There must be something else in the Universe to observe the single proton for it to have rotation, etc, according to quantum physics. Extend this idea to the centrifugal force on the water in the bucket in a Universe with nothing else in it, and the centrifugal force is similarly both there and not there, in a quantum superposition until observed. The value of Planck's constant is thus a function of the large-scale distribution of energy in the Universe, rather than a fixed property of spacetime itself.