From: yanicktoutain@gmail.com   
      
   Stefan Ram a =C3=A9crit=C2=A0:   
   > Luigi Fortunati  writes:   
   > >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).   
   > This is true from the point of view of the space traveler if   
   > he considers himself to be at rest. (But which traveler would   
   > seriously consider himself to be at rest?)   
   >   
   > However, if we do not look at this from a special coordinate system,   
   > we can say that each twin travels a different world line (travel   
   > route) in spacetime between the start of the spacecraft and its   
   > landing. The length of each of these world lines, measured in the   
   > metric of spacetime, gives the the time that has passed for each   
   > of them. And these lengths are independent of any particular   
   > reference system, so it is actually easier to consider this invariant   
   > point of view than "simultaneities" that depend on reference systems.   
   >   
   > Quantitatively, let dS and dT denote the lengtStefan Ram a =C3=A9crit=C2=A0:   
   > Luigi Fortunati  writes:   
   > >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).   
   > This is true from the point of view of the space traveler if   
   > he considers himself to be at rest. (But which traveler would   
   > seriously consider himself to be at rest?)   
      
   I read you write this "But which traveler would seriously consider   
   himself to be at rest?"   
   Your question is very strange.   
   The other day on the train I heard the conversation of two academic   
   professors of relativity.  The first saying to the second: "But what is   
   the station platform waiting for to move??!!  The second: "You're right.   
   The departure time is over by gamma times three minutes" The first -   
   outbidding - "With my relativist colleagues we refuse to pay the carbon   
   tax for aircraft travels as long as the terminals which move while we   
   are at rest refuse to pay it first"   
      
   The second "Why only the terminals? All these poors moving in relation   
   to us should pay too. Their relative movements in relation to us, the   
   intellectual elite, contribute to global warming"   
      
   I then stopped listening to them to reread "The Dialectic of Nature"   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)