XPost: sci.physics.particle, tnn.physics   
   From: ralph@eddlewood.demon.co.uk   
      
   My knowledge of quantum theory is close to zero, but I am interested in   
   it, and some of its consequences. This post is an invitation for   
   correction as much as anything.   
      
   The particular issue is the collapse of the wave function, or the state   
   vector, according to choice. My understanding is that the wave-particle   
   duality can be resolved by considering the wave as the probability   
   distribution of the positions of the particle. When the position becomes   
   known, the wave "collapses" in the sense that it is no longer required.   
      
   The difficulty with this is the question: known to whom? I have read a   
   book in which the author laboured to suggest that this collapse, the   
   transition from possibility to certainty, could only happen in the   
   presence of consciousness.   
      
   Now I am delighted to find that Karl Popper produced an argument against   
   this proposition which I find compelling and relatively accessible. I   
   would be interested to know whether it is well-known, and how well   
   regarded.   
      
   Popper prefers propensities to probabilities, and that appeals to me, as   
   an ex-marketing man. We used to describe consumers as having a   
   propensity to buy brands in a market, ranging from 1 if they only ever   
   bought one brand, down to 0 if they would not buy that particular brand   
   whatever the circumstances. Given these propensities, a consumer going   
   into a store would buy the product at the top of their list, given that   
   it was on display, at an acceptable price, and that a brand for which   
   they had a lower propensity was not better priced or promoted.   
      
   Popper's argument is spelt out is his "quantum theory and the schism in   
   physics" which I will greatly shorten here, whilst hoping to preserve   
   the essence. He pictures a series of time-slices in which all the   
   information in the universe is captured on a piece of film. Bear with   
   this, the point will become clearer. He also refers to the wave-function   
   as the wave packet.   
      
   "Let e be the event whose presence or absence we wish to predict, and   
   let s1, s2 ... be classical film strips attached to later and later   
   time-slices. Let   
                            pred (e, s1)   
   be a prediction with respect to e in the light of the appropriate still   
   of film strip s1. We shall then find that pred (e, s1) and pred (e, s2)   
   do not, in general, agree, and that the latter will generally be   
   preferable as a predictor to the former.   
      
   The transition from pred (e, s1) to pred (e, s2) corresponds exactly to   
   the transition from the probability statement p (e, s1) to p (e, s2)   
   where p (a,b) denotes the probability of a given the information b. But   
   the transition from p(e,s1) to p(e,s2) is, as we have seen, precisely   
   what quantum theorists have described as a "reduction of the wave   
   packet". They have suggested that this reduction of the wave packet is   
   connected with, or dependent on, a) the measuring experiment by which we   
   obtain new information s2 and b) the realization or actualization of   
   what was, so far, only potential. (Heisenberg's transition from the   
   possible to the actual). These two points a) and b) are often combined   
   in the suggestion c) that it is only under the stimulus of our own   
   interference with the physical system, only owing to our measuring   
   experiment, that the transition from the possible to the actual takes   
   place. In our picture, in contrast, the transition from the possible to   
   the actual takes place whenever a new state of the world emerges;   
   whenever a new time-slice is actualized or realised, whether observed,   
   or measured, or not. (In fact, observations and measurements are so   
   extremely rare that almost all realizations of potentialities happen   
   independent of them.)   
      
   As long as anything happens, as long as there is any change, it will   
   always consist in the actualization of certain potentialities. Thus a   
   new filmstrip, (and with it a new opportunity for a reduction of the   
   wave packet) appears: whenever any interaction takes place. Whether or   
   not we know or observe the new state s2, and whether or not we replace   
   pred (e, s1) by pred (e, s2) in our attempts to predict e, is completely   
   incidental, and does not in any way bring about the actualization of   
   potentialities.   
      
   *The world changes without reference to us*   
      
   ....   
      
   Of course, some changes are due to our own experiments, and these are   
   both practically and theoretically important to us. But it looks to me   
   very much like a symptom of either myopia or megalomania to allow one's   
   view of the world, or of science, to be dominated, or even coloured, by   
   the disturbances created by one's own experiments. Transitions from the   
   potential to the actual and quantum interactions were going on before   
   anybody interfered with anything, and they will continue going on long   
   after we have left off interfering."   
      
   Comments welcome.   
      
   --   
   ralph   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)