From: PointedEars@web.de   
      
   Paul B. Andersen wrote:   
   > Den 03.02.2026 16:14, skrev Thomas 'PointedEars' Lahn:   
   >> Paul B. Andersen wrote:   
   >>> Den 03.02.2026 10:07, skrev Maciej Woźniak:   
   >>>> Anyway, for any context motion is absolute.   
   >>> Speed is relative, acceleration is absolute.   
   >> Wrong.   
   >   
   > Acceleration is absolute in Newtonian mechanics.   
      
   That is not so.  If two reference frames are non-inertial (in the Newtonia   
   sense), then it is possible that one is not accelerating relative to the other.   
      
   That is precisely the case (approximately), when a falling observer is   
   observing a nearby falling object and we assume approximatively that the   
   gravitation field is uniform.  Then that object would be observed to be at   
   rest even though it would be accelerating for an inertial observer.   
      
   > Maciej quote of me is taken from a thread where we> discussed   
   accelerometres, which are measuring   
   > the proper acceleration.   
      
   I have read the thread.  If you said anything obviously incorrect there, I   
   would have corrected you there.   
      
   > Proper acceleration is absolute in SR and GR.(And in NM)   
      
   What do you mean by that?   
      
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