From: mlfasf@comcast.net   
      
   On 3/28/22 3:36 AM, Richard Livingston wrote:   
   > On Friday, March 25, 2022 at 5:57:18 AM UTC-5, Mike Fontenot wrote:   
      
   >> [...] At any given instant "tau" in the   
   >> life of the given inertial observer, it's clear that there is just a   
   >> single answer to the question "How old is that particular distant person   
   >> (she) right now (at the given time "tau" in the life of the inertial   
   >> observer): it is what the particular HF (he) who happens to be   
   >> momentarily co-located with the distant person (she), says it is, at the   
   >> instant when he is age "tau". The only way there could be any other   
   >> allowable answer is if the synchronization of the clocks isn't valid,   
   >> and that is impossible if the velocity of light in that inertial   
   >> reference frame is equal to the universal constant "c".   
   >   
   > I think I mostly agree with you, but still think that the problem with   
   > "now" at a distant location is that people take it as something   
   > real and meaningful, and I think an argument can be made that it   
   > is not very meaningful.   
   >   
      
   My argument above is that, IF those clocks are synchronized (according   
   to the given observer), then he can't help but conclude that the current   
   age of that distant person IS completely meaningful TO HIM.  And the   
   only way that those clocks AREN'T synchronized according to him, is if   
   the velocity of light in his inertial reference frame ISN'T equal to the   
   universal constant "c".  But the fundamental assumption of special   
   relativity IS that light will be measured in all inertial reference   
   frames to have the value "c".  Therefore, FOR any given inertial   
   observer (he), the current age of a distant person is completely   
   meaningful to him.   
      
   But what about a non-inertial observer?  In particular, what about a   
   given observer who is undergoing a constant acceleration?  What does HE   
   say the current age of a distant person is?  It turns out to be possible   
   for such an accelerating observer to rely on an array of clocks and   
   associated "helper friends" (HF's) to give him the answer.  Unlike in   
   the inertial case, those clocks DON'T run at the same rate.  But the   
   ratio of the rates of those clocks can be CALCULATED by the given   
   observer.  And if he (and the HF's) are initially stationary and   
   unaccelerated, they can start out with synchronized clocks (and ages).   
   Then, if they all fire their identical rockets at the same instant, they   
   can each CALCULATE the current reading of each of the other clocks, at   
   each instant in their lives.  The calculations of each of the HF's all   
   agree.  So, at any instant in their lives during that acceleration, they   
   each share the same "NOW" instant with all of the other HF's.  That   
   means that the given observer (he), at any instant "tau" in his life,   
   can obtain the current age "T" of some distant person (her), by asking   
   the HF, who happens to be momentarily co-located with her at that NOW   
   instant, what her age is then.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)