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Yes, this is the emperor's new clothes of MWI, and it doesn't take any specialist knowledge to see it. Quantum mechanical theories produce probabilities for thi

Yes, this is the emperor's new clothes of MWI, and it doesn't take any specialist knowledge to see it. Quantum mechanical theories produce probabilities for things happening. We can conduct repeated experiments and verify those probabilities against the results. If every outcome actually happens, there is no longer any place for those probabilities. It is meaningless to talk about the relative probabilities of events A and B happening if both A and B actually happen, deterministically. These probabilities aren't just numbers produced by the theory, they are the predictive content of the theory, the very thing we're supposed to be interpreting, and MWI has no place for them. The way this problem is often discussed is to talk about "recovering the Born probabilities", which frames the problem wrongly. It makes it sound like the problem is that MWI merely isn't producing some numbers we like. MWI proponents respond to this by going through absurd contortions involving things like decision theory as a way of causing the desired numbers to pop out of a calculation. But the problem isn't "recovering the probabilities". The problem isn't finding some way of performing a calculation that results in these particular numbers. The problem is that these probabilities have no physical meaning in MWI, and it's a catastrophic problem because those probabilities have a very real meaning in the actual world as we observe it. It really is as simple as "how can all the things happen at once when we know some of the things are more likely than others?" And, like "why is the emperor naked?" it's a question that can literally be asked by a child. An "interpretation" that renders the core predictive content of the theory meaningless is a bad interpretation and a waste of everyone's time.

sebzim4500 4y ago
I agree with a lot of what you have said, but I would strongly disagree with your conclusion. >An "interpretation" that renders the core predictive content of the theory meaningless is a bad interpretation and a waste of everyone's time. Given that the different interpretations do not make different predictions, the only relevant way to judge them is to ask the question "is X interpretation a useful way to think about the universe". This can be answered empirically, practitioners of both MWI and CI have both made important advances in quantum physics, therefore neither are a waste of anybody's time. There is a reason why students generally get taught both, there is nothing wrong with having multiple ways to think about things.

sebzim4500 4y ago

I agree with a lot of what you have said, but I would strongly disagree with your conclusion. >An "interpretation" that renders the core predictive content of the theory meaningless is a bad interpretation and a waste of everyone's time. Given that the different interpretations do not make different predictions, the only relevant way to judge them is to ask the question "is X interpretation a useful way to think about the universe". This can be answered empirically, practitioners of both MWI and CI have both made important advances in quantum physics, therefore neither are a waste of anybody's time. There is a reason why students generally get taught both, there is nothing wrong with having multiple ways to think about things.