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 that have 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 world and the ability to identify three dimensions with the help of the senses.
According to analytical geometry, three-dimensional space at each of its points is described by three characterizing quantities called coordinates. The coordinate axes located perpendicular to each other at the intersection point form the origin with zero value. The position of any point in space will be determined relative to the three coordinate axes having a different numerical value at each given interval. The 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 intersection point with the given plane. There are also coordinate schemes such as spherical and cylindrical systems.
In linear algebra, the concept of three-dimensional measurement is described using the concept of linear independence. Physical space is three-dimensional because the height of any object does not depend 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 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 to a rope is located in a space of smaller dimension. Most physical laws are related to the three-dimensional dimension of space, for example, the laws of inverse squares. In three-dimensional space there can be two-dimensional, one-dimensional and zero-dimensional spaces, while it itself is considered part of the four-dimensional space model .
The isotropy of space is one of its key properties in classical mechanics. Space is called isotropic because when the reference frame is rotated by any arbitrary angle, changes in the measurement results do not occur. The law of conservation of angular momentum 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, isotropic space is such a medium whose physical properties are independent of direction.