Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!mgnetp!ihnp4!zehntel!hplabs!sdcrdcf!sdcsvax!akgua!mcnc!ecsvax!dgary From: dgary@ecsvax.UUCP Newsgroups: net.philosophy Subject: Re: Gravity anyone? Message-ID: <3100@ecsvax.UUCP> Date: Tue, 14-Aug-84 11:02:33 EDT Article-I.D.: ecsvax.3100 Posted: Tue Aug 14 11:02:33 1984 Date-Received: Fri, 17-Aug-84 01:10:47 EDT References: decwrl.3290 Lines: 47 < Quoting ... > >From: merrill@gigi.DEC (Rick GIGI::Merrill DECRITE) Mon Aug 13 08:46:28 1984 >Is mass the cause of gravity or does the movement of the gravitons create >the effect of mass? The exchange of virtual particles like gravitons for gravity, Ws and Zs and photons for electroweak, and gluons for strong (color) force are ways of dealing with the "action at a distance" of the forces of nature. Of these particles, only the electroweak ones have been detected (all but the photon this year, in fact). Making gluons would require an accelerator the size of the solar system with something like a quasar as power source, and Glashow says this seems a little much to ask from the Reagan administration. Gravitons are even more theoretical than the other particles. To my knowledge, all currently accepted theories of gravitation are geometrical in nature, with Einstein's General Theory still holding up well as the front-runner. To see how a geometric view of force works, imagine that we are at the Earth's equator and you and I begin walking north. We eventually realise that we are drawing closer together, even though we are carefully walking in a straight line. By repeating the trip with different sized loads we can determine that the "force" between us is proportional to our inertial masses, a mystery indeed (why should gravitational "charge" equal inertial mass, anyway?). But when we discover we are on a curved surface (the Earth) we understand what gives pretty quickly. Replace "north" with "forward in time" and convert the Earth's 2-dimensionasurface to a 4-dimensional one and you have a good measure of General Relativity. There's a good deal more, of course, but all that can be summed up as Einstein did, by saying that "space tells matter how to move, and matter tells space how to curve." You might wonder if the other forces of nature can be dealt with geometrically. The answer is yes, if you allow some of the coordinates to be so tightly curved that moving in a given direction returns you to your starting point in an infinitesimal distance. Such geometrical unified field theories (called Kaluza-Klein theories if my memory and spelling are right) have undergone a recent resurgance of interest. Not directly to the point I admit, but maybe that helps. And yes, this really does belong in net.sci, but I followed the original poster's newsgroup choice. D Gary Grady Duke University Computation Center, Durham, NC 27706 (919) 684-4146 USENET: {decvax,ihnp4,akgua,etc.}!mcnc!ecsvax!dgary