Quantum Mechanics and the Nature of Spacetime

Summary

In this chapter we have addressed the objections against the reality of spacetime according to which special relativity may be regarded as a theory of a four-dimensional world, whilst other physical theories, including some still unconfirmed theories such as quantum gravity and string theory, may tell a different story. We have again stressed that it is the experimental evidence supporting the consequences of special relativity that would be impossible if the world were three-dimensional. Obviously there are two options with such a claim — either it is wrong (and should be proven wrong) or if correct, then the world is really four-dimensional at the macroscopic scale and the interpretations of other theories cannot contradict that result. In this sense special relativity alone can provide a solution to the question of the nature of spacetime.

We have also analyzed the apparent contradiction between the static four-dimensional picture of the world depicted by special relativity and the probabilistic nature of quantum mechanics. We have seen that any claim that such a contradiction is genuine should be based on a clear understanding of the nature and origin of probabilities in quantum mechanics; only then would we know whether the probabilistic behaviour of quantum objects contradicts the four-dimensionalist view. As an example to show that it is not unthinkable to have both — real spacetime and objective quantum probabilities — we examined the 4-atomistic model of the quantum object. The conclusion we have drawn is that there might be a link between a model of the quantum object (that resolves the quantum paradoxes) and the dimensionality of the world. So it may turn out that, not only does quantum mechanics not contradict the four-dimensionalist view, but it may provide an independent argument in its support.