From: ralivingston1952@charter.net   
      
   On Tuesday, May 18, 2021 at 8:06:39 AM UTC-5, Luigi Fortunati wrote:   
   > It is correct to say that in the elevator stopped at the floor   
   > (1) an electromagnetic force acts between the man and the elevator   
   > (2) a gravitational force acts between the Earth and man   
   > (3) a gravitational force acts between the Earth and the elevator   
   > (3) no gravitational force acts between the elevator and the man?   
   >   
   > It is correct to say that in the elevator in free fall   
   > (1) a gravitational force acts between the Earth and man   
   > (2) a gravitational force acts between the Earth and the elevator   
   > (3) no gravitational force acts between the elevator and the man.   
   > (4) no electromagnetic force acts between the elevator and the man?   
   >   
   > [Moderator's note: I think that the above are meant as questions, i.e.   
   > "Is it correct...?" -P.H.]   
      
   I would say "no" and "no":   
   -First of all, the influence of gravity and electromagnetism do not turn   
   ON or OFF based on the motion of the objects.  Whether the elevator   
   is stopped or moving all charges act on all other charges and all   
   gravitational "forces" act on all objects.   
   -Current thinking is that gravity is not a "force", but rather a distortion   
   of space-time.  The "force" that we feel is the force required to make   
   an object deviate from its natural trajectory through space-time.  This   
   is entirely analogous to a centrifuge.  There is no force pushing a mass   
   outward, the outward path is the most natural path for the object to   
   move in a straight line.  The force is the one that pushes the object   
    toward   the center, which is the force that makes the object follow   
   a curved path.   
   -Stopped (1) and Free Fall (4):  Electromagnetic forces act in both cases.   
   They are what prevent the man from passing through the floor or   
   walls of the elevator, whether stopped or falling.   
   -Stopped (2)(3)and ("3") and falling (1)(2)(3):  The gravitational distortion   
   of   
   space-time makes the man and elevator naturally follow the falling   
   path.  An external force is required to keep the elevator stationary in   
   our "stopped" frame.  Note that our "stopped" frame is an accelerating   
   one, not a rest frame.  When the elevator is falling freely, the man and   
   elevator are following a "straight line" in the curved space-time around   
   the earth.  The only force required is when the elevator is "stopped" in   
   our non-inertial frame we on earth call "at rest".  This is an accelerating   
   frame and thus a force is required to keep objects "stationary" in this   
   frame.   
      
   Rich L.   
      
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