From: richalivingston@gmail.com   
      
   Can anyone give a clear explanation why information has to be conserved   
   in quantum mechanics?   
      
   I was not taught this when first learning about QM in the 1970's.  As   
   best as I can tell the idea comes from the idea that the QM wave   
   function evolves per a unitary operator that can, in principle, be   
   reversed to recover the past state as well as calculate the future state   
   of the system.   
      
   It seems to me that this argument is missing two important facts: -The   
   wave function is not real, it is only a mathematical tool for predicting   
   the probabilities of future states -The actual future is one of many   
   predicted by the wave function, and likewise can be the result of many   
   different possible past states.   
      
   It seems to me that each time the wave function "collapses" that   
   information is lost.  Is there a good argument why this is wrong?   
      
   Rich L.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)