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WikiProject Mathematics (Rated B-class, Low-importance)
WikiProject Mathematics
This article is within the scope of WikiProject Mathematics, a collaborative effort to improve the coverage of Mathematics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
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 Field:  Geometry

What is the origin of the name?[edit]

What is the origin of the name? Rigadoun (talk) 18:53, 14 February 2007 (UTC)

I'm trying to find a source for this. "Gombóc" is the Hungarian word for "dumpling", (although the shape seems to be spelt "Gömböc" in Hungarian). --Canley 00:05, 15 February 2007 (UTC)

"Gömböc" in Hungarian is a folklore figure, rather fat. "Gömb" means sphere, and "Gömböc" refers to a sphere-like object. The mathematical "Gömböc" described in this page appears to have some connection to the sphere. One can define the "flatness" (F) and "thickness" (T) of convex 3D objects. According to the definition given in Várkonyi & Domokos (2007), for both properties the minimal value is 1, the sphere has F=T=1 and the only nondegenerate type of object sharing this property is the "Gömböc". --Domokos 24 February 2007

How does it behave when spun around its vertical axis? Anything like the Flip-over top? Leob 00:06, 29 June 2007 (UTC)


Where can I buy one? Capuchin 13:41, 24 July 2007 (UTC)

I too require one. --NEMT 23:46, 24 July 2007 (UTC)
From what I hear, the only way to get one is to download the description (from where?) to your 3D printer. —Tamfang 07:44, 1 December 2007 (UTC)

There seems to be a site under development at linked from Gábor's Domokos personal homepage. It looks like commercial products are in development. DanBri (talk) 18:56, 9 December 2007 (UTC)

Currently you can get a numbered model for €1000 and up (depending on the number you choose), or a 3D picture of one embedded in a cube. It ought to be easy to mold, so there ought to be cheaper ones soon. —Tamfang (talk) 19:10, 21 December 2007 (UTC)
On the gömböc home page you can now order cheaper versions. But the 'easy to mold'-statement is not entirely right. According to the website, precision of 0.1mm is required to get the perfect shape, even 0.2mm off in the mold and it wouldn't work. - Peipei (talk) 21:49, 15 February 2009 (UTC) This should also be added to the links part of the page, however if you check the cited sources it will link you to the page. I think for clarity of page and for additional information the link should be added. (talk) 22:49, 9 October 2009 (UTC)


What does the word "artificial" mean in the context of the introduction? Is it a specific classification of shapes, or merely meant to indicate that it is a shape specifically designed for a purpose? --Starwed 08:53, 7 August 2007 (UTC)

I believe the latter. Capuchin 10:00, 7 August 2007 (UTC)

Up to similarity they are unique[edit]

This puzzling sentence needs to be made into intelligible English. I have given it a try in the article, "Except for similar figures, it is unique" but am not sure this was meant (as far as I understand, there are probably other, non-similar mono-monostatic bodies). Can anyone improve on this? Hgilbert 00:59, 1 September 2007 (UTC)

unistable polyhedron[edit]

It is conjectured that there also exist convex polyhedra with just one stable face and one unstable point of equilibrium. The minimum number of faces could be large.

Richard K. Guy and Ken Knowlton found an unistable polyhedron circa 1959, with 19 faces. Or did I misunderstand something? —Tamfang 07:49, 1 December 2007 (UTC)

Yes, the unistable polyhedron you talk about has indeed only one stable point of equilibrium but has also three points of unstable equilibrium but what is conjectured is a convex polyhedra with just one stable face and one unstable point of equilibrium. So this polyhedra don't match the challenge.
Zertrin (blabla) 10:27, 14 April 2008 (UTC)
Oh? One is obvious; what are the other two? —Tamfang (talk) 17:48, 14 April 2008 (UTC)
In fact you have the first on the opposed edge of the stable face and the two other are at the both tips the most distant. You can see it there : [1]. Zertrin (blabla) 18:26, 19 April 2008 (UTC)
*forehead slap* —Tamfang (talk) 03:17, 24 April 2008 (UTC)

What is the correct Hungarian plural of the word?[edit]

gömbcök? gömböcök? or gömböcek? -andy (talk) 00:31, 3 June 2008 (UTC)

Hi, gömböcök. -- (talk) 20:40, 20 September 2008 (UTC)

Flatness and thinness[edit]

The article says that they need to be suitably defined, but never gets around to defining them. Neither does the page at The Mathematical Intelligencer article defines them in a way that doesn't seem to type-check: we're taking the max and min and ratios of vectors (unless a "position vector" is a scalar). It would be nice to get a good encyclopaedic definition. Bhudson (talk) 14:47, 20 June 2008 (UTC)

Maybe one should take the length of the vector. In any case, due to Lemma 1 in the Mathematical Intelligencer article, "F=1" is equivalent to the existence of only one stable equilibrium, and "T=1" is equivalent to the existence of only one unstable equilibrium. If this is true, then "F=T=1" is not an additional restriction on the shape of the gömböc, let alone making it unique. -- (talk) 19:54, 9 December 2008 (UTC)

Malicious link[edit]

A link at the bottom of the page, to, downloads JS/Downloader.Agent and Win32/Heur viruses. I've removed it. Don't-stop-the-music (talk) 21:36, 13 February 2009 (UTC)

Simple explanation[edit]

OK, this article provoked me into about 20 minutes of annoyed thought while I worked out what stops objects like eggs, cones and pencils from being Gömböcs. I suggest the following plain-language explanation:

A Gömböc has only two points of equilibrium because, unlike common objects, it can't be balanced on its side.

Which makes me wonder about dinner plates, but I guess they just require a very steady hand.

Incidentally, is it really true that "The Gömböc mimics the 'self-righting' abilities of shelled animals such as turtles", given that turtles weren't discovered to use Gömböc-like shapes until after the invention of the shape? It's only some kinds of turtles, and besides, turtles doesn't have uniform density, and their geometry is only "close to optimal". Perhaps it would be more accurate to say "Shelled animals such as turtles mimic the self-righting ability of the Gömböc", considering the form of the Gömböc to have always existed in an objective sense. Then again I suppose the form of a turtle has also always existed in an objective sense. Maybe "Some shelled animals can self-right in almost the same way as a Gömböc" is best. (talk) 00:15, 15 February 2009 (UTC)

You have a point about mimicry. (Is objective really the word you want? How about Platonic?) We could say: "The shells of certain turtles resemble the Gömböc, and thus tend to right themselves." —Tamfang (talk) 05:10, 17 February 2009 (UTC)
Dinner plates, of course, have two stable points of equilibrium, gravy up and gravy down. Rich Farmbrough, 09:40 24 February 2009 (UTC).


I am taking out the "mm" defn of tolerance since this is size dependent. Rich Farmbrough, 09:40 24 February 2009 (UTC).

did you bring enough gum for the class to share?[edit]

This shape represents a class (i.e., it is not unique); the shape has very fine tolerances, outside which it is no longer mono-monostatic.

Does this mean that the shape can vary in some ways without losing monomonostasis but not in other ways? Or that there are other monomonostatic shapes, but they cannot be continuously deformed to the Gömböc without losing monomonostasis? If the latter, what are they? or have they only been proven to exist without showing what they are?

Or does the first clause mean that the Gömböc is one of a class of shapes defined by some property other than monomonostasis? and if so, what property (and why mention it here)? —Tamfang (talk) 00:52, 28 February 2009 (UTC)

It means that there is more than one mono-monostatic shape, (which can be very different each others) but that for one given shape the deformation tolerance without losing monomonostasis is very thin.
The photo in the article shows a solution shape that does differ from a spherical shape, because it is possible to find an monomonostatic shape which looks like a sphere. (hardly distinguishable from the sphere). I does obtain a 3D-representation of the spherical-like solution from the equations given by the two researchers with the software Maple. If you are interested in looking at it : email me Face-wink.svg
If you want more information I advise you to read the publications of the two reseachers (the second in particular) :
(sorry for the bad english)Zertrin (blabla) 15:11, 7 March 2009 (UTC)

Unnecessary Sentence?[edit]

Does anyone else believe that the phrase "gömböc refers to a sphere-like object. (It is mostly known in the folk culture as kis gömböc, a round creature in the loft that remained from a killed pig, which swallows everyone one after the other who goes to see what happened to the previous ones. They are eventually rescued by a young pigman that was swallowed last.[4])" is not needed? Seriously, a folk monster doesn't contribute to our knowledge of Gombocs. Especially since the sentence is so long Occamsrazorwit (talk) 13:26, 28 September 2009 (UTC)

It may be unclearly written, but I think it's important to know where the name comes from. —David Eppstein (talk) 15:07, 28 September 2009 (UTC)


This article is crying out for an animated gif to show the shape at work and the rising c of gVictuallers (talk) 15:44, 8 October 2009 (UTC)

Spelling : initial capital, use of article (the/a)[edit]

If I understand the definition correctly, a Gömböc is something of the same class as a cube or a sphere. In the beginning of this Talk page, I read something about a Hungarian folklore figure "Gömböc" that lent its name to the object. I have the following questions:

  • Is the word Gömböc really spelled with an initial capital?
  • If so, why? We usually don't write cube or sphere with capitals, so why is that other shape's name written with a capital.

And a related question:

  • Should the article 'a' be omitted as if Gömböc were a proper name?
  • If so, why?

For example, somewhere in the article it says:

  • "The shape of the Indian Star Tortoise resembles Gömböc. "
  • "The balancing properties of Gömböc were associated with..."
  • " stable and unstable point in Gömböc ..."
  • "No other practical applications of Gömböc are known, probably because Gömböc is ..."

We don't speak of "the balancing properties of Cube," do we?

Or have I completely misunderstood the word? Is there actually only one 'real' individual phenomenon that goes by the name of Gömböc, and is kept in an undisclosed place somewhere in the world?

To be honest, I have the presumption that the above example sentences really should have been written as:

  • "The shape of the Indian Star Tortoise resembles a gömböc. "
  • "The balancing properties of gömböcs were associated with..."
  • " stable and unstable point in a gömböc ..."
  • "No other practical applications of gömböcs are known, probably because gömböcs are ..."

Johan Lont (talk) 13:24, 9 October 2009 (UTC)

Absence of articles is often sign that writer's first language is not English. —Tamfang (talk) 00:03, 20 October 2009 (UTC)
Yes. And that he was sleepy and in rush :-D Seriously, the term was probably coined by a person who admitted being not fluent in English, thus this is the case when native speakers with minor knowledge of geometry might decide better on capitalization, single/plural and article issues. Sorry for not making enough time. One more note, the discovered shape refers not to a unique body, such as sphere, but to a class of bodies. Even the commercial replicas are officially produced in different shapes, but under the same name. Materialscientist (talk) 00:36, 20 October 2009 (UTC)

I had the same questions. Thank you for starting the thread, Johan. I have uncapitalized most instances and changed some "a"s and "the"s. Here are some related thoughts.

We are witnessing the introduction of a new word into the English language (and also into Hungarian and every other language). Since the new English word is coming from a foreign language you may want to review Wikipedia:Manual_of_Style#Foreign_terms.

Wikipedia is likely to be one of the main ways in which people are introduced to the word. While recognizing that it is not normally Wikipedia's place to create conventions but rather to cite them, let me suggest that in this case we nip in the bud a mistaken, nascent "convention", emerging out of ignorance, of capitalizing "gömböc" in English. Supporting arguments:

  1. The inventors of the word are ambivalent about capitalization. Note the capitalization at the "official gömböc shop", and note on the navigation bar at that site the uncapitalized links "what is a gömböc" and "usage of a gömböc".
  2. While the gömböc was at first treated as an artificial shape that was invented ("the Gömböc"), it has shifted and will continue to shift toward being treated as a natural shape that was discovered ("a gömböc").
  3. I even uncapitalized the two instances of "kis gömböc" in the word origin explanation because "kis gömböc" is not capitalized in the Hungarian folk tale reference.

See the next thread for related issues regarding the plural, spelling with 'ö' versus 'o', and pronunciation. IOLJeff (talk) 17:28, 15 May 2011 (UTC)

conventions: pronunciation, spelling with ö versus o, and plural form[edit]

These three issues are interrelated. Per my arguments in the previous thread regarding capitalization, let me suggest that Wikipedia take a gentle leadership role in establishing some sensible conventions since clear conventions have not yet emerged. Remember, Wikipedia articles are not set in stone.

pronunciation - Whatever conventional English pronunciation has emerged is likely not the Hungarian pronunciation. In Hungarian "gömböc" rhymes with "room puts" (same vowel sound in both words). The conventional English pronunciation, especially based on the spelling "gomboc" (to be discussed next) more likely rhymes with "bomb clock". This is the way Stephen Fry pronounces it at 3:12 in the QI reference video.

ö versus o - Several of the references, including the New York Times Magazine Anglicize the spelling to "gomboc". This is how English speakers are likely to type it on their computers.

plural - A thread above explains that the plural in Hungarian is "gömböcök". The English references cited do not use this (thank goodness), but rather "gömböcs", "gombocs", or "gömböc" as a non-count noun. The Hungarian pronunciation of the singular "gömböc", ending with an s sound, sounds plural to an English speaker. (Perhaps this is why some references use the non-count "gömböc" for the plural.)

If the conventional English pronunciation ends with a k sound rather than s, and especially if the conventional English spelling uses o instead of ö, then it is natural for English speakers to use "one gomboc, two gombocs", rhyming with "bomb clock" and "bomb clocks". Therefore, I will change the content page along these lines and await other editors' feedback. IOLJeff (talk) 18:39, 15 May 2011 (UTC)

Why should Wikipedia endorse a pronunciation which is plain wrong? What really bothers me is that it actually has an IPA transcription of what an English-only speaker with no idea how to pronounce this would say when shown the spelling. WP is one of the first sites people will look at when researching the topic, and it explicitly confirms that "Yes, you should say /ˈɡɒmbɒk/". I think this is wrong (especially considering the international audience of the English-only Wikipedia) and the IPA transcription should be removed. BarroColorado (talk) 15:51, 2 April 2014 (UTC)
And if we spell it with ‹ö›, who is harmed? (The steadily shrinking set of users of pre-Unicode software, I guess.) Those who can't be bothered with diacritics will write ‹o› no matter what we do. Those who don't care about funny foreigner-talk will say /ɡɒmbɒk/ no matter what we do.
Maybe the English spelling ought to be gimberts.
I do have a bit of concern for those who can't find the article because they come looking for Gomboc. If only Wikipedia had a way to steer them here! —Tamfang (talk) 18:38, 2 April 2014 (UTC)

I think the correct English plural is "gömböces" (/gømbøtsəz/). If a word ending in a sibilant is pluralized by adding a sibilant, a schwa is inserted between the sibilants, e.g. "boxes". I've found only one occurrence of "gömböces" in English though. "Gömböcs" sounds like /gømbøtʃ/ to me. phma (talk) 05:06, 11 January 2015 (UTC)


Could we trim back the "Numbered Gömböcs" section advertising for the Perhaps just a single reference to the commercial venture? (talk) 15:20, 8 June 2010 (UTC)

spammy article[edit]

The "production" and "media" sections read (in part) like sales brochures, and there's way too many links to the manufacturer's shopping site and general site. Articles are supposed to be cited to sources independent of the subject. I inserted an advert tag but Materialscientist reverted.[2] I'll leave it out for now but the article needs cleanup. (talk) 04:00, 30 September 2010 (UTC)

I missed the point of that tag first. Cleaned up now. Unfortunately, science, its popularization, and notable cultural events on one side and business initiatives of the Gomboc inventor on the other side got mixed up, but I think it is Ok now, i.e. I would tolerate that small bit of "ads" which is left. Materialscientist (talk) 05:59, 30 September 2010 (UTC)

Error for tolerance?[edit]

This edit changed "Their published solution was less sensitive; yet it has a shape tolerance of 10−4, that is 0.1 mm for a 10 cm size." to "...a shape tolerance of 10−3...". The cited source supports 0.1 mm and 10 cm, but the 10-x is Wikipedia's. Shouldn't the tolerance actually be 10-2, given by 0.1 mm / 10 cm? I'd have changed it myself but I'm worried I'm missing something...

Note the tolerance figure is given in both the Mathematical solution and Production sections. Adrian J. Hunter(talkcontribs) 09:22, 24 September 2014 (UTC)

0.1 mm is 0.01 cm, so the ratio is 0.01 cm / 10 cm = 0.01/10 = 10-3 (talk) 04:18, 24 October 2014 (UTC)

Of course. Not sure what was going through my head a month ago. Thanks. Adrian J. Hunter(talkcontribs) 09:18, 24 October 2014 (UTC)

Countless varieties[edit]

The term "countless varieties" in the intro paragraph seems like jargon. Is there a number? Is it infinite? It seems like this phrasing should be more specific. Yosho27 (talk) 08:05, 10 June 2017 (UTC)