On Monday, March 23, 2020 at 8:25:23 PM UTC, richali...@gmail.com wrote:   
   > On Thursday, March 19, 2020 at 11:53:17 AM UTC-5, ben...@hotmail.com wrote:   
   > > On Sunday, March 15, 2020 at 3:13:52 PM UTC, Jos Bergervoet wrote:   
   > > > On 20/03/15 12:18 PM, ben6993 wrote:   
   > >...   
   > >...Unless .... and this is anathema to all bona fide=20   
   > > physicists, but I am currently wondering if time for an antiparticle is   
   > > travelling backwards, as nominally shown in a Feynmann diagram.  So a Bell   
   > > test starts at say Alice's measurement and ends at Bob's measurement.  Or   
   > > vice versa.  ...   
   >   
   > This would not be relativisticly consistent.  That is, if we are to say   
   > that \the causal chain starts with Alice's measurement which eventually   
   > causes Bob's, then to be consistent with the relativity principle there   
   > must not be any observer who sees Bob's measurement happening first,   
   > thus "causing" Alice's result.  It has been demonstrated that entangled   
   > correlation does occur between two spatially separated events (i.e.   
   > Alice's and Bob's measurements) and so there would be observers who can   
   > see either Alice's or Bob's measurement happening first.  If causality   
   > is to have meaning we can't accept this.   
      
   If an observer saw Alice's measurement for the positron travelling backwards   
   in time to the Source, then that observation/measurement would render the   
   pair of particles to be no longer entangled, and so not a pair entitled to   
   be in a Bell experiment.  I admit that I either do not understand 'weak   
   measurement' or believe it to be a measurement which is not provable to be   
   on a single particle.  A non-weak measurement to me is one  which changes   
   the spin sign of a particle.   
      
   >   
   > If you only allow forward causality (i.e. the result of a measurement   
   > only depends on events within its past light cone), then the moment of   
   > emission of the entangled particles is the only time common to both   
   > Alice and Bob. This requires hidden variables (as you are trying to make   
   > sense of).  The Bell Inequality applied to such experiments, however,   
   > proves that the results of the measurements at Alice and Bob cannot be   
   > solely determined by a local hidden variable on the particle.  The   
   > statistics are wrong and the inequality is violated.   
      
   Causality?  Knowing Alice's measurement, even in a time reversal setting for   
   Alice, does not imply that we know what Bob's measurement will be.  In the   
   analysis of the results after the experiment, the measurements are inputted   
   into a 2x2 table and that associates A and B measurements post-experiment.   
   Knowing what the row (A value) is for a particle pair gives no information   
   on what the column (B value) is.  Well, we could maliciously somehow ensure   
   that Bob's measurement is fixed once we know the A result.  But I do not   
   know how to do that with an HV formula.   At least not a formula that would   
   withstand scrutiny for fairness by independent scrutineers.   
   >   
   > The solution I subscribe to is retro causality.  That is, the particle   
   > is not emitted until its destination is determined and is consistent   
   > with the constraints of polarization/spin/etc.  This requires some sort   
   > of communication cannot be used to communicate information beyond the   
   > fact that out there, from the future, hence the term "retro causality".   
   > This  communication somewhere, is something that can accept the   
   > photon/particle w/spin.   
   >   
   Yes, I agree, and this is what I meant by time reversal not helping at first   
   impression.   
      
   Superdeterminism as I understand it uses forward causality, as does   
   determinism.  IMO it relies on the future eventually becoming what it will   
   be, and that will not correspond to countless particles available in all   
   places and HV vector directions.  But that seems to me to lead to failing to   
   break the inequalities just as often as breaking them.  In a similar way,   
   deliberately having missing data in the data sets can lead to breaking   
   inequalities, or not, depending on the bias introduced in the snipping of   
   the data.   
      
   I am not sure about retro-causality as you describe it.  It seems to imply   
   information of some kind is travelling backwards in time.  It also at first   
   glance seems to suffer from the same problem that IMO superdeterminism   
   suffers from.  That is why should the particular measurement break the   
   inequalities?   
      
   My idea has IMO the advantage that the whole stream of antiparticles in a   
   Bell experiment has its distributions of HVs moulded by Alice and those are   
   passed on to particles beamed at Bob. This means that there is no point in   
   making a simulation with say 1 million pairs (as I often have done) with HVs   
   random on a sphere.  As the HVs in my time-reversed scenario are not random.   
      
   I do not yet know why the moulding of the HVs for Bob does break the   
   inequalities. But it seems to me that superdeterminism has no mechanism for   
   breaking the inequalities except by chance outcomes.   
      
   > This is a somewhat controversial idea.  I'm not sure how many mainstream   
   > physicists subscribe to this, but it is discussed by serious physicists.   
   >   
   > BTW, I too abhor the idea of the multiverse.  The number of entire   
   > universes spawned every instant is unimaginable, and I think fails the   
   > Occam's Razor test.   
   >   
   > Rich L.   
      
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