From: usenet@schweikhardt.net   
      
   Luigi Fortunati  wrote   
   	in :   
   [...]   
   # But then, why do two extraordinarily different systems like the Earth's   
   # mass (6*10^24kg) generate the force of 90kg-weight on my body (mass   
   # 90kg) and my body generates the *same* opposing force of -90kg-weight   
   # on the Earth?   
      
   Asking "why" in physics usually means "is there a more elementary   
   explanantion?"   
      
   Do you accept   
      
       F = G*m1*m2/r^2     (1)   
      
   as an empirical observation?   
      
   Indeed, nobody has ever measured the effect of your body's gravitational   
   force on the Earth. The orders of magnitude for the respective   
   accelerations are too different. Verification of that formula is only   
   technically feasible for large pairs of masses, say Earth/Moon or   
   Sun/Jupiter by observing both bodies in orbit around their barycenter.   
   This requires each body being subject to equal but opposite forces.   
      
   The answer could be "because the masses in (1) appear without preference   
   for either." Or "because multiplication is commutative". Or "because   
   when (1) is written in vector notation, the force vectors have the same   
   magnitude, but opposing direction when the masses are exchanged."   
      
   Regards,   
      
   	Jens   
   --   
   Jens Schweikhardt https://www.schweikhardt.net/   
   SIGSIG -- signature too long (core dumped)   
      
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