From: richalivingston@gmail.com   
      
   On Friday, August 25, 2023 at 12:41:27=E2=80=AFAM UTC-5, Luigi Fortunati wrote:   
   ...   
   > The graduated belt of my animation is directly *bound* to the Earth and   
   > its rotation.   
   >   
   > This makes its measurement (direct and immediate) more reliable than   
   > the measurement at distance with light.   
      
   I'll try one last time to make this point.  The time "now" for events outside   
   the light cone, e.g. events that are spatially separated, are not uniquely   
   defined for different observers.   
      
   I must ask what meaning you attach to a time "now" back on earth?  It   
   is not the time you can see, via light, from earth.  In fact there is nothing   
   you can do to interact with earth "now" in any way.  The only way to   
   know what is happening "now" is to wait for that event to enter your   
   past light cone, at which time you can see it.  At that later time you can   
   know what happened back when you identified a time as "now".   
      
   If you want to define some time as "now" by some mechanism like you   
   describe, that is OK.  But the conventional way to define "now" is to   
   synchronize  clocks as described in most any book on special relativity.   
   That process allows you to define a "now" that conforms with what   
   we all normally think of as "now".  It gives a different result for different   
   inertial observers, but it gives a result that each observer can make   
   sense of as "now".  That is, if they do some experiment such as send   
   a time message via light, the result is consistent with special relativity.   
      
   There is another factor that you are not taking into account:  The   
   Lorentz contraction of each side of the belt will be different for   
   moving observers.  This may seem as it should be negligible for   
   such a slow moving belt, but note that magnetic fields are the result   
   of just such a difference in Lorentz contraction even though the   
   electrons in a wire are moving at less than 1 mm/second.  In the   
    case of your belt model, a rapidly moving observer will see that   
   one side of the belt has shrunk compared to the other, and thus   
   the earth is rotated relative to what the "stationary" observer   
   calculates.   
      
   Rich L.   
      
   [[Mod. note -- That's a very clear (and completely correct) exposition.   
   Thank you!   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
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