Three-dimensional space

Encyclopedia : T : TH : THR : Three-dimensional space

The space human beings live in is known as three-dimensional space. The three dimensions are commonly called length, width, and breadth, though there is really no difference between the meaning of the three words. In giving the dimensions of a box you could call any edge the length, any edge at right angles to the first the width, and the edge at right angles to the first two the breadth (or height).

Rene Descartes gave a method which now bears his name "Cartesian geometry", also called analytic geometry, which describes every point in three-dimensional space by means of three co-ordinates. Three co-ordinate axes are given, each making a right angle with the other two at their mutual crossing point, called the origin. They are usually labeled x, y, and z. Relative to these axes, the position of any point in three-dimensional space can be given by an ordered triple of real numbers, each number giving the distance of that point from the origin measured along the given axis, which is equal to the distance of that point from the plane determined by the other two axes.

Other methods of describing the location of a point in three-dimensional space include cylindrical co-ordinates and spherical co-ordinates.

Three-dimensional space has a number of properties that distinguish it from spaces of other dimensions. It is, for example, the only dimension in which it is possible to tie a knot in a piece of string. Many of the laws of physics, such as the various inverse square laws, depend on dimension three.

According to Einstein, our familiar three-dimensional space is really part of a larger four-dimensional space-time, and string theory predicts that there may be up to 26 physical dimensions.

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.