The coordinate system that describes our geometry best and maps the entire space-time completely is like spherical coordinates (like polar), where radial directions represent time dimension and the distance from the origin gives the magnitude of the time dimension.

In order to simplify our graphics, we will reduce spatial dimensions, and we will consider space as a one-dimensional line by leaving two dimensions of the three dimensions out. However, spatial dimensions are not open-ended to infinity, but they are closed (like spherical) and curved to make circles. Circumferences represent spatial dimensions in this coordinate system. Total length of the spatial dimension (circumference) increases with the increase in time dimension (radius).

Figure 4.1 Coordinate system

In this coordinate system, there is a unique center, which is not on space, just like the center of a circle, which is not on the circle’s circumference.

The expression “time”, which represents the radius in our coordinate system, is definitely not the quantity of clock-ticks. In fact, it is simply the “radius of curvature of spatial dimension”, or it is the time dimension.