And because if every outcome happens the probabilities of those outcomes are meaningless, and those probabilities are the predictive content of a quantum mechanical theory. It's an "interpretation" that requires you to ditch the entire value of the thing you're "interpreting". You don't need to know anything about QM other than that it has been empirically tested and is probabilistic in nature to reject the many worlds interpretation on this basis.
Each time I mention this online I state it more confidently, in the hope that some day someone will Cunningham's law me and change my mind. If I haven't committed some gross misunderstanding it's disappointing that so many physicists fall for such obvious bunk. I've already seen the attempted arguments listed at [1] and none of them are remotely convincing.
Hey if you’ve got David Deutsch dead to rights you should book a meeting and have him hand you his Fellowship in the Royal Society.
I’m not a physicist but I am an interested layman, I’m pretty sure I’ll catch wind of the Nobel Prize you’d win for proving him wrong about everything.
This isn't some unique insight of mine. There's a section about it in the wikipedia page for MWI, which I linked in my comment. Everett himself referenced the problem and attempted, unconvincingly, to argue around it in his original paper.
The mystery to me is why the obvious flaw in the idea hasn't killed it dead for so many smart people, such as David Deutsch. Instead they engage in bizarre logical contortions to try and recover the Born probabilities and some shadow of a meaning for them. If you think there's some actual merit in their attempts, listed at the wiki link I pasted, I'm all ears.
Right, it’s well known that if you’re committed to getting probabilities out of amplitudes things go off the rails. Everett himself couldn’t go the full way.
Fully deterministic, you see the part of the wave function that you see. You’re entangled with the apparatus.
Deutsch, and his protege Marletto go the whole way: no free will, no arrow of time, no subjective human experience at all.
Now? No measurement problem. No interpretations of collapse.
These people have decided that the subjective experience of observing an experiment is of secondary importance to clean math.
I appreciate that “you and I don’t exist in any way we’d recognize it” is a big pill to swallow, but I find the idea that humans looking in microscopes mutates the universe a bigger pill.
Superdeterminism (a bad name for ordinary determinism plus a ridiculous unspecified mechanism that links the very thoughts and intentions of an oberver to the system being observed) is even worse. MWI having thrown the baby out with the bathwater, superdeterminism then discards the entire building and everyone living in it. You can "explain" anything with a theory of this nature just as you can with intelligent design. It has no value as an intepretation of a perfectly well functioning mathematical framework like QM.
And the question here is one of interpretation. You say that MWI gives you "clean math" but this isn't about the maths. The maths of quantum mechanics is what it is regardless of how you interpret it. Whether the Schrödinger equation describes the evolution of the system state and observation is a state vector collapse, or the Schrödinger equation describes the evolution of a multiverse and the apparent state vector collapse is an artifact of distinct outcomes decohering, the maths is exactly the same. MWI's claim that it's somehow "mathematically cleaner" or "just what the maths is saying" is nonsense. It's there in the name. It's an interpretation.
QM is a highly effective theory (or rather framework for theories) that has been tested to the umpteenth degree. The question of intepretation is a philosophical one more that a mathematical one, and certainly fascinating. To my mind a "good" interpretation would have to give some actual meaning to the functional components of the theory. If QM predicts something will happen 30% of the time and I test it and it happens 30% of the time, an interpretation that fails to give a meaning to that predictable, observed fact is no use to me.
You seem to think the problem others have with your preferred interpretations is that they are too small-minded to accept that reality is the way these ideas imply. This isn't the case at all. I don't find "free will" an interesting concept and I'm perfectly happy to contemplate a multiverse, deterministic or otherwise, if that's what the scientific method leads us to. What I'm not happy to do is to launch off into a world of wacky, unfalsifiable notions that remove meaning from our existing theories rather than adding it.
I could equally well make claims about the psychology of MWI's adherents, suggesting emotional explanations for why they seem bound to make ever more absurd claims in defence of their idea rather than accepting that it's flawed. I won't, though, because doing that is arrogant and presumptuous.
I’m a seriously interested layman at best, so I could be failing to understand some of the subtleties, if so I apologize.
I’ve got no agenda around Everett’s initial idea and monograph being the end state. To your point, there are some known flaws with his initial formulation.
I find the idea that QM needs an interpretation absurd, MWI was a step on the path to that way of thinking. At a high level, the notion that all possible outcomes of an observable-producing operator on the wave function are equally “real” is clarifying.
I tend to agree with Deutsch and Marletto that “that which is admissible is admitted”.
It’s possible we’re in violent agreement.
QM, and more specifically QEM and QCD make wildly accurate predictions. As long as no one is talking about a causal structure unique to “consciousness” or some ridiculous narcissism like that, I’m very satisfied to rely on the falsifiable and well-tested laws.
Each time I mention this online I state it more confidently, in the hope that some day someone will Cunningham's law me and change my mind. If I haven't committed some gross misunderstanding it's disappointing that so many physicists fall for such obvious bunk. I've already seen the attempted arguments listed at [1] and none of them are remotely convincing.
[1] https://en.wikipedia.org/wiki/Many-worlds_interpretation#Pro...