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From: rimey@ernie.BERKELEY.EDU (Ken &)
Newsgroups: net.physics
Subject: Re: Blimey, Rimey! (Actually wave equations and many worlds)
Message-ID: <11420@ucbvax.BERKELEY.EDU>
Date: Thu, 16-Jan-86 12:51:13 EST
Article-I.D.: ucbvax.11420
Posted: Thu Jan 16 12:51:13 1986
Date-Received: Sat, 18-Jan-86 00:45:14 EST
References: <117@ucbmiro.ARPA> <2629@umcp-cs.UUCP> <11396@ucbvax.BERKELEY.EDU> <501@hounx.UUCP>
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Reply-To: rimey@ernie.UUCP (Ken Rimey)
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Summary: QM is not quantified ignorance.

In article <501@hounx.UUCP> kort@hounx.UUCP (B.KORT) writes:

>Perhaps my level of understanding is a bit naive, but don't
>the wave equations encode our state of knowldege (uncertainty)
>about the state of affairs prior to measurement?  Also, don't
>we have the basic problem that measurement involves interacting
>with the thing being measured ... ?  When the probability wave
>collapses ... aren't we simply experiencing a quantum jump in
>our state of knowledge?  ...

>If this view is sound, then the wave equation is not so much
>a description of what's "out there" as it is a description of
>"what we know" about that which is "out there."
>
>				-- Barry Kort
>				...ihnp4!houxm!hounx!kort

Well said, but I don't think it's true.

Consider a lone free particle.  In general, we don't know where it is,
so we invent a wave function to give the probabilities of it being
here or there.  But in the real world, this wave function does not behave
as if it described a distribution of hypothetical positions of a classical
particle.  Instead:

	1.  It's evolution in time is entirely self-determined.  There
	is no "velocity" that can be specified independently of position.

	2.  The values of the wave function are complex numbers who's
	squared magnitudes are the aforementioned probabilities.  As
	the wavefunction evolves, it can destructively interfere with
	itself.

If quantum mechanics did nothing but quantify our ignorance about what
we are looking at, how would it explain, say, the discrete energy levels
of atoms?

						Ken Rimey
						rimey@dali.berkeley.edu
						ucbvax!rimey