Three-dimensional space is a geometric model of the world in which we live. It is called three-dimensional because its description corresponds to three unit vectors having a direction in length, width and height. The perception of three-dimensional space develops at a very early age and is directly related to the coordination of human movements. The depth of his perception depends on the visual ability of awareness of the surrounding world and the ability to identify three dimensions with the help of the senses.
According to analytical geometry, three-dimensional space at each point is described by three characterizing quantities, called coordinates. The coordinate axes, located perpendicular to each other, at the point of intersection form the origin, which has a value of zero. The position of any point in space is determined relative to three coordinate axes that have a different numerical value at each given interval. Three-dimensional space at each individual point is determined by three numbers corresponding to the distance from the reference point on each coordinate axis to the point of intersection withgiven plane. There are also coordinate schemes such as spherical and cylindrical systems.
In linear algebra, the concept of a three-dimensional dimension is described using the concept of linear independence. Physical space is three-dimensional because the height of any object does not depend in any way on its width and length. Expressed in the language of linear algebra, space is three-dimensional because each individual point can be defined by a combination of three vectors that are linearly independent of each other. In this formulation, the concept of space-time has a four-dimensional meaning, because the position of a point at different time intervals does not depend on its location in space.
Some properties that a three-dimensional space has are qualitatively different from the properties of spaces that are in a different dimension. For example, a knot tied on a rope is located in a space of less dimension. Most of the physical laws are related to the three-dimensional dimension of space, for example, the laws of inverse squares. 3D space can contain 2D, 1D, and 0D spaces, while it is considered part of the 4D space model.
The isotropy of space is one of its key properties in classical mechanics. Space is called isotropic because when the reference system is rotated through any arbitrary angle, there are no changes in the measurement results. Law of conservation of momentmomentum is based on the isotropic properties of space. This means that in space all directions are equal and there is no separate direction with the definition of an independent axis of symmetry. Isotropy has the same physical properties in all possible directions. Thus, an isotropic space is a medium whose physical properties do not depend on direction.
