Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!decvax!ittvax!dcdwest!sdcsvax!sdcrdcf!hplabs!sri-unix!crummer@AEROSPACE 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 CrummerThe 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