Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!ll-xn!ames!necntc!cullvax!drw From: drw@cullvax.UUCP (Dale Worley) Newsgroups: sci.philosophy.tech,sci.physics Subject: Aspect Experiment and Meaning of QM Message-ID: <1216@cullvax.UUCP> Date: Wed, 27-May-87 10:26:00 EDT Article-I.D.: cullvax.1216 Posted: Wed May 27 10:26:00 1987 Date-Received: Fri, 29-May-87 06:10:31 EDT Organization: Cullinet Software, Westwood, MA, USA Lines: 42 Xref: mnetor sci.philosophy.tech:103 sci.physics:1464 According to the "standard interpretation" of QM (exposited by biep@cs.vu.nl), the imperfect knowledge of the universe implied in the wave function is an actual property of the universe, i.e., such physical variables as "position" don't have a single, definite value. djo@pbhyc gives a reasonable exposition of the contrary view, that all physical variables have a definite value at every instant, even if we those values are hard or impossible to observe at some time. This is often called the "hidden variable" model. All philosophical flaming, you say? Not so... If one makes the three assumptions: (1) information always travels slower than the speed of light, (2) physical variables always have a definite value, and (3) physical laws are only based on local interactions (true automatically for common types of differential equations) [I may have these assumption a little wrong] one can derive certain restrictions on the outcomes of certain experiments. These restrictions are called "Bell's inequality", and are independent of the details of the physical theory, as long as it satisfies the three assumptions. The important thing is that most or all hidden variable theories predict that Bell's inequality will be satisfied, but that the standard interpretation of QM requires that it will be violated in certain instances. That is, there are experiments that must have different outcomes depending on whether the standard interpretation or a hidden variable theory describes the actual physical universe. At present, the experimental evidence tends to support the standard interpretation, although I believe that no one has yet done an experiment that fully satisfies the requirements for Bell's inequality, so the jury's actually still out... Dale -- Dale Worley Cullinet Software UUCP: ...!seismo!harvard!mit-eddie!cullvax!drw ARPA: cullvax!drw@eddie.mit.edu Un*x (a generic name for a class of OS's) != Unix (AT&T's brand of such)