From: goldenfieldquaternions@gmail.com   
      
   On Wednesday, April 12, 2017 at 2:55:38 PM UTC-5, Tom Roberts wrote:   
      
   >   
   > > My, maybe biased, opinion is, that in case of n-body problem, using GR   
   > > is practical 'impossible' when stars are evolved.   
   >   
   > I'm not sure what you mean. The post-Newtonian approximation to GR   
   > applies when gravity and speeds are "small", and that can include many   
   > (but not all!) systems of stars. As I said before, it is is extremely   
   > challenging to apply GR without approximation to an n-body problem.   
   >   
      
   In PPN relativity to O(G^2/c^4) general relativity becomes similar   
   to Maxwell's electrodynamics. A gravitational wave would generated   
   in much the same way a quadrupole oscillation in classical   
   electrodynamics would produce an electromagnetic wave. There are   
   of course no dipole radiation moments for gravitational radiation.   
   The gravitational radiation would of course propagate at the speed   
   of light.   
      
   LC   
      
      
   [[Mod. note -- (The author surely knows this, but others may not.)   
   "PPN" refers to the "parameterized post-Newtonian" formulation, which   
   is a generalization of the post-Newtonian approximation to GR to also   
   include other theories of gravity (e.g., the Brans-Dicke theory).   
   -- jt]]   
      
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