Time and Invariance

SummaryThe aim of this paper is to infer conclusions about the temporality of the physical world from central features of the measurement of time. In order to do so it makes a distinction between the passage of time and the measurement of the passage of time. Whilst the passage of time can be experienced on the basis of, say, chaotic processes, the measurement of the passage of time requires certain physical regularities. But regularity is not sufficient and it is important to highlight the connection between time, regularity and invariance in the measurement of time, especially with respect to classical physics, the Special theory of relativity and quantum mechanics. It is only after this connection has been clarified that the paper considers the dispute on whether the physical world is static or dynamic. As there are clearly both time-symmetric physical laws and time-asymmetric physical processes, the question is empirically underdetermined because the evidence is at present compatible with two incompatible views about the temporality of the physical world.