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. 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. 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.
