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From: kube@cogsci.berkeley.edu.UUCP
Newsgroups: sci.philosophy.tech,sci.physics
Subject: Re: Bell Inequalities, etc.
Message-ID: <19045@ucbvax.BERKELEY.EDU>
Date: Tue, 26-May-87 21:59:04 EDT
Article-I.D.: ucbvax.19045
Posted: Tue May 26 21:59:04 1987
Date-Received: Thu, 28-May-87 01:49:25 EDT
References: <1275@cci632.UUCP> <766@klipper.cs.vu.nl> <650@pbhyc.UUCP> <19028@ucbvax.BERKELEY.EDU> <651@pbhyc.UUCP>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: kube@cogsci.berkeley.edu.UUCP (Paul Kube)
Organization: University of California, Berkeley
Lines: 49
Keywords: aspect superluminance hidden variables Bell's inequality
Xref: utgpu sci.philosophy.tech:84 sci.physics:1387

In article <651@pbhyc.UUCP> djo@pbhyc.UUCP (Dan'l Oakes) writes:
>In article <19028@ucbvax.BERKELEY.EDU> kube@cogsci.berkeley.edu.UUCP (Paul Kube) writes:
>>
>>So, everybody, what do you want to give up: the impossibility of FTL
>>information transfer, that the particle was spinning happily left all
>>along, or the relevance of mathematics for physics? 
>
>Actually, we can accept a much weaker condition -- the inadequacy of our
>[current] mathematical model to describe the physical reality. 

Fine, though it's nice to have a reason for doing so.

Most everyone feels uncomfortable with noninstrumentalist
interpretations of quantum mechanics.  I am suspicious of anyone who
says they understand them.  Einstein thought it obvious that reality
couldn't be strangely indefinite in the way required by these
interpretations of QM.  It would be nice if there were a way to decide
the question; and that, in fact, is exactly what experiments based on Bell's
inequality are designed to do.

Keep in mind that Bell's inequality doesn't depend on a choice of
interpretation of quantum mechanics.  It's just an exercise in
elementary applied probability theory; given the assumption that
certain random variables are independent (representing absence of
superluminal linkages) and that certain conditional probabilities are
either zero or one (representing that given a value of particle
state--WHATEVER IT HAPPENS TO BE--and an apparatus configuration,
experimental outcome is determined) you get the inequality
(representing relationships among probabilities of outcomes
conditioned on apparatus configuration).  

As it turns out, relative frequencies of outcomes observed in certain
experiments violate the inequality.  This prima facie shows that
either there are superluminal signals or there's a strange
indefiniteness to particle state (coincidentally of the type required
by a noninstrumentalist interpretation of QM).  

To argue for rejecting both of these conclusions, someone should
either point out an error in the derivation of the inequality (pretty
unlikely), some failing of the experiments (they've been repeated), or
some particular infelicity in the application of the former to the
interpretation of the latter.  I would like to see this.   But it's not
enough just to say that it's always possible that our mathematics
fails to correspond to reality (especially in this case where the
mathematics was developed to describe, in a very general way, what
should be observable in case there is some definite reality for our
classical state variables to correspond to).

--Paul kube@berkeley.edu, ...!ucbvax!kube