Spacetime

Major confusions and misconceptions are involved in the understanding of what the concept of spacetime represents. Unlike the adoption of the developed by Hermann MinkowskiMinkowski  four-dimensional (spacetime)Spacetime formalism, Minkowski’s argumentsMinkowski’s arguments for the reality of spacetime have been effectively ignored. Even worse—some physicists (including a number of relativists) claim that spacetime and Minkowski’s four-dimensional formalism are “just a description”“just a description” and that the question of the reality of spacetime belongs to philosophy. Most relativists appear to understand well both (i) that, as the dimensionality of the (macroscopic) world is a fundamental feature of the world (arguably as fundamental as its very existence), it is not just a description, and (ii) that it is physics (not philosophy) which can determine the dimensionality of the world. Nevertheless, as the question of the nature of spacetime naturally plays a central role in the foundations of spacetime physics,Spacetime physics  it is necessary to state explicitly and in great detail what Minkowski himself advocated, i.e., what the concept of spacetime actually represents. In this chapter Minkowski’s argumentsMinkowski’s arguments—general and specificMinkowski’s specific argument (based on the nature of length contraction)Length contraction—are stated, elaborated and extended by demonstrating that none of the experiments, which confirmed the kinematic relativistic effects, would be possible if spacetime were not real [3, 5].