[lmm]

> How is the answer “everything that can happen does happen, just in an alternate universe that is identical except for the outcome of one single measurement” a parsimonious answer to the measurement problem?

Because it drops straight out of the schroedinger equation, which is something you were already believing.

Do you consider believing in distant galaxies, rather than a novel type of astronomical object, to be more or less parsimonious? It means multiplying the size of the universe by millions; nevertheless most of us accept it.

[jahnu]

And, I don't think that many-worlds even says that "everything that can happen does happen". It does say that a lot of branching goes on though :)

Might as well quote Sean Carroll again, he's an expert and I am not:

"The Schrödinger equation tells us that there's a wave function that evolves over time and then you can ask how I can divide that wave function into a set of decohered non-interacting worlds and those are the worlds that happen. It is nowhere close to saying everything happens. It is what is predicted by the Schrödinger equation That is what happens."

https://www.preposterousuniverse.com/podcast/2024/05/06/ama-...

Interestingly, people seem less bothered by the idea that the universe might be infinite in size even though that has a similar feature that a lot of things happen. So it just seems to me that the discomfort is people worrying about the idea that there are copies of themselves out there somewhere when they really shouldn't. At least no more than if in an infinite universe there would also be infinite repetition and infinite identical "yous". This is starting to sound like a Douglas Adams bit now :D

[SAI_Peregrinus]

Infinite "yous" does not follow from an infinite universe unless one adds a constraint on the distribution of matter in that universe. E.g. one could have a finite observable universe that we see, then an infinite expanse of cheese. No extra "you", unless you're cheese. Infinite does not imply random.

[skirmish]

But if I observe a Shroedinger's cat after opening the box every morning, I do get at least duplicated. Repeat this lots of times, and MWI says there are for sure 2^n copies of me as the lowest estimate.

Counting all daily QM-influenced events everybody experiences (a cosmic ray either passed through me or decayed before it reached me, a radon atom either decayed in the air right next to me or not when I went to my cellar etc.), I think it is fair to say there are nearly infinite copies of you in various multiverse branches (of course, some who collected lots of radioactive decay events are already dead from cancer by now).

[n4r9]

If you observe the position of a system whose quantum wavefunction has non-zero probability over a non-empty interval, then according to MWI would you not create an uncountable infinity of duplicates of yourself?

Arguably this would be limited by the reporting accuracy of your equipment, but perhaps the thought experiment can be tweaked to get around that...