On Wednesday, November 22, 2023 at 6:23:48 AM UTC-6 John Clark wrote: On Tue, Nov 21, 2023 at 7:45 PM Brent Meeker <meeke...@gmail.com> wrote:
>> There is plenty of direct evidence that quantum weirdness exists, even the father of the Copenhagen Interpretation Niels Bohr admitted that "*Anyone who is not shocked by Quantum theory does not understand it *". Something must be behind all that strangeness and whatever it is it must be odd, very very odd. Yes, many world's idea is ridiculous, but is it ridiculous enough to be true? If it's not then something even more ridiculous is. As for the Copenhagen interpretation, I don't think it's ridiculous, I think it's incoherent, and if you ask 10 adherents what it's saying you'll get 12 completely different answers, but they all boil down to "*just give up, don't even try to figure out what's going on*". But I think one must try. * > I think that's very unfair to Bohr. His basic observation was that we do science in a classical world of necessity.* Bohr was a great scientist but I think he was a lousy philosopher. Bohr thought there was a mystical interface between quantum events and conscious awareness, some call it the "Heisenberg Cut", but neither Bohr nor Heisenberg could explain the mechanism behind this mysterious phenomenon nor could they say exactly, or even approximately, where the hell the dividing line between the classical world and the quantum world is. By contrast Many Worlds has no problem whatsoever explaining the mechanism behind the Heisenberg cut or where the dividing line is because the Heisenberg cut does not exist and there is no dividing line, everything is quantum mechanical including the entire universe. I think this is the reason the Many Worlds interpretation is more popular among cosmologists than among scientists in general. The Heisenberg cut is a weakness with the Copenhagen Interpretation. However, all interpretations of QM when chased down their rabbit holes lead to nests of problems that fail to close. LC > *Only in a classical world can we make measurements and keep records that we can agree on. * But the Copenhagen adherents can't agree even among themselves what a "measurement" is or what a "record" means, but Many Worlds people are in agreement, all measurements are a change in a quantum state but a quantum change is not necessarily a measurement. > *when we study the microscopic world we must use quantum mechanics, but our instruments must be classical. * We can pretend our instruments are classical, in our everyday life we can pretend that everything is classical, but we've known for nearly a century that is just a useful lie we tell ourselves because reality is not classical, it is quantum mechanical. *> You can treat a baseball as a quantum system composed of elementary particles; but your measurements on it must still give classical values. * As I said before, you can live your entire life by pretending that classical physics is all there is and in fact billions of people have had successful lives doing so, but that doesn't make it true. In theory classical measurements can be exact, but quantum measurements cannot be even in theory. If we wish to study the fundamental nature of reality we're going to need to perform experiments with things when they are in very exotic conditions that we will never encounter in everyday life, and when we perform these difficult experiments we find the things get weird, very very weird, and that demands an explanation. And waving your hands and saying there is a Heisenberg cut is not an explanation. * > Since the development of decoherence theory this boundary can be quantified in terms vanishing of cross-terms in a reduced density matrix. * Forget theory, every time the precision of our quantum *EXPERIMENTS* improves the lower limit of this mythical boundary between the classical world and the quantum world gets larger, I think it's as large as the entire universe. > *What is left unexplained, in MWI as well as Copenhagen, is the instantiation of a random result with probability proportional to the diagonal elements of the reduced density matrix.* If the concept of "probability" is to make any sense and not be paradoxical it must be a real number between 0 and 1, and all the probabilities in a given situation must add up to exactly 1. Gleason's theorem proved that given those restraints, probability can always be expressed by the density matrix, that is to say the Born Rule. So the real question is; Schrodinger's equation is completely deterministic so why do we need probability at all? The Copenhagen people have a range of answers to that question, some say Schrodinger's equation needs to be modified by adding a random element, but they can't agree on exactly what it should be, others say it is improper to even ask that question, but they can't agree among themselves exactly why it is improper. The Many Worlds people have a clear and simple explanation, until you open the box and look you have insufficient information to know for certain if you are in the branch of the Multiverse where Schrodinger's cat is alive or the branch in which the poor cat is dead. Before you open the box all you can do is play the odds, and the Born Rule tells you the way to make the best guess possible. John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis> bqp -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/b6f48c98-d5c1-4d33-b287-cccdae80731dn%40googlegroups.com.
