Three-dimensional space

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Though actual perceptible space-time is a 4-dimensional Minkowski space (see special relativity), human beings usually perceive space as a three-dimensional space as long they don't notice anything with high relative velocity.

"Cartesian geometry" or analytic geometry can describe every point in three-dimensional space by means of three coordinates. Three "coordinate 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. In society, when Cartesian dimensions of objects are required, they are commonly called length, width, and height (though due to symmetry, there is no canonical way to identify which edge of a box is the length or width or height).

Other popular methods of describing the location of a point in three-dimensional space include cylindrical coordinates and spherical coordinates, though there are an infinite number of possible methods. See Euclidean space.

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 ^[1]. Many of the laws of physics, such as the various inverse square laws, depend on dimension three.^{[citation needed]}

The understanding of Three-dimensional space in humans is thought not to be completely intuitive, and must be learned during infancy using an unconscious inference. The visual ability to perceive the world in three dimensions is called Depth perception.

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