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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 6: History and Philosophy of Physics

AGPhil 6.3: Vortrag

Mittwoch, 12. März 2025, 17:30–17:45, HS XVII

History and Metaphysics of Shape Dynamics — •Paula Reichert — Mathematisches Institut, LMU München, Theresienstr. 39, 80333 München

This talk will discuss the history and metaphysics of shape dynamics. Shape dynamics is a relationalist theory of gravity in the spirit of Leibniz and Mach. It has been introduced by Barbour and Bertotti in the 1980s. In shape dynamics, space and time are relational. This makes it a rival theory both to Newtonian gravity and to Einstein's general relativity. In this talk, I will distinguish three ontologies of space and time: 1) Newtonian absolute space and absolute time, 2) Leibnizian relational space and relational time, and 3) Einsteinian relativistic spacetime. I will show how the standard route from Newtonian absolute space and time has led via Galiliean spacetime and Minkowski spacetime to curved spacetime. Relationalists, however, followed a different path. They developed a theory of 3d conformal space + 1d relational time instead of 4d relativistic spacetime. Still, shape dynamics and general relativity agree on the relevant set of solutions. One reason for this to work is that time, in shape dynamics, is essentially given by the expansion rate of the universe (the dilational momentum or York time) and enters the time-dependent Hamiltonian, taking up the role of (relative) scale. After having outlined the different historical routes and the metaphysical and physical differences between shape dynamics and general relativity, I will shortly compare future prospects of the two theories.

Keywords: Shape Dynamics; Relationalism; Metaphysics; Ontology; Spacetime