From: nicolaas.vroom@pandora.be   
      
   On Saturday, 23 June 2018 20:08:43 UTC+2, Tom Roberts  wrote:   
      
   > Not in GR. In GR, the local laws of physics are the same everywhere,   
   > including the laws that govern the ticking of watches. So the two   
   > watches tick at the same rate (assuming they are identical).   
      
   The question is what are the laws that govern the ticking of the watches?   
   In general physical processes depent about certain parameters (T,P,V etc)   
   and if these parameters change the behaviour of these processes change.   
   For example: if you place to identical clocks side by side they behave   
   the same because all the parameters are identical.   
      
   > 	[This also applies to SR, for watches moving differently.   
   > 	 Note that this English phrasing implies we are discussing   
   > 	 the watches' intrinsic tick rates, and NOT how someone   
   > 	 else might observe them.]   
      
   IMO the general assumption should be that the start and end of the   
   experiment should be the same.   
      
   > Other methods of comparison are possible; all physically realizable ones   
   > yield the same result, including a very different approach: start with   
   > them together and synchronized, move them slowly to the tower's top and   
   > bottom, wait a while, move them slowly back together, and compare their   
   > displayed times.   
      
   The question: is what is the result of the experiment.   
      
   > All too many elementary books and discussions talk about "clocks ticking   
   > slower" than other clocks.   
      
   Also here the same question: What was the result of the experiment.   
   The conclusion can be that the # of ticks on the clocks is different.   
      
   > In GR this is just plain wrong -- all clocks   
   > tick at their usual rate, no matter where they are located or how they   
   > might move (relative to anything) [@].   
      
   The issue is if they always tick at their usual rate i.e. constant rate.   
   To answer that you have to compare the clocks with a standard clock   
   (Which also uses light signals)   
      
   > Relativity is more subtle, and   
   > more complicated, than those books and discussions can capture (because   
   > they make a fundamentally wrong assumption about clock tick rates,   
   > essentially ignoring the first postulate of SR).   
      
   IMO the most important step is to explain the experiments you perform   
   accurately and the results of the experiments.   
   Only after that you can say how GR (or SR) explains the results.   
   Suppose at the beginning of the experiment at position A the # of counts   
   of all the clocks is the same (zero) and at the end of the experiment   
   the # of counts of 'all' the clocks (at position B) is different.   
   I think there is nothing wrong with that.   
   I also see no problem if you claim that the average ticking rate of these   
   clocks is different.   
   The true question is what is the cause.   
   If some of the clocks are put in orbit around the Sun and the planets   
   of course gravity is at stake.   
   For simpler experiment the average speed of each clock is an issue.   
      
   Nicolaas Vroom.   
      
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