On Tue, Feb 4, 2014 at 3:35 PM, LizR <[email protected]> wrote: > On 4 February 2014 23:25, Bruno Marchal <[email protected]> wrote: > >> >> On 04 Feb 2014, at 00:29, LizR wrote: >> >> On 4 February 2014 12:23, Jesse Mazer <[email protected]> wrote: >> >>> On Mon, Feb 3, 2014 at 5:48 PM, <[email protected]> wrote: >>> >>>> >>>> But more generically speaking, would this inference for blocktime sit >>>> at the edge of relativity or at its core. What I mean is, beyond that it is >>>> an implication of relativity, have there been or are there any >>>> prospects for developing blocktime as it arises from relativity to such >>>> point, predictions get made? Or any other kind of reinforcement? Or does >>>> blocktime go on to imply something beyond blocktime? >>>> >>> >>> If "block time" is taken as a definite ontological statement about all >>> times "existing" in exactly the same sense, rather than just referring to >>> the idea of treating time as a dimension conceptually or in our >>> mathematical models, then I think it's a metaphysical postulate that goes >>> beyond anything directly implied by relativity. Relativity says that all >>> frames, with their different definitions of simultaneity, are on equal >>> footing as far as the laws of physics are concerned, but it doesn't deal >>> with ontology. If someone proposes that one frame's definition of >>> simultaneity is "metaphysically preferred" in the sense it defines the >>> "true present", but adds the caveat that this frame is not in any way >>> physically preferred so that no conceivable experiment could determine >>> which frame it is, this wouldn't contradict the physics. It would be an >>> "interpretation" of SR, similar to the different "interpretations" of QM >>> which postulate different things about ontology (the real existence of >>> other worlds in the MWI, or a single world with hidden variables in Bohmian >>> mechanics, for example) but are indistinguishable experimentally. >>> >> >> SR directly demonstrates block time via the relativity of simultaneity. >> This can be tested experimentally. >> >>> >>> That said, if you subscribe to any form of Occam's razor or even a >>> criteria of "elegance" when it comes to choosing between different >>> metaphysical hypotheses, it seems a lot simpler to assume that there is no >>> metaphysically preferred definition of simultaneity, just as I think many >>> would agree the MWI is the simplest way of interpreting the physical theory >>> of QM. Adding extra "purely metaphysical" entities to a theory, which don't >>> correspond to anything that appears in the mathematical formalism of the >>> theory itself (which would apply to things like a "true present" or to >>> hidden variables in QM), seems a bit like postulating that there are >>> invisible intangible elves sitting on each person's head which have no >>> causal effects on anything we can measure; sure it's logically possible, >>> but it seems like a very inelegant and arbitrary way for reality to work. >>> >>> The MWI is deterministic, however, and hence has hidden variables. >> >> But not "hidden variable" in the EPR sense. In the MWI, there are hidden >> universes, they are not variable, but terms in the universal wave, and we >> just don't know which terms apply to us. If it was hidden variable in the >> EPR sense, then by Bell, they would be non-local, and you would conclude >> falsely (like Clark) that the MWI has to be non local (which I doubt very >> much). >> >> No, as I explained elsewhere, Bell's inequality rests on 4 assumptions, > and the easiest assumption to remove is that time is asmmetric at the > fundamental level (which *in any case* physics indicates it isn't, except > for neutral kaon decay - which I dount has ever been used in an EPR > experiment). >
As I've said to you in the post at http://www.mail-archive.com/[email protected]/msg46130.html, the type of time-symmetry seen in modern physics--which just says that the same laws can be used to retrodict past states as are used to predict future states, but doesn't say you *need* information about the future as well as the past to predict the state in a given region of spacetime--is not enough to evade the conclusions of Bell's theorem. In order to do that you'd need either a theory where determining the state of a region does require knowing both its past and its future, or you'd need some strong restrictions on the possible boundary conditions, both of which would be pretty exotic assumptions, not ones I'd consider to be the "easiest" modification of Bell's assumptions. In the case of the type of dynamical time-symmetric (or CPT-symmetric) theories that physicists have found useful in describing nature, where you can use a set of initial conditions to predict a later state, the argument about conditioning on a slice of the past light cone I mentioned at http://www.mail-archive.com/[email protected]/msg45832.html(and which matches Bell's discussion of conditioning on slices of past light cones in his "La nouvelle cuisine" paper) still works fine to show that if the theory is local realistic (and doesn't include parallel universes), Bell inequalities should not be possible to violate. Jesse -- 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 post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
