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From: gwyn@BRL.ARPA
Newsgroups: net.physics
Subject: Re:  Quantum Mechanics
Message-ID: <391@sri-arpa.ARPA>
Date: Mon, 15-Jul-85 00:39:27 EDT
Article-I.D.: sri-arpa.391
Posted: Mon Jul 15 00:39:27 1985
Date-Received: Wed, 17-Jul-85 05:21:02 EDT
Lines: 11

From:  Doug Gwyn (VLD/VMB) 

The "multiple worlds" view was shown to be observationally
indistinguishable from the "collapsing wave function" view.
Last time I read an interview with Wheeler, he had basically
given up on the "multiple worlds" theory because of this.

The linearity issue is an important one, although I worry
more about other aspects than the one you mentioned (square
of amplitude to get probability being nonlinear).  There is
no reason to expect probabilities to add linearly.