From: fortunati.luigi@gmail.com   
      
   Il giorno mercoledì 19 luglio 2023 alle 09:07:26 UTC+2 Stefan Ram ha scritto:   
   > For example, if I see a flash coming from a lamp one light-year away,   
   > I know that the flash there was not produced simultaneously with my   
   > observation, but one year before it...   
      
   Of course, everything we see concerns phenomena that occurred in the past,   
   even our Sun we see as it was 8 minutes ago and not as it is now.   
      
   But special relativity doesn't concern what is observed, it concerns what   
   happens in the references in motion with respect to the observer.   
      
   And what happens in the spaceship frame (where the Earth is in motion) is this:   
   1) The Earth rotates once on the way out and once on the way back (2 rotations   
   in all).   
   2) At the end of the journey, the terrestrial twin aged 8 days (twice the   
   traveling twin) and, therefore, the Earth rotated 8 times.   
   3) The remaining 6 terrestrial rotations that are missing and that did not   
   occur during the outward and return journeys must have occurred (necessarily)   
   during the U-turn.   
      
   What I want to point out is that in (1) there is the *dilation* of terrestrial   
   time (which runs slower in the spaceship frame) and in (3) there is the   
   *contraction* of terrestrial time (which runs faster in the spaceship frame).   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)