Some constants are relevant for all physical phenomena: the speed of light pertains to the causal structure of spacetime and hence all physical processes. Others are relevant only to particular interactions, for example the fine structure constant. Why is Planck's constant one of the former? I motivate the possibility that there could have been multiple, interaction-specific 'Planck constants. Although there are indeed good reasons to eschew this possibility, it suggests a further question: what is the actual conceptual significance of Planck's constant in quantum physics? I argue that it lies principally in relating classical and quantum physics, and I draw out two main perspectives on this relation, represented by the views of Landsman and Lévy-Leblond.
There will be a dinner following the seminar, open to all (at your own expense). Please email email@example.com by Wednesday morning before the seminar if you would like to attend.
Philosophy of Physics Seminar Convenors for HT19: James Read and Simon Saunders