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 regarded as a set of dynamically related here-and-nows. Because of these dynamical relations, characterized by empirical time-symmetric laws, a local present can be viewed as formally ‘moving’ along the world line of an observer. His history is approximately a succession of strongly correlated (local groups of) events, dynamically controlled by proper time, while the global dynamical state depends on an arbitrarily chosen foliation of the objective and invariant spacetime (Sect. 5.4).