Don Geddis: I don’t agree that “multiple worlds are observed, in subatomic phenomena. That’s what superposition is.” That is your preferred interpretation. I prefer to think that the wavefunction is real, but it is a function over potential configurations, only one of which is real. Superposition reflects the influence of other physically equivalent configurations. I would not call my interpretation a “collapse” interpretation. The wavefunction is always there, in the sense that nature “knows” the probability amplitude for points in configuration space other than the that represented by the real state of the universe.
I am also puzzled by your statement that “determinism is observed”. It most certainly is not. When an atom is in an excited state, the time and direction of the photon emitted is essentially random. Isn’t it more satisfactory to just acknowledge this than to postulate an infinity of other worlds being spawned for every possible direction and time of emission?
Caledonian: There is no difference at the level of predictions, because I’m not calling for any new laws of physics beyond QM. It’s a matter of what makes sense as interpretation.