On Wednesday, February 8, 2017 at 5:52:01 PM UTC+2, pora...@gmail.com wrote:   
   > On Tuesday, January 17, 2017 at 1:03:44 AM UTC+2, fil...@gmail.com wrote:   
   > > On Tuesday, January 10, 2017 at 5:46:13 PM UTC-8, Nagaraju Palagani wrote:   
   > > > Because of gravity, if we drop something, it falls down, instead   
   > > > of up. Well everybody knows that! But we do not know the mechanism   
   > > > that governs gravity?   
   > >   
   > > No. We only have a model that tells us how paths of free fall are coupled   
   > > to energy-momentum(*). General relativity is a non-quantum theory so this   
   > > sort of thing is perhaps not that surprising:   
   > > this is a situation similar to where Lagrangian mechanics was with its   
   > > least action principle: no mechanism underlying the odd property of nature   
   > > choosing extremal paths for particle motions. Then came quantum mechanics   
   > > in the Feynman formulation showing how those extremal paths arise from   
   > > certain wave reinforcement and cancellation.   
   >   
   > ============================   
   > does the Feynman diagram explain why  the change in direction (after   
   collision )   
   > is in angle say ''x''   
   > and not angle ''y ''   
   > iow   
   > why just the angle he is suggesting ??   
   > ==========================   
   >   
   > TIA   
   > Y.P   
   > ===============================================   
   >   
   > [[Mod. note --   
   > * 9 excessively-quoted lines snipped here.   
   > * To answer the poster's question, this depends on how precisely the   
   >   initial conditions are specified.  If they are specified sufficiently   
   >   precisely [so that the impact parameter of the incoming particle   
   >   (i.e., the lateral offset of its incoming trajectory with respect   
   >   to a collision) is known; obviously the uncertainty principle imposes   
   >   restrictions on just how well this can be done] then yes, the particle's   
   >   future trajectory (including the change in direction) can be computed.   
   >   
   >   But in the usual case the impact parameter is completely unspecified   
   >   (we *don't* know the incoming particle trajectory's lateral position   
   >   to ultra-high accuracy) and in this case even classical mechanics can't   
   >   do what you ask.   
   ==============================   
   in other words   
   my above  question  has no answer   
   in current science !!  ??   
   ===   
   TIA   
   Y.Porat   
   =====   
   > -- jt]]   
      
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