There are different approaches to physics:
- Insurance Company Physics: statistical mechanics.
- Accountant Physics: relativity theory.
- Accountant Physics: quantum mechanics in Copenhagen Interpretation.
- Realistic Physics: physics as computation, constructive physics.
In 2 the physicist in thought experiments is worrying about the absolute simultaneity of events in different galaxies, but does not ask if this is of any interest to anybody. It is like Georg Cantor worrying about his transfinite numbers of counting different levels of infinities believing his theory had been communicated to him by God but suffering from doubts and depression. In his later years Einstein expressed similar sentiments concerning his grand scale relativity theory.
In 4 the emphasis is put on simulating real phenomena left to evolve according to their own logic without any need of human observation, with understanding required to write computer programs.
In 1 the physicist computing mean-values over projected ensembles of atom velocities, is like an insurance mathematician computing mean-values over projected ensembles of peoples life lengths.
In 1-3 the physicist is active and in 4 passive, vs the reality under study.
In 3 only what is observed by the physicist is said to exist and is then affected by the physicist and so involves self-observation.
In 2-3 the emphasis is put on what can be accounted for, like the expenditures of a company covered by receits, which can leave out much of reality. The objective is to set up a correct accounting book according to some form of business law.
In 4 computational simulation and observation can be done without any interference from the physicist.
4 seeks to simulate reality, while 1-3 supports illusion.