hull@hao.UUCP (Howard Hull) (08/18/85)
> From: Doug Gwyn (VLD/VMB) <gwyn@BRL.ARPA> > > (5) Only one electron in the whole universe. > > 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). I also thought there might be one or two others on the net wondering the same thing, which is why I put up this question instead of using mail. Thanks in advance... Howard Hull {ucbvax!hplabs | allegra!nbires | harpo!seismo } !hao!hull
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (08/19/85)
> > 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.
tmb@talcott.UUCP (Thomas M. Breuel) (08/19/85)
In article <1702@hao.UUCP>, hull@hao.UUCP (Howard Hull) writes: > > From: Doug Gwyn (VLD/VMB) <gwyn@BRL.ARPA> > > (5) Only one electron in the whole universe. > > 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). I also thought there might be > one or two others on the net wondering the same thing, which is why I put > up this question instead of using mail. Thanks in advance... Doug Gwyn's explanation is oversimplified and inaccurate. You shouldn't think of one material particle zigzagging around in space giving the appearance of many particle. In the 'one electron' view, the electron *is* the quantum mechanical function describing interactions of other particles with what we would classically consider electrons. 'Collisions' of electrons are just special distinguished features in the time development of this function (we cannot observe collisions directly anyhow, only their effects on the probability of later interactions). Thomas.
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (08/21/85)
> > > zigzagging back and forth in time to produce all the ==== > Doug Gwyn's explanation is oversimplified and inaccurate. You shouldn't > think of one material particle zigzagging around in space giving ===== I suppose if you can't read, it does appear inaccurate. Of course I simplified the answer (but not, I think, oversimplified). The fellow who asked the original question obviously isn't up to having it answered any other way. I posted a more complete explanation in response to Howard Hull's inquiry.