UPDATE 27 NOV: THIS EVENT HAS BEEN CANCELLED SINCE THE SPEAKER'S PLANE HAS BEEN CANCELLED DUE TO SEVERE WEATHER CONDITIONS IN POLAND
On 27 November, Tomasz Placek (Jagiellonian University) will deliver a talk entitled “A No-Go Result for a Relativity-Proof Dynamic Concept of Time” for the HPP/Ian Ramsey Centre's 2019-2020 seminar series.
Combining relativity with the intuitive notions of past, present, and future is a challenging task. It is natural to define the present by a simultaneity relation, which is standardly postulated to be transitive, reflexive, and symmetric, i.e., an equivalence relation. Yet van Benthem’s theorem (in his The Logic of Time, 1983) shows that the only equivalence relations definable on a Minkowski space-time and invariant under that space-time’s automorphisms, is the identity and the universal relation. In contrast to explicating time in terms of simultaneity, there is a different tradition (James, Eddington, Whitrow, Ellis) that links time to real change (becoming), the radical consequence being: no real change, then no time. On this dynamic view, an event’s present is defined in terms of a co-presence relation rather than simultaneity, with co-presence being explicated by a pattern of real changes. Recently the dynamic time was explored independently by Müller (Foundations of Physics 2019) and Placek (Synthese 2019). Müller defines co-present events as events sharing the same causally relevant factors, whereas Placek starts with giving the modal truth conditions of sentences like “e' belongs to the future of e”. The results of these authors are relativity-friendly, yet each result has a (different) defect. These defects, we claim, are the consequences of a general no-go result, the proof of which we will give. We will prove that no concept of dynamic time can satisfy all desiderata from this list: For any event e, (1) no two of Past(e),Present(e), and Future(e) overlap; (2) any history h with event e is partitioned by Past(e),Present(e), and Future(e); (3) Past(e) is settled; (4) Past(e) and Future(e) are symmetric in the sense that e' ∈ Past(e) iff e ∈ Future(e'), and (5) a co-presence relation CP, defined by CP(e', e) ⇔df e' ∈ Present(e), is transitive.
TOMASZ PLACEK majored in physics and philosophy at the Jagiellonian University in Kraków, Poland. He received a PhD in philosophy from the Jagiellonian University in 1991 followed by a habilitation in 2001. He was appointed a visiting scholar at the Universities of Princeton and New York as well as the London School of Economics. His current area of research is metaphysics and philosophy of physics with a particular interest in branching space-time theories and their applications in areas such as determinism and causality, theories of probability, interpretations of quantum mechanics, and questions concerning human agency. Professor Placek is the author of Intersubjectivity and Mathematical Intuitionism, Kluwer AP 1999, and Is Nature Deterministic? Jagiellonian UP, 2001.