All points of F in the coordinates x, y, z can be bijectively associated with the points of the actual physical space in which there is no movement, the point mentally can be described equally. To specify the motion must specify the inertia of the system and get them to coordinate transformations. For this we must expand the viewing area of the coordinate q in F (until a single value). Mentally connect the same point O and a point similar to L by a straight line in the real physical space. According to this line mentally Assume the light signal from a point O, in the direction of L.

The distance from O to light signal is denoted R (OS). Once the signal reaches the L and go farther the distance from L to the light signal is denoted R (LS). Now these terms – O, L and the point of moving the light signal S, consider a space F. If the center coordinates to choose a point O, then (using the distance to the light signal) in F can be defined as the coordinate q: q = R (OS) / c. If the center coordinates to select a point L, then so: q '= R (LS) / c. In fact, in the space F Center coordinates defines its coordinate system. In each coordinate system coordinate q (or q ') can be bijectively mapped to the coordinate time of physical space. This is true in some neighborhood, corresponding to the center coordinates.