From: nicolaas.vroom@pandora.be   
      
   On Saturday, 14 July 2018 18:17:41 UTC+2, Tom Roberts  wrote:   
   > On 7/11/18 7:57 PM, Nicolaas Vroom wrote:   
   > > First of all identical processes (experiments) have identical   
   > > descriptions.   
   >   
   > Not true.   
      
   The idea is when we try to perform the same experiment the descriptions   
   and the results should be the same. (repeatability)   
   You can ofcourse only do that when you remove everything what is   
   observer dependent. The description (model) should be observer independent.   
   My observations are subjectif. The descriptions should be objectif.   
      
   > In the example discussed in this thread, the train observer   
   > describes it as "the stone falls straight down", while the embankment   
   > observer describes it as "the stone falls in a parabolic arc". These are   
   > different descriptions of a single process, due to the observers'   
   > different perspectives.   
      
   Correct. They are subjectif (If that is the correct defintion)   
      
   > You yourself give another counterexample to this claim:   
   >   
   > > Consider a train which travels in a straight line from A to B.   
   > > Observer A at A sees the train fading away and becoming smaller.   
   > > Observer B at B sees the train awaking at the horizon and becoming   
   > > larger.   
   >   
   > That's two different descriptions of a single phenomenon. They differ   
   > because they are descriptions from different perspectives.   
      
   Correct. But the real description should be observer independent.   
   This requires a certain transformation to come to one common   
   description. An objectif description.   
      
   > There is one "reality", one world. But trying to single out "one   
   > reference frame, one coordinate system" is USELESS -- all are equally   
   > valid; they give different descriptions of phenomena based on their   
   > different perspectives. We do this ALL THE TIME, and I don't see why you   
   > have difficulty with it. Note you CANNOT separate an observer from her   
   > perspective; for many cases in physics, "perspective" means "coordinates".   
      
   If you want to predict the position of the stars you also use one   
   reference frame and one clock (Time keeping system)   
      
   > You cannot avoid the fact that different perspectives of a given   
   > phenomenon will yield different descriptions of it. Ditto for   
   > "perspective" => "coordinates".   
      
   A given phenomenon can give different observations.   
      
   > Note that no physical phenomenon can possibly depend on an observer's   
   > perspective or coordinates (nature uses neither), so the physical laws   
   > that describe the phenomenon must be independent of both.   
      
   Correct. But for me physical laws are equivalent to descriptions.   
   A different name is model or mathematical equations.   
      
   > > This recognition between what we observe (which is observer   
   > > dependent) and what actual is, is very important, because it is   
   > > observer independent.   
   >   
   > Yes. But every description requires a perspective (coordinates).   
      
   This depents what we mean with description.   
   I prefer a clear distinction between observation (me) and a description (we).   
   IMO a law is a description of the physical reality   
   but not every description is directly a law (mathematical construct)   
      
   > > In [the world] the actual processes take place.   
   >   
   > Yes. Physical processes take place in the world; we humans describe them   
   > using a MODEL, and such descriptions inherently require a   
   > perspective/coordinates, because that is how we formulate models.   
      
   Here the model should be indepent of our human perspective.   
   The coordinates used as part of the model should be human independent.   
      
   > > In [the world] there is also a clear distinction between processes   
   > > based on electromagnetic phenomena and gravitational phenomena.   
   >   
   > Nonsense.   
      
   ?   
   Thats why you should decouple the observations from the descriptions.   
   This is specific to unravel the laws of falling objects i.e. masses.   
      
   > It is our MODELS that distinguish this. Nature just does   
   > whatever she does (which we do not "know", we only model).   
      
   Now this discussion becomes tricky. (It is a yes and a no)   
   What we humans want is to understand how nature operates.   
   What we also want is to make/build 'tools' as acurate as possible.   
   As such we can make tools (a clock) to measure time (or count).   
   The issue is not all clocks are totally the same.   
   If that is the case you need a model (description) to clearly   
   identify what makes the difference and to explain the difference.   
      
   See also my reply to jt (posted 16 July) in this discussion.   
      
   > We have CHOSEN to use different models for gravitation   
   > and electrodynamics.   
      
   Because these processes are physical different and require   
   different laws.   
   A graviton goes straight from A to B. A photon does not   
   go straight from A to B, when there is something in between.   
   Of course certain 'aspects' can be the same.   
   A the bottom line: We can very little learn from thought experiments.   
      
   Nicolaas Vroom.   
      
   --- SoupGate-Win32 v1.05   
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