On Friday, September 22, 2017 at 12:43:21 AM UTC-5, rockbr...@gmail.com wro=   
   te:   
   > On Thursday, September 21, 2017 at 1:30:37 AM UTC-5, Luigi Fortunati wrot=   
   e:   
   > > Newton claims that gravity is a force, Einstein denies it: for him it   
   > > is not a force (it is something else).   
   > Let's throw a wrench into the gears here!   
   [A 5-D family of metrics that includes Schwarzschild and Newton as instance=   
   s]   
      
   Compare:   
   Bargmann structures and Newton-Cartan theory   
   C. Duval,* G. Burdet, H. P. K=C3=BCnzle, =E2=80=A0and M. Perrin   
   Physical Review D Volume 31, Number 8, 1841-1853.   
   1985 April 15   
      
   However, they only deal with the case a = 0 and do not generalize   
   to non-zero a.   
      
   > The metric (and 0 constraint)   
   > dx^2 + dy^2 + dz^2 - 2aU/(1 + 2aU) (x dx + y dy + z dz)^2/(x^2 + y^2 + z^2)   
   >  + 2 dt du + a du^2 - 2U dt^2 = 0   
   > with the proper time ds given by   
   > ds = dt + a du   
      
   ... where U is the potential per unit mass. For a point-like source   
   of mass M that's U = -GM/r, where r^2 = x^2 + y^2 + z^2.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)