Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site utastro.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!ut-sally!utastro!ethan From: ethan@utastro.UUCP (Ethan Vishniac) Newsgroups: net.physics Subject: Re: The Epistemological Aspect Message-ID: <622@utastro.UUCP> Date: Mon, 8-Oct-84 19:23:12 EDT Article-I.D.: utastro.622 Posted: Mon Oct 8 19:23:12 1984 Date-Received: Fri, 12-Oct-84 04:42:36 EDT References: <12668@sri-arpa.UUCP> Organization: UTexas Astronomy Dept., Austin, Texas Lines: 37 [] Well actually, it's not just that the 'timing' of the collapse of the wave function is not predicted. It is predicted in the sense that its rather peculiar properties are well defined. Loosely stated it can be put this way: It is impossible for two measurements to imply inconsistent things about the state of a system even if the system was initially prepared as a superposition of states. In the case of a single particle this is taken to mean that if you measure the position of the particle then future measurements must be consistent with that measurement i.e. must not involve the particle moving faster then the speed of light. In the case of a correlated system like two atoms whose spins sum to zero this means that the measurements of the spins of the atoms (as long as they are undisturbed) must sum to zero regardless of whether the atoms are subsequently separated and given separate homes (oops wrong discussion). This does not *necessarily* imply faster-than-light propagation of wave function collapse. I'm an agnostic on this subject, but I believe that there are alternative views. An example is the many-worlds picture in which a superposition of states is literally a superposition of possible future world lines you might be following. In that case there is an objective reality to all quantities at all times that does not entail ftl propagation of signals. Playing these games of alternate interpretations of quantum mechanics is frustrating because one lacks means for distinguishing between possibilities. "I can't help it if my Ethan Vishniac knee jerks" {charm,ut-sally,ut-ngp,noao}!utastro!ethan Department of Astronomy University of Texas Austin, Texas 78712