Brent Meeker wrote: > Stathis Papaioannou wrote: > > Peter Jones writes: > > > > > >>By youur definitions, it's a straight choice between metaphysics and > >>solipsism. > >>I choose metaphsyics. > >>We can posit the unobservable to expalint he observable. > > > > > > Solipsism is a metaphysical position. > > > > > >>(BTW: it it is wrong to posit an unobserved substrate, why is it > >>OK to posit unobserved worlds/branches ?) > > > > > > It's debatable, but perhaps MWI is a better and simpler explanation of > > the facts of quantum mechanics than is CI, for example. > > Multiple-worlds are a consequence of dropping the collapse of the wave > function, > which was inexplicable and ad hoc.
It's neither. If anything there is an embarassment of explanations for it, and number of motivations for positing it. A genuine problem with MWI: it starts with the assumption that the universe is in a 'pure' state. However, unitary evolution under the SWE is unable to fully transform a pure state into a genuine mixture. It can generate (by mechanisms similar to environmental decoherence) an approximate mixture -- For All Practical Purposes. Since collapse does, by stipulation, produce orthogonal states, there is a difference between collapse interpretations and MW. The residual interferences could be detectable. (It is also believed by many that collapse itself is detectable). "In fact it turns out that in the general case , there will be a unique pair of orthogonal perception states accompanying a pair of orthogonal cat states. This is something known as the Schmidt decomposition of an entangled state. However this is not much use for resolving the measurement paradox (...) because gernerally this mathematically preferred pair of cat states (..) would not be the desired |live cat> + | dead cat> at all, but some linear superposition of these! [...] Since the mathematics alone will not single out the |live cat> and |dead cat> states as being in any way 'preferred' we still need a theory of perception before we can make sense of [MWI] and such a theory is lacking.Moreover the onus on such a theory would be not only to explain why superpositions of dead and alive cats (or anything else macroscopic) occur in do not occur in the physical world but also why the wonderous and extraordinarily precise squared-modulus rule actually gives the right answers for probabilities in quantum mechanics!" R. Penrose, Road to Reality p809 Is MWI a complete solution to the paradoxes of QM? Is an Universal Wave Function feasible ? A genuine problem with MWI: Reasonableness of all-embracing unitary evolution. MWI-ers claim that the unitary evolution of the SWE (or some variation) is the single all-embracing law of the universe -- the other main part of the QM universe, the process of collapse (AKA reduction) is not needed. However, QM itself is not an all-encompassing physical theory because it does not include gravity and relativity. It might be possible to include gravity in an extended WE, but the conventional SWE requires a derivative against time, wich is difficult to achieve in a way that is compatible with the requirements of relativity. There is also a more conceptual argument against large-scale branching; since all branches co-exist in the same space-time, and since the disposition of matter determines how space bends in general relativity, large-scale differences between the branches would leave space not "knowing" which way to bend. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~----------~----~----~----~------~----~------~--~---
