On Sun, Jan 5, 2025 at 7:46 AM John Clark <[email protected]> wrote:
> > *About a month ago Sean Carroll uploaded a very good video explaining the > Many Worlds theory, but it's over an hour long so I know there's about as > much chance of a dilettante such as yourself of actually watching it is > there is of you reading a post of mine if it's longer than about 100 words. > * > > *The Many Worlds of Quantum Mechanics | Dr. Sean Carroll > <https://www.youtube.com/watch?v=FTmxIUz21bo&t=8s> * > I watched this video, but it is not as comprehensive as Carroll's book "Something Deeply Hidden". However, something came up in the question period that might warrant a comment. Talking about the Born rule, Carroll justifies it by saying that if you measure the spin of 1000 unpolarized particles, you get 2^1000 different UP-DOWN sequences. However, the vast majority of these sequences will show proportions of UP vs DOWN close to the Born rule prediction of 50/50. In the limit, if such a limit makes sense, the proportion of sequences that show marked deviations from the Born Rule proportions will form a set of measure zero, and can be ignored. That is just the law of large numbers at work, and is all very well if the amplitudes are such that the Born probabilities are equal to 0.5. But it is easy to rotate your S-G magnets so that the Born probabilities are quite different, say, 0.9-Up to 0.1-DOWN. Now take 1000 trials again. According to Everett, you necessarily get the same 2^1000 sequences of UP-DOWN that you had before. The law of large numbers will then tell you that the majority of these will have approximately a 50/50 UP/DOWN split, which is grossly in violation of the Born rule result of a 90/10 split. In other words, MWI. or Everettian QM. has a problem reproducing the Born rule. It works in the simple case of equal probabilities, but fails miserably once one departs substantially from equal probabilities. Bruce -- 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 [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/CAFxXSLR0eNrjuTi-8vt_jMsCe3H7qB4UF84H6n6%3Dp8MMYaY4Gg%40mail.gmail.com.
