From: richalivingston@gmail.com   
      
   On Tuesday, June 14, 2022 at 10:15:18 AM UTC-5, Tom Roberts wrote:   
   > On 6/13/22 10:43 AM, Richard Livingston wrote:   
   > > Events that are on each others light cone are effectively   
   > > simultaneous (the metric separation is zero), and that is true for   
   > > all observers.   
   > Yes, for such pairs of events the metric separation is zero, and that   
   > applies for all observers (it is really independent of observer and   
   > coordinates).   
   >   
   > But that is not at all what "simultaneous" means. Rather, that is a   
   > lightlike interval.   
   >   
   > Simultaneous means at the same time, and that is a coordinate-dependent   
   > concept (because a coordinate system defines what one means by "time")   
   > -- for a given coordinate system all events with the same value of the   
   > time coordinate are simultaneous with each other. In an inertial   
   > coordinate system, for each such value the locus of events is   
   > necessarily a 3-D spacelike hypersurface. In general, for different   
   > coordinate systems these loci are completely different.   
   >   
   > Tom Roberts   
      
   I agree, that is what "simultaneous" means, and I shouldn't have used   
   that word.  The idea I did not state clearly enough is that *perhaps*   
   from the point of view of the physics of causality, that two events with   
   zero metric separation should be considered simultaneous and co-located.   
    I realize that this is not a standard concept in current physics, and I   
   still have some doubts about it, but applying this concept to   
   entanglement experiments would relieve much of the confusion about how   
   such entangled results can happen without invoking faster than light   
   communication.   
      
   Rich L.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)