On Mon, Nov 18, 2024 at 10:05:56AM +1100, Bruce Kellett wrote: > On Mon, Nov 18, 2024 at 9:30 AM Russell Standish <[email protected]> > wrote: > > On Sat, Nov 16, 2024 at 03:52:25PM +1100, Bruce Kellett wrote: > > > > On Sat, Nov 16, 2024 at 3:28 PM Russell Standish <[email protected]> > wrote: > > > > On Sat, Nov 16, 2024 at 03:08:03PM +1100, Bruce Kellett wrote: > > > On Sat, Nov 16, 2024 at 2:41 PM Russell Standish < > [email protected] wrote: > > > > > > I don't think it requires this assumption. In fact "physically > real" > > > is a rather nebulous concept anyway. > > > > > > > > > If you want the 'other worlds' to be physically real, then the > original wave > > > function must be physically real. > > > > That's a non-sequitur. The 'other worlds' are as real as this one. > The > > reality of the wave function doesn't enter into it. > > > > > > It does if the wave function is purely epistemic. In other words, if it > is > > merely a means of calculating probabilities, then the supposed 'other > worlds' > > do not exist. The probabilities are the probability that one, and only > one, > > outcome is realized for each experiment. > > You've lost me here. Even if the wf is epistemic, it has no bearing on > whether other branches are as real as this one or not. > > > It does have a significant bearing on the reality of the other branches. One > of > the frequently stated arguments for many worlds is that it avoids the problem > of the wave function collapse. The collapse of the wave function is only a > problem if the wave function is a physical object, because then you run into > problems with instantaneous action at a distance or FTL physical action. If > the > wave function is purely epistemic, namely, nothing more than a summary of our > knowledge about the physical system, there is no problem with collapse, > because > the result of an experiment merely updates our knowledge, and the wave > function > is updated to reflect this change in knowledge. This is exactly what happens > in > classical probability. > > If the wave function is purely epistemic, there is no problem with collapse, > and the additional worlds that MWI introduces play no useful role and can > readily be discarded. The other worlds need be real only if the wave function > itself is real, and some way of avoiding a physical collapse is required. Once > you avoid the collapse problem, the many-worlds scenario becomes otiose.
I do agree with you that an epistemic wave function has no problem with collapse, but I've always said the collapse issue was rather secondary compared with the issue of what privileges one branch over all the others as being "real". Stating that all branches are equally real with the one we observer obviates the need for something to say one branch is more real than the others, without committing to saying whether anything is real, or even what "real" really means. In contrast to your last statement, I find "single world interpretations" otiose, in much the same way as I find Christian theology otiose. > > If you insist that you can have a purely epistemic wave function, and also > have > all the other branches being as real as this one, then there is no knock-down > argument against your position. But such a position is clearly contrived, and > otiose, having no basis in quantum theory. > The latter sentence is a non-sequitur. See above. > 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 > /CAFxXSLSMUArjgkfk5Du2fgmJSNn_oZAKirgg7GFGA_U8k7gpTw%40mail.gmail.com. -- ---------------------------------------------------------------------------- Dr Russell Standish Phone 0425 253119 (mobile) Principal, High Performance Coders [email protected] http://www.hpcoders.com.au ---------------------------------------------------------------------------- -- 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/Zzp9s3n2-PBHjqFL%40zen.
