I know the debate about Schrodinger's cat is usually about things like consciousness but I want to talk about what it might say about isolated systems. Does the wave function of isolated systems remain in a superposition of observable states no matter how large the system gets? Say you have the radioactive material isolated from the cat in the box and the box the cat is isolated from the outside environment, wouldn't a live/dead cat be two observable states of an isolated system until the box is open and the wave function collapses locally? This collapse isn't just because of the Scientist opening the box, but the state of the cat interacts with his lab, the car on the highway and the entire observable universe. So if an isolated system remains isolated do all probable states of that isolated system occur? If you extrapolate that out to the universe and the universe is an isolated system doesn't that mean that every probable universe exist because there's nothing external to the universe to collapse it's wave function. I was reading a paper where Max Tegmark said this was a postulate of Everett. All isolated systems evolve according to the Schrodinger's equation. So our universe could be an observable state of an isolated system and if this observable state is isolated then you can have probable states within probable states. This would occur maybe for trillions of years until two observable states of the isolated system interacted and maybe you get something like a big bang and everything reboots. I saw where Penrose talks of Objective Reduction where isolated systems self collapse after they reach a certain threshold due to quantum gravity but I haven't seen much evidence for that. I think Tegmark may have a point if the universe is an isolated system.