTC)

Richard Nolle, who coined the term uses "SuperMoon". Because the term is used to describe a lunar event, it isn't a proper noun and as such capitalisation is inappropriate if the continuous word "supermoon" is used. As Andy said, there is no "official" term, however "supermoon" appears to be most commonly used. - Jessiessica (talk · contribs)

Extreme Supermoons

About the section: "Dates of supermoons between 1950 and 2050"

The article has a list of past and predicted extreme supermoons but no definition of an "extreme supermoon".

?? Wanderer57 (talk) 19:18, 19 March 2011 (UTC)

In the referenced tables there is the following explanation...

"X = EXTREME SUPERMOON (MOON AT 100% OR GREATER MEAN PERIGEE)"

Sounds again like (deliberately?) confused and confusing use of astronomical terms by an astrologer. HiLo48 (talk) 19:50, 19 March 2011 (UTC)

From my email exchange with him, it's clear to me that Nolle is using a scale on which "0%" is the mean apogee distance and "100%" is the mean perigee distance. It's not as transparent as one would prefer, but I wouldn't call it "deliberately confused and confusing". —Tamfang (talk) 21:13, 19 March 2011 (UTC)

It's bad science. It just pushes all of this stuff further into the realm of Pseudoscience HiLo48 (talk) 21:19, 19 March 2011 (UTC)

What's bad science — Raising the question whether perigee+syzygy has interesting effects? Inventing terminology? Failing to bury the matter when it's found that there is no significant effect? —Tamfang (talk) 21:25, 19 March 2011 (UTC)

I did originally include Nolle's definition but it was removed for the above-mentioned reasons. The reason why I included dates of extreme supermoons only is because there are just too many supermoons to list with an average of 5 a year. The links provided lead to the dates of the rest of the supermoons. - Jessiessica (talk · contribs)

syzygy

One well-meaning editor recently removed the tidal effect of syzygy because it was not supported by a reference about the tidal effect of perigee! See Tide#Range variation: springs and neaps. —Tamfang (talk) 21:15, 19 March 2011 (UTC)

Here is astronomer Phil Plait's quote addressing the tidal effect at perigee:

“ When the Sun, Earth, and Moon are near a straight line in space — that is, at new or full Moon — these effects are maximized. We get what are called spring tides, with extra-high high tides, and extra-low low tides.

If this happens at perigee, the effects are even stronger. The tidal force from the Moon can be as much as 50% greater! While that sounds dangerous, it’s not like we’ll see huge earthquakes and roaring tidal waves from this, because even at their strongest, the tidal forces are fairly weak. It does mean people in low-lying regions and who usually experience monthly spring tide floods should take extra precautions, but it won’t be the epic disaster some people are breathlessly claiming.

”

- Jessiessica (talk · contribs)

50%? Holy cow, amazing. If this crackpot astrology stuff were true then the moon and sun wouldn't have to be perfectly (and I use that term loosely) aligned to create disasters, they could be offset by quite a bit. 'Kinda' aligned sun and moon happens quite often.98.165.15.98 (talk) 03:08, 20 March 2011 (UTC)

Earth-moon distance range

Quoting the article: "The Moon's distance varies each month between approximately 354,000 km (220,000 mi) and 410,000 km (254,000 mi) due to its elliptical orbit around Earth.[1][2]"

This statement is straightforward and is about astronomy, not astrology. The part that bothers me are the two references.

Please will someone provide a reputable astronomical source for this sentence? It would be comforting to have at least one sentence in the article on solid ground.

Thanks, Wanderer57 (talk) 00:35, 20 March 2011 (UTC)

Try the wikipedia article on the moon. If wikipedia cannot source itself then something's horribly wrong.98.165.15.98 (talk) 03:09, 20 March 2011 (UTC)

Oddly enough, Wikipedia cannot source itself. "The threshold for inclusion in Wikipedia is verifiability, not truth; that is, whether readers can check that material in Wikipedia has already been published by a reliable source." If an article in W can be a source for another article, one can end up in a situation where (for example) article A is a source for article B, and article B for article C, and article C for article A, and there is no outside source at all. Hence the rule that a source must be outside Wikipedia. Wanderer57 (talk) 16:26, 20 March 2011 (UTC)

Wikipedia's got an article on moon's perigee and apogee distances, article's "MOON", if it's wrong someone should change it. Or we can have 2 conflicting numbers.98.165.15.98 (talk) 10:31, 22 March 2011 (UTC)

I wasn't suggesting that our Moon article is incorrect. "Do not use Wikipedia as a source" is a Wikipedia rule. See Wikipedia as a source. Wanderer57 (talk) 12:24, 22 March 2011 (UTC)

Is astronomer Phil Plait (ref [1]) not a reliable source on astronomy? - Jessiessica (talk · contribs)

No he's not reliable because the tidal forces are not 50% greater at perigee.98.165.15.98 (talk) 03:10, 20 March 2011 (UTC)

I suppose that ad hominem attack trumps all his work as an astronomer over the years. - Jessiessica (talk · contribs)

I'm sorry for any misunderstanding I caused. My request for another source for the range of the moon-earth distance was not intended to reflect on the reputation of Phil Plait or anyone else. It seemed to me that moon-earth distance must be well-documented in "standard reference works" about astronomy. I think it would be reassuring to readers like myself, coming to this topic without much background, to have a older and very authoritative source rather than an article just recently created as part of the discussion about this peculiar theory about the earthquake. Wanderer57 (talk) 16:51, 20 March 2011 (UTC)

Brightness and gravitation

I noticed there's no calculation for the increase in brightness (during full moon) and increase in gravitational force. Both follow an inverse-square law, so the results will be the same: I get an increase of 10% during supermoon compared to average, and 16% compared to, um, infinumoon. This seems way higher than I would have expected for a tidally-locked-yet-not-geocentric object, so can somebody verify this? SamuelRiv (talk) 04:32, 20 March 2011 (UTC)

Tide follows an inverse-cube law (because it's about the difference in gravitational force on the near and far points of the Earth, not about the force itself). Using the numbers in Orbit of the Moon, I get a ratio of 1.39 between perigee and apogee. —Tamfang (talk) 04:44, 20 March 2011 (UTC)

Good point, *headslap*, and I get the same ratio, which means the tides yesterday would be 18% larger than the mean for a full moon, and 39% larger than at apogee, but of course saying the tides are x higher can be misleading because of the topography of the oceans. And my original calculation is wrong (I forgot to square it) - the moon was 12% brighter than average and 24% brighter than at apogee. Those results are confirmed by a couple other blogs, so I'll pop that in. SamuelRiv (talk) 17:29, 20 March 2011 (UTC)

The moon In noted on 26,27ths of September 2007 was 60-70% bigger than what I saw yesterday. why aren't those called supermoons. http://www.flickr.com/photos/challiyan/5540532572/ --Challiyan (talk) 10:39, 20 March 2011 (UTC)

If you mean the moon in 2007 was 70% of the size or brightness you saw yesterday, that may be correct. If you can give us two photographs taken with the same lens from the same site in 2007 and yesterday, or with a relative object (like a skyscraper) in view, then we might be able to give an accurate measurement and figure out what's up. SamuelRiv (talk) 17:29, 20 March 2011 (UTC)

Perigee-syzyrgy

I've been trying to figure out how often the perigee-syzyrgy happens, but I can't seem to find any real information on it anywhere here or elsewhere on the Internet. Anybody have more info on this? I think this would be a good thing to have in the article to help clear up people's misconceptions. --Flib (talk) 14:10, 20 March 2011 (UTC)

How often it 'happens' will depend on your definition of how closely together the two events need to be to be considered 'at the same time' etc - any answer is going to be rather arbitrary. AndyTheGrump (talk) 15:59, 20 March 2011 (UTC)

If you use the same criteria as Nolle does for extreme supermoons, you'll find ther is no obvious pattern to their frequency. There have been 14 extreme supermoons since 1900 but they don't occur at regular intervals. For example there were 4 supermoons between 1900 and 1970, and then 3 in a space of only 3 years between 1972 and 1975.- Jessiessica (talk · contribs)

Astrology, really?

I'm wanting to change the intro to this article from "In astrology" to "In astronomy." But as I started to edit, it said not to call it astronomy, because the term "supermoon" was coined by an astrologer. The definition section tells that astronomers don't widely accept the term, but that doesn't mean it applies to the astrology (not astronomy) theme. This is an astronomy (not astrology) topic. QQQ (talk) 15:44, 20 March 2011 (UTC)

Not really - astronomers neither use the term 'Supermoon', nor attach any particular significance to it. AndyTheGrump (talk) 15:54, 20 March 2011 (UTC)

But they do use the other term, correct? "Supermoon" is also the term used in news broadcasts, including NASA. The article does not discuss astrology, but astronomy, so there is no need to mention astrology in the lede. If astrology is relevant to the naming, it can be mentioned there, say by noting that the coiner is an astrologist. Per Wikipedia:Fringe_theories#Pseudoscience, there's no reason to give astrology parity here. — kwami (talk) 20:46, 20 March 2011 (UTC)

The truth is astronomers rarely even use the term perigee-syzygy (google it), which just goes to show how important such an event is to them. Supermoons/perigee-syzygys are not even on the astronomical radar because the real difference between a perigee and a supermoon is only ruled by an arbitrary criteria imposed by astrologer Richard Nolle. - Jessiessica (talk · contribs)

The current content of the article suggests that the only connection with astrology is Richard Nolle, who coined the word. What did he himself say about it? The word sounds to me more like a handy tabloid headline word than an astrological term. But surely it is primarily a scientific topic, whether or not the article properly reflects that? Is most or all of the content covered elsewhere by "perigee"? If so, then maybe a merge is required. Unless its significance for astrology can be established, I would propose to delete all the links/tags to astrology. I don't see any links to Dubliners in the article for Quark. Martinevans123 (talk) 17:50, 22 March 2011 (UTC)

File:Perigee Moon 19 March 2011 Lincoln Memorial.jpg

Is this a fake photo? Or is Lincoln Memorial a micro-architecture? The moon in Beijing 5 min ago is not as big as even one-fourth that moon. ––虞海 (Yú Hǎi) ✍ 16:00, 20 March 2011 (UTC)

It's as big as a stair window (0.5m x 0.5m) 50 meters from what I saw it. ––虞海 (Yú Hǎi) ✍ 16:03, 20 March 2011 (UTC)

The photo was taken with a zoom or telephoto lens, by the look of it - the building is further away than it seems, making the moon look bigger. AndyTheGrump (talk) 17:32, 20 March 2011 (UTC)

See also Moon illusion. (I don't know if that helps, exactly - but I think it is related)  Chzz  ►  17:35, 20 March 2011 (UTC)

The photo was taken with a 400mm telephoto lens and the image was probably cropped too. Bubba73 ^{You talkin' to me?} 20:29, 20 March 2011 (UTC)

See this, for example. Bubba73 ^{You talkin' to me?} 23:55, 20 March 2011 (UTC)

In other words, they "cheated" by using a telescope. They really need to make that clearer on APotD. SamuelRiv (talk) 12:40, 21 March 2011 (UTC)

How is that cheating? It is just a standard camera lens. That is the perspective you have if you are a long way away from the Lincolm Memorial. Bubba73 ^{You talkin' to me?} 15:57, 21 March 2011 (UTC)

Perigee

This isn't actually perigee (not exact enough), it's a near minimum perigee, isn't it? Doesn't that affect the term "perigee-syzygy"? 184.144.166.85 (talk) 12:26, 21 March 2011 (UTC)

It is mentioned in the definition section that the two don't necessarily coincide perfectly each time. The point of supermoon is the point of perigee with the point of syzygy varying from the same time (extreme supermoon) to 12 hours away (regular supermoon). This is mentioned in the definition section. - Jessiessica (talk · contribs)

Utterly unscientific article

From Peter Cadogan, "The Moon, our sister planet" (Cambridge University Press, 1981), Ronaldo Rogério de Freitas Mourão, "Encyclopedic Dictionary of Astronomy and Astronautics" (CNPq, 1987), etc:

Synodic revolution: 29,23 days.

Sidereal revolution: 27,32 days.

Draconic or nodic revolution: 27,21 days.

Tropical lunar month: 27,32 days.

Anomalistic revolution: 27,55 days.

Regression of line of nodes or eclipse year: 346,62 days.

Rotation of line of apsides: 8,85 years.

Rotation of line of nodes or precession: 18,61 years.

Octaeteris cycle: 8,0 years.

Metonic cycle: 19,0 years.

Saros cycle: 18,03 years.

From various popular media sources:

Supermoon period: "nearly 20 years", "about 18 years", "when it is 90 % from perigee", etc.

NASA has a definition of the phenomenon, sort of:

"Footnote: Less-perfect perigee moons occur more often. In 2008, for instance, there was a full Moon four hours from perigee. Many observers thought that one looked great, so the one-hour perigee moon of 2011 should be a real crowd pleaser."

The periods mentioned on top were discovered by the Great Astronomers of Antiquity, such as Aristarchus of Samos, Hipparchus and Claudius Ptolemy.

The supermoon period was invented by the Great Astrologers of Present-Day Era, such as Richard Nolle, and was picked up by the popular press, I presume to NASA webmasters' great exasperation. Aldo L (talk) 17:31, 21 March 2011 (UTC)

Can we please use periods instead of commas to denote fractions?98.165.15.98 (talk) 10:26, 22 March 2011 (UTC)

Aldo L: It is unclear to me if you are criticizing the article itself or the topic, with the title you gave to this section.

I don't see the relevance of the statistics about the duration of various cycles to the topic. Please will you be more specific?

Thanks, Wanderer57 (talk) 19:42, 21 March 2011 (UTC)

Hello, thanks for following up. On 27 August 2003 Mars was in a very similar situation: at opposition near its periapsis. It also made a lot of press but we don't have an article about that, just one paragraph plus one sentence, in our Wiki article about Mars. Why just that? Because this is not a specific cycle or a specific periodicity, nor it's a component of the celestial mechanics of the body. It is just an ephemeris position. All the hype about "supermoon" this and "supermoon" that is because some charlatan decided to attract attention. Of course I enjoyed watching the moon last night, but it was the same phenomenon that I have observed several times in all these years of amateur astronomy: the full moon near perigee. Nothing else. I don't see the point of a Wikipedia article. A paragraph in some other article about the Moon will suffice. Aldo L (talk) 02:57, 22 March 2011 (UTC)

You are right - from the scientific perspective, there is no justification for this article. But you could say that about many Wikipedia articles - perhaps most. Biographies of Hollywood stars, and articles about Japanese manga characters aren't science either. Rightly or wrongly, Wikipedia has such articles, and strives to get the facts (such as they are) right about such topics too. The 'Supermoon' phenomenon is astrological hokum, but it is hokum that a lot of people seem to have given credence to - at least we can show that this is hokum, with an article that explains why. Maybe in the process, we might get one or two readers interested in real science, which would be no bad thing. AndyTheGrump (talk) 03:34, 22 March 2011 (UTC)

OK, I see your point. Let's make this clear in the introduction to the article, so readers will be warned. Aldo L (talk) 16:15, 22 March 2011 (UTC)

"a close approach"

First sentence of this article:

"A perigee-syzygy of the Earth-Moon-Sun system or "supermoon" is a full or new moon that coincides with a close approach by the Moon to the Earth."

As far as I can figure, the criteron of "closeness" described in the article (and discussed above) would include any case where the distance was 5 or 6% less than the average earth-moon distance. Calling this a "close approach" is stretching the meaning of "close" beyond its breaking point IMO.

I suggest an alternate wording: "A perigee-syzygy of the Earth-Moon-Sun system or "supermoon" is a full or new moon that occurs when the Moon is at least 6% closer than average to the Earth."

Wanderer57 (talk) 20:20, 21 March 2011 (UTC)

Where did you get the 5-6% figure from? The reason why we do not go into detail in the definition is that the definition is quite complicated and confusing. Any attempt to explain it in 1 sentence will only result in ambiguous/arbitrary words. i.e. closer than what? The average Earth-Moon distance? Because a supermoon is greater than 6% closer than the average Earth-Moon distance. Closer than the average perigee difference? You see my point. This is why there is a whole section on the definition. Perhaps we can do better in that 1 sentence, but I don't see how 5-6% is accurate. - Jessiessica (talk · contribs)

Thank you. I do see your point. It is very difficult to be precise about something when the person who defined it was so extraordinarily careless in their definition.

The 5-6% "statistic" was obtained as follows. I went to Nolles' webpage where he has apogee and perigee distances for the year 2011. The highest apogee is 406,655 and the lowest perigee is 356,577. From these numbers, Nolles calculates the "closer distance below which a moon may qualify as a supermoon" (my terminology, not his) as 361,585 [356,577 plus 10% of the difference (406,665 - 356,577)] OR 406,665 less 90% of the difference.

Based on this, I believe Nolles is saying in effect that a supermoon is a full or new moon that occurs when the Moon is 361,585 kilometres or less from the Earth.

I then looked up the average Earth-Moon distance. For simplicity I went according to our article Moon. The semi-major axis is 384,399 km, essentially the same as the average of the "apogee" and the "perigee", 384,400 km.

361,585 is 5.93% less than 384,400. Or rounded off, 6%.

With this information, the definition of a supermoon can be expressed as "a full or new moon that occurs when the Moon is at least 6% closer than average to the earth."

A more felicitous way of expressing this might be as "a full or new moon that occurs when the Moon is closer than 94% of its average distance from the earth."

Wanderer57 (talk) 00:42, 22 March 2011 (UTC)

Run aground

The last two edits to this topic seem perfectly fair. The source given here indeed offers only observational evidence. But yes, I would argue that this statement does deserve to be kept in the article. One is left wondering, however, what exactly would constitute "scientific evidence". Surely if sandbanks not normally visible become visible, this suggests the tide is very low. Could this not be easily corroborated by checking tide minima at the agreed measuring places? Or putting the question the other way round - what else could explain the appearance of these sandbanks? Doesn't five ships at the same time sound a bit more than mere coincidence? Reading the reference by Phil Plait in Discover Magazine, it seems like a perfectly reasonable association between moon proximity and navigational difficultly has been”tainted” in some way by a coincidental earthquake and tsunami? Martinevans123 (talk) 13:13, 23 March 2011 (UTC)

Yes. The Sun-Moon-Earth alignment and the Moon distance both affect the tides in a way that has been known for some centuries. The topic is covered in both Tide and Moon. We are not likely to do as well here and it would be better to refer readers to those articles IMO.

The tide tables for the Soylent do indeed show a large range of tides around March 19 (both before and after, it is not a one-day thing.) What seems odd is that the Captains who ran vessels aground apparently did not check the tide tables. They will have some spaining to do.

Rather than redirect "Perigee-syzygy" to "Supermoon", I think it would be better to redirect "Supermoon" to a "Perigee-syzygy" article. This would give a reader who looks up supermoon a scientifically more credible name.

Wanderer57 (talk) 19:22, 23 March 2011 (UTC)

Given that the tides were predicted, the reason for the groundings was poor navigation, not the "mystical" Supermoon. My point being that it WASN'T mystical. That addition should be removed. HiLo48 (talk) 19:37, 23 March 2011 (UTC)

Perhaps Captains learn to allow for a typical Spring Tide and feel they need not always check their tables? But if something, like a sandbank, is generally hidden, even at the lowest typical tide, it's hard to learn when exactly it will appear? or even pose a greater hidden risk. Especially with pehaps many years between similar lunar events. But yes, if the tide tables accurately take account of the Perigee-syzygy, some failure of tables and depth charts seems likely. But even with depth charts, I'd guess that the sands in The Solent are constantly shifting. The second point raised by Wanderer57 poses a larger question. I'd not be unhappy to see Supermoon as a sub-section within Perigee-syzygy. Thanks. Martinevans123 (talk) 19:41, 23 March 2011 (UTC)

There is a perigee article, and a syzygy article, but no perigee-syzygy article. While some would probably argue that perhaps we should create one, I think that will only give more scientific credence to a pseudoscientific concept. I've looked, and I could only find 1 incidence of a scientist using the term perigee-syzygy. It is an event that astronomers and other scientists really pay no heed to. Nobody even gave a rat's about perigee-syzygys until this whole supermoon business started. If we created a perigee-syzygy article, people may assume that supermoons are based on a scientific concept when they're really not. While we could do better, I think this article does a fair job of presenting evidence to suggest that supermoons are pseudoscience. - Jessiessica (talk · contribs)

Wait a minute

According to the information I can find, the Japan earthquake was on March 11, one day before the moon was at first quarter. The moon distance must have been somewhere in its mid-range then because it was at apogee on March 6 and perigee on March 19.

That is about as far from a "supermoon" as one can get, isn't it? Wanderer57 (talk) 19:34, 23 March 2011 (UTC)

You're absolutely right. Any claimed connection of the "supermoon" with the Japanese earthquake is total rubbish. It shows that astrologers are very unscientific people, or hope that their audience is. HiLo48 (talk) 19:39, 23 March 2011 (UTC)