From: goldenfieldquaternions@gmail.com   
      
   On Sunday, August 4, 2019 at 6:59:13 PM UTC-5, Mike Fontenot wrote:   
   > Inertial observers can legitimately use the famous time-dilation result   
   > of special relativity to determine simultaneity at a distance. Observers   
   > who are currently accelerating can't.   
   >   
   > To be an inertial observer during some period of your life, do you have   
   > to be a PERPETUALLY inertial observer? I.e., is it required that you   
   > must NEVER have accelerated in the past, and that you can guarantee that   
   > you will NEVER accelerate in the future?   
   >   
   > Or, can you be an inertial observer if it has been long enough since you   
   > stopped accelerating, and if you can guarantee that you will not   
   > accelerate for some period of time into the future?   
   >   
   > Or, can you be an inertial observer for some period of time, provided   
   > that you don't accelerate during that period?   
   >   
   > The question matters, because the answer specifies WHO is entitled to   
   > use the famous time-dilation result, and WHEN can they use it, in order   
   > to determine simultaneity at a distance.   
   >   
   > Different answers to that question have produced several different   
   > published procedures for answering the question, "How old is that   
   > particular distant person, who is moving with respect to me, RIGHT NOW?".   
   >   
   > Dolby and Gull, in their "Radar Simultaneity", say that an observer is   
   > an inertial observer if he has not accelerated too recently, and will   
   > not accelerate too far into the future (and they exactly specify how   
   > much is too much). Dolby and Gull's method is clearly non-causal.   
   >   
   > Minguzzi says that an observer is an inertial observer if he hasn't   
   > accelerated too recently, but there is no requirement that he can't   
   > accelerate at any time in the future.   
   >   
   > The "Momentarily Co-Moving Inertial Frames Montage" (MCMIFM) says that   
   > an observer is an inertial observer if he isn't CURRENTLY accelerating,   
   > even if he has accelerated infinitesimally-recently in the past, or will   
   > accelerate infinitesimally-soon in the future ... i.e., he can use the   
   > time dilatation result throughout any period of time in which he is not   
   > accelerating.   
   >   
   > What say you?   
   >   
   > [[Mod. note -- It would be useful if you were to provide references   
   > for the statements you attribute to Dolby and Gull, and to Minguzzi.   
   > Expecting readers to guess which of the possibly many works these   
   > authors have written is the one you're referring to, wastes everyone's   
   > time (and leads to further confusion if readers guess incorrectly).   
   > -- jt]]   
      
   I would say it depends upon the length scale to physical objects the observer   
   is interacting with or observing. If these objects are 1 light second away   
   then if the observer is inertial for 1 second that might suffice.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)