From: fortunati.luigi@gmail.com   
      
   Tom Roberts il 02/01/2024 09:17:26 ha scritto:   
   > Note that "all physics is local" [Einstein and others], so these various   
   > descriptions of accelerations of distant objects never appear in the   
   > laws of physics.   
      
   No distant objects.   
      
   The two little men (at the center of the Earth and in the elevator in   
   free fall) pass in front of each other in acceleration (when   
   approaching) and in deceleration (when moving away) and, therefore,   
   they are not far away at all: they are 'next to each other.   
      
   During their meeting, they cannot perceive the force of gravity but   
   they can easily measure their mutual gravitational acceleration (even   
   in 4 or more dimensions).   
      
   Luigi Fortunati   
      
      
   [[Mod. note -- A corollary of what Tom Roberts wrote is that our modern   
   conceptions of physics involve *local* equations.   
      
   In the situation you describe, the two little men's relative velocity   
   when they meet (for later reference, I'll call this velocity V) is the   
   integrated result of different *local* accelerations with respect to   
   the Earth over their past trajectories.  When the two little men meet,   
   their relative velocity V is effectively an "initial condition" for   
   their dynamics right around the meeting -- the relative velocity could   
   just as well have come from (say) the "free fall" elevator starting out   
   at rest with respect to the Earth a kilometer away, and firing a rocket   
   to accelerate to the velocity V with respect to the Earth.   
      
   In contrast, the two little men can make a direct *local* measurement   
   of their differential gravitational acceleration, which is a reflection   
   of the local gravitational field and is unaffected by initial conditions.   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)