David Yates

LANCOG Universidade de Lisboa

Thinking about Spacetime

9 June 2017, 16:00

Faculdade de Letras de Lisboa

Sala Mattos Romão (Departamento de Filosofia)

Abstract: Quantum gravity research suggests that spacetime is not fundamental, but is in some sense emergent. There is little clarity about what ‘emergent’ means, but it is often taken to mean something like merely phenomenological. Emergent spacetime thus threatens the existence of the “local beables”—meters, pointers, dials—that we observe to gain evidence for fundamental physical theories, which gives rise to a problem of empirical incoherence. In this talk, I will first recast this problem in terms of spatiotemporal truth: in order to defend the empirical coherence of quantum gravity, we need to explain how there can be true propositions about things like meters, pointers and dials despite the fact that spacetime is not fundamental. Spacetime functionalism and certain causal theories of reference offer the promise of such an explanation, by positing non-transparent spatiotemporal concepts. Non-transparency would allow spatiotemporal truths to have non-spatiotemporal truthmakers, but I will argue that some spatiotemporal concepts are at least partially transparent. Combining partial transparency with the claim that at least some spatiotemporal property attributions are true, it follows that such propositions are made true by a structure closely resembling the spacetime of the manifest image. If the fundamental ontology of quantum gravity is indeed non-spatiotemporal, then it must ground a robustly emergent spacetime, in which local beables live and bear the spatiotemporal properties that serve as truthmakers of ordinary empirical claims.