From: utzoo!decvax!cca!gwyn@BRL@sri-unix Newsgroups: net.physics Title: Re: the ultimate rocket Article-I.D.: sri-unix.3974 Posted: Thu Nov 11 23:59:04 1982 Received: Mon Nov 15 01:32:46 1982 From: Doug Gwyn Re: magnetic monopole existence The conventional Maxwell differential equations for the electromagnetic field do not include magnetic sources (monopoles). These equations can be brought into patently invariant form under special-relativistic (Lorentz) transformations. However, magnetic sources can be added (analogously to electric charge density) and still maintain Lorentz-invariance. The asymmetry in the equations is what normally makes people desire to restore symmetry by postulating magnetic charges . Since in fact there is abundant evidence for electric charge and none for magnetic charge, the real question changes to "why aren't there any magnetic charges in reality?". They are NOT ruled out on special-relativistic grounds. (By the way, one should beware of "by definition" arguments!) One possible explanation for the absence of magnetic charges can be found in "classical" unified field theory a la Einstein-Schrodinger. In the best of these theories, an equation can be derived from general-invariance arguments that is usually interpreted as the exact vanishing of magnetic charge density. This IS a relativistic result, but in a much deeper sense than usual. Indeed, I would venture to say that no more than a few dozen people understand what Einstein was trying to do with his unified field theory effort; certainly the usual textbook statements about this show lack of understanding. Other possible explanations may be found in specifically quantum theories, although I am not an expert in that area. (Also, from the searches for magnetic monopoles, I would guess that these theories do NOT explain their absence.)