On Tuesday, August 29, 2017 at 2:21:38 AM UTC-5, Luigi Fortunati wrote:   
   > I'm standing in front of the mirror at a distance  with my clock that   
   > marks the time .   
   >   
   > The clock image in the mirror marks a delayed time of 2d/c (compared to   
   > t) due to the time it takes to light to get to the mirror and return (as   
   > long as i stand still and the mirror as well).   
   >   
   > But what if I am running at constant speed parallel to the mirror? The   
   > distance is always equal to  but the light does not go and goes back   
   > to the same point, because in the meantime I have moved away.   
   >   
   > And then the light has to travel a greater distance due to the   
   > inclination of the path and therefore the delay time of the clock image   
   > is greater than 2d/c.   
   >   
   > This longer delay measures my speed compared to the mirror.   
   >   
   > What if the mirror was moving while I was still standing?   
   >   
   > In that case, the light should no longer extend its path because it   
   > would leave me firm and return from me always.   
   >   
   > If all this was true (and it is not possible) it would be enough to   
   > compare the time of the watch with that of the image to find out if one   
   > moves or moves the other: if the delay is equal to 2d/c it moves the   
   > mirror, if it is the bigger the clock moves.   
   >   
   > How is it possible?   
   >   
   > --   
   > Luigi Fortunati   
   >   
   > Credere e' piu' facile che pensare   
   > Believing is easier than thinking   
      
   Your thought experiment is exactly what leads to the Lorentz   
   transform, provided you assume that there is no way  to distinguish   
   the two cases by observing the time on the reflected clock.  (That   
   assumption is motivated by the measured constancy of the speed of   
   light, e.g. the Michealson-Morely experiment.)  The solution is to   
   realize that the observed rate of the clocks, as seen from the frame   
   moving wrt your experimenter, is slowed.   
      
   Rich L.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)