From: ram@zedat.fu-berlin.de   
      
   Luigi Fortunati  writes:   
   >Richard Livingston mercoledi 07/09/2022 alle ore 05:12:12 ha scritto:   
   >>In general relativity, the physical (spatial) distance from A to B is always   
   >>the same as from B to A.  This is not true of the time for light travel   
   >>however.  If A is higher in a gravitational field than B, the round trip   
   >>light travel time is longer for A to B to A (from the point of view of A)   
   >>than it is for B to A to B (from the point of view of B).  For any single   
   >>observer the round trip times are the same either way.  That may seem   
   >>paradoxical, but it is actually true and consistent.   
   >I absolutely agree with what you wrote.   
      
     Richard wrote about two points in /space/.   
      
     In GR, a geodesic usually is a curve in /space-time/.   
      
     It's points are not (x, y, z), but (t, x, y, z).   
     One should not think of its end points as being two points in space!   
      
     A geodesic has no direction by itself.   
      
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