Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site brl-vgr.ARPA Path: utzoo!watmath!clyde!burl!ulysses!harpo!decvax!ittvax!dcdwest!sdcsvax!sdcrdcf!hplabs!hao!seismo!brl-tgr!brl-vgr!gwyn From: gwyn@brl-vgr.UUCP Newsgroups: net.physics,net.astro.expert Subject: Re: cosmology Message-ID: <1617@brl-vgr.ARPA> Date: Tue, 8-May-84 18:08:15 EDT Article-I.D.: brl-vgr.1617 Posted: Tue May 8 18:08:15 1984 Date-Received: Sat, 12-May-84 08:40:30 EDT References: <253@utastro.UUCP> Organization: Ballistics Research Lab Lines: 82 Xref: 190 8 On the off-chance that no one else is really interested in this topic, I will try to keep future additions brief. (Come on! Let's hear somebody else at least say whether he cares about any of this stuff!) I doubt that Ethan Vishniac & I are going to eventually agree on the answers to the various issues. Partly this is because it is hard to get unambiguous answers to cosmological questions through experiment and observation. For example, it is NOT known that the observed universe is expanding in any real sense. What IS known is that there is an observed Hubble phenomenon, namely, the red shift of galaxies whose distance has been determined by non-Hubble means is roughly proportional to their distance from us. The conclusion that these galaxies are receding from us proportionally to their distance, which is an expansion, is simply the usual INTERPRETATION of the Hubble phenomemon based on the assumption that the red shift is caused by a Doppler effect (relative velocity of light emitter and receiver). This is not the only possible interpretation of this effect; for example, E. A. Milne (who accepted special relativity but not the general theory) explained the effect via his "kinematic relativity" (actually, I am prepared to yield that Milne's idea was really expansion) and various non-mainstream cosmological models predict this effect directly from path integrals of the "photons". (The "tiring photon" idea has been seriously proposed by reputable theoreticians in the past.) I don't think Ethan fully understood what I was saying about the natural appearance of the cosmological constant in the Einstein-Schr"odinger unified field theory. The best reference for this particular point is "Space-Time Structure" by Erwin Schr"odinger (1950, Cambridge University Press). The same author also had a marvelous treatise on cosmology entitled "Expanding Universes" (1956, Cambridge) which I wish I had a copy of (can anybody supply me with one?). I redeveloped the E-S unified field theory from first principles in my Master's thesis, although the cosmological constant receives only brief mention there. The important thing about this generalization of general relativity is that the way in which the cosmological constant is produced forces one to acknowledge that (a) it is non-zero, and (b) its particular value is determined by the measurement standard (e.g. meter), somewhat the same as the way the speed of light depends on the relation between the time and space measurement standards (although the analogy is not exact). In terms of distance units comparable with the "radius of the universe" (which is a meaningful concept in any natural cosmology engendered by this alternative theory), the cosmological constant is around 1; in terms of laboratory units (e.g. cm^-2), it is quite small, < 10^-50. Until we have "measured" the radius of curvature of the universe in lab units, the value of this constant in cm^-2 will not be accurately known. The first reference I have found to the "self-gauging" universe is A. S. Eddington, "The Mathematical Theory of Relativity" (2nd Ed., 1924, Cambridge). Another interesting point is that the deSitter cosmology is related to (invariant with respect to, I think, but am not entirely sure) the deSitter group that at one point attracted some interest from the elementary particle theoreticians. The E-S theory raises the idea that there is an inherent relation between the large-scale structure of the universe and the behavior of elementary particles; of course these days this idea is in vogue, but it was pooh-poohed when originally suggested. One more note: The E-S unified field theory is NOT just classical general relativity "with an additional term". Its formulation reaches deeply into the fundamental concepts that lead to the idea of metric and geodesic, so the older ideas of these do not necessarily apply to the extended theory. The E-S theory under the usual interpretation of the meanings of the quantities appearing in it leads to nonlinear electromagnetic field equations of Born-Infeld type (C. R. Johnson showed this for the similar Einstein-Straus- Kaufman theory in Physical review D, 1971-1973). Sciama and Corben suggest that the non-zero torsion of the extended theory is related to spin and isospin, and it is easy to see how the E-S theory includes a "classical two-valuedness" due to an internal symmetry of the theory. These ideas cannot be handled by standard general relativity alone, as is well known. I happen to think that Einstein knew what he was doing when he went off to work on the unified field theory. I realize this is not the consensus viewpoint of the physics community, but on reading nearly all the available criticism of Einstein's program I have found little evidence of understanding of his reasons for pursuing this approach. One gets the impression that the majority of physicists thought that he was getting senile or something. "I may be crazy but if so at least I am in good company!"