`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.`

Brent 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 Ican understand why the Elitzur–Vaidman bomb tester works if there isno other world but this one. The Copenhagen interpretation peoplewould say that I should just treat mathematics as a black box andaccept the results of the calculation and not even try to understandwhat'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>iws On Sat, Nov 18, 2023, 6:58 AM John Clark <johnkcl...@gmail.com> wrote: /I read an article called The multiverse is unscientific nonsense <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 because:* *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 cosmology. * * * *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* *=========* lis * * --You received this message because you are subscribed to the GoogleGroups "Everything List" group.To unsubscribe from this group and stop receiving emails from it, sendan email to everything-list+unsubscr...@googlegroups.com.To view this discussion on the web visithttps://groups.google.com/d/msgid/everything-list/CAJPayv2nETBQAqcrE4exjAjhhOi%2BRPfo7W4M3C_PbZEmk%3DwE%3Dg%40mail.gmail.com<https://groups.google.com/d/msgid/everything-list/CAJPayv2nETBQAqcrE4exjAjhhOi%2BRPfo7W4M3C_PbZEmk%3DwE%3Dg%40mail.gmail.com?utm_medium=email&utm_source=footer>.

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