3D Work Selection

Three-dimensional space has a number of properties that distinguish it from spaces of other dimension numbers. For example, at least 3 dimensions are required 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.
The understanding of three-dimensional space in humans is thought to be learned during infancy using unconscious inference, and is closely related to hand-eye coordination. The visual ability to perceive the world in three dimensions is called depth perception.
With the space r^3, the topologists locally model all other 3-manifolds.