Talk:Rubik's Cube

From Wikipedia, the free encyclopedia

This is the talk page for discussing improvements to the Rubik's Cube article.
Please sign and date your posts using four tildes (`~~~~`). New discussion topics go at the bottom of the page; click here to start a new topic. New to Wikipedia? Welcome! Frequently asked questions. This is not a forum for general discussion about the article's subject.	Talk page guidelines Be polite Assume good faith No personal attacks Don't bite the newcomers!

Rubik's Cube has had a peer review by Wikipedia editors which is now archived. It may contain ideas you can use to improve this article.

This article is a former featured article candidate. Please view its sub-page to see why the nomination failed. For older candidates, please check the archive.

Rubik's Cube has been listed as a good article under the good-article criteria. If you can improve it further, please do.
If it no longer meets these criteria, you can delist it, or ask for a review.

This article is within the scope of WikiProject Mathematics.
Mathematics grading:	GA Class	Mid Importance	Field unassessed.

I copied this article (which I wrote) over from Nupedia since Wikipedia is getting much more traffic. Mark Jeays

Great article. Singmaster's book is certainly the definitive one, but perhaps some mention should be made of Thistlethwaite's "decent though nested subgroups" algorithm? --LDC

Good idea. I haven't used that method, though. Perhaps you or someone else could add a paragraph on it. I didn't want to get into lengthy discussions on the methods of solving the cube however perhaps an overview of some of the common methods would be good. Mark Jeays

I think so. Since we are not restricted by the five-paragraph-rule here, we can extend to our heart's content :-) For example, I would love to see an elaboration on the group theory aspect, and then I could make a link from group theory to here. --AxelBoldt

I've added a link to someone's solution to the puzzle. It is listed as being GNU FDL licensed, so perhaps we can add it at Rubiks_Cube/Solution. However, I want to wait until I understand how subpages will be changed. -- Bignose

Oh, duh. Just realised the solution link is authored by Mark Jeays. Hi, Mark! Please add the solution to Wikipedia if you like. -- Bignose

Hi! I was thinking of adding it (perhaps one solution only, since there is a good bit of extraneous stuff such as personal records and my ramblings that wouldn't be suitable). Also it could go in how-tos. I will try to do this later today (Nov. 21) but if someone else wants to, go right ahead. I think a separate page would be suitable. Mark Jeays

Hi. I thought I'd say that I have a Rubik's Cube Java applet, which runs in a browser window! I think it may be a ask-permission before you place it on your site, but if I got permission, do you think we'd be allowed to have a virtual Rubik's Cube on this page?

That's exactly the kind of thing I'd love to see more of here (along with images in general). Yes, you'd have to get the author's permission not just to post it here, but to release it under the GFDL. I also don't think the present Wiki software can handle Java applets directly yet, so it won't be possible to directly put it into the Wiki--it would have to be a page of its own with a link to it from the Wiki. --LDC

I think Wikipedians should not only be writing and editing articles, but promoting the site, and creating multimedia content suitable for articles - Mark Ryan

To comply with GFDL, we'd probably have to show the full source code to the Java applet too (which is a good idea in any event). --AxelBoldt

I returned the spoiler warning. Many details of the cube's mechanics, such as the fact that centre squares cannot be moved and the fact that each cubie is unique, are not obvious to people when they first encounter the puzzle; figuring those things out can be part of the challenge. -- Jod

really? Those two facts can be deduced in about 30 seconds. We're not revealing the solution here. -- Tarquin 22:27 May 8, 2003 (UTC)

Well, you can and I can deduce it, but honestly many people can't, at least not right away, or not if it doesn't occur to them at all to look at it that way. I really think it's just fair to add the warning, even if only Great Fools need it. Anyhow, I think your repositioning of the warning works fine.

Who calculated the number or positions and how? Are all those positions reachable from the solved puzzle? I ask because by taking the cube apart and then putting it together many positions that are unsolvable can be created. Just try taking one piece and then reinsert it rotated in 180 degrees.--AstroNomer 01:02, Aug 16, 2003 (UTC)

Well, the rubik's cube is an interresting mathematical problem but also an interresting mechanism who knows about the internal of the rubik's cube ? Can someone put a cube in part to take photos ? Ericd 01:45, 16 Aug 2003 (UTC)

I've pulled mine apart and shot it as you suggested. It's in the workings section. Curis 10:48, 15 July 2006 (UTC)

A semidirect product isn't a direct product! Phys 17:01, 28 Aug 2003 (UTC)

\semidirect does not work.

Okay, which should we be using: the direct product or the semidirect product? -- Anon

The sub/sup stuff needs to be sorted out... we're mixing math with it, and it looks funny. -- Taral 18:07, 7 Sep 2004 (UTC)

[edit] Rubik's Cube as a mathematical group

the text "One choice is the following group, given by generators: (The last generator is a 3 cycle on the edges). C_p = [U², D², F, B, L², R², R²U'FB'R²F'BU'R² ]" has me wondering about that last 3-cycle 'generator'. Wouldn't the simpler R²UD'F²U'D or equivalent be a better example? I'm confused by the extra pooh. 69.195.36.86 06:01, 17 Jan 2005 (UTC)

I wrote the original section. I needed a three cycle, and I took the first that I could find. Its effect on the cube is nice and clean. The resulting group was checked with GAP, to see that it indeed has the stated properties. If you are convinced that you get the same group with the generator you indicate, and it is easier to understand that way, then feel free to change it. (If you need them, GAP definitions for the cube group can be found on the Net). Sander123 15:32, 17 Jan 2005 (UTC)

[edit] "Positions" vs. "Permutations"

I find the explanation of the solution a bit confusing. There's a blurring of the distinction between "positions" and "permutations". The Rubik's cube group is not a group of "positions", whose elements are actual fixed positions of the cube. The elements of the groups are permutations, the group of which acts on the set of all possible positions of the cube. In other words, the Rubik's cube group acts on the symmetric group S₂₇, where the symmetric group represents actual positions. Of course, the action is really on some suitably nice subgroup of the symmetric group, namely the group of all realisable positions.

The "cube group" is first described as a group of "positions", then later it is intersected with another group generated by various "flips, twists", and so on. The positions themselves are not flips or twists, so this doesn't make sense. Revolver 01:13, 16 Apr 2004 (UTC)

[edit] Patent issues

A recent news article mentioned the possibility that the patent on Rubik's Cube had expired. Anyone know if this is the case? -- blahpers 17:28, 2004 Oct 29 (UTC)

[edit] Typing error?

This sentence: "The puzzle consists of the 26 unique miniature cubes ("cubies") on the surface" should probably have the number 27 instead as mentioned in the section above. Sir48-DK.

What you are referring to is,

This gives the impression that the cube is made up of 27 smaller cubes (3 × 3 × 3).

But there is no 27th cube in the center of Rubik's Cube. —Sean κ. + 00:25, 6 Jun 2005 (UTC)

[edit] Broken links

I changed the missing link How to solve the Rubik's Cube to Optimal solutions for Rubik's Cube.

Any idea what has happened to the original article? There are many links in the Wiki to this missing article. Jryden 02:45, 23 July 2005 (UTC)

Ah, nevermind. A little research does wonders. So this article is moved to wikibooks. Okay, is this link change suitable and should I modify any other links. Any veterns have a suggestion. I'll leave my change in for now. Jryden 02:50, 23 July 2005 (UTC)

~sigh~ I should have read further, the link I choose was farther down in the paragraph. It seems to make sense just to remove the text altogether. Again, any concerns with this? It was (see Optimal solutions for Rubik's Cube for one such solution) Jryden 02:55, 23 July 2005 (UTC)

[edit] 25th Anniversary

The BBC this morning are saying that today is the 25th anniversary of the Rubik's Cube, and there seems to be some speed cubing event later in the day to commemorate it. Unfortunately I can't find much on the web about it, and there doesn't seem to be any clear statement of exactly what the anniversary is of (surely not the patent, first sales perhaps).

If anyone can firm up the details this might be one for Selected Anniversaries. -- Solipsist 06:48, 26 July 2005 (UTC)

Indeed. BTW, I managed to get a link from BBC News -- Simon Heywood 11:06, 26 July 2005 (UTC).

Nice - the foot of that article points back to Wikipedia for more information. -- Solipsist 11:56, 26 July 2005 (UTC)

[edit] Possible Typo(?)

In the solutions section of the article the last paragraph states "...(8! × 3⁸⁻¹) × (12! × 2¹²⁻¹)/2..." Isn't that the same as (8! × 3⁷) × (12! × 2¹¹)/2 ?

Should it have read: (8! × 3⁸−1) × (12! × 2¹²−1)/2 ?

--Bob 07:47, 30 July 2005 (UTC)

Nope, that's not a typo. Corners can be oriented in 3^8 ways by taking apart the pieces, but without doing so, the orientations have to add up to 0 mod 3. That means the orientation of the first 7 corners determines that of the eighth, so 3^7. Similar for the edges.

[edit] Cheap imitations

This article doesn't mention the cheap imitation Rubik's Cubes. Whenever I try to work with those cheap things, all of the colorful stickers fall off. :) — Stevey7788 (talk) 20:45, 5 August 2005 (UTC)

True. It's very hard to find real Rubik's cubes nowadays. -- Eagle^a^mⁿ 05:18, 10 October 2005 (UTC)

Isn't "Rubik's" the so called official Rubik's cube maker? --- Acdx 23:29, 24 December 2005 (UTC)

Try buying them online from www.rubiks.com Calculusfreak 20:42, 7 August 2006 (UTC)

[edit] Probable error in maximal length of a minimal solution

In section "Permutations", the article states that any cube position can be solved in at most 23 turns. Presumably this refers to (quarter or half) face turns. But the citation provided does not seem particularly authoritative. Mathworld states that any cube can be solved in at most 29 face turns, a result due to Michael Reid. Computer programs that search for minimal solutions have have solved every position attempted in at most 20 or 21 face turns. Reducing this gap between the known upper bound on the length of a minimal solution and the hardest known positions is perhaps the most important unsolved problem in the theory of Rubik's cube.

--Rodney Topor

Changed it to 29 --acipsen

I think someone proved a month or two ago that all positions can be solved in 28 moves or less, but I can't find a source for that. --67.65.44.206 15:36, 7 October 2006 (UTC)

Woops, I forgot to log in.

[edit] Introduction

The intro says this:

"It is a plastic cube comprising 26 smaller cubes that rotate around a typically unseen kernel. Each of the nine visible facets on a side of the Rubik's Cube exhibits one of six colours. When the puzzle is solved, each side of the Rubik's Cube is a different colour, but the rotation of each face allows the smaller cubes to be rearranged in many different ways. The challenge of the puzzle is to return the cube to its original state, in which each face of the cube consists of nine squares of a similar colour."

But the Rubik's Cube is not actually made of smaller cubes. I think this would be a better intro: "The 3X3X3 Rubik's Cube is made of 12 edge pieces with 2 faces each, 4 corner pieces with 3 faces each, plus a kernel with 6 different face pieces composing 3 axes which are all perpendicular. The cube has 9 square faces on each side, for a total area of 56 square faces, and occupies the volume of 27 cubic faces. Typically the faces of the cube are covered by stickers in 6 colors, one for each side of the cube. When the puzzle is 'solved,' each side of the cube is supposed to be a solid color."

Picky, picky, picky.... You're getting too technical. Calculusfreak 20:44, 7 August 2006 (UTC)

Discussion? oneismany 10:37, 8 December 2005 (UTC)

Change "and occupies the volume of 27 cubic faces" to something more accurate and I say go for it. --Monguin61 09:02, 17 December 2005 (UTC)

You are welcome to change it to better describe the volume of 27 smaller cubes, but I was struggling because what is the unit of measurement? The size of the faces? The number of faces? The 4X4 has 64 cubic units and the 5X5 125 cubic units ... can we agree on the name of the unit? oneismany Update: I (stupidly) ignored the section below and renamed the units to 'unit cubes', after reading it. oneismany 23:47, 10 February 2006 (UTC)

I would say leave it as it is, except for perhaps putting the word "cube" in quotation marks. The explanation you have here, while correct and well put together, may be a little overwhelming for an introduction. I would say put this information into the "Workings" section, which needs help and clarification anyway. (The Swami 20:09, 17 December 2005 (UTC))

The "Workings" section mentions 56 "cubies" on the "surface". But cubes are volumes, not surfaces, and this information doesn't help to solve the puzzle. oneismany 23:43, 10 February 2006 (UTC)

[edit] What are the pieces called?

We ought to decide on a name to use for the individual centre, edge and corner pieces and stick to it. The names I've seen include cube, small cube, cubie, cubelet and piece. IMO we should save cube for when we're talking of the Rubik's Cube as a whole.... -- Smjg 12:43, 22 December 2005 (UTC)

My book on the subject (by the mathematician David Singmaster, 1980) uses the terms unit cube and piece interchangeably. --Heron 14:30, 22 December 2005 (UTC)

The speedcubing community uses the following terms quite consistently

Cubie = any edge or corner
edge piece = one of the 12 edges
corner piece = one of the 8 corners
kernel = the core part with 6 rotating axes

Blonkm 17:36, 27 June 2006 (UTC)

[edit] Render of the Rubik's cube

I made a render of the cube today, feel free to use it anywhere you like. Including this article.

Link

I might also supply a non-scrambled version in a while

-- 25 December 2005

[edit] Rubik's Tesseract

Someone with a better understanding than mine might want to write about higher-dimensional analogs such as Rubik's Tesseract Archola 08:03, 26 December 2005 (UTC)

Then you might be interested in this [4-dimensional Rubik's cube game] which lets you actually play with a (simulated) 4D cube. Have fun!—Tetracube 05:08, 12 January 2006 (UTC)

[edit] Idiot's Cube

Do you think it'd be appropriate to create a page for the Idiot's Cube? If not its own page, it ought to be mentioned somewhere in this article under "Parodies" or something. The reason I'm asking is that it might not quite fit in...oh here's the pic.

Image:Idiot's cube.jpg

Peaceman 03:18, 18 January 2006 (UTC)

I would suggest creating a seperate page for the Idiot's cube. I agree that it doesn't belong here, but it certainly deserves a mention/link. I'd say go for it. (The Swami 03:43, 19 January 2006 (UTC))

[edit] Originally possed as a problem for students

I read somewhere that Rubik ogininally devised the cube as a an exercise for his students, to help them think logically and geometrically. Anyone know more about this?

As I recall, Professor Rubik was a professor in industrial design and wanted his students to see that it was possible to create highly complex structures from simple concepts. Unfortunately I have no official source. --Blonkm 20:40, 1 July 2006 (UTC)

[edit] Brit-Am spellings

Wikipedia is neutral between British and American spellings. Wikipedia:Manual of Style states, in part:

...when either of two styles is acceptable, it is inappropriate for a Wikipedia editor to change from one style to another unless there is some substantial reason for the change. For example, with respect to British spelling as opposed to American spelling, it would only be acceptable to change from American spelling to British spelling if the article concerned a British topic. Revert warring over optional styles is unacceptable; if the article uses colour rather than color, it would be wrong to switch simply to change styles, although editors should ensure that articles are internally consistent. If in doubt, defer to the style used by the first major contributor.

and:

Cultural clashes over grammar, spelling, and capitalisation/capitalization are a common experience on Wikipedia. Remember that millions of people have been taught to use a different form of English from yours, including different spellings, grammatical constructions, and punctuation. For the English Wikipedia, while a nationally predominant form should be used, there is no preference among the major national varieties of English.

Please do not make wholesale changes from one system of spelling to another. Thank You! John Reid 01:04, 13 March 2006 (UTC)

[edit] stupid cartoon =

Rubik the Amazing Cube is reported twice in the article and its producers are reported as both Hanna-Barbera and Ruby-Spears. Hanna-Barbera is incorrect. —The preceding unsigned comment was added by 24.33.28.52 (talk • contribs) 01:20, 10 May 2006 (UTC).

I've moved conflicting section below, although I'm not an expert in the area. The Ruby-Spears mentioning was in a different section (Rubik's Cube in Popular Culture) than Hanna-Barbera (Popularity), and not sure which one would be more appropriate.

From [[1983]] to [[1984]], [[Hanna-Barbera]] produced twelve episodes of ''[[Rubik, The Amazing Cube]]'', a [[Saturday morning cartoon]] based upon the toy, which aired on [[American Broadcasting Company|ABC]] as part of "The Pac-Man/Rubik, Amazing Cube Hour."

TheJC ^Talk_{Contributions} 05:39, 8 June 2006 (UTC)

User:sander123 As the contradiction is removed now, I removed the contracdict item from the main page. Btw imdb lists 4 producers.

[edit] alternative (imitation) "cube" dodecahedron

i used to have one of these, it was mechanically identical to the cube but each corner piece was sliced at a 45 degree angle to create a new face, this intersected the adjacent cubies so that the original faces were now smaller sqares at a 45 degree angle to the grid and there were now 8 additional triangular faces

the effect was somthing similar to this:

http://en.wikipedia.org/wiki/Image:Truncatedhexahedron.jpg

edit: sig 213.249.159.244 09:41, 26 June 2006 (UTC)

[edit] cleaning up links

I cleaned up the links and put them in the cube wiki--Blonkm 21:19, 1 July 2006 (UTC)

[edit] edit pass

I did an edit pass on this, cleaning up some wordiness, clarifying some things, and improving consistency (e.g. Cube is capitalized when it refers to the whole puzzle, as it is short for Rubik's Cube, a proper noun). I also did a major reorganization on the notation section to make it flow more logically and adding info on Ideal's unorthodox notations (as I remember them -- can't find my Cube books at the moment, perhaps someone can verify). Since the article seems to use the British "colour" I've stuck with that. Jerry Kindall 06:56, 13 July 2006 (UTC)

[edit] Permutations section

There needs to be more of an explanation of the mathematical formula in the section called "Permutations" that illustrates step-by-step.

[edit] Invisible cube?

The article says: "The 3×3×3 version, which is the version usually meant by the term "Rubik's Cube," has nine square faces on each side, for a total area of fifty-four faces, and occupies the volume of twenty-six unit cubes (not counting the invisible cube in the center)." (bolding added by me).

What is meant by this? I want to just remove that, but is what is meant that there is conceptually a space for a twenty-seventh cube? In an actual Rubik's Cube, there is no cube in the center (there is just the central axis) -- this makes it sound like there is. Any thoughts? --Twilightsojourn 12:33, 8 August 2006 (UTC)

Conceptually, if you cut the cube into sub-cubes, the center of the cube is the 27th "sub-cube" or "cubie". But it is not really relevant here, since the Rubik's Cube isn't actually made of 27 sub-cubes, but with a central axis, as you said. I vote to remove the bolded statement.—Tetracube 19:45, 8 August 2006 (UTC)

I agree. I also vote to remove the bolded section -- and perhaps reword the entire sentence, to make it a bit clearer (maybe saying that there are 26 cubies, instead of that it "occupies the volume of twenty-six unit cubes"?). --Twilightsojourn 20:15, 8 August 2006 (UTC)

[edit] Spelling error?

I'm not a native English speaker, so I'm not sure about this, but it looks like the following sentence is missing a verb:

"Some Cubes have also commercially produced with markings on all of the squares..."

Shouldn't this be:

"Some Cubes have also been produced commercially with markings on all of the squares..." Stingray 19:50, 16 August 2006 (UTC)

I do believe you are right! Good catch! --Twilightsojourn 20:19, 16 August 2006 (UTC)

I've edited the article to fix the error. I hope it's correct now. Stingray 08:38, 17 August 2006 (UTC)

[edit] Popular culture

This is from this article

"and when Homer solves a basket full of Cubes after becoming a genius in "HOMЯ""

However, clicking on the link to "HOMR" tells us that Homer's IQ in that episode is increased to 105. 150 is genius. 105 is slightly above average.

Also, there's a "Fresh Prince of Bel Air" episode where Carlton is trying to get into Princeton. Will just stops by the recruiters office for some reason or another and Will solves the Rubik's cube sitting on his desk. This impresses the recruiter and gets Will a spot at Princeton. Carlton was already having trouble with the pressure of getting in and this all makes it worse. He ends up blowing the interview completely and I think he even tries to solve the cube himself and can't do it.

[edit] GA Re-Review and In-line citations

Note: This article has a small number of in-line citations for an article of its size and subject content. Currently it would not pass criteria 2b.
Members of the Wikipedia:WikiProject Good articles are in the process of doing a re-review of current Good Article listings to ensure compliance with the standards of the Good Article Criteria. (Discussion of the changes and re-review can be found here). A significant change to the GA criteria is the mandatory use of some sort of in-line citation (In accordance to WP:CITE) to be used in order for an article to pass the verification and reference criteria. It is recommended that the article's editors take a look at the inclusion of in-line citations as well as how the article stacks up against the rest of the Good Article criteria. GA reviewers will give you at least a week's time from the date of this notice to work on the in-line citations before doing a full re-review and deciding if the article still merits being considered a Good Article or would need to be de-listed. If you have any questions, please don't hesitate to contact us on the Good Article project talk page or you may contact me personally. On behalf of the Good Articles Project, I want to thank you for all the time and effort that you have put into working on this article and improving the overall quality of the Wikipedia project. Agne 05:44, 26 September 2006 (UTC)

[edit] Has a 6x6x6 cube really been made?

The introduction to this page suggests that it is possible to make one (I've only read the introduction so far). I've played with a virtual one on a website, but I'm sure I remember reading somewhere that it was impossible to physicaly make one. The same article said that it was possible to make a 7x7x7 one but nothing larger. (wik@def.me.uk)

See this. It claimed, a few years ago, that 6x6x6 cubes would be available to the public within a few months. They still aren't available, but some prototypes (such as the one in the video at the bottom of the page) exist. I haven't heard of any "limited edition" 7x7x7 cubes. I'll change the introduction accordingly. --Ravi12346 15:45, 7 October 2006 (UTC)

[edit] Spoiler Warning

Should there be a spoiler warning over the "solutions" part of the article, since it kinda spoils the fun of figuring it out for one's self? Ninety ^wazup? 23:11, 14 December 2006 (UTC)

Retrieved from "http://en.wikipedia.org../../../r/u/b/Talk%7ERubik%27s_Cube_1215.html"