From: tjroberts137@sbcglobal.net   
      
   On 8/18/18 11:51 PM, Phillip Helbig (undress to reply) wrote:   
   > In article <19886fb9-8614-4aee-acb1-2c1356393302@googlegroups.com>,   
   > Lawrence Crowell  writes:   
   >> Two anti-masses will repel as can be seen with   
   >> ma = -GMm/r^2,   
   >> where for M and m negative this equation picks up an additional minus   
   >> sign.   
      
   That is a NEWTONIAN equation, and is irrelevant.   
      
   > While (if I remember Steve Carlip's comments on this correctly) this is   
   > correct, it is not obvious where the extra minus sign comes from.  The   
   > two on m and M cancel, so if you like the extra one is the one seen   
   > explicitly in the equation above.  But where---via a simple, heuristic   
   > argument---does it come from?  We can't just assume that that which we   
   > wish to prove is true and insert it for that reason.   
      
   In GR, negatively massive objects have an effect on geometry such that   
   the timelike and null geodesics of small particles diverge from them (as   
   opposed to positively massive objects for which such geodesics   
   converge). Small particles with negative mass follow timelike geodesics,   
   just like positive-mass particles.   
      
   For two negative-mass objects that both have significant effects on the   
   geometry, I don't know the answer except that this case must go smoothly   
   into the above case as one object's mass is decreased.   
      
   Tom Roberts   
      
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