From: fortunati.luigi@gmail.com   
      
   Richard Livingston gioved=EC 05/05/2022 alle ore 22:05:20 ha scritto:   
   > -"Who is at rest?" is the wrong question.  The relevant question is "wh=   
   o   
   > is in an inertial frame?"  If you are in an inertial frame you can let =   
   go   
   > of an object and it will float where you left it.  If you let go of an   
   > object and it accelerates away, then you are not in an inertial frame.   
      
   And, therefore, the free-fall elevator is not an initial frame because   
   if you let go of an object, it  accelerates toward the floor if the   
   gravity is that of a black hole and if the object is below the center   
   of the elevator where gravity acting on the object is greater than   
   gravity acting on the entire elevator!   
      
   [[Mod. note -- No, the correct conclusion is to observe that inertial   
   frames are always of limited size, with the actual size limit depending   
   on your tolerance (threshold) for how small an acceleration difference   
   (a.k.a tidal acceleration) is "negligable".   
      
   If your freely-falling elevator is big enough that you notice the   
   acceleration differences between different free-falling objects in   
   the elevator (all of which were initially at rest with respect to   
   the elevator), and/or between these and the elevator itself, that's   
   a statement that your elevator is too big for any one inertial frame   
   to cover the entire elevator.  If you want to apply the concept of   
   "inertial frame" in the elevator, then you need a smaller elevator   
   and/or a looser tolerance for acceleration differences.   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)