But don't quantum measurements appear only to our (classical) perception? If someone (probably not in our Universe i.e. someone who doesn't interact with our Un

But don't quantum measurements appear only to our (classical) perception? If someone (probably not in our Universe i.e. someone who doesn't interact with our Universe in any physical way) hypothetically able to write down the full Hamiltonian of our Universe (assuming that quantum gravity theory exists, so that is possible) then there is no external to this Hamiltonian "measurement devices", so wavefunction of the Universe does not collapse and the time evolution of Universe is reversable as soon as you can just multiply time to -1 in evolution operator. But I don't understand why do they talk about time reversability of physical systems and don't mention CPT symmetry[1]? Standard model is not actually time symmetrical, but you one should also reverse charge and reflect spatial coordinates to obtain symmetry after time reversal because there are violations of CP symmetry [2]. [1] https://en.wikipedia.org/wiki/CPT_symmetry https://en.wikipedia.org/wiki/CPT_symmetry [2] https://en.m.wikipedia.org/wiki/CP_violation https://en.m.wikipedia.org/wiki/CP_violation