Talk:Saros cycle
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[edit] merge with saros 131
Why is there even a saros 131 page? What about the other 60 or so active saros series? This page will not become better if we add all such details. Tom Peters 22:57, 30 May 2006 (UTC)
- Then propose Saros 131 for deletion. I don't know enough about the topic and wanted to throw it open to people more knowledgable than I. As it is. Saros 131 is a orphan article (nothing links to it), the birthday reference is obscure, and the article is generally confusing. I was trying to find articles to link to it and found this one. Thatcher131 02:39, 31 May 2006 (UTC)
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- Apparently someone has merged saros 131 into the article anyway as an example. However I find it clumsy: repeats info, headings are a mish-mash (no clear hierarchy), numbering and edits thereof are confusing (where are the 1,2,3 1,2,3 sequences promised in the text) etc. Whoever wants this info in the article, please clean up! Tom Peters 11:56, 2 June 2006 (UTC)
[edit] ?
The phrase "the saros was discovered by ancient astronomers" is a bit vauge.
According to John P. Pratt's article on the "Symbolism of the Passover" the saros discovery came from "ancient Chaldea"...
Can anyone elaborate / confirm / deny this?
- It was certainly known by astronomers in Mesopotamia (Babylonians also known as Chaldeans) several centuries BC as shown by clay tablets. Tom Peters 22:57, 30 May 2006 (UTC)
[edit] Series vs Cycles
Cna this distictin be drawn more clearly? I found the article confusing, espscially as I cme form somthing talking about 1000yr plus cycles to an article which starts with 18 year cycles. Rich Farmbrough 14:29, 3 November 2005 (UTC)
Yes, please, could someone fix this article? It is very, very confusing. 18 years? 1370 years? 24.82.85.97 06:35, 31 January 2006 (UTC)
- Read carefully. The cycle lasts 18 years (+ about 11 days): after 18 years a similar eclipse occurs again. There is a series of such eclipses, 18 years apart. Such a series "lives" for about 1370 years on everage: after such a time, there will be no more eclipses multiples of 18 years after the last one. If you can re-formulate the article to make this clearer, please do so. Tom Peters 22:57, 30 May 2006 (UTC)
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- I agree, the saros cycle section is very confusing and needs to be clarified. The length of the series in tems of years and saros cycles should be explicity defined in the first paragraph of this section. The origin of 1370 year cyclicity needs to be described. The underlying cause as to why series, instead of just cycles, are used needs to be described in words. The numbering system is confusing as well. I don't know enough about this subject to fix this myself. Lunokhod 11:48, 2 January 2007 (UTC)
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- I elaborated. Is it clear now? Tom Peters 02:22, 3 January 2007 (UTC)
- Could you put the subsections "Partial lunar eclipses (Southern edge of shadow)", "Total lunar eclipses", and "Partial lunar eclipses (Northern edge of shadow)" into a table? These should not be in the text portion of this article. It is not clear why there is a "..." between adjacent entries. If you are only going to list 6 partial eclipses, perhaps it would be best to just say in paragraphy form "Examples of partial of lunar eclipses in this cycle are xxx, yyy, and zzz". Lunokhod 10:36, 4 January 2007 (UTC)
- I elaborated. Is it clear now? Tom Peters 02:22, 3 January 2007 (UTC)
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[edit] astrology link?
I noticed that a link has been added to http://www2.bitstream.net/~bunlion/bpi/EclSaros.html which is written by an astrologer, who uses some astrological terms and notation and elaborates on zoodiacal signs and divination of eclipses. Apart from the astrology I do not find much factually wrong with that page (except that "saros" is NOT derived from a Greek word meaning "to repeat": the Greek verb saroein means "to sweep clean". Halley took it from the Suda lexicon, which garbled the facts. The Bab. SAR meant something like "universe", or as a number, 3600); but it adds little that is not or can not be on this page, and I find it odd to refer to astrological pages. Tom Peters 01:27, 8 January 2007 (UTC)
- I don't have an opinion as to whether this link is removed of not. I only added this because I thought that the first half of the external link did a better (though more lengthy) job of descrbing the Saros cycle that this wiki topic did. I don't necessarily have a problem with providing a link with astrological significations, as eclipse cycles (especially when they are approximate) have more to do with historical and cultural issues than science. If more good quality external links were found, these could be organized under "astrology", "history", etc. Lunokhod 10:17, 8 January 2007 (UTC)
- Oh well. Reading this and that page, I think I see your point. It's a matter of sequence: saros (and inex etc.) are spin-offs from the more generic eclipse cycle, so this page does not repeat the explanations how an eclipse cycle works from the eclipse cycle page. Also this is a merge with a separate page for saros series 131 . I'm afraid that if this page is made more self-sufficient by repeating material, then soon someone will propose a merge with eclipse cycle; but then other pages need to be merged in too; and then that page becomes too long, and someone else will propose a split. I've seen these dynamics happen in Wikipedia ad nauseam. I believe the general preference is to keep articles manageably short, and spawn expansive sections to a main article (see {{main| }}). Since all these cycles have names accepted in literature, I believe in this case separate lemmata are appropriate. Anyway, hence the link back to eclipse cycle at the begin of the this article. Tom Peters 12:39, 8 January 2007 (UTC)
- Don't worry, I don't think that its a good idea to merge eclipse cycle with this page. In the next couple of days I'm going to try to expand the explanation here a bit, and slim down the 131 example. And I really don't mind if you delete the link if you don't like it. If I would have read the page to the bottom where the astrology stuff was, I probably wouldn't have added it. Lunokhod 16:48, 8 January 2007 (UTC)
- Oh well. Reading this and that page, I think I see your point. It's a matter of sequence: saros (and inex etc.) are spin-offs from the more generic eclipse cycle, so this page does not repeat the explanations how an eclipse cycle works from the eclipse cycle page. Also this is a merge with a separate page for saros series 131 . I'm afraid that if this page is made more self-sufficient by repeating material, then soon someone will propose a merge with eclipse cycle; but then other pages need to be merged in too; and then that page becomes too long, and someone else will propose a split. I've seen these dynamics happen in Wikipedia ad nauseam. I believe the general preference is to keep articles manageably short, and spawn expansive sections to a main article (see {{main| }}). Since all these cycles have names accepted in literature, I believe in this case separate lemmata are appropriate. Anyway, hence the link back to eclipse cycle at the begin of the this article. Tom Peters 12:39, 8 January 2007 (UTC)
[edit] inter-article redundancies
After Lunokhod's rewrite, this page now contains much explanation not only how eclipses recur, but also why an eclipse occurs. Much of this is also treated in eclipse, solar eclipse, lunar eclipse, and eclipse cycle. Do we want, and our readers need, this redundancy, i.e. do Wikipedia articles need to be self-sufficient? Or do we design some hierarchy where a page (like this) elaborates on a concept treated elsewhere? Tom Peters 15:27, 10 January 2007 (UTC)
[edit] "last paragraph"
Lunokhod asks whether the last paragraph in the section on Saros series is necessary. It gives the references for the Saros series statistics and identification numbers; that's why it was preceding the discussion of these data. Lunokhod, you requested sources for every factoid, so I'd say keep them (including specific reference to the table in Meeus's latest book). Tom Peters 14:52, 12 January 2007 (UTC)
[edit] "Lunar eclipse series are not as long-lived."?
Could someone explain why lunar Saros series are not as long lived as solar ones? It appears to me that the series would have the same length, as the only difference is that one occurs at the ascending node, and the other at the descending node. Also, given that the shadow of the Earth is larger than that of the Moon, I would expect that a lunar Saros series might even be a bit longer than a solar Saros series. Lunokhod 11:11, 19 January 2007 (UTC)
- I could, but there are several approaches or levels to describe this, and an explanation would be longish. See Newcomb 1882. Simply I think it is essentially due to this: a total solar eclipse is counted if even a part of the lunar umbra touches the Earth, which is much bigger than the Moon. A total lunar eclipse is only counted if the whole Moon enters the shadow of the Earth, which diameter is somewhat smaller than the Earth itself (shadow cone angle = solar parallax = 8.8"); a partial lunar eclipse will be a total solar eclipse as seen from part of the Moon, but is appreciated differently as seen from the Earth. So the requirements and constraints are tighter for lunar than for solar eclipses. Anyway it is a purely phenomenological observation: the Saros series as collected and studied by Oppolzer, van den Bergh, Meeus, et alii, show that for lunar eclipses they do not last as long as for solar eclipses. I made a short general remark because I couldn't find a specific statement in literature of someone who counted the statistics. Also mind that the quoted longevity of solar Sarosses depends on the compilation that you look at. The 3000-year or so intervals that have been completely computed, contain only about 100 complete Saros series; if you use another interval you may include or loose some series and change the extrema. Tom Peters 13:22, 20 January 2007 (UTC)
