Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!qantel!hplabs!sri-unix.ARPA!gwyn@BRL.ARPA From: gwyn@BRL.ARPA Newsgroups: net.physics Subject: Re: Faster than light. Message-ID: <390@sri-arpa.ARPA> Date: Mon, 15-Jul-85 00:32:18 EDT Article-I.D.: sri-arpa.390 Posted: Mon Jul 15 00:32:18 1985 Date-Received: Wed, 17-Jul-85 05:20:38 EDT Lines: 50 From: Doug Gwyn (VLD/VMB)I agree that there is a logical problem. I was pointing out that the instantaneous collapse of the wave function in a special frame was indicative of the logical problem. I too think we need a better quantum theory of measurement. The logical relativistic problem is perhaps best seen by considering the following slight modification of the passing spaceship scenario: observer A E observer B spaceship --> E is an emitter of two particles in exactly opposite directions with exactly correlated spin. Due to the quantum nature of the particle emission, nothing is known about the spins except that they are correlated so that if one measures a spin component of one of them, the statistical distribution (call this D1) of a tilted component measurement of the other one will be different (involves cosine of the relative component tilt angle) than it would have been if the first measurement had not been done (call this distribution D2). Now, observer A measures a spin component of a particle sent in his direction, and shortly thereafter (separated by a spacelike interval w.r.t. the frame in which A, B, & E are all at rest) observer B, who is slightly farther away from E, measures the tilted spin component of the other correlated particle. According to QM, the result of an ensemble of such experiments is that B measures statistical distribution D1. The state of B's particle is supposed to be established "instantaneously" when A makes his measurement. There is no real paradox so long as we think in the rest frame. Now consider the situation from the viewpoint of a passing spaceship traveling at very high speed in the direction shown. If the collapse of the wave function is "instantaneous" as seen by the spaceship, and if B is not too much farther from E than A, then B will measure the spin "before" A does. QM says that B will find statistical distribution D2 (and A something like D1) in this case. Now, we all know that the statistics at B will really still be D1, not D2 (since the spaceship is irrelevant to the quantum phenomenon going on here). Surely there is something fundamentally wrong with the idea that the wave function collapses "instantaneously". What is a correct replacement for this bogus idea? This is more or less the thinking of Einstein that led him to reject the conventional formulation of quantum theory. (He also did not like the idea that there was a fundamental randomness, but that is a separate issue.)