From: sylvia@not.at.this.address   
      
   On 27/09/2017 8:01 AM, Luigi Fortunati wrote:   
   > The planet P distant 20 light-year, photographed with a telescope from   
   > Earth, appears as it was 20 years ago.   
   >   
   > An spaceship approaching P at gamma=4, while passing beside the earth,   
   > also takes a photo on planet P with the telescope.   
   >   
   > According to my calculations, in the spaceship picture, planet P appears   
   > as it was 160 years ago.   
   >   
   > Is my calculation accurate?   
   >   
      
   The meaning of "ago" is not well defined in this context.   
      
   I think I can see where you're heading with this. Let me stop you right   
   there. If there were some counter on the planet which displays a number   
   that increments at some rate, then both the photograph taken from Earth,   
   and the photograph taken from the space ship, will show the same number   
   on the counter.   
      
   Sylvia.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)