# The MWI of Quantum Mechanics [closed]

Suppose that Bob and Alice decides to do a quantum experiment, more precisely, The Shroedinger Cat Experiment. Alice goes to the Andromeda Galaxy, and wait for Bob’s results. According with the MWI, the wave function never collapses, suppose that in one world Bob found the cat alive, in the other world, Bob found the cat dead. In one branch Bob send to Alice the message “ I found the cat alive” and in the other branch, Bob send to Alice the message “I found the cat dead”. If the splitting of the wave function is only local to Bob, Alice will receive at the same time both messages, so she thought that the cat is in a superposition of dead and alive. That is not possible, because the cat after opening the box, must be alive or dead. Conclusion, the wave function split also the Andromeda Galaxy. There are then, Two Alices, One that receive the message saying the cat is alive, and the other Alice who receive the message the cat is dead. To receive a message, the Andromeda Galaxy must be in the same light cone of Bob My question is:

1. Is this correct? The Andromeda Galaxy also split?

2. The splitting universe is only what is in Bob’s future light cone ? Or also the whole universe including those zones outside Bob’s light cone also split?

3. According with the MWI, the energy is conserved, the energy of the new branches of the wave function comes at expense of the already existing branches. What is the mechanism by which the new branches take the energy of the existing ones before performing the quantum experiment?

First you wrote

the wave function never collapses

Then you wrote

the cat after opening the box, must be alive or dead.

If you make two assumptions that directly contradict each other, you can conclude anything you like.

• It might not have been worded perfectly by the OP, but I don't think their question has a contradiction. Even in many worlds, it is true that Bob will observe the cat to be either alive or dead (not a superposition), each possibility leads to a branch, so the next step of the OP is correct: "In one branch Bob send to Alice the message “ I found the cat alive” and in the other branch, Bob send to Alice the message “I found the cat dead”. Commented Aug 7 at 19:23
• @Andrew Nobody has ever observed any branches of the universe. MWI simply doesn't want to understand that quantum mechanics is an ensemble theory. It's the ensemble theory of experiments, not the ensemble theory of the entire universe. There is absolutely no need to split the universe into two every time you want to measure a quantum. A measurement is the irreversible exchange of a single quantum of energy. That's it. We are talking about 1e-19J or much less that gets exchanged between two systems. That the entire universe splits when that happens is just a really bad campfire story. Commented Aug 7 at 19:54
• @Andrew: "Even in many worlds, it is true that Bob will observe the cat to be either alive or dead (not a superposition)". Perhaps you are using the label MWI in some unconventional way. In the usual meaning, there is no collapse, the state evolves unitarily, and there is no reason to think that it ever takes on any given value. Could you elaborate on what you mean by MWI? Commented Aug 7 at 20:28