Was Spacetime a Glorious Historical Accident?

          @misc{ scivideos_PIRSA:08100040,
            doi = {10.48660/08100040},
            url = {https://pirsa.org/08100040},
            author = {Barbour, Julian},
            keywords = {},
            language = {en},
            title = {Was Spacetime a Glorious Historical Accident?},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2008},
            month = {oct},
            note = {PIRSA:08100040 see, \url{https://scivideos.org/pirsa/08100040}}
          }
          

Abstract

Exactly half a century after Minkowski’s justly famous lecture, Dirac’s efforts to quantize gravity led him “to doubt how fundamental the four-dimensional requirement in physics is”. Dirac does not appear to have explored this doubt further, but I shall argue that it needs to be considered seriously. The fact is that Einstein and Minkowski fused space and time into a four-dimensional continuum but never directly posed the two most fundamental questions in dynamics: What is time? What is motion? It was an historical accident that Einstein attempted to implement Mach’s principle after he had created special relativity; otherwise he would have been forced to address these questions, which have never been properly considered. I shall show how they can be answered and suggest that: 1) time and space are utterly different; 2) the dynamical law of the universe may define absolute simultaneity in a manner that is still consistent with local validity of Minkowski’s marvellous notion of spacetime.