On Fri, Mar 4, 2022 at 1:04 AM John Clark <johnkcl...@gmail.com> wrote:
> On Wed, Mar 2, 2022 at 7:05 PM Bruce Kellett <bhkellet...@gmail.com> > wrote: > > >> Many worlds can explain all known experimental results without >>> resorting to non-local influences because many worlds is not a >>> realistic theory. >>> >> >> > *In that case, if you believe that MWI is local, give me the local >> account of Bell-type correlations of spin measurements at spacelike >> separations.* >> > > OK, the key is understanding what "the collapse of the wave function" > means physically. Many Worlds says everything that is not forbidden is > mandatory so everything Schrodinger's wave equation does not rule out > does physically happen, so "collapse" just means that different solutions > to Schrodinger's equation are ... well... different. And the great virtue > of tautologies is that they're always true. Richard Feynman said all the > weirdness in quantum mechanics can be found in the 2 slit experiment, so I > will use that to illustrate the point. This is how I think Many Worlds > would describe the two-slit experiment and several variations of it. > I take the fact that you have changed the subject to a many worlds account of the two-slit experiment as clear evidence that you do not have a local many worlds account of the question at issue, namely, a local account of Bell-type correlations. Don't worry. No one else has such a local account either. Saibal's account below is every bit as non-local as the original quantum account. Many Worlds says that in the usual experiment the universe splits after the > photon passes the two slits because the 2 worlds are different, a photon in > one world went through the right slit and a photon in another world went > through the left slit. But when the photons hit the film they no longer > exist in either world, so the 2 worlds are identical once more, so the > universes fuse back together again. Looking back from that fused world we > find evidence that the photon went through slit X only and evidence it went > through slit Y only and this causes an interference pattern. There is > nothing special about an observer in any of this, the same thing would > happen if nobody looked at the film, or even if you used a brick wall > instead of film, because the important thing is not that the photon makes a > record (whatever that is) but simply that it is destroyed. Mind has > nothing to do with any of this so unlike the Copenhagen interpretation Many > Worlds doesn't need to explain it, or explain what “measurement" means, or > “record", or “observation", or “consciousness". That is a gargantuan > advantage! The key point is that worlds split when they become different > and merge when they become the same again. > You equivocate on the word "world". What you are really talking about here are just components of a superposed wave function. Such superposed components can interfere, whereas separate worlds (or branches) are disjoint and cannot interfere. Now do the two-slit experiment again but instead of using film to stop the > photon after it passes the slits let the photon head out into infinite > space. If Many Worlds is correct then the entire universe splits into 2 > when the photon hit's the 2 slits and never recombines. There is nothing > special about you the observer, you split just like everything else, you > know that the photon went through one and only one slit, but you don't know > which one. The 2 slit experiment can be set up in such a way that you can > tell which slit the photon went through, but if you do that then the > photons will not produce an interference pattern on the film. This is > because even after the photon hits the film in both worlds and is destroyed > the worlds remain different because in one the physical memory pattern in > your brain encodes that the photon went through slot right and in the > other slot left, so the different worlds don’t merge back together, and so > no interference pattern is seen in either world. > > Many Worlds predicts that even if you could devise an experiment that > could detect which slit the photon went through without changing the photon > in any way (it would pose enormous technical challenges but I think that > might be possible, perhaps by using Stimulated Emission) there still would > be no interference pattern because although the photons are identical the > universes would still be different because your brain has different memory > patterns which means the physical structure of your brain is still > different in the two universes. Separate worlds only emerge if there is a > difference between them, if the worlds evolve in such a way that the > difference disappears then re-coherence occurs. For obvious reasons > re-coherence can only occur if the 2 worlds are only very very slightly > different and have only been separated for a short time, and that's why > experiments of this sort are difficult and it explains why in our everyday > world we don’t see macro objects becoming entangled, and even atoms aren’t > usually entangled for long at room temperature. > > *> I will salute you if you can do this, because no one else has ever >> managed in the past* > > > As much as I'd like to take the credit for it nothing I said is original > with me, I just used my own words to describe what other people have > done. > No, it is not original. And it is not a local account of the correlations under discussion either -- so no lollipops from me!. Bruce > > *Realism is completely beside the point.* > > > Nope. If Many Worlds was a realistic theory and thus a photon always > remained in one and only one definite state both before and after passing > a slit and before and after a measurement is made then none of the above could > possibly work. > -- 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/CAFxXSLT_uiazcjXm7089RVy_8xP7S%2BThtaY4x4gS4TAWQ-sT_w%40mail.gmail.com.
