# Talk:Three-dimensional space

WikiProject Mathematics (Rated C-class, Top-importance)
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Mathematics rating:
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Field: Geometry

## 2d=3d

It's said that a 3D object is several 2D objects stacked on-top of each-other to create thickness but how can several 2D planes with a thickness of 0 add up to be something that has thickness and thus create a 3D object?

Because you're stacking together an uncountably infinite number of 2D objects. Infinity times 0 is not necessarily 0 (technically, it's undefined). Crispy (talk) 00:43, 26 March 2009 (UTC)

## 3d networks as spaces

This article may be improved by adding a mention of Graphs (ie networks of nodes or connectivity information) that have dimension of 3 through Dimensional_analysis. This type of structure is an alternative to the axis-based way of thinking about the dimensionality of space in the universe. See also Fractal dimension on networks. Danwills (talk) 03:51, 12 November 2008 (UTC)

The article would benefit from a link to Dimensional analysis, and but I don't think this application of dimensional analysis belongs in the article. --Una Smith (talk) 01:39, 2 July 2009 (UTC)

## SVG Drawing

The article's first picture is badly in need of proper formatting to get rid of the "jaggies". I suggest conversion to SVG. - KitchM (talk) 21:44, 10 October 2009 (UTC)

## Hypersphere

This space is above (in dimension) the sphere or the 2-sphere:

If the 2-sphere lives in her own but also can be viewed embedded in $\mathbb{R}^3$ and is defined as $p\in\mathbb{R}^3$ such that $p=(x,y,z)^{\perp}$ and $x^2+y^2+z^2=1$.

And the hypersphere -very well known to a real topo-geometer- is: a set consisting of point in the 4-dimensional euclidean space $\mathbb{R}^4$ which are equidistant to the origin, usually we take distance one. In other words: $p\in\mathbb{R}^4$ such that, if $p=(x,y,z,t)^{\perp}$ then $x^2+y^2+z^2+t^2=1$. So, i don't know why unsavvy geeks think they know and write lies, and only producing that math look stupid... well, that it seems a law in these wikiplaces. --kmath (talk) 22:28, 25 September 2011 (UTC)

Anyway not all is lost: check 3-sphere for education--kmath (talk) 22:37, 25 September 2011 (UTC)
Huh? Hypersphere refers to any number of dimensions, though n-sphere is a more common synonym. Indeed the former is sometimes restricted to 3 or more dimensions, but here we already state explicitly that n = 2. Double sharp (talk) 13:20, 28 August 2013 (UTC)

Just as a 3D object casts a 2D shadow (kinda) should it be noted that a theoretical 4D (not time) object would cast a 3D shadow? (kinda.) or is this all too original researchy? 74.132.249.206 (talk) 11:13, 15 October 2011 (UTC)

That wouldn't be about 3D, it would be about 4D. And there's already something at Four-dimensional space saying that. Dmcq (talk) 11:59, 15 October 2011 (UTC)

As a submersions of a 4-manifold into a 3-manifolds, in fact locally watching close the case R^4->R^3, worth to know, thinka--kmath (talk) 18:29, 31 October 2011 (UTC)

## Undid Vandalism, but ...

I undid some clear vandalism, but have no idea what the article is supposed to look like. I just did this 'en passant' and have other things I must do. Can some Samaritan look this over? DeepNorth (talk) 14:16, 11 November 2012 (UTC)

## Merger proposal

This article should be merged with space as that article is also explicitly dedicated to three-dimensional space.Rgdboer (talk) 22:26, 5 November 2013 (UTC)

Nah, space focuses more on space in physics, that is, the spacetime with time held constant. This page is about a mathematical ideal, does not put physics and reality into account. In mathematics there are 4-dimensional space or n-dimensional, this page is for n=3. We collects its mathematical property, insights and geometries here. --14.198.220.253 (talk) 20:47, 28 November 2013 (UTC)
I propose that we add a "for physical space, see space." redirect (something like that) and fix the leading paragraph, ie. put the description on physics a little bit lower than the mathematical description.
A section and paragraphs on the significance of 3-dimensional space in physics, and a redirect to space for detailed article. --14.198.220.253 (talk) 20:57, 28 November 2013 (UTC)
Really late oppose, but I don't want this merged. I have the same reasons as "14.198.220.253", in that this is a mathematical... thing. For example, four-dimensional space doesn't focus at all on the effects of physics, just a mathematical... thing. Pikachu Bros. (talk) 17:36, 19 March 2014 (UTC)

Yes, I see your point: parts of the other page having reference to physicality would not apply to this page. The WP:namespace logic is clear, and have taken down the merger tags. Thank you for clearing that up; three dimensions need not be materialized.Rgdboer (talk) 02:08, 24 March 2014 (UTC)

## Length, width, height, depth and ..... breadth?... what?

What exactly is Breadth? I know an 3 dimensional object top-down has depth and a 3 dimensional object looked at sideways has height... But what is breadth? Breadth and Length both point to the same article called "Length". I find that sentence very unclear. please clarify it. 195.177.247.202 (talk) 14:37, 7 August 2014 (UTC)

Since three dimensions is three dimensions whichever way you look at it, you can call the dimensions anything you want. Older textbooks called them width, breadth, and height. They would show a picture of a rectangle, with the distance from side to side labeled width and the distance from top to bottom labeled breadth. The idea was that we were looking down on the rectangle from above, and the third dimension, height, came up out of the page. More modern textbooks usually assume the rectangle is standing up in front of us. The distance from side to side is still width, but now they call the distance from bottom to top height, and the distance a three dimensional object extends behind the rectangle depth. If you think this important enough to put in the article, I'll try to find a reference. Rick Norwood (talk) 14:55, 7 August 2014 (UTC)