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From: crummer%AEROSPACE@sri-unix.UUCP
Newsgroups: net.physics
Subject: Re: The Epistemological Aspect
Message-ID: <12668@sri-arpa.UUCP>
Date: Thu, 4-Oct-84 12:18:08 EDT
Article-I.D.: sri-arpa.12668
Posted: Thu Oct  4 12:18:08 1984
Date-Received: Sun, 7-Oct-84 21:31:27 EDT
Lines: 29

From:            Charlie Crummer 

The Aspect (Alain Aspect from Paris) experiment is the equivalent of a famous
gedankenexperiment proposed by Einstein, Podolsky, and Rosen (EPR) in 1937.
(Check Science Abstracts for the exact reference.)  The EPR experiment was
meant as a reductio ad absurdum of the so-called Copenhagen (Bohr) interpre-
tation of quantum mechanics.  The gist is this:  Think of a box with impene-
trable walls.  Put one particle in it.  The wave function spreads uniformly
throughout the box.  (The Copenhagen school says that the wave function 
contains ALL of the information about the system.)  The box is like one of 
those magician's boxes where you can slip a divider down the middle and take 
the box apart into two pieces without looking inside them.  Do this. (The wave
function is changed but it resides equally is both boxes.)  Leaving one box
in Cucamonga, take the other to Newark.  One box is opened.  Supposing that
no particle is found.  The Copenhagen interpretation maintains that the 
observer of this box now KNOWS FOR SURE that the particle will be found in 
the other box because his observation changed the system by collapsing the wave
function (instantaneously?) into that box.  (The timing isn't part of the 
experiment and isn't predicted.)  He calls his friend and tells him
that he will SURELY (probability = 1) find the particle in his box.  This goes
on and on and the predictor is ALWAYS right.  "Ridiculous!", says Einstein,
"Absurd!", says Podolsky, "Yeah!", says Rosen, "Unfortunately, however, that's
the way it is.", says Aspect.

For a description of the Aspect experiment (he didn't actually use a magician's
box, Newark, or Cucamonga) see Scientific American a year or so back. (Reader's
Guide will tell you.)

  --Charlie