[ExI] Criticisms of Many Worlds Interpretation (MWI)

Sat Sep 16 14:11:54 UTC 2023

On Fri, Sep 15, 2023, 11:29 PM Stuart LaForge <avant at sollegro.com> wrote:

> On 2023-09-15 05:29, Jason Resch wrote:
> > On Fri, Sep 15, 2023, 12:16 AM Stuart LaForge via extropy-chat
> > <extropy-chat at lists.extropy.org> wrote:
> >> 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
> >
> > How is this experiment any different from any single photons
> > interferometer experiment (where we say, replace the bomb with a red
> > or blue stained piece of glass) and use photons from a red light
> > laser, and use photon arrival locations to infer the color of the
> > glass placed in the path of one of the photons?
>
> It's not different. The bomb detector was a thought experiment, but
> since physicists didn't want actual bombs going off in their lab, they
> confirmed the predictions of the thought experiment using an experiment
> very similar to one you discuss here.
>

Ahh okay. Scientists are always adding bombs to their thought experiments
to make them more vivid. Schrodinger's cat originally used a bunch of gun
powder rather than some poison.

> > It's less explosive than a bomb (just an explosion of some IR photons
> > after the photon gets absorbed by the blue glass). But the outcomes
> > are the same.
> >
> > It also seems to be equivalent to the two slit single electrons
> > experiment where we put a detector at only one slit and don't observe
> > the electron there.
>
> Yes, the two-slit single-electron experiment with a detector at one slit
> is pretty close to the bomb tester.

��

> > I haven't seen people say before that these experiments confirm MW.
>
> I wouldn't say confirm, but merely add credence to, like a larger
> posterior probability. Incidentally, the authors of the original
> experiment say by way of explanation on
> https://www.tau.ac.il/~vaidman/lvhp/m28.pdfpage 993 of their 1993 paper:
>

Thank you for this reference.

> "In the MWI there is no collapse and all "branches" of the photon's
> state (5) are real. These
> three branches correspond to three different "worlds." In one world the
> photon is scattered by the object, and in two others it does not. Since
> all
> worlds take place in the physical universe, we cannot say that nothing
> has
> "touched" the object. We get information about the object without
> touching it in one world, but we "pay" the price of interacting with the
> object in the other world."
>
> https://www.tau.ac.il/~vaidman/lvhp/m28.pdf

I like putting it that way, it is certainly makes the unobserved
outcome/universe seem far more real (the other world gives us information
about a bomb) as compared with merely seeing some interference fringes in a
shadow.

>
> > They do, of course, confirm a superposition of particle positions, but
> > that has never been the issue with CI. CI accepts the superposition,
> > it only adds that it disappears after an observation is made, whatever
> > that may be, even if the observation happens to be "not observing an
> > electron go through the right slit" or not observing an explosion of
> > IR photons in the blue stained glass.
>
> Yes but how CI and MWI resolve the superposition is at the crux of their
> difference. Both interpretations agree that the superposition of a
> quantum 6-sided die would be a linear sum of the states 1 through 6:
>
> |1> + |2> + |3> + |4> + |5> + |6>
>
> The difference happens when a measurement is made. Lets say you roll the
> die and observe a "6". In CI, that means the terms |1> + |2> + |3> + |4>
> + |5> of the superposition, which were actual states a moment ago, are
> destroyed or simply cease to exist.
>
> In MWI, however, when you make an observation, the superposition simply
> separates into its component states with each sorting into their own
> timelines: A|1>, B|2>, C|3>, D|4>, E|5>, and F|6>. So if you observe a
> "6", you discover that you are observer "F" in the F timeline.
>

And presumably there is some time delay between a bomb exploding and the
observer becoming aware of it (light travels only 1 foot per nanosecond) so
there could be a significant macroscopic difference before observation
causes collapse and makes the component of the wave function with the
explosion suddenly disappear. Especially if the nearest conscious observer
is far away. Let's say this experiment was done on the moon. Then both
outcomes would last for a second after the bomb exploded (before
observation by us on Earth collapsed it to one possibility).

>
> > So I am curious what you see in the Elitzur-Vaidman bomb test that
> > implies MW. (If it's anything above and beyond the other superposition
> > affirming experiments I mention above).
>
> The Elitzur-Vaidman bomb tester and the experiments you mention above
> are not affirming superpositions, they are affirming that they are
> superpositions of real states. Only something real can cause something
> to happen in the real world. If something counterfactual is causing
> observable events in the real world, that counterfactual thing has to
> real too. It's just real somewhere else.
>

They makes sense. Deutsch was making a similar argument that the shadow
photons from other universes cause the real effect of a complex shadow
pattern we observe in our world. So we know they must be real. I've never
understood the anti-realist position that some advocates of CI or QB have
taken. It just seems like complete denialism to me.

Jason
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