It is strange that we wait to subject a science's fundamental concepts to a pointed critique until it has reached a certain degree of completeness. So it is that the concepts of space and time have only now found a final clarification through Einstein's theory of relativity after physics was already a mostly complete science. But we can now say that it deserves the glory of a real, exact, natural science since the hitherto unnoticeable veil has been lifted from its elementary concepts.

The concept of motion as a change in position over time combines the most important categories in physics; for that reason its investigation is the starting point for the solution to space-time problems.

The most simple conception of motion is the “kinematic.” For example, if a billiard ball moves on a horizontal surface, its position is characterized by its distance from two adjacent edges of the billiard table; that the ball is in motion is a function of these changing distances. We speak of the kinematic concept of motion because it consists only of changes in spatial lengths. But what would one observe if the billiard ball was portrayed as a fixed point and the billiard table underneath was moved? Again, there are changes in both distances. Assume that I see the billiard table through a cardboard tube, so that I can only survey the green surface.