The important question here is how do you know you find yourself in the cat universe more often? How can that possibly be measured? It's a difficult question when it comes to conscious experience.

Imagine instead of a single experimenter observing a billion possible outcomes, a billion experimenters observing a single possible outcome.

I propose to measure this by writing down the results on a piece of paper, and then counting them.

The hope of MWI is to produce a simpler theory by eliminating an axiom. If this forces us to axiomatize "conscious observers" then it has already failed. Though I admit it may be fun to think about.

That's the funny thing, MWI works perfectly fine without conscious observers. It's predictions match other QM interpretations. The problem comes from introducing ourselves as a conscious observer and trying to understand what it means to be consciously aware of a single outcome.

Yeah, this is indeed the key question.

My guess would be that they are all consciously experienced, some more and some less. The alternative seems to be to say that they are so called "p-zombies". Very similiar to us, evolving according to the same laws, but not concious. But it's really up in the air.

Okay, let me rephrase. Many Worlds states that there is no collapse; the entanglement continue to propagate. Many Worlds is the familiar label for saying there's entanglement, and that's it.

> 1. How does the Born rule arise?

> 2. More generally, how does randomness arise?

As you said, with Many Worlds there is no randomness. The multiverse is entirely deterministic. Randomness is a Copenhagen-like concept.

There is a "universe" with an alive cat and a "universe" with a dead cat. These universes have a certain waveform distribution.

Neither of these universe are any more real or extant than the other (they have the same magnitude).*

* Though consciousness and its observations seems to follow only one path. This is a peculiarity outside the realm of physics.

>* Though consciousness and its observations seems to follow only one path. This is a peculiarity outside the realm of physics.

Of course physics can answer this: the human minds on the different branches can't physically interact. They can't share memories. Each one is going to remember experiencing only its own branch.

Sure, but why am "I" the one and not the other?

Whether this is a problem or not depends on what your conception of consciousness/identity is. I see a conflict or unanswered problem there; you may not.

There's multiple, and each of them have their own experiences since the split. The other versions of yourself are basically other people that just happen to share a part of your history.

Wondering why you're a specific one of them and not the other seems equivalent to me to wondering why you're you and not some another person in our own world. I think it's an interesting question, but I'm not sure what an answer to it could possibly look like (since any answer that says why you're you somehow needs to work out differently for other people to explain why they're themselves too) which implies the question is malformed somehow. (If your consciousness were ... someone else, or even switched people it was tracking somehow, it's not like anyone would notice.)

> seems equivalent to me to wondering why you're you and not some another person in our own world.

Indeed.

Randomness is an empirical observation. Identically prepared quantum states, when measured, produce different experimental results, distributed probabilistically.

MWI's solution to this is to say the experiments are wrong, and the results are actually the same. It rejects empiricism to simplify the theory. But that's not good science.

> Neither of these universe are any more real or extant than the other (they have the same magnitude)

What is meant by "magnitude?" It can't be the measure of the wavefunction because those can easily be different, e.g. if the particle's decay probability is not 50%. This is the Born rule problem again.

If the universe is deterministic, how can there be entanglement or branching at all? What need is there for a multiverse if you have determinism?

It’s as if non-determinists aren’t sure that 2 doesn’t act like a 3 sometimes because of decoherence and so 2 + 3 = 6 as a result.

Where am I going wrong in this line of thinking? How could randomness be injected into a system without superpositioning of quarks? Is that literally the only way?

Is Hawking radiation the smoking gun we think it is?

Edit: I admit I am tired when posting but this topic is perhaps one of the most fascinating of all. I can’t stay away.

The waveform is deterministic. It does not "collapse" to a randomly chosen value; it continues to be all the values in perptuity.

It's like matrix multiplication: yes you can wind up with more elements after the operation, but the result as a whole is entirely deterministic.

If you defined matrix multiple multiplication where you collapsed the result down to a single unspecified vector, then you would have "randomness" (according to the selection).

Many worlds says "don't choose"; keep the entire matrix, and the results will get larger and larger.

The universe is not fundamentally rolling dice, though it appears that way from your perspective since you can only see a single slice of the matrix.

> This is a peculiarity outside the realm of physics.

So the “realm of physics” is now disconnected from empirical reality? Great.

> empirical reality

Unfortunately, yes. Empirical reality is limited by the empiricist.

Sure. But I wouldn't say it's outside the realm of physics.

I think more concisely, we don't understand it yet.

You will find answers to 1 and 2 in https://arxiv.org/abs/quant-ph/0503009