Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site brl-tgr.ARPA Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!vax135!cornell!uw-beaver!tektronix!hplabs!qantel!dual!lll-crg!seismo!brl-tgr!gwyn From: gwyn@brl-tgr.ARPA (Doug Gwyn) Newsgroups: net.physics Subject: Re: Collison with ONE particle? Message-ID: <788@brl-tgr.ARPA> Date: Mon, 19-Aug-85 01:02:51 EDT Article-I.D.: brl-tgr.788 Posted: Mon Aug 19 01:02:51 1985 Date-Received: Sun, 25-Aug-85 13:51:32 EDT References: <494@sri-arpa> <496@sri-arpa.ARPA> <1702@hao.UUCP> Organization: Ballistic Research Lab Lines: 65 > > This sounds like an idea attributed to Feynman and Wheeler. > > The idea is that a positron can be considered an electron > > going backward in time. If one thinks solely in terms of > > particle collisions in space-time, it becomes possible to > > propose that there is only one electron/positron trajectory > > zigzagging back and forth in time to produce all the > > electrons and positrons that we observe. > I was curious about how you describe a collision between two identical > particles using only one particle in a space-time continuum (in which every > space-time point is assumed to be unique). This is Feynman's theory, not mine! In any case, nothing prohibits a point of space-time from hosting more than one particle concurrently. There is no problem with the "same" particle appearing twice at the same event, since each of its appearances is a different point on its infinite zig-zag worldline. Presumably all the concurrent appearances are just the returns from positrons (backward-traveling electron) bouncing off events in the past. A space-time diagram helps one understand this theory. The collision between an electron and a positron would look something like: \ photons / \ / \ / ^ \ / | \ / | o / \ time / \ / \ / \ electron/ \positron distance --> Now, you can think of the electron and positron converging on "o" or you can think of the electron bouncing backward in time and being interpreted as a positron "after" (farther along its wordline) the bounce. In the following diagram, I have shown the "same" electron participating in more than one collision at the same time: \ photons / \ / \ / \ / \ / \ / ^ \ / \ / | \ / \ / | o same time o / \ / \ time / \ / \ / \ / \ / / \ / \ / electron/ \ / \ /same electron o o distance --> Feynman really was looking for a way to assign physical meaning to the advanced solution of the wave equation as well as the conventionally accepted retarded solution. If you follow that idea far enough, this theory is what you come up with.