From: tjroberts137@sbcglobal.net   
      
   On 7/22/19 5:41 PM, Nicolaas Vroom wrote:   
   > But geometrical projections is mathematics ......   
      
   Geometry, and specifically geometrical projections, can have physical   
   consequences:   
      
        You can carry a ladder through a narrow doorway in some   
        orientations but not others -- the geometrical projection   
        of ladder's length onto doorway's width determines this.   
      
        Yes, collisions between ladder and doorframe are the cause,   
        but the geometrical projection determines whether such a   
        collision will occur.   
      
   > The problem is time dilation of moving clocks. If you want to know   
   > the time of moving clock which moves away from you, you get a time   
   > count that is always earlier than the actual time at the moment when   
   > you receive that information. The reason is simple communication time   
   > between sending and receiving any message (which is a function of   
   > distance) Sending and receiving does not cause any physical effect on   
   > the clocks in use.   
      
   You are confusing Doppler shift with "time dilation". The usual approach   
   to separate them is to use a set of assistants arrayed along the path   
   of the moving clock, each at rest in the observer's frame with a   
   clock synchronized to the observer's clock; the assistants note the time   
   on the moving clock as it passes, and also their own clock, and they   
   send these notes to the observer, who can then measure "time dilation"   
   without any light delays or Doppler shift. (The moderator already   
   mentioned this approach in this thread.)   
      
   > What causes a physical effect is the internal operation of a clock   
      
   No. The internal operation of a clock is unaffected by its motion   
   (relative to anything) -- that's the first postulate of SR.   
      
        The laws of physics govern the internal operation of   
        every clock, and the first postulate says they are the   
        same in every locally inertial frame.   
      
   > The moving clock runs physical slower compared to a clock at rest.   
      
   Only if the first postulate is wrong. Zillions of experiments show that   
   it is correct.   
      
   The observer will OBSERVE the moving clock to run slower than her own   
   clock, but the moving clock ITSELF is unaffected (i.e. it does NOT run   
   "physically slower").   
      
        Be careful what your words mean. "This clock runs slower"   
        refers to the clock AND NOTHING ELSE, and is therefore   
        wrong. "This observer measures that moving clock to run   
        slower than her own clock" is a correct statement of "time   
        dilation".   
      
   As I keep saying, modern physics requires precision in thought and word.   
      
   Tom Roberts   
      
   --- SoupGate-Win32 v1.05   
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