[ExI] Criticisms of Many Worlds Interpretation (MWI)

[Stuart LaForge]

On 2023-09-14 10:22, BillK via extropy-chat wrote:
> I thought it would be useful to get a summary of the MWI objections,
> so I asked around in the AI members club. All the responses were
> fairly similar, so I have copied the answer I liked best below.
[snip]
> I interpret that as saying that as yet quantum mechanics still has
> many theoretical difficulties.  :)

Yes. Accounting for gravity being the most glaring difficulty.

> BillK
> -------------------------------
> 
> MWI Criticism Summary
[snip]
> One of the main criticisms of the MWI is its lack of testability and
> falsifiability. Since the theory posits the existence of an infinite
> number of parallel universes, each with different outcomes, it becomes
> impossible to experimentally verify or disprove this claim. This lack
> of empirical evidence raises concerns about the scientific validity of
> the MWI as it deviates from the traditional scientific method.

It might be testable. For example, I think the Elitzur-Vaidman bomb 
tester only makes sense if MWI is true.

https://en.wikipedia.org/wiki/Elitzur%E2%80%93Vaidman_bomb_tester
https://www.youtube.com/watch?v=byEaU9ILHmw
Basically the bomb detector works because a photon gets super-positioned 
into two routes by a beam splitter in a Mach-Zender interferometer and 
interferes with itself. If the bomb is a dud, then the photon will pass 
through the bomb and take both paths at once through the interferometer 
and will recombine at the 2nd beam splitter always getting detected at 
detector A due to constructive interference and never at detector B 
because of destructive interference.

But if bomb is live, it acts as a which way detector preventing the 
photon from entering a superposition and interfering with itself. This 
means that either the bomb will explode 50% of the time or it will hit 
either detector A or detector B 25% of the time each. If it hits 
detector A, then you you have no way of knowing if the bomb is live or a 
dud. But if it hits detector B, then you know it is a live bomb, because 
it did not take both paths at once and interfere with itself and it did 
not blow up the bomb.

This means that the counterfactual photon caused a counterfactual bomb 
to explode, destroying itself in the process, and preventing it from 
interfering with the observed photon. This causes the photon to only 
take one path, end up at detector B, and thereby prove that the bomb is 
live and not a dud. It would not make sense that the photon would not 
blow up the bomb and not interfere with itself unless something happened 
to the other photon. Stuff that does not happen should not be able to 
cause stuff to happen here. Unless the stuff that doesn't happen here 
happens in another universe and that is what causes stuff to happen 
here.

Stuart LaForge