Epilog

Abstract

Four weeks before his death, Albert Einstein wrote in a letter of condolence to the family of his life-long friend Michael Besso (Dukas and Hoffman 1979):¹ “For us believing physicists, the division into past, present and future has merely the meaning of an albeit obstinate illusion.” There is no doubt that Einstein meant this remark seriously. Evidently, it refers to the four-dimensional (‘static’) spacetime picture of a ‘block universe’ that his theory of relativity uses so efficiently. This picture seems to be at variance with the experience of a present passing through time (the ‘flow’ or ‘passage of time’). In contrast, the objective (classical) spacetime framework contains only a concept of local events, which may be given the status of an ensemble of dynamically related here-and-nows. Because of the actual dynamical relations (based on symmetric laws) a local present can be viewed as ‘moving’ along the world line of an observer (a succession of events), intrinsically controlled by proper time, while the global dynamical states (Sect. 5.4) depend on the arbitrarily chosen foliation of an objective and invariant spacetime.