From: richalivingston@gmail.com   
      
   On Sunday, January 1, 2023 at 10:01:21 AM UTC-6, Phillip Helbig (undress to   
   reply) wrote:   
   ...   
   > Imagine a completely empty universe. Would there still be inertia? If   
   > one argues that there wouldn't be, because there is nothing acceleration   
   > could be relative to, would that change if one introduced one or more   
   > other bodies of arbitrarily small mass? If one then observes the   
   > expected inertia, how can that be due to arbitrarily small masses? One   
   > might argue that that would lead to a small amount of inertia and adding   
   > more and more mass in the form of other bodies would increase inertia.   
   > ...   
      
   Actually, combining simple ideas from QM and SR give us momentum:   
   -Consider a mass $m$ at rest.  Per SR this mass represents an energy $mc^2$.   
   -Per QM this energy is represented by a frequency $\omega = mc^2 /\hbar$.   
   Therefore the QM wave function is something like:   
   $\Psi = \Psi_0 e^{i mc^2 t /\hbar}$   
   -Now consider an observer moving at $-\beta$ wrt this mass.  They will   
   transform the time to $t =>  \gamma t' - \gamma \beta x'$ (using units of   
   seconds for time and space).   
   -This gives the wave function in the observers frame as:   
   $\Psi = \Psi_0 e^{i ((\gammamc^2  /\hbar) t' - (\gamma mc^2  /\hbar) x')}$   
   -Note that in QM the wave number, $\gamma \beta mc^2$, is the momentum   
   of the mass.   
   -This means that if that mass had originally been in the observers frame, he   
   would have had to impart an energy $(\gamma -1) mc^2$ to the mass with   
   an accompanying momentum imparted of $\gamma \beta mc^2$.  This is   
   what we mean by inertia, that it takes energy and momentum to make an   
   object move.   
      
   I don't think we need to invoke the mass of the universe to explain inertia,   
   unless it is that mass that generates the Minkowski space-time geometry.   
      
   Rich L.   
      
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    * Origin: you cannot sedate... all the things you hate (1:229/2)