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   From: helbig@asclothestro.multivax.de (Phillip Helbig (undress to reply))   
   Newsgroups: sci.physics.research   
   Subject: Re: Apparent rotation   
   Date: 11 Jan 2023 08:32:14 GMT   
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   From: helbig@asclothestro.multivax.de   
      
   In article , Luigi Fortunati   
    writes:   
      
   > wugi lunedì 09/01/2023 alle ore 13:15:37 ha scritto:   
   >   
   >> I think that, as Richard Livings said elsewhere, acceleration in general   
   >> and rotation in particular are 'absolute' in the sense of non-inertial.   
   >> Any inertial system will 'detect' acceleration and rotation, and their   
   >> 'inertia'.   
   >>   
   >> As to why this is so, and whether Mach's principle and far away universe   
   >> parts should be called for, I doubt it.   
      
   >> Now then, how does the EM field 'decide' about its local behaviour and   
   >> metric? Does Mach and the far away universe possibly intervene here 'in   
   >> the second degree'? That, I wouldn't know...   
   >   
   > Why bother the distant universe if rotation (like any other   
   > acceleration) are "absolute"?   
   >   
   > Matter is made up of atoms with a nucleus inside.   
   >   
   > If we rotate the matter (ie the atoms) the nuclei that "float" inside   
   > them "push" outwards and generate centrifugal force opposed by the   
   > centripetal force of the molecular bonds.   
   >   
   > The presence of these two opposing internal forces of matter is   
   > confirmed by the internal tension of the rotating bodies.   
      
   Yes.  No-one debates the fact that accelerations are absolute.  The   
   question is WHY that is the case.  Imagine an empty universe with one   
   object in it, say a merry-go-round.  Should it be possible to tell if it   
   is rotating, as it would be under normal conditions?  If so, with   
   respect to what is it rotating?  There is nothing else in the Universe.   
      
   Some would claim that there would be no way to tell in such a case, i.e.   
   no inertia.  Add a small amount of matter to the universe and there   
   would be a small amount of inertia.  Add more and there would be more.   
   And so on.  That would make sense if inertia is somehow caused by the   
   presence of other matter, which is the essence of Mach's Principle.   
   Certainly the Lense-Thirring effect indicates that the idea that   
   relative rotation has physical effects is not absurd.   
      
   As far as I know the extent to which, if any, Mach's Principle is real   
   is still an open question.   
      
   The alternative seems to be absolute space, which is usually associated   
   with Newton rather than Einstein.   
      
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