From: tjroberts137@sbcglobal.net   
      
   On 7/6/18 9:34 AM, Nicolaas Vroom wrote:   
   > On Sunday, 1 July 2018 19:39:21 UTC+2, Tom Roberts  wrote:   
   >> Note that physics is subtle and requires precision in thought and   
   >> word. [... You did] not specify how the comparison is performed.   
   >   
   > The comparison is done at two specific moments. First at moment t1   
   > when the two clocks depart at P1. Secondly at moment t2 when the two   
   > clocks arrive at P2.   
      
   OK. That is clearly a comparison of total elapsed proper times for the   
   two clocks. That is most definitely NOT a comparison of their tick rates.   
      
   > [... repetitions ad nauseum]   
      
   Heed the dictum: do not attempt to discuss quantities that you did not   
   measure. While that is normally associated with quantum mechanics, it   
   also applies in relativity.   
      
   As I have said before: If you want to directly compare two clocks' tick   
   rates, you physically cannot do that if they are not co-located and   
   co-moving -- anything else requires signals, and you must unwind the   
   effects of the signals (Doppler shifts); do that and you find that   
   identical clocks a;ways tick at identical rates.   
      
   >> As I said, this is as much about English word usage as it is about   
   >> physics.   
   >   
   > IMO physics is the most important.   
      
   English phrasing is also important: if you are not sufficiently precise,   
   your words can be interpreted in multiple ways, giving multiple answers   
   [#]. In particular, you have never said what you mean by "clock rate". I   
   have tried to supply the missing information....   
      
   	[#] In some cases ALL interpretations are wrong, such as   
   	when you say "clock A ticks faster than identical clock B".   
      
   > It is the physics (inner workings) of a clock that describes its   
   > beheviour.   
      
   OK. In SR and GR, the local laws of physics are the same in any locally   
   inertial frame. Since clock tick rates are determined by such laws,   
   clocks ALWAYS tick at their usual rate; this is so regardless of how   
   they might move or where they might be located.   
      
   Bottom line: This whole brouhaha is caused by your insistence on   
   discussing tick rates, when they are not measured. DON'T DO THAT.   
   Discuss what is actually measured and you won't go wrong.   
      
   Tom Roberts   
      
   --- SoupGate-Win32 v1.05   
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