Kian Salimkhani

It is standardly believed that the generally time-reversal symmetric fundamental laws of physics themselves cannot explain the apparent asymmetry of time. In particular, it is believed that CP (charge conjugation parity symmetry) violation is of no help. In this article, I want to push back against a quick dismissal of CP violation as a potential source for the arrow of time and argue that it should be taken more seriously for conceptualizing time in physics. After briefly reviewing the general debate on the direction of time, I note that CP violation is a key feature of our best physical theory which also has large-scale explanatory import regarding the matter–anti-matter asymmetry of the universe. I then investigate how CP violation may help explain the directionality of time. I argue that accounts à la Maudlin, which posit an intrinsic fundamental direction of time, are not convincing and instead I propose using recent results from work on the dynamical approach to relativity theory: if matter field symmetries are more fundamental than spatiotemporal symmetries, the established (fundamental) directionality of the former may explain the (derivative) directionality of the latter.