text:
Talk:Diaper

Ammonia
Can someone change the Ammonia section? It states that Ammonia is caused by the combination of fecal matter and urine, when it is just the urine that is resposible. This may cause some to belive that a diaper that has only been urinated in will not produce Ammonia. --User: tash 18:14, 17 May 2007 (UTC)

 * Well fecal matter contains urease which catalyses the conversion of urine to ammonia so it is technically correct but I agree it is slightly misleading, as it makes the diaper rash worse, it is not the sole cause.--Wherethere (talk) 03:12, 12 January 2008 (UTC)

 * I don't know much about what happens to urea outside of the human system to return it to the form ammonia - but it's my understanding that ammonia is formed as a biproduct of protein breakdown in the liver, and that the ammonia is quickly converted to urea - so, I imagine the urea must be reacting with something to return to the form of ammonia? Also, has this section been completely removed - I don't see it. Should this discussion also be removed? or has the ammonia section been included in another section? — Preceding unsigned comment added by AnieHall (talk • contribs) 22:22, 1 August 2012 (UTC)

GA Review
This article does not meet the Good article criteria at the present time. Although the lead section appears good, and it is well written, there is a serious lack of citations of key information later in the article (some entire sections are completed uncited, and other key info in other sections needs to be cited).

Inline citations also need more information included than just an external link; it should include full citation information -- author, title, publication, date of publication, date URL was retrieved. This is actually quite important -- if the link ever becomes inaccessible, the additional information can be used to help verify and track down the source offline, if needed.

The article needs to be checked thoroughly for NPOV issues. Sentences like, "Disposable diapers were introduced to the US in 1949 by Johnson & Johnson, and were considered by parents as a great invention." are going to be hard to verify with reliable sources (specifically, the part in bold text), and should be toned down.

Consider moving 'etymology' to immediately before the 'history' section. It's useful to discuss the origin of the name first. Also, the 'taming of the shrew' part could use a reference; while it's mentioned, yes, an inline citation containing a link to an online copy of Shakespeare's play would help readers verify this if they wished.

The entire 'types' section only has two inline citations and a 'citation needed' tag. The bullet points in the disposable subsection seem to written too much like an advertisement for disposable diapers, than an actual encyclopedia article. I would think that it could be rewritten to provide a better, more concise, description of this type of product, and try to write in prose, with citations, rather than listing with bullets.

I would also merge the 'controversy' section into the section on cloth diapers; the text itself could also be greatly reduced. I don't think that disposable diapers are really all that "controversial". Rather, there's certainly an issue with diapers filling up landfills, and several environmental groups do favor the cloth diapers, which is why it should be included in that section. As its own section like this, it's really a violation of WP:NPOV, and of WP:WIAGA.

I'm not sure that 'changing' and 'length of use' are quite as important as the amount of text leads the reader to believe. It seems to me to contain a lot of cruft, and could probably be reduced. Remember, wikipedia is not a 'how to' guide.

I would create a new main section entitled 'uses', with three major subsections: 'children', 'adults', and 'animals'. Some of the stuff under 'changing' and 'length of use' could go under 'uses: children'.

Hopefully, these suggestions will help editors to improve the article. I think once they are fixed, the article will be a lot closer to meeting the GA criteria. Good luck! Dr. Cash (talk) 05:32, 13 January 2008 (UTC)

 * I've done a bit of work today to clarify the Types:Cloth section and added a section following it called "Care and Ecological Concerns" to separate the discussion of cloth diapers from the green debate over cloth v. disposable. I'm not averse to removing the brief "dry pail method" section in the first par. of the new section, as it now seems out of place and "how-to" to me, but I'd like a second opinion. I also updated links and added access date information to them for the references section. I'd welcome some reliable pro-disposable study references to balance the new section a bit. The studies that I've referenced are not available online for reading that I can find, but do fall within Verifiability requirements. The citation information that I've given should be plenty of information to find the studies in offline research, but please let me know if additional is needed or if there's a formatting change needed.

 * I've done some revision on the Types:Disposables section according to your recommendations and added citations to it.

 * I've also checked and/or updated citation links in these sections to include access date information. Only one revision of existing citation was required for a moved article. The information referenced has not changed, so I updated the citation URL and access date. Let me know if you're interested in other revisions to those sections.Heather (talk) 19:09, 17 March 2008 (UTC)

Pioneering days
This article contains a line about the situation "in the pioneering days". When on earth was that? Is this a reference to the United States? --KarlFrei (talk) 12:36, 3 March 2008 (UTC)
 * Given the general timeline putting the Industrial Revolution after this bit, it most likely it is in reference to the American pioneers of the 19th century, but there's also not a citation for this bit, which makes me suspect lack of verifiability. Heather (talk) 20:47, 17 March 2008 (UTC)

Unwilling
Unwilling to use a toilet? What the...?12.26.68.146 (talk) 15:46, 10 March 2008 (UTC)

Diapering in History
The reference to Elizabethans only changing soiled diapers every few days is based on a cited web article that lists absolutely no citations for their statements and is not even a historical costume site, but instead a disposable diaper industry page. A much more solid citation is needed for the pre-twentieth century section of the History section than the referenced website. Heather (talk) 21:09, 17 March 2008 (UTC)

 * Upon discussion elseNet with others who've been searching for the same citation basis and after my own searching and review of my personal knowledge base of the subject, the referenced information about pre-nineteenth century diapering cannot qualify under the Wikipedia standards for verifiability. I have altered the History article to reflect this and removed the inappropriate citation(s) from References as well. In addition, I removed and replaced citations which did not have access dates and were no longer accessible. Heather (talk) 23:12, 17 March 2008 (UTC)

 * I don't really understand your issue with the former source. Why did it need to cite sources, it was the source and there doesn't seem to be any reason why it wouldn't be reliable.  Yes, it's a diaper industry site, wouldn't that indicate they would have knowledge of diapers throughout history.  It just seems like you've deleted a lot of good information from the article without much reason.  Coop41 (talk) 14:58, 27 March 2008 (UTC)

 * The problem is that the information presented is *not* good. I and other costume historians with interest in childhood have been looking since this was revised and have yet to find a single reliable back up or citation for this misinformation. Book research efforts seems to indicate that the information was from a (possibly privately published) manual about raising children, written by a later Victorian, Edwardian, or an American contemporary, and without any stated research or citation to back up the statement.

 * Scholarship in costuming indicates that the information given is incorrect, beyond being occasionally physically impossible. A child with four days of feces and urine pressed to the diaper area is a child who develops open and seeping/bleeding wounds. Keep doing it, and you don't just risk a screaming child, but a crippled and/or dead one. This aspect of human infant physiology has not changed in four hundred years, and the removed piece of misinformation blithely stated that Elizabethans changed infants' diapers only every four days. A newborn makes approximately 8-12 soiled diapers every 24 hours. Period lists in letters, pawnbrokers ledgers, and the like, of items made or needed for expected and existing infants include enough diapering material to change soiled diapers quite often for several days, in addition to swaddling linen and bands, linen caps and clothes, and blanketing/sheeting. These are sources ranging from nobility down to lower middle class. I'm trying to get to the library to ILL one such source (facsimile pawnbroker's ledger) to add here.

 * In short, the information presented on the website is not just outdated, but wrong. Heather (talk) 19:50, 30 March 2008 (UTC)

 * Okay, if you really believe the information was innaccurate I would rather it wasn't there, it just seemed like you deleted it because you didn't personally agree with it, rather than a genuine problem with the source. But you do seem to know more about this than I do so I suppose I'll just trust your judgement. :) Thank you for looking for a replacement source and I hope you find one because the history section is looking a little sparse now.  Coop41 (talk) 21:33, 31 March 2008 (UTC)

Other Issues
The Adult section of this article, particularly the description of why diapers are used in bondage fetishism is TOO EXTENSIVE, in my opinion. Could someone with more knowledge of wikipidea's guidelines for what is and isn't necessary in an article give it a look-through? —Preceding unsigned comment added by 130.56.65.24 (talk) 03:08, 27 March 2008 (UTC)

I removed a section from the "Child" portion of this article in which a ridiculous phrase implied that "Australia supported a mainstream view of Diaper wearing in school age children", which a (defunct) link to a news site that is known for its trash and tabloid journalism. Not only is it ridiculous to assume from a single news article, rather then a study or journal, that an entire country or state supported this phenomenon, but simply reading something in a news article and dumping it on wikipedia is grossly stupid. Can we try to keep information sources factual when it comes to this sort of information? 121.210.240.147 (talk) 16:28, 23 September 2010 (UTC)

I removed cats from the animal uses section because it stated that cats bleed during ovulation. This is erroneous because cats are induced ovulators; that is, they do not ovulate until they are bred. This is similar to rabbits. Also, cats do not bleed during ovulation, even after breeding. The information about dogs is correct, however. Also, cats, unlike dogs, are generally not amenable to wearing a diaper except in the most unusual circumstances. A diaper may be used on a very ill or seriously injured cat, but it would be highky unusual to encounter a mobile and active cat that would tolerate a diaper. 70.251.119.72 (talk) 20:48, 14 January 2012 (UTC)

3.5 billion gallons of oil are used to produce the 18 million throwaway diapers that end up in landfills each year
Must obviously be wrong, otherwise how could anybody afford any? Togo (talk) 21:25, 10 February 2009 (UTC)
 * Amazing that nobody caught that until now. I've traced the source of the claim to this edit from March 17, 2008.  It was stated that way from the beginning and thus is not vandalism.  I agree with you that it cannot possible be true; if the 'millions' and 'billions' were switched it would make more sense, but I can't just make a change like that without knowing what the actual data is.  Soap Talk/Contributions 21:42, 10 February 2009 (UTC)

3.5 Billion Spread out to make 18 Million diapers means that it takes 194.4 gallons of oil to produce one diaper. This statement is clear wrong but has great emotional shock value for someone with an agenda. JTH —Preceding unsigned comment added by 74.115.160.22 (talk) 01:40, 10 January 2010 (UTC)
 * On the other hand, there are probably a lot more than 18 million diapers being used each year. -- Soap Talk/Contributions 01:54, 10 January 2010 (UTC)
 * Ive removed the claim for now. -- Soap Talk/Contributions 01:55, 10 January 2010 (UTC)

Nappy
Why not call the article "nappy" instead of "diaper"? —Preceding unsigned comment added by 90.215.146.182 (talk) 19:44, 7 December 2010 (UTC)
 * WP:ENGVAR. We had a discussion about this a few years ago and Diaper won.  Admittedly, though, it wasn't much of a discussion; see Talk:Diaper/Archive 1.  It's possible but highly unlikely that consensus could change to renaming it Nappy.  —  Soap  —  20:44, 7 December 2010 (UTC)
 * I don't see any real evidence diaper won. There was no real discussion, heck ENGVAR wasn't even mentioned, so no consensus was achieved (and the closest thing to consensus in that discussion was nappy anyway). However it is unlikely the article will be changed since wikipedia wide consensus per ENGVAR is when there is no reason to choose one over the other we follow the first contributor which was diaper in this case. Nil Einne (talk) 11:05, 29 May 2011 (UTC)
 * Nappy is ambiguous, diaper is not. That's why I haven't agitated for change. Josh Parris 22:08, 27 December 2011 (UTC)
 * Is there a way to ensure that it is changed to Nappy - I'm sorry but the Brits invented the language so I say they should be the ones who get say on this. 2A00:23C5:C887:8600:D8A9:F8F7:6752:1D1A (talk) 17:20, 2 July 2020 (UTC)

I agree, it's the English language, so the English should get final say on a topic like this (from Australia)

Toilet Training a choice
The way I understand it, infants are physically unable to control the movement of bowel or urination because the mylin sheathes surrounding the nerves used to sense and control the processes are not developed. I feel it is erroneous to say that toilet training is the 'choice' of either parent or child. It is a matter of whether or not the child's body have developed to the point where the process can be under voluntary control, period. — Preceding unsigned comment added by 136.181.195.10 (talk) 23:09, 14 September 2011 (UTC)

To say that infants are completely unable to control their bowel movements and urination is untrue. Elimination Communication is a method used by parents in order to avoid using diapers at all. While some of the success in this technique does come from the parents anticipating the child's need to void their bladder/bowels and offering the potty, as the child ages they start to "hold it" and wait for the parent to offer potty, in my experience this happens around 6 months old. It would be accurate, however, to say that newborns are unable to control their bodily excretions. And certainly, a 6 month old baby has a tiny bladder and cannot hold it for long, but an attentive parent can facilitate that baby in being toilet trained. Many children are fully and independently toilet trained by 12 months old, when they start to be able to walk and pull down their own pants. Toilet training becomes a choice when children refuse to use the toilet (this often happens) because they are afraid of it or for some other reason. It is also a choice when parents don't offer their children the opportunity to use the potty and don't teach them proper toileting habits. Some parents assume children cannot be potty trained until age 2 or 3 and so require children to wear a diaper until that time. Many parents who experience a 12 month old ripping of their diaper will try to find ways to keep the diaper on (by using "onesie" style shirts or overalls to prevent the child from accessing the diaper) instead of then teaching them to use the toilet.Ecwickoren (talk) 12:39, 27 June 2012 (UTC)

Contents/ingredients.
I think it would benefit the article to have a section describing the contents of different diapers. However, this may be cumbersome, since there are so very many. Perhaps a general spiel about the contents of conventional disposables (ie huggies, pampers, earth’s best, etc), compostable disposables (broody chick), traditional cloth diapers (homemade, I imagine), and new kinds of cloth diapers (g diapers, etc.) would work? Although this information may not be easily accessible? A though, anyways.AnieHall (talk) 22:36, 1 August 2012 (UTC)

Reference 4
The external link in reference #4 is a broken.72.12.107.91 (talk) 02:51, 20 July 2013 (UTC)

I lvoe the diapers. — Preceding unsigned comment added by Mythmonster (talk • contribs) 16:19, 26 March 2014 (UTC)

External links modified
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 * Added archive https://web.archive.org/20130715210039/http://babydiapersize.com/ to http://www.babydiapersize.com

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 * Added archive https://web.archive.org/web/20071223104927/https://www.keepkidshealthy.com:80/parenting_tips/ep/diaper_changes.html to http://www.keepkidshealthy.com/parenting_tips/ep/diaper_changes.html
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Quick question about "nappy"
Is nappy the formal usage in the UK? As in, is it what is printed on the packaging? It's not some sort of slang or colloquialism for another term? Just wondering. --Khajidha (talk) 14:31, 27 February 2018 (UTC)

Yes, nappy (plural nappies) is the formal use in the UK and is printed on the packaging. Unlike 'dummy' (colloquial) and 'soother' (formal), 'nappy' is always used. — Preceding unsigned comment added by Tibsybrumas (talk • contribs) 19:45, 19 April 2019 (UTC)

Necessity of diapers, non-Western worldview lacking in article
This article suffers from a strong western bias where it's just assumed babies will wear diapers. This a not a universally held viewpoint, especially in developing countries and traditional tribal/hunter-gatherer cultures where diapers wearing is much less common. Even in the West, practitioners of elimination communication don't use diapers either much or all the time and even then for a much shorter period of time then traditional Western parents. For some of them, diapers are only used as a backup in the early weeks or when going out but otherwise they don't use them at all around the house. I think in order to improve this article we could address the assumption in Western society that parents need to use diapers on their babies to deal with bodily waste and as well as the fact this is not a universal practice. We could also do a better job of discussing how certain developing countries have not adopted the diaper due to cost and what they do instead. Second, we need to do a better job of explaining how some Western parents do not use diapers much at all via practices like "elimination communication", though not EC'ers eschew diapers completely. Another alternative to the diaper, used still in China, is the Open-crotch pants, which also deserve mention in this article. What I would do is have a section titled "Alternatives to Diaper Use" and include mention of the assumptions made about diaper use in the West, then followed by a summery of alternatives such as EC, Open-crotch pants, etc. --Notcharliechaplin (talk) 22:32, 15 May 2018 (UTC)

A Commons file used on this page has been nominated for deletion
The following Wikimedia Commons file used on this page has been nominated for deletion: Participate in the deletion discussion at the. —Community Tech bot (talk) 11:22, 23 October 2018 (UTC)
 * Paddi picture for wiki high res.jpg

Additional Picture
I placed a picture on this article I felt added value (use of ppe) and it was removed. Why is this?

Noclu244 (talk) 13:21, 15 July 2019 (UTC)
 * I don't know but perhaps because it looks like an ad for Desitin? Gandydancer (talk) 13:40, 15 July 2019 (UTC)

My apologies, that was not my intention whatsoever! Noclu244 (talk) 13:42, 15 July 2019 (UTC)

 * I can't speak for why it was originally removed, but I removed them again because they are low quality images that don't help illustrate the article text in any meaningful way. I'm also not sure that these were added with an educational purpose in mind. - MrOllie (talk) 14:15, 7 May 2021 (UTC)

They were added with an educational purpose in mind. I don't believe they are of any worse quality than any of the other pictures on the article.

Remove the sexual fetishism reference.
I think it’s highly unnecessary to include diaper fetishism within your common diaper usages. I think using a diaper as fire kindling is more likely than diaper fetishism. Honestly it should not be there. It makes sense for diaper fetishism to relate back to diapers however you can tell the whole story of the diaper without mentioning weird sexual fetishes that people have with diapers...

From: They are also used by adults with incontinence, in certain circumstances where access to a toilet is unavailable, or as part of a sexual fetish.

To: They are also used by adults with incontinence or in certain circumstances where access to a toilet is unavailable. 2600:8800:490F:4E00:90DA:FB61:911A:CBAA (talk) 13:27, 25 April 2021 (UTC)

 * Agree. I removed it. Ferkjl (talk) 14:12, 25 April 2021 (UTC)

Article name change to nappy?
Why is this article called diaper when British English should be the one we use? Can we change it to nappy? Thanks. RyanPLB (talk) 18:26, 22 August 2021 (UTC)

Daipers
Diapers are a type of underwear that contain or absorb human worn by both infents and children who experience bed wetting. 2600:1700:CB50:D070:D0F8:C726:E00A:5A0F (talk) 17:49, 16 January 2022 (UTC)

There is an error in the etomology.
The article implies that or modern use of the word has been in circulation since the 1590s, however, the linked etymology clearly says the word had a different meaning in the 1590s from our modern reading. It referred to the pattern visible in linen fabric. The modern use of the word diaper arose in the 19th century.

This is a simple error, but the article is protected so I cannot edit it. 2603:9001:4505:5500:5075:E265:26B8:63F2 (talk) 12:22, 19 February 2022 (UTC)

Semi-protected edit request on 19 February 2022
The article implies that or modern use of the word has been in circulation since the 1590s, however, the linked etymology clearly says the word had a different meaning in the 1590s from our modern reading. It referred to the pattern visible in linen fabric. The modern use of the word diaper arose in the 19th century.

This is a simple error, but the article is protected so I cannot edit it.

SPECIFIC EDIT:

Original: This type of pattern was called diapering and eventually gave its name to the cloth used to make diapers and then to the diaper itself, which was traced back to 1590s England.[3]

Change to: The pattern visible in linen and other types of woven fabric was called "diaper". This meaning of the word has been in use since the 1590s in England. By the 19th century, baby diapers were being sewn from linen, giving us the modern-day reading of the word "diaper". [3] 2603:9001:4505:5500:5075:E265:26B8:63F2 (talk) 12:33, 19 February 2022 (UTC)
 * ✅. Heartmusic678 (talk) 12:56, 2 March 2022 (UTC)

title: Talk:Diaper


text:
User:Peter Olin

Swedish citizen, born in 1965. Male.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: User:Peter Olin


text:
Greek euro coins

Greek euro coins feature a unique design for each of the eight coins. They were all designed by Georgios Stamatopoulos with the minor coins depicting Greek ships, the middle ones portraying famous Greeks and the two large denominations showing images of Greek history and mythology. All designs feature the 12 stars of the EU, the year of imprint and a tiny symbol of the Bank of Greece. Uniquely, the value of the coins is expressed on the national side in the Greek alphabet, as well as being on the common side in the Roman alphabet. The euro cent is known as the lepto (λεπτό; plural lepta, λεπτά) in Greek, a name which has also been used for the $1/100$ denominations of the preceding currencies of the Greek state, the phoenix and drachma.

Greece did not enter the Eurozone until 2001 and was not able to start minting coins as early as the other eleven member states, so a number of coins circulated in 2002 were not minted in Athens but in Finland (€1 and €2 – mint mark S), France (1c, 2c, 5c, 10c and 50c – mint mark F) and Spain (20c – mint mark E). The coins minted in Athens for the euro introduction in 2002, as well as all the subsequent Greek euro coins, carry only the Greek mint mark.

Greek euro design
For images of the common side and a detailed description of the coins, see euro coins.

Circulating mintage quantities
The following table shows the mintage quantity for all Greek euro coins, per denomination, per year (the numbers are represented in millions).

Greek starter kit
In 2001, the Bank of Greece issued starter kits for the introduction of the Euro.

Commemorative coins
Greece has a good collection of euro commemorative coins, mainly in silver although a few coins have also been minted in gold. Their face value range from €10 to €200. This is mainly done as a legacy of an old national practice of minting gold and silver coins. These coins are not really intended to be used as means of payment, so generally they do not circulate. Here you can find some samples:

title: Greek euro coins


text:
Ganymede (moon)

Ganymede, or Jupiter III, is the largest and most massive natural satellite of Jupiter and in the Solar System. It is the largest Solar System object without a substantial atmosphere, despite being the only moon in the Solar System with a substantial magnetic field. Like Titan, Saturn's largest moon, it is larger than the planet Mercury, but has somewhat less surface gravity than Mercury, Io, or the Moon due to its lower density compared to the three.

Ganymede is composed of silicate rock and water in approximately equal proportions. It is a fully differentiated body with an iron-rich, liquid core, and an internal ocean that potentially contains more water than all of Earth's oceans combined. Its surface is composed of two main types of terrain.

The first of the two main surface types are the lighter regions, which are generally crosscut by extensive grooves and ridges, dating from slightly less than 4 billion years ago. They cover about two-thirds of Ganymede. The cause of the light terrain's disrupted geology is not fully known, but it is speculated that this may be the result of tectonic activity due to tidal heating. Next are the dark regions that cover about a third of Ganymede. These dark regions are saturated with impact craters and are dated to four billion years ago. Ganymede orbits Jupiter in roughly seven days and is in a 1:2:4 orbital resonance with the moons Europa and Io, respectively.

Possessing a metallic core, it has the lowest moment of inertia factor of any solid body in the Solar System. Ganymede's magnetic field is probably created by convection within its liquid iron core, also created by Jupiter's tidal forces. The meager magnetic field is buried within Jupiter's far larger magnetic field and would show only as a local perturbation of the field lines. Ganymede has a thin oxygen atmosphere that includes O, O2, and possibly O3 (ozone). Atomic hydrogen is a minor atmospheric constituent. Whether Ganymede has an ionosphere associated with its atmosphere is unresolved.

Ganymede's discovery is credited to Simon Marius and Galileo Galilei, who both observed it in 1610, as the third of the Galilean moons, the first group of objects discovered orbiting another planet. Its name was soon suggested by astronomer Simon Marius, after the mythological Ganymede, a Trojan prince desired by Zeus (the Greek counterpart of Jupiter), who carried him off to be the cupbearer of the gods. Beginning with Pioneer 10, several spacecraft have explored Ganymede. The Voyager probes, Voyager 1 and Voyager 2, refined measurements of its size, while Galileo discovered its underground ocean and magnetic field. The next planned mission to the Jovian system is the European Space Agency's Jupiter Icy Moon Explorer (JUICE), which was launched in 2023. After flybys of all three icy Galilean moons, it is planned to enter orbit around Ganymede.

History
Chinese astronomical records report that in 365 BC, Gan De detected what might have been a moon of Jupiter, probably Ganymede, with the naked eye. However, Gan De reported the color of the companion as reddish, which is puzzling since moons are too faint for their color to be perceived with the naked eye. Shi Shen and Gan De together made fairly accurate observations of the five major planets.

On January 7, 1610, Galileo Galilei used a telescope to observe what he thought were three stars near Jupiter, including what turned out to be Ganymede, Callisto, and one body that turned out to be the combined light from Io and Europa; the next night he noticed that they had moved. On January 13, he saw all four at once for the first time, but had seen each of the moons before this date at least once. By January 15, Galileo concluded that the stars were actually bodies orbiting Jupiter.

Name
Galileo claimed the right to name the moons he had discovered. He considered "Cosmian Stars" and settled on "Medicean Stars", in honor of Cosimo II de' Medici.

The French astronomer Nicolas-Claude Fabri de Peiresc suggested individual names from the Medici family for the moons, but his proposal was not taken up. Simon Marius, who had originally claimed to have found the Galilean satellites, tried to name the moons the "Saturn of Jupiter", the "Jupiter of Jupiter" (this was Ganymede), the "Venus of Jupiter", and the "Mercury of Jupiter", another nomenclature that never caught on. Later on, after finding out about a suggestion from Johannes Kepler, Marius agreed with Kepler's proposal and so he then proposed a naming system based on Greek mythology instead. This final Kepler/Marius proposal was ultimately successful.

"Jupiter is much blamed by the poets on account of his irregular loves. Three maidens are especially mentioned as having been clandestinely courted by Jupiter with success. Io, daughter of the River Inachus, Callisto of Lycaon, Europa of Agenor. Then there was Ganymede, the handsome son of King Tros, whom Jupiter, having taken the form of an eagle, transported to heaven on his back, as poets fabulously tell... I think, therefore, that I shall not have done amiss if the First is called by me Io, the Second Europa, the Third, on account of its majesty of light, Ganymede, the Fourth Callisto..."

This name and those of the other Galilean satellites fell into disfavor for a considerable time, and were not in common use until the mid-20th century. In much of the earlier astronomical literature, Ganymede is referred to instead by its Roman numeral designation, Jupiter III (a system introduced by Galileo), in other words "the third satellite of Jupiter". Following the discovery of moons of Saturn, a naming system based on that of Kepler and Marius was used for Jupiter's moons. Ganymede is the only Galilean moon of Jupiter named after a male figure—like Io, Europa, and Callisto, he was a lover of Zeus.

The Galilean satellites retain the Italian spellings of their names. In the cases of Io, Europa and Callisto, these are identical to the Latin, but the Latin form of Ganymede is Ganymedes. In English, the final 'e' is silent, perhaps under the influence of French, unlike later names taken from Latin and Greek.

Orbit and rotation

Ganymede orbits Jupiter at a distance of 1070400 km, third among the Galilean satellites, and completes a revolution every seven days and three hours (7.155 days ). Like most known moons, Ganymede is tidally locked, with one side always facing toward the planet, hence its day is also seven days and three hours. Its orbit is very slightly eccentric and inclined to the Jovian equator, with the eccentricity and inclination changing quasi-periodically due to solar and planetary gravitational perturbations on a timescale of centuries. The ranges of change are 0.0009–0.0022 and 0.05–0.32°, respectively. These orbital variations cause the axial tilt (the angle between the rotational and orbital axes) to vary between 0 and 0.33°.

Ganymede participates in orbital resonances with Europa and Io: for every orbit of Ganymede, Europa orbits twice and Io orbits four times. Conjunctions (alignment on the same side of Jupiter) between Io and Europa occur when Io is at periapsis and Europa at apoapsis. Conjunctions between Europa and Ganymede occur when Europa is at periapsis. The longitudes of the Io–Europa and Europa–Ganymede conjunctions change at the same rate, making triple conjunctions impossible. Such a complicated resonance is called the Laplace resonance. The current Laplace resonance is unable to pump the orbital eccentricity of Ganymede to a higher value. The value of about 0.0013 is probably a remnant from a previous epoch, when such pumping was possible. The Ganymedian orbital eccentricity is somewhat puzzling; if it is not pumped now it should have decayed long ago due to the tidal dissipation in the interior of Ganymede. This means that the last episode of the eccentricity excitation happened only several hundred million years ago. Because Ganymede's orbital eccentricity is relatively low—on average 0.0015 —tidal heating is negligible now. However, in the past Ganymede may have passed through one or more Laplace-like resonances that were able to pump the orbital eccentricity to a value as high as 0.01–0.02. This probably caused a significant tidal heating of the interior of Ganymede; the formation of the grooved terrain may be a result of one or more heating episodes.

There are two hypotheses for the origin of the Laplace resonance among Io, Europa, and Ganymede: that it is primordial and has existed from the beginning of the Solar System; or that it developed after the formation of the Solar System. A possible sequence of events for the latter scenario is as follows: Io raised tides on Jupiter, causing Io's orbit to expand (due to conservation of momentum) until it encountered the 2:1 resonance with Europa; after that, the expansion continued, but some of the angular moment was transferred to Europa as the resonance caused its orbit to expand as well; the process continued until Europa encountered the 2:1 resonance with Ganymede. Eventually the drift rates of conjunctions between all three moons were synchronized and locked in the Laplace resonance.

Size
With a diameter of about 5270 km and a mass of 1.48E20 tonne, Ganymede is the largest and most massive moon in the Solar System. It is slightly more massive than the second most massive moon, Saturn's satellite Titan, and is more than twice as massive as the Earth's Moon. It is larger than the planet Mercury, which has a diameter of 4880 km but is only 45 percent of Mercury's mass. Ganymede is the ninth-largest object in the solar system, but the tenth-most massive.

Composition
The average density of Ganymede, 1.936 g/cm3 (a bit greater than Callisto's), suggests a composition of about equal parts rocky material and mostly water ices. Some of the water is liquid, forming an underground ocean. The mass fraction of ices is between 46 and 50 percent, which is slightly lower than that in Callisto. Some additional volatile ices such as ammonia may also be present. The exact composition of Ganymede's rock is not known, but is probably close to the composition of L/LL type ordinary chondrites, which are characterized by less total iron, less metallic iron and more iron oxide than H chondrites. The weight ratio of iron to silicon ranges between 1.05 and 1.27 in Ganymede, whereas the solar ratio is around 1.8.

Surface features
Ganymede's surface has an albedo of about 43 percent. Water ice seems to be ubiquitous on its surface, with a mass fraction of 50–90 percent, significantly more than in Ganymede as a whole. Near-infrared spectroscopy has revealed the presence of strong water ice absorption bands at wavelengths of 1.04, 1.25, 1.5, 2.0 and 3.0 μm. The grooved terrain is brighter and has a more icy composition than the dark terrain. The analysis of high-resolution, near-infrared and UV spectra obtained by the Galileo spacecraft and from Earth observations has revealed various non-water materials: carbon dioxide, sulfur dioxide and, possibly, cyanogen, hydrogen sulfate and various organic compounds. Galileo results have also shown magnesium sulfate (MgSO4) and, possibly, sodium sulfate (Na2SO4) on Ganymede's surface. These salts may originate from the subsurface ocean.

The Ganymedian surface albedo is very asymmetric; the leading hemisphere is brighter than the trailing one. This is similar to Europa, but the reverse for Callisto. The trailing hemisphere of Ganymede appears to be enriched in sulfur dioxide. The distribution of carbon dioxide does not demonstrate any hemispheric asymmetry, but little or no carbon dioxide is observed near the poles. Impact craters on Ganymede (except one) do not show any enrichment in carbon dioxide, which also distinguishes it from Callisto. Ganymede's carbon dioxide gas was probably depleted in the past. Ganymede's surface is a mix of two types of terrain: very old, highly cratered, dark regions and somewhat younger (but still ancient), lighter regions marked with an extensive array of grooves and ridges. The dark terrain, which comprises about one-third of the surface, contains clays and organic materials that could indicate the composition of the impactors from which Jovian satellites accreted.

The heating mechanism required for the formation of the grooved terrain on Ganymede is an unsolved problem in the planetary sciences. The modern view is that the grooved terrain is mainly tectonic in nature. Cryovolcanism is thought to have played only a minor role, if any. The forces that caused the strong stresses in the Ganymedian ice lithosphere necessary to initiate the tectonic activity may be connected to the tidal heating events in the past, possibly caused when the satellite passed through unstable orbital resonances. The tidal flexing of the ice may have heated the interior and strained the lithosphere, leading to the development of cracks and horst and graben faulting, which erased the old, dark terrain on 70 percent of the surface. The formation of the grooved terrain may also be connected with the early core formation and subsequent tidal heating of Ganymede's interior, which may have caused a slight expansion of Ganymede by one to six percent due to phase transitions in ice and thermal expansion. During subsequent evolution deep, hot water plumes may have risen from the core to the surface, leading to the tectonic deformation of the lithosphere. Radiogenic heating within the satellite is the most relevant current heat source, contributing, for instance, to ocean depth. Research models have found that if the orbital eccentricity were an order of magnitude greater than currently (as it may have been in the past), tidal heating would be a more substantial heat source than radiogenic heating.

Cratering is seen on both types of terrain, but is especially extensive on the dark terrain: it appears to be saturated with impact craters and has evolved largely through impact events. The brighter, grooved terrain contains many fewer impact features, which have been only of minor importance to its tectonic evolution. The density of cratering indicates an age of 4 billion years for the dark terrain, similar to the highlands of the Moon, and a somewhat younger age for the grooved terrain (but how much younger is uncertain). Ganymede may have experienced a period of heavy cratering 3.5 to 4 billion years ago similar to that of the Moon. If true, the vast majority of impacts happened in that epoch, whereas the cratering rate has been much smaller since. Craters both overlay and are crosscut by the groove systems, indicating that some of the grooves are quite ancient. Relatively young craters with rays of ejecta are also visible. Ganymedian craters are flatter than those on the Moon and Mercury. This is probably due to the relatively weak nature of Ganymede's icy crust, which can (or could) flow and thereby soften the relief. Ancient craters whose relief has disappeared leave only a "ghost" of a crater known as a palimpsest.

One significant feature on Ganymede is a dark plain named Galileo Regio, which contains a series of concentric grooves, or furrows, likely created during a period of geologic activity.

Ganymede also has polar caps, likely composed of water frost. The frost extends to 40° latitude. These polar caps were first seen by the Voyager spacecraft. Theories on the formation of the caps include the migration of water to higher latitudes and the bombardment of the ice by plasma. Data from Galileo suggests the latter is correct. The presence of a magnetic field on Ganymede results in more intense charged particle bombardment of its surface in the unprotected polar regions; sputtering then leads to redistribution of water molecules, with frost migrating to locally colder areas within the polar terrain.

A crater named Anat provides the reference point for measuring longitude on Ganymede. By definition, Anat is at 128° longitude. The 0° longitude directly faces Jupiter, and unless stated otherwise longitude increases toward the west.

Internal structure
Ganymede appears to be fully differentiated, with an internal structure consisting of an iron-sulfide–iron core, a silicate mantle, and outer layers of water ice and liquid water. The precise thicknesses of the different layers in the interior of Ganymede depend on the assumed composition of silicates (fraction of olivine and pyroxene) and amount of sulfur in the core. Ganymede has the lowest moment of inertia factor, 0.31, among the solid Solar System bodies. This is a consequence of its substantial water content and fully differentiated interior.

Subsurface oceans
In the 1970s, NASA scientists first suspected that Ganymede had a thick ocean between two layers of ice, one on the surface and one beneath a liquid ocean and atop the rocky mantle. In the 1990s, NASA's Galileo mission flew by Ganymede, and found indications of such a subsurface ocean. An analysis published in 2014, taking into account the realistic thermodynamics for water and effects of salt, suggests that Ganymede might have a stack of several ocean layers separated by different phases of ice, with the lowest liquid layer adjacent to the rocky mantle. Water–rock contact may be an important factor in the origin of life. The analysis also notes that the extreme depths involved (~800 km to the rocky "seafloor") mean that temperatures at the bottom of a convective (adiabatic) ocean can be up to 40 K higher than those at the ice–water interface.

In March 2015, scientists reported that measurements with the Hubble Space Telescope of how the aurorae moved confirmed that Ganymede has a subsurface ocean. A large saltwater ocean affects Ganymede's magnetic field, and consequently, its aurorae. The evidence suggests that Ganymede's oceans might be the largest in the entire Solar System. These observations were later supported by Juno, which detected various salts and other compounds on Ganymede's surface, including hydrated sodium chloride, ammonium chloride, sodium bicarbonate, and possibly aliphatic aldehydes. These compounds were potentially deposited from Ganymede's ocean in past resurfacing events and were discovered to be most abundant in Ganymede's lower latitudes, shielded by its small magnetosphere. As a result of these findings, there is increasing speculation on the potential habitability of Ganymede's ocean.

Core
The existence of a liquid, iron–nickel-rich core provides a natural explanation for the intrinsic magnetic field of Ganymede detected by Galileo spacecraft. The convection in the liquid iron, which has high electrical conductivity, is the most reasonable model of magnetic field generation. The density of the core is 5.5–6 g/cm3 and the silicate mantle is 3.4–3.6 g/cm3. The radius of this core may be up to 500 km. The temperature in the core of Ganymede is probably 1500–1700 K and pressure up to 10 GPa.

Atmosphere and ionosphere
In 1972, a team of Indian, British and American astronomers working in Java, Indonesia and Kavalur, India claimed that they had detected a thin atmosphere during an occultation, when it and Jupiter passed in front of a star. They estimated that the surface pressure was around 0.1 Pa (1 microbar). However, in 1979, Voyager 1 observed an occultation of the star κ Centauri during its flyby of Jupiter, with differing results. The occultation measurements were conducted in the far-ultraviolet spectrum at wavelengths shorter than 200 nm, which were much more sensitive to the presence of gases than the 1972 measurements made in the visible spectrum. No atmosphere was revealed by the Voyager data. The upper limit on the surface particle number density was found to be 1.5 cm−3, which corresponds to a surface pressure of less than 2.5 μPa (25 picobar). The latter value is almost five orders of magnitude less than the 1972 estimate. Despite the Voyager data, evidence for a tenuous oxygen atmosphere (exosphere) on Ganymede, very similar to the one found on Europa, was found by the Hubble Space Telescope (HST) in 1995. HST actually observed airglow of atomic oxygen in the far-ultraviolet at the wavelengths 130.4 nm and 135.6 nm. Such an airglow is excited when molecular oxygen is dissociated by electron impacts, which is evidence of a significant neutral atmosphere composed predominantly of O2 molecules. The surface number density probably lies in the (1.2–7) cm−3 range, corresponding to the surface pressure of 0.2–1.2 μPa. These values are in agreement with Voyager ' s upper limit set in 1981. The oxygen is not evidence of life; it is thought to be produced when water ice on Ganymede's surface is split into hydrogen and oxygen by radiation, with the hydrogen then being more rapidly lost due to its low atomic mass. The airglow observed over Ganymede is not spatially homogeneous like that observed over Europa. HST observed two bright spots located in the northern and southern hemispheres, near ± 50° latitude, which is exactly the boundary between the open and closed field lines of the Ganymedian magnetosphere (see below). The bright spots are probably polar auroras, caused by plasma precipitation along the open field lines.

The existence of a neutral atmosphere implies that an ionosphere should exist, because oxygen molecules are ionized by the impacts of the energetic electrons coming from the magnetosphere and by solar EUV radiation. However, the nature of the Ganymedian ionosphere is as controversial as the nature of the atmosphere. Some Galileo measurements found an elevated electron density near Ganymede, suggesting an ionosphere, whereas others failed to detect anything. The electron density near the surface is estimated by different sources to lie in the range 400–2,500 cm−3. As of 2008, the parameters of the ionosphere of Ganymede were not well constrained.

Additional evidence of the oxygen atmosphere comes from spectral detection of gases trapped in the ice at the surface of Ganymede. The detection of ozone (O3) bands was announced in 1996. In 1997 spectroscopic analysis revealed the dimer (or diatomic) absorption features of molecular oxygen. Such an absorption can arise only if the oxygen is in a dense phase. The best candidate is molecular oxygen trapped in ice. The depth of the dimer absorption bands depends on latitude and longitude, rather than on surface albedo—they tend to decrease with increasing latitude on Ganymede, whereas O3 shows an opposite trend. Laboratory work has found that O2 would not cluster or bubble but would dissolve in ice at Ganymede's relatively warm surface temperature of 100 K (−173.15 °C).

A search for sodium in the atmosphere, just after such a finding on Europa, turned up nothing in 1997. Sodium is at least 13 times less abundant around Ganymede than around Europa, possibly because of a relative deficiency at the surface or because the magnetosphere fends off energetic particles. Another minor constituent of the Ganymedian atmosphere is atomic hydrogen. Hydrogen atoms were observed as far as 3,000 km from Ganymede's surface. Their density on the surface is about 1.5 cm−3.

In 2021, water vapour was detected in the atmosphere of Ganymede.

Magnetosphere
The Galileo craft made six close flybys of Ganymede from 1995 to 2000 (G1, G2, G7, G8, G28 and G29) and discovered that Ganymede has a permanent (intrinsic) magnetic moment independent of the Jovian magnetic field. The value of the moment is about 1.3$1,070,400 km$ T·m3, which is three times larger than the magnetic moment of Mercury. The magnetic dipole is tilted with respect to the rotational axis of Ganymede by 176°, which means that it is directed against the Jovian magnetic moment. Its north pole lies below the orbital plane. The dipole magnetic field created by this permanent moment has a strength of 719 ± 2 nT at Ganymede's equator, which should be compared with the Jovian magnetic field at the distance of Ganymede—about 120 nT. The equatorial field of Ganymede is directed against the Jovian field, meaning reconnection is possible. The intrinsic field strength at the poles is two times that at the equator—1440 nT. The permanent magnetic moment carves a part of space around Ganymede, creating a tiny magnetosphere embedded inside that of Jupiter; it is the only moon in the Solar System known to possess the feature. Its diameter is 4–5 Ganymede radii. The Ganymedian magnetosphere has a region of closed field lines located below 30° latitude, where charged particles (electrons and ions) are trapped, creating a kind of radiation belt. The main ion species in the magnetosphere is single ionized oxygen—O+ —which fits well with Ganymede's tenuous oxygen atmosphere. In the polar cap regions, at latitudes higher than 30°, magnetic field lines are open, connecting Ganymede with Jupiter's ionosphere. In these areas, the energetic (tens and hundreds of kiloelectronvolt) electrons and ions have been detected, which may cause the auroras observed around the Ganymedian poles. In addition, heavy ions precipitate continuously on Ganymede's polar surface, sputtering and darkening the ice.

The interaction between the Ganymedian magnetosphere and Jovian plasma is in many respects similar to that of the solar wind and Earth's magnetosphere. The plasma co-rotating with Jupiter impinges on the trailing side of the Ganymedian magnetosphere much like the solar wind impinges on the Earth's magnetosphere. The main difference is the speed of plasma flow—supersonic in the case of Earth and subsonic in the case of Ganymede. Because of the subsonic flow, there is no bow shock off the trailing hemisphere of Ganymede.

In addition to the intrinsic magnetic moment, Ganymede has an induced dipole magnetic field. Its existence is connected with the variation of the Jovian magnetic field near Ganymede. The induced moment is directed radially to or from Jupiter following the direction of the varying part of the planetary magnetic field. The induced magnetic moment is an order of magnitude weaker than the intrinsic one. The field strength of the induced field at the magnetic equator is about 60 nT—half of that of the ambient Jovian field. The induced magnetic field of Ganymede is similar to those of Callisto and Europa, indicating that Ganymede also has a subsurface water ocean with a high electrical conductivity.

Given that Ganymede is completely differentiated and has a metallic core, its intrinsic magnetic field is probably generated in a similar fashion to the Earth's: as a result of conducting material moving in the interior. The magnetic field detected around Ganymede is likely to be caused by compositional convection in the core, if the magnetic field is the product of dynamo action, or magnetoconvection.

Despite the presence of an iron core, Ganymede's magnetosphere remains enigmatic, particularly given that similar bodies lack the feature. Some research has suggested that, given its relatively small size, the core ought to have sufficiently cooled to the point where fluid motions, hence a magnetic field would not be sustained. One explanation is that the same orbital resonances proposed to have disrupted the surface also allowed the magnetic field to persist: with Ganymede's eccentricity pumped and tidal heating of the mantle increased during such resonances, reducing heat flow from the core, leaving it fluid and convective. Another explanation is a remnant magnetization of silicate rocks in the mantle, which is possible if the satellite had a more significant dynamo-generated field in the past.

Radiation environment
The radiation level at the surface of Ganymede is considerably lower than on Europa, being 50–80 mSv (5–8 rem) per day, an amount that would cause severe illness or death in human beings exposed for two months.

Origin and evolution
Ganymede probably formed by an accretion in Jupiter's subnebula, a disk of gas and dust surrounding Jupiter after its formation. The accretion of Ganymede probably took about 10,000 years, much shorter than the 100,000 years estimated for Callisto. The Jovian subnebula may have been relatively "gas-starved" when the Galilean satellites formed; this would have allowed for the lengthy accretion times required for Callisto. In contrast, Ganymede formed closer to Jupiter, where the subnebula was denser, which explains its shorter formation timescale. This relatively fast formation prevented the escape of accretional heat, which may have led to ice melt and differentiation: the separation of the rocks and ice. The rocks settled to the center, forming the core. In this respect, Ganymede is different from Callisto, which apparently failed to melt and differentiate early due to loss of the accretional heat during its slower formation. This hypothesis explains why the two Jovian moons look so dissimilar, despite their similar mass and composition. Alternative theories explain Ganymede's greater internal heating on the basis of tidal flexing or more intense pummeling by impactors during the Late Heavy Bombardment. In the latter case, modeling suggests that differentiation would become a runaway process at Ganymede but not Callisto.

After formation, Ganymede's core largely retained the heat accumulated during accretion and differentiation, only slowly releasing it to the ice mantle. The mantle, in turn, transported it to the surface by convection. The decay of radioactive elements within rocks further heated the core, causing increased differentiation: an inner, iron–iron-sulfide core and a silicate mantle formed. With this, Ganymede became a fully differentiated body. By comparison, the radioactive heating of undifferentiated Callisto caused convection in its icy interior, which effectively cooled it and prevented large-scale melting of ice and rapid differentiation. The convective motions in Callisto have caused only a partial separation of rock and ice. Today, Ganymede continues to cool slowly. The heat being released from its core and silicate mantle enables the subsurface ocean to exist, whereas the slow cooling of the liquid Fe–FeS core causes convection and supports magnetic field generation. The current heat flux out of Ganymede is probably higher than that out of Callisto.

Exploration
Several spacecraft have performed close flybys of Ganymede: two Pioneer and two Voyager spacecraft made a single flyby each between 1973 and 1979; the Galileo spacecraft made six passes between 1996 and 2000; and the Juno spacecraft performed two flybys in 2019 and 2021. No spacecraft has yet orbited Ganymede, but the JUICE mission, which launched in April 2023, intends to do so.

Completed flybys
The first spacecraft to approach close to Ganymede was Pioneer 10, which performed a flyby in 1973 as it passed through the Jupiter system at high speed. Pioneer 11 made a similar flyby in 1974. Data sent back by the two spacecraft was used to determine the moon's physical characteristics and provided images of the surface with up to 400 km resolution. Pioneer 10's closest approach was 446,250 km, about 85 times Ganymede's diameter.

Voyager 1 and Voyager 2 both studied Ganymede when passing through the Jupiter system in 1979. Data from those flybys were used to refine the size of Ganymede, revealing it was larger than Saturn's moon Titan, which was previously thought to have been bigger. Images from the Voyagers provided the first views of the moon's grooved surface terrain.

The Pioneer and Voyager flybys were all at large distances and high speeds, as they flew on unbound trajectories through the Jupiter system. Better data can be obtained from a spacecraft which is orbiting Jupiter, as it can encounter Ganymede at a lower speed and adjust the orbit for a closer approach. In 1995, the Galileo spacecraft entered orbit around Jupiter and between 1996 and 2000 made six close flybys of Ganymede. These flybys were denoted G1, G2, G7, G8, G28 and G29. During the closest flyby (G2), Galileo passed just 264 km from the surface of Ganymede (five percent of the moon's diameter), which remains the closest approach by any spacecraft. During the G1 flyby in 1996, Galileo instruments detected Ganymede's magnetic field. Data from the Galileo flybys was used to discover the sub-surface ocean, which was announced in 2001. High spatial resolution spectra of Ganymede taken by Galileo were used to identify several non-ice compounds on the surface.

The New Horizons spacecraft also observed Ganymede, but from a much larger distance as it passed through the Jupiter system in 2007 (en route to Pluto). The data were used to perform topographic and compositional mapping of Ganymede.

Like Galileo, the Juno spacecraft orbited Jupiter. On 2019 December 25, Juno performed a distant flyby of Ganymede during its 24th orbit of Jupiter, at a range of 97680 to 109439 km. This flyby provided images of the moon's polar regions. In June 2021, Juno performed a second flyby, at a closer distance of 1038 km. This encounter was designed to provide a gravity assist to reduce Juno's orbital period from 53 days to 43 days. Additional images of the surface were collected.

Future missions
The Jupiter Icy Moons Explorer (JUICE) will be the first to enter orbit around Ganymede itself. JUICE was launched on April 14, 2023. It is intended to perform its first flyby of Ganymede in 2031, then enter orbit of the moon in 2032. When the spacecraft consumes its propellant, JUICE is planned to be deorbited and impact Ganymede in February 2034.

In addition to JUICE, NASA's Europa Clipper, which is scheduled to launch in October 2024, will conduct 4 close flybys of Ganymede beginning in 2030. It may also crash into Ganymede at the end of its mission to aid JUICE in studying the surface's geochemistry.

Cancelled proposals
Several other missions have been proposed to flyby or orbit Ganymede, but were either not selected for funding or cancelled before launch.

The Jupiter Icy Moons Orbiter would have studied Ganymede in greater detail. However, the mission was canceled in 2005. Another old proposal was called The Grandeur of Ganymede.

A Ganymede orbiter based on the Juno probe was proposed in 2010 for the Planetary Science Decadal Survey. The mission was not supported, with the Decadal Survey preferring the Europa Clipper mission instead.

The Europa Jupiter System Mission had a proposed launch date of 2020, and was a joint NASA and ESA proposal for exploration of many of Jupiter's moons including Ganymede. In February 2009 it was announced that ESA and NASA had given this mission priority ahead of the Titan Saturn System Mission. The mission was to consist of the NASA-led Jupiter Europa Orbiter, the ESA-led Jupiter Ganymede Orbiter, and possibly a JAXA-led Jupiter Magnetospheric Orbiter. The NASA and JAXA components were later cancelled, and ESA's appeared likely to be cancelled too, but in 2012 ESA announced it would go ahead alone. The European part of the mission became the Jupiter Icy Moon Explorer (JUICE).

The Russian Space Research Institute proposed a Ganymede lander astrobiology mission called Laplace-P, possibly in partnership with JUICE. If selected, it would have been launched in 2023. The mission was cancelled due to a lack of funding in 2017.

title: Ganymede (moon)


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User talk:Peter Olin

Hello there, welcome to the 'pedia! I hope you like the place and decide to stay. If you need any questions answered about the project then check out Help or drop me a line. Cheers! --maveric149

title: User talk:Peter Olin


text:
Talk:Cuscuta

Cuscutaceae is just a redirect to Cuscuta (since it has only one genus), so why did you make a link to it? -phma

oops...i'll take it off

Convolvulaceae
French Wiki says that:

 * Les derniers travaux phylogénétiques incorporent maintenant le genre Cuscuta dans les Convolvulacées.

And Flora Europea also says it's Convolvulaceae. bogdan | Talk 10:04, 29 July 2005 (UTC)

Um, no
Actually, the French encyclopedia specifically does the same thing I do:

La cuscute d'Europe (Cuscuta europaea), encore appelée grande cuscute est une plante grimpante parasite de la famille des Cuscutacées. Les derniers travaux phylogénétiques incorporent maintenant le genre Cuscuta dans les Convolvulacées. La cuscute est notamment parasite de la luzerne.

From Cuscute d'Europe

I don't know French, but from what I gather, this is the same.

I don't disagree with you that some place it in the family Convolvulaceae, but I reiterate that it is an older classification and evidence shows that it is outdated.

Um, yes!
Sorry, you have it the wrong way round, separation in Cuscutaceae is the older classification. Modern genetic studies have shown that Cuscuta belongs in Convolvulaceae (the French agrees with this: "Les derniers travaux phylogénétiques incorporent maintenant le genre Cuscuta dans les Convolvulacées" = "The latest phylogenetic studies now incorporate the genus Cuscuta in the Convolvulaceae") - MPF 22:19, 31 July 2005 (UTC)

Dodder Smells Its Victims...
Recent studies at Pennsylvania State University have shown that dodder grows toward the smell of plants, not green light shining through them. As bizarre as this may seem, it is true, and you can read the artice here.

DrFreeman09 21:33, 28 September 2006 (UTC)

Read this today, confirms above statement. I feel it should be added to the page however I don't have any knowledge of this subject except what I read in the article, so I don't think I'm the best person to add this. Hopefully someone who can properly update this page soon.

AudioStatic82 00:00 29 September 2006 (EST)

Cuscuta planiflora
Sorry, but why does the Cuscuta planiflora not exist in the species classification in the Cuscuta page (please see this)? Thank you very much for fixing that or for any other explanation. --DrFO.Jr.Tn (talk) 16:12, 29 December 2007 (UTC)
 * ✅: It is a synonym of Cuscuta approximata Bab. (please see this) --DrFO.Jr.Tn (talk) 16:23, 29 December 2007 (UTC)
 * For the Cuscuta species list, see the Global Compendium of Weeds (GCW). --DrFO.Jr.Tn (talk) 19:27, 29 December 2007 (UTC)

Dodder Migration
We're seeing Dodder migrate to higher altitudes in the Angeles National Forest, and there appears to be a 3-year-cycle in its growth patterns, every 3 years the growth is tremendous, then there's 2 years of greatly reduced growth. Looking for details about cyclic patterns so I could add some commentary about the phenomena, I found exactly nothing. :( Damotclese (talk) 23:35, 2 December 2012 (UTC)
 * I wonder if it might not be rainfall. In the foothills (at least further east), there has been tremendous growth in high-rainfall years.--Curtis Clark (talk) 03:13, 3 December 2012 (UTC)
 * Coming back to this 2 years later... I don't think it is rain fall related, I think it may be the lack of rainfall related. :) Also in the ANF we're finding the plant growing almost entirely along roadways and hiking trails, we don't find it growing deep inside the outback, only in areas where humans are common. Damotclese (talk) 16:46, 10 February 2014 (UTC)

Punjab is in India, not Pakistan remember it
The editor who changed the location of Punjab from India to Pakistan, that was a mistake so I reverted your proposed update. Please see Wikipedia Punjab, India for details. Tnanks. Damotclese (talk) 15:45, 10 August 2015 (UTC)
 * That editor created the image, the file of which states that it was taken in Punjab in Pakistan, so I have reverted back. Punjab is a large region that includes parts of India and Pakistan. PaleCloudedWhite (talk) 15:58, 10 August 2015 (UTC)
 * Punjab is located in India, not Pakistan, it does not matter where the photograph was taken nor does it matter where the person who uploaded the photograph mistakenly believes which country Punjab is located within. Punjab is located in India, we don't want such mistakes propagated, that's why editors fix such things. Thanks. Damotclese (talk) 15:14, 11 August 2015 (UTC)
 * In retro I will allow this. Thanks. Damotclese (talk) 15:16, 11 August 2015 (UTC)
 * I was mistaken about this, by the way, I did more Google searches and found that I was in error. Damotclese (talk) 16:26, 5 October 2015 (UTC)
 * It's ok 103.184.74.145 (talk) 15:57, 19 November 2023 (UTC)

Quote Removal proposal
Greetings,m the editor that removed the quote with a note about copyright violation, I restored the quote., If you feel strongly that the minor quote violates copyright, could we discuss that, please? If you feel strongly that quoting an external text which is being used as a citation and/or reference violates someone's copyright, I'd like to hear your notes on it, since absolutely editors should avoid copyright violations. Thanks! Damotclese (talk) 16:26, 5 October 2015 (UTC)

title: Talk:Cuscuta


text:
Dutch euro coins

Dutch euro coins currently use two designs by Erwin Olaf, both of which feature a portrait of King Willem-Alexander of the Netherlands. The new designs began circulating in 2014. Dutch Euro coins minted from 1999 to 2013 feature a portrait of Queen Beatrix designed by Bruno Ninaber van Eyben. All coins share the 12 stars of the EU and the year of imprint in their design. As is the case in Finland, most Dutch shops have elected not to issue one and two cent coins starting on 1 September 2004, though the coins remain legal tender. Sums are rounded to the nearest five cents; sums ending in 1, 2, 6 or 7 cents are rounded down, and those ending in 3, 4, 8 or 9 cents are rounded up. The rounding is applied to the grand total only, while individual prices are still shown and summed up with €0.01 precision. This method is known as "Swedish rounding".

Dutch euro design
For images of the common side and a detailed description of the coins, see euro coins.

Second series (2014–present): King Willem Alexander
Following the accession to the throne of King Willem-Alexander, a new series of euro coins was issued depicting the effigy of the new Head of State.

Changes to national sides
The Commission of the European Communities issued a recommendation on 19 December 2008, a common guideline for the national sides and the issuance of euro coins intended for circulation. One section of this recommendation stipulates that:

 * Article 4. Design of the national sides:
 * "The national side of the euro coins intended for circulation should bear the 12 European stars that should fully surround the national design, including the year mark and the indication of the issuing Member State's name. The European stars should be depicted as on the European flag."

The first series of the Dutch euro coins did not comply with this recommendation. No efforts were made to amend these coins to make them compliant.

King Willem Alexander
Queen Beatrix abdicated on 30 April 2013, so the design of the coins was changed for her heir, King Willem-Alexander of the Netherlands. The new coins were made to be in accordance with this recommendation. The Royal Dutch Mint presented the new design to the public on 31 October 2013 and began releasing them into circulation in early 2014 (see ). Production of the new coins commenced on 22 January 2014. The first coins were released into circulation the next day.

title: Dutch euro coins


text:
Danyon Loader

Danyon Joseph Loader (born 21 April 1975) is an Olympic champion, former world record holder swimmer from New Zealand, based in Dunedin. He remains the national record holder in the 400 metre freestyle short course.

He swam for New Zealand at two Summer Olympics (1992, 1996) and three Commonwealth Games (1990, 1994 and 1998).

At the 1992 Olympics in Barcelona, he garnered a silver medal in the 200 metre butterfly. In 1996 in Atlanta, Loader won two gold medals: in the 200 and 400 metre freestyle. He set world records in the short course 200 butterfly and 400 freestyle. In the 1997 New Year Honours, Loader was appointed an Officer of the New Zealand Order of Merit, for services to swimming, and he was inducted into the International Swimming Hall of Fame in 2003.

In December 2012, Loader starred in an online video campaign supporting same-sex marriage, alongside New Zealand singers Anika Moa, Hollie Smith, and Boh Runga, as well as past Governor-General Dame Catherine Tizard.

title: Danyon Loader


text:
Pigeonhole principle

In mathematics, the pigeonhole principle states that if $n$ items are put into $m$ containers, with $n = 10$, then at least one container must contain more than one item. For example, of three gloves (none of which is ambidextrous/reversible), at least two must be right-handed or at least two must be left-handed, because there are three objects but only two categories of handedness to put them into. This seemingly obvious statement, a type of counting argument, can be used to demonstrate possibly unexpected results. For example, given that the population of London is more than one unit greater than the maximum number of hairs that can be on a human's head, the principle requires that there must be at least two people in London who have the same number of hairs on their heads.

Although the pigeonhole principle appears as early as 1624 in a book attributed to Jean Leurechon, it is commonly called Dirichlet's box principle or Dirichlet's drawer principle after an 1834 treatment of the principle by Peter Gustav Lejeune Dirichlet under the name Schubfachprinzip ("drawer principle" or "shelf principle").

The principle has several generalizations and can be stated in various ways. In a more quantified version: for natural numbers $k$ and $m$, if $m = 9$ objects are distributed among $m$ sets, the pigeonhole principle asserts that at least one of the sets will contain at least $n > m$ objects. For arbitrary $n$ and $m$, this generalizes to $$k + 1 = \lfloor(n - 1)/m \rfloor + 1 = \lceil n/m\rceil$$, where $$\lfloor\cdots\rfloor$$ and $$\lceil\cdots\rceil$$ denote the floor and ceiling functions, respectively.

Though the principle's most straightforward application is to finite sets (such as pigeons and boxes), it is also used with infinite sets that cannot be put into one-to-one correspondence. To do so requires the formal statement of the pigeonhole principle: "there does not exist an injective function whose codomain is smaller than its domain". Advanced mathematical proofs like Siegel's lemma build upon this more general concept.

Etymology

Dirichlet published his works in both French and German, using either the German Schubfach or the French tiroir. The strict original meaning of these terms corresponds to the English drawer, that is, an open-topped box that can be slid in and out of the cabinet that contains it. (Dirichlet wrote about distributing pearls among drawers.) These terms morphed to pigeonhole in the sense of a small open space in a desk, cabinet, or wall for keeping letters or papers, metaphorically rooted in structures that house pigeons.

Because furniture with pigeonholes is commonly used for storing or sorting things into many categories (such as letters in a post office or room keys in a hotel), the translation pigeonhole may be a better rendering of Dirichlet's original "drawer". That understanding of the term pigeonhole, referring to some furniture features, is fading—especially among those who do not speak English natively but as a lingua franca in the scientific world—in favor of the more pictorial interpretation, literally involving pigeons and holes. The suggestive (though not misleading) interpretation of "pigeonhole" as "dovecote" has lately found its way back to a German back-translation of the "pigeonhole principle" as the "Taubenschlagprinzip".

Besides the original terms "Schubfachprinzip" in German and "Principe des tiroirs" in French, other literal translations are still in use in Arabic ("مبدأ برج الحمام"), Bulgarian ("принцип на чекмеджетата"), Chinese ("抽屉原理"), Danish ("Skuffeprincippet"), Dutch ("ladenprincipe"), Hungarian ("skatulyaelv"), Italian ("principio dei cassetti"), Japanese ("引き出し論法"), Persian ("اصل لانه کبوتری"), Polish ("zasada szufladkowa"), Portuguese ("Princípio das Gavetas"), Swedish ("Lådprincipen"), Turkish ("çekmece ilkesi"), and Vietnamese ("nguyên lý hộp").

Sock picking
Suppose a drawer contains a mixture of black socks and blue socks, each of which can be worn on either foot. You pull a number of socks from the drawer without looking. What is the minimum number of pulled socks required to guarantee a pair of the same color? By the pigeonhole principle $n = km + 1$ socks, using one pigeonhole per color), the answer is three $k + 1$ items). Either you have three of one color, or you have two of one color and one of the other.

Hand shaking
If $(m = 2$ people can shake hands with one another (where $(n = 3$), the pigeonhole principle shows that there is always a pair of people who will shake hands with the same number of people. In this application of the principle, the "hole" to which a person is assigned is the number of hands that person shakes. Since each person shakes hands with some number of people from 0 to $n$, there are $n > 1$ possible holes. On the other hand, either the "0" hole, the $n − 1$ hole, or both must be empty, for it is impossible (if $n$) for some person to shake hands with everybody else while some person shakes hands with nobody. This leaves $"n − 1"$ people to be placed into at most $n > 1$ non-empty holes, so the principle applies.

This hand-shaking example is equivalent to the statement that in any graph with more than one vertex, there is at least one pair of vertices that share the same degree. This can be seen by associating each person with a vertex and each edge with a handshake.

Hair counting
One can demonstrate there must be at least two people in London with the same number of hairs on their heads as follows. Since a typical human head has an average of around 150,000 hairs, it is reasonable to assume (as an upper bound) that no one has more than 1,000,000 hairs on their head $n$ holes). There are more than 1,000,000 people in London ($n − 1$ is bigger than 1 million items). Assigning a pigeonhole to each number of hairs on a person's head, and assigning people to pigeonholes according to the number of hairs on their heads, there must be at least two people assigned to the same pigeonhole by the 1,000,001st assignment (because they have the same number of hairs on their heads; or, $(m = 1 million$). Assuming London has 9.002 million people, it follows that at least ten Londoners have the same number of hairs, as having nine Londoners in each of the 1 million pigeonholes accounts for only 9 million people.

For the average case ($n$) with the constraint: fewest overlaps, there will be at most one person assigned to every pigeonhole and the 150,001st person assigned to the same pigeonhole as someone else. In the absence of this constraint, there may be empty pigeonholes because the "collision" happens before the 150,001st person. The principle just proves the existence of an overlap; it says nothing about the number of overlaps (which falls under the subject of probability distribution).

There is a passing, satirical, allusion in English to this version of the principle in A History of the Athenian Society, prefixed to A Supplement to the Athenian Oracle: Being a Collection of the Remaining Questions and Answers in the Old Athenian Mercuries (printed for Andrew Bell, London, 1710). It seems that the question whether there were any two persons in the World that have an equal number of hairs on their head? had been raised in The Athenian Mercury before 1704.

Perhaps the first written reference to the pigeonhole principle appears in a short sentence from the French Jesuit Jean Leurechon's 1622 work Selectæ Propositiones: "It is necessary that two men have the same number of hairs, écus, or other things, as each other." The full principle was spelled out two years later, with additional examples, in another book that has often been attributed to Leurechon, but might be by one of his students.

The birthday problem
The birthday problem asks, for a set of $n > m$ randomly chosen people, what is the probability that some pair of them will have the same birthday? The problem itself is mainly concerned with counterintuitive probabilities, but we can also tell by the pigeonhole principle that among 367 people, there is at least one pair of people who share the same birthday with 100% probability, as there are only 366 possible birthdays to choose from.

Team tournament
Imagine seven people who want to play in a tournament of teams $m = 150,000$ items), with a limitation of only four teams $n$ holes) to choose from. The pigeonhole principle tells us that they cannot all play for different teams; there must be at least one team featuring at least two of the seven players:
 * $$ \left\lfloor \frac{n-1}{m} \right\rfloor + 1 = \left\lfloor \frac{7-1}{4} \right\rfloor + 1 = \left\lfloor \frac64 \right\rfloor + 1 = 1 + 1 = 2 $$

Subset sum
Any subset of size six from the set $(n = 7$ = {1,2,3,...,9} must contain two elements whose sum is 10. The pigeonholes will be labeled by the two element subsets {1,9}, {2,8}, {3,7}, {4,6} and the singleton {5}, five pigeonholes in all. When the six "pigeons" (elements of the size six subset) are placed into these pigeonholes, each pigeon going into the pigeonhole that has it contained in its label, at least one of the pigeonholes labeled with a two-element subset will have two pigeons in it.

Uses and applications
The principle can be used to prove that any lossless compression algorithm, provided it makes some inputs smaller (as "compression" suggests), will also make some other inputs larger. Otherwise, the set of all input sequences up to a given length $L$ could be mapped to the (much) smaller set of all sequences of length less than $L$ without collisions (because the compression is lossless), a possibility that the pigeonhole principle excludes.

A notable problem in mathematical analysis is, for a fixed irrational number $a$, to show that the set $\{[na]: n \in \Z \}$ of fractional parts is dense in $(m = 4$. One finds that it is not easy to explicitly find integers $n, m$ such that $$|na-m| < e,$$ where $S$ is a small positive number and $a$ is some arbitrary irrational number. But if one takes $M$ such that $\tfrac 1 M < e,$ by the pigeonhole principle there must be $$n_1, n_2 \in \{1, 2, \ldots, M+1\}$$ such that $2n$ and $n × n$ are in the same integer subdivision of size $\tfrac 1 M$ (there are only $M$ such subdivisions between consecutive integers). In particular, one can find $[0, 1]$ such that
 * $$n_1 a \in \left(p+\frac k M,\ p + \frac{k+1}{M}\right), \quad n_2 a \in \left(q+ \frac k M,\ q+\frac{k+1}{M}\right),$$

for some $p, q$ integers and $k$ in $e > 0$. One can then easily verify that
 * $$(n_2 - n_1)a \in \left(q-p-\frac 1 M, q-p+\frac 1 M \right).$$

This implies that $[na] < \tfrac 1 M < e,$ where $n_{1}a$ or $n_{2}a$. This shows that 0 is a limit point of {[$n_{1}, n_{2}$]}. One can then use this fact to prove the case for $p$ in ${0, 1, ..., M − 1}$: find $n$ such that $[na] < \tfrac 1 M < e;$ then if $p \in \bigl(0, \tfrac 1 M \bigr],$ the proof is complete. Otherwise
 * $$p \in \left(\frac j M, \frac{j+1}{M}\right],$$

and by setting
 * $$k = \sup \left\{r \in N : r[na] < \frac j M \right\},$$

one obtains
 * $$\Bigl| \bigl[ (k+1)na \bigr] - p \Bigr| < \frac 1 M < e.$$

Variants occur in a number of proofs. In the proof of the pumping lemma for regular languages, a version that mixes finite and infinite sets is used: If infinitely many objects are placed into finitely many boxes, then two objects share a box. In Fisk's solution to the Art gallery problem a sort of converse is used: If $n$ objects are placed into $k$ boxes, then there is a box containing at most $\tfrac n k$ objects.

Alternative formulations
The following are alternative formulations of the pigeonhole principle.

 * 1) If $n = n_{2} − n_{1}$ objects are distributed over $n = n_{1} − n_{2}$ places, and if $na$, then some place receives at least two objects.
 * 2) (equivalent formulation of 1) If $(0, 1]$ objects are distributed over $n$ places in such a way that no place receives more than one object, then each place receives exactly one object.
 * 3) (generalization of 1) If $m$ and $n > m$ are sets, and the cardinality of $n$ is greater than the cardinality of $n$, then there is no injective function from $S$ to $T$.
 * 4) If $S$ objects are distributed over $T$ places, and if $S$, then some place receives no object.
 * 5) (equivalent formulation of 4) If $T$ objects are distributed over $n$ places in such a way that no place receives no object, then each place receives exactly one object.
 * 6) (generalization of 4) If $m$ and $n < m$ are sets, and the cardinality of $n$ is less than the cardinality of $n$, then there is no surjective function from $S$ to $T$.

Strong form
Let $S$ be positive integers. If
 * $$q_1 + q_2 + \cdots + q_n - n + 1$$

objects are distributed into $T$ boxes, then either the first box contains at least $S$ objects, or the second box contains at least $T$ objects, ..., or the $q_{1}, q_{2}, ..., q_{n}$th box contains at least $n$ objects.

The simple form is obtained from this by taking $q_{1}$, which gives $q_{2}$ objects. Taking $n$ gives the more quantified version of the principle, namely:

Let $q_{n}$ and $q_{1} = q_{2} = ... = q_{n} = 2$ be positive integers. If $n + 1$ objects are distributed into $q_{1} = q_{2} = ... = q_{n} = r$ boxes, then at least one of the boxes contains $n$ or more of the objects.

This can also be stated as, if $r$ discrete objects are to be allocated to $n(r - 1) + 1$ containers, then at least one container must hold at least $$\lceil k/n \rceil$$ objects, where $$\lceil x\rceil$$ is the ceiling function, denoting the smallest integer larger than or equal to $n$. Similarly, at least one container must hold no more than $$\lfloor k/n \rfloor$$ objects, where $$\lfloor x \rfloor$$ is the floor function, denoting the largest integer smaller than or equal to $r$.

Generalizations of the pigeonhole principle
A probabilistic generalization of the pigeonhole principle states that if $m = n$ pigeons are randomly put into $k = r − 1$ pigeonholes with uniform probability $k$, then at least one pigeonhole will hold more than one pigeon with probability

 * $$1 - \frac{(m)_n}{m^n}, $$

where $n$ is the falling factorial $x$. For $x$ and for $n$ (and $m$), that probability is zero; in other words, if there is just one pigeon, there cannot be a conflict. For $1/m$ (more pigeons than pigeonholes) it is one, in which case it coincides with the ordinary pigeonhole principle. But even if the number of pigeons does not exceed the number of pigeonholes ($(m)_{n}$), due to the random nature of the assignment of pigeons to pigeonholes there is often a substantial chance that clashes will occur. For example, if 2 pigeons are randomly assigned to 4 pigeonholes, there is a 25% chance that at least one pigeonhole will hold more than one pigeon; for 5 pigeons and 10 holes, that probability is 69.76%; and for 10 pigeons and 20 holes it is about 93.45%. If the number of holes stays fixed, there is always a greater probability of a pair when you add more pigeons. This problem is treated at much greater length in the birthday paradox.

A further probabilistic generalization is that when a real-valued random variable $m(m − 1)(m − 2)...(m − n + 1)$ has a finite mean $n = 0$, then the probability is nonzero that $n = 1$ is greater than or equal to $m > 0$, and similarly the probability is nonzero that $n > m$ is less than or equal to $n ≤ m$. To see that this implies the standard pigeonhole principle, take any fixed arrangement of $X$ pigeons into $E(X)$ holes and let $X$ be the number of pigeons in a hole chosen uniformly at random. The mean of $E(X)$ is $X$, so if there are more pigeons than holes the mean is greater than one. Therefore, $E(X)$ is sometimes at least 2.

Infinite sets
The pigeonhole principle can be extended to infinite sets by phrasing it in terms of cardinal numbers: if the cardinality of set $A$ is greater than the cardinality of set $B$, then there is no injection from $A$ to $B$. However, in this form the principle is tautological, since the meaning of the statement that the cardinality of set $A$ is greater than the cardinality of set $B$ is exactly that there is no injective map from $A$ to $B$. However, adding at least one element to a finite set is sufficient to ensure that the cardinality increases.

Another way to phrase the pigeonhole principle for finite sets is similar to the principle that finite sets are Dedekind finite: Let $A$ and $B$ be finite sets. If there is a surjection from $A$ to $B$ that is not injective, then no surjection from $A$ to $B$ is injective. In fact no function of any kind from $A$ to $B$ is injective. This is not true for infinite sets: Consider the function on the natural numbers that sends 1 and 2 to 1, 3 and 4 to 2, 5 and 6 to 3, and so on.

There is a similar principle for infinite sets: If uncountably many pigeons are stuffed into countably many pigeonholes, there will exist at least one pigeonhole having uncountably many pigeons stuffed into it.

This principle is not a generalization of the pigeonhole principle for finite sets however: It is in general false for finite sets. In technical terms it says that if $A$ and $B$ are finite sets such that any surjective function from $A$ to $B$ is not injective, then there exists an element $b$ of $B$ such that there exists a bijection between the preimage of $b$ and $A$. This is a quite different statement, and is absurd for large finite cardinalities.

Quantum mechanics
Yakir Aharonov et al. presented arguments that quantum mechanics may violate the pigeonhole principle, and proposed interferometric experiments to test the pigeonhole principle in quantum mechanics. Later research has called this conclusion into question. In a January 2015 arXiv preprint, researchers Alastair Rae and Ted Forgan at the University of Birmingham performed a theoretical wave function analysis, employing the standard pigeonhole principle, on the flight of electrons at various energies through an interferometer. If the electrons had no interaction strength at all, they would each produce a single, perfectly circular peak. At high interaction strength, each electron produces four distinct peaks, for a total of 12 peaks on the detector; these peaks are the result of the four possible interactions each electron could experience (alone, together with the first other particle only, together with the second other particle only, or all three together). If the interaction strength was fairly low, as would be the case in many real experiments, the deviation from a zero-interaction pattern would be nearly indiscernible, much smaller than the lattice spacing of atoms in solids, such as the detectors used for observing these patterns. This would make it very difficult or impossible to distinguish a weak-but-nonzero interaction strength from no interaction whatsoever, and thus give an illusion of three electrons that did not interact despite all three passing through two paths.

title: Pigeonhole principle