Talk:Cube

Trivia
If each edge of a cube is replaced by a one ohm resistor, the resistance between opposite vertices is 5/6 ohms, and that between adjacent vertices 7/12 ohms.

...Above text was deleted by IP user. I copied it here rather than reverting or allowing it to be lost in case anyone cares. Tom Ruen 09:25, 10 January 2006 (UTC)

New stat table
I replace stat table with template version, which uses tricky nested templates as a "database" which allows the same data to be reformatted into multiple locations and formats. See here for more details: User:Tomruen/polyhedron_db_testing
 * Tom Ruen 00:53, 4 March 2006 (UTC)

added face/facet/side
to clarify meaning. 0waldo 02:12, 17 May 2006 (UTC)


 * Was it in doubt? &mdash;Tamfang 15:16, 17 May 2006 (UTC)

Equation
The equation for a cube is $$|x|+|y|+|z|=s\sqrt{2}$$, where $$s$$ is the length of a side. Is this worth mentioning? If no one objects, I will add it. ForrestVoight 15:06, 13 June 2006 (UTC)


 * Are you sure that's a cube and not an octahedron? -- Jitse Niesen (talk) 13:31, 13 June 2006 (UTC)


 * For a cube, try max(|x|, |y|, |z|) = s/2, instead. -- The Anome 13:37, 13 June 2006 (UTC)

Oops, thats an octahedron. Do you think it should go on the octahedron page? ForrestVoight 15:06, 13 June 2006 (UTC)


 * Yes, go ahead. Cube, Sphere and Octahedron could each have a brief passage comparing the &infin;-norm (measure polytope), 2-norm (sphere) and 1-norm (cross polytope).  &mdash;Tamfang 17:32, 13 June 2006 (UTC)


 * That's an excellent idea. -- The Anome 21:28, 14 June 2006 (UTC)


 * I've added three sentences to Norm (mathematics). &mdash;Tamfang 22:15, 14 June 2006 (UTC)

those idiot redirections
are apparently part of a long pattern, see Long term abuse/Videogamer. &mdash;Tamfang 05:21, 25 August 2006 (UTC)

Hypercubes
We need some terminology cleaned up. The name measure polytope is rare at best. I have changed it to hypercube and "n-cube". There is a move being considered of the page "measure polytope" to "hypercube" (see their talk pages). Zaslav 02:02, 16 November 2006 (UTC)

"Combinatorial cubes"
I replaced this, which was incomprehensibly vague, by a brief description of the cube graph and the 3-dimensional Hamming graph. A full discussion of either one appears in separate articles, hypercube graph and Hamming graph. If the person who wanted to describe k-ary n-cubes wishes to write a readable article, it should appear under that title (but first check to see if it's different from a Hamming graph). Zaslav 07:44, 21 November 2006 (UTC)

Request: Internal angles
An IP editor left the following request in the article: "Could someone please add the internal angles within a cube. I am particularly interested in the angles of the internal diagonal. Thank you." -- Jitse Niesen (talk) 10:40, 5 January 2007 (UTC)

Definition
I've just had a long discussion with the father of a nine year old who was told at school that the number of sides a solid cylindrical object (e.g. tin can) has is two, and the number of edges is zero. This is all based upon the understanding in the school syllabus where a side is a flat surface, and an edge is where two sides meet. This leads to things like a sphere as having no sides. Well all this seems rather badly defined to me, and made me wonder if the definition here is all that it could be.

I think side is good term for 2 dimensional objects like a square or a triangle etc. A 3D object is better described in terms of surfaces (although I can see that using a term such as face, side or facet is not being incorrect). I hesitate to change this without some feedback, but I wonder if the definition would better be something like:

A cube is a three-dimensional solid object bounded by six square flat surfaces, with three surfaces meeting at each vertex.
 * I think that would be better. However, one person (and anom. at that) doesn't make a consensus.  I think you better wait.  76.188.26.92 20:18, 2 November 2007 (UTC)

How would this look
I was just looking at the tesseract page and I saw a 3D projection of a rotating 4-cube. This would be what we would see if a rotating, clear tesseract suddenly appeared in front of us. I thought that if 3Dals (meaning three-dimensional [object/being]) could see a simplified 4Dal, then a 2Dal may see asimple 3Dal. Could someone describe a projection of a rotting cube as a Flatlander would see it to me? An animation would probably be helpful, if it isn't to much trouble. Merci bien, 76.188.26.92 20:23, 2 November 2007 (UTC)


 * A Flatlander sees only a line, varying in length; with appropriate lighting, the line is divided into segments of different shades. —Tamfang (talk) 04:36, 7 August 2009 (UTC)
 * A rotting cube would appear to a Flatlander as a smelly line. :-) Double sharp (talk) 15:20, 5 March 2013 (UTC)


 * Nope. Just as 4D projects down to us as 3D, so 3D projects down to a flatlander as 2D. It will start as a hexagonal zonogon, i.e. whose opposite sides are parallel and equal-sized. As the cube rotates, the side pairs will morph in length and angle. Depending on the projection, this description may be approximate due to 3D perspective. If the cube is transparent so the flatlander can see inside, there will also be two extra vertices and six additional edges joining them alternately to the outer vertices - all done with overlapping (and possibly approximate) quadrilateral zonogons, more commonly known as parallelograms. As the cube rotates, the four vertex pairs will take it in turn to disappear inside for a while. As the cube rots, edges will wiggle, then blur, then disappear so the thing becomes a shapless pulsing blob, shades of colour will vary, and the smell will worsen for a while before fading away to leave a small, hardened residue stuck to flatland. HTH &mdash; Cheers, Steelpillow (Talk) 11:30, 7 March 2013 (UTC)

Circumscribing sphere for cube is wrong.
AFAIK the formula for a circumscribing sphere for a cube needs to be the square root of _A squared_ times three, over two. As it is currently, I think it's wrong. —Preceding unsigned comment added by 86.160.220.110 (talk) 22:18, 30 September 2009 (UTC)


 * The radical didn't cover the a. I reformatted a bit; clearer now? —Tamfang (talk) 20:17, 11 October 2009 (UTC)

It seems wrong as of http://en.wikipedia.org/w/index.php?title=Cube&oldid=327931331 since the space diagonal should be precisely twice the radius of circumscribed sphere. sqrt(3)*a is not twice (sqrt(3)/2)*a   VoidLurker (talk) 17:43, 26 November 2009 (UTC)


 * If sqrt(3)*a is not twice (sqrt(3)/2)*a, how would you change it? —Tamfang (talk) 08:19, 28 November 2009 (UTC)

Net faces or nets
I was a bit confused about the sentence "A cube has 11 net faces", since I read it as something like "The net of a cube has 11 faces" (or "The cube has 11 faces of type net", but that gave no meaning..). At first I thought it was a typo, but then I got it. To me it seems like "A cube has 11 (different) nets" would be clearer, or perhaps even "There are 11 distinct nets of the cube", but I'm not a native English speaker, so I would like the opinion of others on this issue. Danmichaelo (talk) 11:10, 23 May 2011 (UTC)


 * You're right, "11 net faces" makes no sense. —Tamfang (talk) 17:00, 27 May 2011 (UTC)

Added Coxeter diagram for the trigonal trapezohedron
for the sake of completeness. — Robin Leroy (talk) 00:01, 22 April 2013 (UTC)
 * Looks good! Tom Ruen (talk) 05:00, 22 April 2013 (UTC)

Reader feedback: How can you cut a cube to ge...
183.179.103.36 posted this comment on 12 November 2013 (view all feedback).

"How can you cut a cube to get the largest section ?"

The largest section (cutting the cube with a plane) is the one obtained through the diagonals of one of the sides, the area of this section is
 * $$ A = \sqrt{2} a^2 $$

Nicoguaro (talk) 04:16, 24 November 2013 (UTC)

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 * Rhombicdodecahedron.jpg

Bad writing
In this passage:

"The cube can also be represented as a spherical tiling, and projected onto the plane via a stereographic projection. This projection is conformal, preserving angles but not areas or lengths"

it is not stated what projection is being discussed.

The article defines a cube as a 3-dimensional solid. But this passage appears to be treating it as only the surface of the 3-dimensional cube.

That is why it is important to state exactly what projection is being discussed: a projection that goes from something and to something. It doesn't work to just spout the first words that come to mind as though you are speaking to a college classmate.50.205.142.35 (talk) 06:44, 3 January 2020 (UTC)

ToC entry #4 broken
Have noticed $$\mathbb{R}^3$$ is not working in in the ToC, anyone know better than me that can fix it? Snus-kin (talk) 22:04, 2 December 2021 (UTC)

Merge from Sum of two cubes
Seems to me that the content of Sum of two cubes really belongs here. Yeah? 67.198.37.16 (talk) 01:59, 17 November 2023 (UTC)


 * No, just like difference of two squares, this is an important factorization. 218.187.68.15 (talk) 01:36, 23 November 2023 (UTC)
 * Agreed. Sum of two cubes is specific enough that merging it into cube would unnecessarily lengthen this article. cm&#610;&#671;ee&#9094;&#964;a&#671;&#954; 01:05, 24 November 2023 (UTC)
 * This article is about geometry. You want Cube (algebra). —Tamfang (talk) 06:32, 26 November 2023 (UTC)
 * Indeed: Cube is certainly the wrong page to even consider a merge to; and I'd also oppose a merge to cube (algebra), as their sum is sufficiently distinct topic warranting separate discussion. For examples, there is also a Sums of three cubes article. Klbrain (talk) 12:06, 3 December 2023 (UTC)


 * There is clearly consensus against this proposal, so I shall remove the merge tags from the articles. JBW (talk) 23:48, 25 February 2024 (UTC)