Philosophy of Physics Seminar (Thursday - Week 4, MT21)

The quantum measurement problem is often described as a standoff or a case of underdetermination – perhaps between Everett, Bohm and GRW, perhaps between Everett, Copenhagen and QBism. (It depends on your audience.) The background assumption is that these various alternatives are all compatible with the quantum formalism, and so any question as to which is preferred turns on second-order issues: distaste for action at a distance, worries about probability, competing intuitions about simplicity. I argue, by contrast, that very large swathes of modern physics, from the exotic to the mundane, rely on the Everett interpretation or something very much like it. Specifically, they rely on something like: unitary, the eliminability of collapse except as an approximation, decoherence-type approaches as an explanation of the macroscopic, the ability to use quantum theory far outside the classic predict-evolve-measure paradigm, and the applicability of the theory to many systems at many levels, not just to a supposed ‘fundamental’ level – at which point we’re most of the way to Everett. (In particular, I will argue that the de Broglie-Bohm theory – especially but not only in its popular ‘primitive-ontology’ form – does not at present solve the measurement problem, even if we disregard the esoterica of high-energy particle physics). Other interpretative strategies might point the way to exciting physics in the future, but only Everett-style approaches can make full sense of the physics of today.