🚀 go-pugleaf

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
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