A good letter to Brandes, but I think you use Schroedinger's cat to much.  If one imagines a clock attached to the poison vial, then it's clear that on opening the box you will see an alive or dead cat and a running clock or one that marks the exact time in the past that the cat was killed.  So decoherence theory has answered the problem of why we don't see superpositions of alive and dead cats.

Personally I'm just as happy (and unhappy) to say that all those worlds we don't see simply never exist and while exactly when they don't exist (as Everett would have it) is puzzling. it's less so than an infinity of worlds that sort of exist but in some orthogonal way that they can never have any effect.  The Elitzur–Vaidman bomb tester works because it has certain probability of working.  Are you so wedded to a frequentist interpretation of probability that you must imagine existing copies of it not working?

I notice that you never entertain QBism and seem to dismiss it as "just not an intuitively satisfying theory; it doesn't have pictures for my mind."  To which I think, "so what; did you have a picture of inertia in Newtonian mechanics?"  Intuition comes from use and familiarity.


On 11/18/2023 7:15 AM, John Clark wrote:
On Sat, Nov 18, 2023 at 9:17 AM Jason Resch <jasonre...@gmail.com> wrote:

    /> That's kind of him to reply.Aren't functional quantum computers
    proof that atoms can be in two places at once?/

I would say so but apparently he would not. And I'll be damned if I can understand why the Elitzur–Vaidman bomb tester works if there is no other world but this one. The Copenhagen interpretation people would say that I should just treat mathematics as a black box and accept the results of the calculation and not even try to understand what's actually going on. But I'd like to at least try.

John K Clark    See what's on my new list at Extropolis <https://groups.google.com/g/extropolis>

    On Sat, Nov 18, 2023, 6:58 AM John Clark <johnkcl...@gmail.com> wrote:

        /I read an article called The multiverse is unscientific
<https://iai.tv/articles/the-multiverse-is-unscientific-nonsense-auid-2668> by
        Jacob Barandes, a lecturer in physics at Harvard University,
        and I wrote a letter to professor //Barandes commenting on it.
        He responded with a very polite letter saying he read it and
        appreciated what I said but didn't have time to comment
        further. This is the letter I sent: /

        *Hello Professor Barandes
        *I read your article The multiverse is unscientific nonsense
        with interest and I have a few comments:*
        *Nobody is claiming that the existence of the multiverse is a
        provenfact, but I think the idea needs to be taken seriously

        *1) Unlike Bohr's Copenhagen interpretation, the Many
        Worlds theory is clear about what it's saying. *
        *2) It is self consistent and conforms with all known
        experimental results. *
        *3) It has no need to speculate about new physics as objective
        wave collapse theories like GRW do.*
        *4) It doesn't have to explain what consciousness or a
        measurement is because they have nothing to do with it, all it
        needs is Schrodinger's equation.
        *I don't see how you can explain counterfactual quantum
        reasoning and such things as the Elitzur–Vaidman bomb tester
        without making use of many worlds. Hugh Everett would say that
        by having a bomb in a universe we are not in explode we can
        tell if a bomb that is in the branch of the multiverse that we
        are in is a dud or is a live fully functional bomb.  You say
        that many worlds needs to account for probability and that's
        true, but then you say many worlds demands that some worlds
        have “higher probabilities than others" but that is incorrect.
        According to many worlds there is one and only one universe
        for every quantum state that is not forbidden by the laws of
        physics. So when you flip a coin the universe splits many more
        times than twice because there are a vast number, perhaps an
        infinite number, of places where a coin could land, but you
        are not interested in exactly where the coin lands, you're
        only interested if it lands heads or tails. And we've known
        for centuries how to obtain a useful probability between any
        two points on the continuous bell curve even though the
        continuous curve is made up of an unaccountably infinite
        number of points, all we need to do is perform a simple
        integration to figure out which part of the bell curve we're
        most likely on.
        *Yes, that's a lot of worlds, but you shouldn't object that
        the multiverse really couldn't be that big unless you are a
        stout defender of the idea that the universe must be
        finite, because even if many worlds turns out to be untrue the
        universe could still be infinite and an infinity plus an
        infinity is still the an infinity with the same Aleph number.
        Even if there is only one universe if it's infinite then a
        finite distance away there must be a doppelgänger of you
        because, although there are a huge number of quantum states
        your body could be in, that number is not infinite, but the
        universe is. *
        *And Occam's razor is about an economy of assumptions not an
        economy of results.  As for the "Tower of assumptions" many
        worlds is supposed to be based on, the only assumption that
        many worlds makes is that Schrodinger's equation means what it
        says, and it says nothing about the wave function collapsing.
        I would maintain that many worlds is bare-bones no-nonsense
        quantum mechanics with none of the silly bells and whistles
        that other theories stick on that do nothing but get rid of
        those  pesky other worlds that keep cropping up that they
        personally dislike for some reason. And since Everett's time
        other worlds do seem to keep popping up and in completely
        unrelated fields, such as string theory and inflationary
        *You also ask what a “rational observer” is and how they ought
        to behave, and place bets on future events, given their
        self-locating uncertainty. I agree with David Hume who said
        that "ought" cannot be derived from "is", but "ought" can be
        derived from "want". So if an observer is a gambler that WANTS
        to make money but is irrational then he is absolutely
        guaranteed to lose all his money if he plays long enough,
        while a rational observer who knows how to make use of
        continuous probabilities is guaranteed to make money, or at
        least break even. Physicists WANT their ideas to be clear,
        have predictive power, and to conform with reality as
        described by experiment; therefore I think they OUGHT to
        embrace the many world's idea.
        *And yes there is a version of you and me that flips a coin 1
        million times and see heads every single time even though the
        coin is 100% fair, however it is extremely unlikely that we
        will find ourselves that far out on the bell curve, so I would
        be willing to bet a large sum of money that I will not see 1
        million heads in a row.  You also say that "the Dirac-von
        Neumann axioms don’t support oft-heard statements that an atom
        can be in two places at once, or that a cat can be alive and
        dead at the same time", but there are only two possibilities,
        either there is an alive cat and a dead cat in two different
        places or there is a live/dead cat that instantly snaps into
        being either alive or dead by the act of "measurement" even
        though the standard textbook Copenhagen interpretation can't
        say exactly what a measurement is, or even approximately what
        it is for that matter. In many worlds a measurement is simply
        any change in a quantum system, it makes no difference if that
        quantum system is a human being or an unconscious brick wall.
        So in that sense many worlds is totalitarian because
        everything that is not forbidden by the laws of Quantum
        Physics and General Relativity must exist.
        *You correctly point out that nobody has ever "seen an atom in
        two places at once, let alone a cat being both alive and
        dead", but nobody has ever seen infinite dimensional operators
        in Hilbert space that the Dirac-von Neumann axioms use either,
        all they've seen is ink on paper in mathematical books. And
        you can't get milk from the word "cow". *
        *I'll close by just saying although I believe there is
        considerable evidence in favor of the many worlds view I admit
        it falls far short of a proof, maybe tomorrow somebody will
        come up with a better idea but right now many worlds is the
        least bad quantum interpretation around. And speculation is
        not a dirty word, without it science would be moribund,
        Richard Feynman said science is imagination in a tight
        straight jacket and I agree with him.

        Best wishes

        John K Clark*


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