From: sylvia@not.at.this.address   
      
   On 3/09/2017 3:15 AM, Luigi Fortunati wrote:   
   > Gregor Scholten sabato 02/09/2017 alle ore 12:54:33 ha scritto:   
   >>> 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.   
   >>   
   >> In both cases (you are moving and the mirror is moving), you can   
   >> consider things either in your own rest frame or in the mirror's rest   
   >> frame.   
   >>   
   >> In your own rest frame S, the path of the light has the length s = 2d,   
   >> and therefore, the light takes the time interval   
   >>   
   >> Delta_t = s/c = 2d/c   
   >>   
   >> for the path.   
   >>   
   >> In the mirror's rest frame S', the path of the light has the longer   
   >> length s' > 2d/c, and therefore takes the longer time interval   
   >>   
   >> Delta_t' = s'/c > 2d/c   
   >>   
   >> This difference in the time interval is what is known as relativistic   
   >> time dilation.   
   >>   
   >> This is true for both cases, so both cases are fully equivalent. It's   
   >> just a matter of the frame of reference you chose (your own or the   
   >> mirror's).   
   >>   
   >>   
   >>> 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.   
   >>   
   >> In your own rest frame, the time delay is always Delta_t = 2d/c.   
   >   
   > I thank you and others who have responded.   
   >   
   > But if the image had an internal clock, what time would it be?   
   >   
      
   An image is not capable of containing a clock, so this question is not   
   well defined.   
      
   Sylvia.   
      
   --- SoupGate-Win32 v1.05   
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