On Tuesday, November 19, 2019 at 3:51:37 PM UTC-6, Luigi Fortunati wrote:   
   > The force of earth's gravity acting on the moon is a centripetal force.   
   >   
   > If this is so (if it is the same force), how is one (the centripetal   
   > force) real and the other (the gravitational one) apparent?   
   >   
   > [Moderator's note: One good answer is probably enough.  Also, followup   
   > questions shouldn't repeat the discussion on this topic here not that   
   > long ago.  -P.H.]   
      
   Whether you consider gravity a real force or an apparent force depends   
   on the theoretical framework you are using.  Under Newtonian gravity   
   theory it is a real force.  Under General Relativity it is an apparent   
   force in that an object unaffected by outside forces follows a geodesic   
   path through space-time, just like an object moving freely in space.   
   Under GR, the force that we experience is the force required to make   
   the object move on a non-geodesic path, e.g. to be stationary on the   
   surface of the earth.   
      
   It is really just terminology.  The calculated behavior is the same.   
      
   Rich L   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)