On Sat, Sep 5, 2020 at 11:29 AM 'Brent Meeker' via Everything List < everything-list@googlegroups.com> wrote:
> On 9/4/2020 4:00 PM, Bruce Kellett wrote: > > On Sat, Sep 5, 2020 at 5:37 AM 'Brent Meeker' via Everything List < > <everything-list@googlegroups.com>everything-list@googlegroups.com> wrote: > >> On 9/4/2020 4:43 AM, Bruce Kellett wrote: >> >> On Fri, Sep 4, 2020 at 9:32 PM smitra <smi...@zonnet.nl> wrote: >> >>> Even if the MWI is false and the wavefunction collapses to produce only >>> one of the possible outcomes with a probability given by the Born rule, >>> you'll still get all possibilities realized in a generic infinite >>> universe, whether it's spatially infinite or a universe that exists for >>> an infinite long time. >>> >>> The only way to find out what exists beyond the realm we've explored s >>> to do experiments. No philosophical reasoning about the interpretation >>> of probabilities can ever settle whether or not the universe is so large >>> or will exists for such a long time that another copy of me exists. >>> That's why these discussions are not so useful as an argument of whether >>> the MWI is correct or not. >>> >> >> >> I think something along those lines was Sean Carroll's answer to the >> points David Albert raised. Unfortunately, it doesn't wash! >> >> Applying the Born rule to the repeated measurement scenario tells you >> that the probability of the extreme branches is low; whereas, the idea that >> all possible outcomes occur on every trial trivially implies that the >> probability of the extreme cases is exactly one. The contradiction couldn't >> be more stark, and waffling about infinite universes isn't going to change >> that -- the theory gives two, mutually contradictory, results. >> >> >> But the probability of *observing* extreme cases isn't 1 for a given >> observer. >> > > > And the probability isn't 1/2^N for a given observer either. The observer > observes what he observes. Probability is relevant for predictions, not > post hoc observations. > > We are talking about the predictions of the theory, not the experiences of > individual observers. I think Sean tried this evasive tactic as well, and > Albert rightly pointed out that that just makes everything idexical, and > ultimately makes science impossible. > > And it is not just the extreme branches that have low probability. Given > the repeated measurement scenario we have been talking about, there are N > repetitions of the experiment, giving 2^N distinct binary sequences of > results. Applying the Born rule to each possible sequence shows that it has > probability 1/2^N. > > > But the theory isn't about the probability of a specific sequence, it's > about the probability of |up> vs |down> in the sequence without regard for > order. So there will, if the theory is correct, be many more sequences > with a frequency of |up> near some theoretically computed proportion |a|^2 > than sequences not near this proportion. > The theory is about the probabilitiies of observations. The observation in question here is a sequence of |up> / |down> results, given that the probability for each individual outcome is 0.5. If the theory cannot give a probability for the sequence, then multiply the probabilities for each particular result in your sequence of measurements. The number of sequences with particular proportions of up or down results is irrelevant for this calculation. Again, you are just attempting to divert attention from the obvious result that the Born rule calculation gives a different probability than expected when every outcome occurs for each measurement. In the Everett case, every possible sequence necessarily occurs. This does not happen in the genuine stochastic case, where only one (random) sequence is produced. Bruce Brent > > But if every result obtains on every trial, the probability of each > sequence is exactly one. In other words, Everett is incompatible with the > Born rule. You can abandon the Born rule if you like, or abandon the > Everettian idea of every outcome occurring on every trial, but you can't > have both. > > The twisting and turning we are seeing by participants on this list is not > going to alter this basic observation. > > 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 everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLRo26Q6booHiKNZr5yUPfJZeVQVjdvFpnPG6bvV2S-xQA%40mail.gmail.com.
