[ExI] Criticisms of Many Worlds Interpretation (MWI)

[Jason Resch]

On Thu, Sep 14, 2023 at 12:24 PM BillK via extropy-chat <
extropy-chat at lists.extropy.org> 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.
> One AI did add the caution :
> It is worth noting that alternative interpretations of quantum
> mechanics, such as the Copenhagen interpretation or the pilot-wave
> theory, have their own merits and drawbacks.


Pilot-wave theory is also a many-worlds theory. Except it further
stipulates that the other people in those other branches are
philosophical zombies.

And as I mentioned in the other thread, CI is a different theory, since it
says matter doesn't always obey the Shrodinger equation.


> The choice between
> interpretations often hinges on personal preference, philosophical
> considerations, and the specific problem being addressed.
>

One can accept that the Shrodinger equation is true always, or they can
deny that it is true always. If it is true always, that implies
many-worlds. I don't see where philosophy enters the picture. Theories are
either true or false, and we have gathered substantial evidence that the
Shrodinger equation is always true, and never found any evidence implying
it ever stops being true.


> ----------
> I interpret that as saying that as yet quantum mechanics still has
> many theoretical difficulties.  :)
>
> BillK
> -------------------------------
>
> MWI Criticism Summary
>
> The Many Worlds Interpretation (MWI) is a controversial interpretation
> of quantum mechanics that was proposed by physicist Hugh Everett III
> in 1957.


Erwin Shrodinger actually proposed it a few years before Everett.

“Schrödinger also had the basic idea of parallel universes shortly before
Everett, but he didn't publish it. He mentioned it in a lecture in Dublin,
in which he predicted that the audience would think he was crazy. Isn't
that a strange assertion coming from a Nobel Prize winner—that he feared
being considered crazy for claiming that his equation, the one that he won
the Nobel Prize for, might be true.” -- David Deutsch


> It suggests that every possible outcome of a quantum
> measurement actually occurs in a separate universe, resulting in a
> branching or splitting of reality. While the MWI has gained some
> popularity among physicists, it also faces significant criticism and
> challenges from various perspectives.
>
> One of the main criticisms of the MWI is its lack of testability and
> falsifiability.


It's those who maintain that the Shrodinger equation doesn't always hold
that have a problem with testability. They haven't even given a
mathematical formulation for when/how/why the universe stops obeying the
Schrodinger equation.


> 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 is false, see the page I cited from Tegmark's book on falsifiability:
https://archive.org/details/ourmathematicalu0000tegm_o1e8/page/124/mode/2up?q=%22Are+theories%22


> This lack
> of empirical evidence raises concerns about the scientific validity of
> the MWI as it deviates from the traditional scientific method.
>

MW is simply QM. If this claim is true about MW, it must be true of QM, yet
no one says that out loud.


>
> Another criticism revolves around the issue of probability. In the
> MWI, probabilities are assigned to different outcomes based on their
> relative frequency across all possible universes. However, this
> approach raises questions about how probabilities can be meaningfully
> defined when there are an infinite number of universes. Critics argue
> that without a clear framework for assigning probabilities, the MWI
> fails to provide a satisfactory explanation for observed phenomena.
>

On the contrary, MW is the only theory that provides a mathematical
explanation for why the Born rule works (via Gleason's theorem). The other
interpretations simply assume the Born rule but fail to explain it or why
it gives the observed probabilities.


>
> Furthermore, the MWI faces challenges in explaining macroscopic
> observations and classical behavior.


Not at all. This is covered completely under the explanation of decoherence.
https://en.wikipedia.org/wiki/Quantum_decoherence


> While it may be able to account
> for quantum phenomena at the microscopic level, it struggles to
> explain why we observe a classical world with definite outcomes rather
> than a superposition of possibilities.


It doesn't. See my "QM primer":
https://docs.google.com/presentation/d/1NThhVw4hrPxOueAQEwr-MNfIQiBaPd9o/edit?usp=sharing&ouid=109779696990142678208&rtpof=true&sd=true


> Critics argue that the MWI
> fails to provide a convincing mechanism for the emergence of classical
> behavior from quantum principles.
>

See my previous two replies.


>
> Additionally, some critics question the philosophical implications of
> the MWI. The theory suggests that every possible outcome exists in a
> separate universe, leading to an infinite number of parallel
> realities.


It is simply the idea that wave function evolves according to the
Shrodinger equation. All other interpretations accept the wave function,
they just say it stops following the Shrodinger equation under certain (not
well defined) conditions. But there is no evidence it ever stops evolving
according to the Shrodinger equation.


> This idea raises philosophical concerns about personal
> identity and consciousness.


And here is, I think, lies the real source of all the objections to
many-worlds. People want to be unique, and not worry about all their other
duplicates out there. It's not a real objection, it's an emotional one.



> Critics argue that it is difficult to
> reconcile our subjective experience with the notion that there are
> countless versions of ourselves in different universes.
>

I don't see how.


>
> Moreover, the MWI has been criticized for its complexity and lack of
> simplicity. Occam's razor, a principle in science that favors simpler
> explanations over more complex ones, is often invoked against the MWI.
>

Occam's razor is about simpler theories, not entities in nature. MW is the
simplest theory.


> Critics argue that the theory introduces unnecessary complexity by
> postulating the existence of an infinite number of parallel universes,
> without providing a clear justification for such a hypothesis.
>

It follows from the equations, that is the justification.

Jason


>
> In conclusion, while the Many Worlds Interpretation has gained
> attention and support from some physicists, it also faces significant
> criticism. The lack of testability and falsifiability, challenges in
> defining probabilities, difficulties in explaining macroscopic
> observations, philosophical implications, and complexity concerns are
> among the main criticisms raised against the MWI.
> -------------------------------------
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