Abstract

The Hamiltonian formulation of Einstein’s General Relativity is the one most readily suited for merger with quantum mechanics. But since the 1950s there has been a worry that change has disappeared, especially from the physically real ‘observables’. The freedom to change time coordinates, already important in Special Relativity and greatly amplified in General Relativity, also seems to disappear from the Hamiltonian formulation. These issues yielded a memorable 2002 exchange between Earman and Maudlin. This talk, building on a reforming literature from the 1980s onward, discusses how the radical relativity of simultaneity, change, and even change in observables are to be found.

Key moves include recognizing that the Hamiltonian formulation is a special case of the more familiar and fundamental Lagrangian formulation (implying that radical conceptual novelty cannot arise) and redefining observables such that equivalent theory formulations have equivalent observables.