Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!houxm!whuxl!whuxlm!akgua!gatech!seismo!brl-adm!brl-smoke!gwyn From: gwyn@brl-smoke.UUCP Newsgroups: net.physics,net.origins Subject: Re: Bogus physics reamplified Message-ID: <1825@brl-smoke.ARPA> Date: Fri, 14-Mar-86 18:37:41 EST Article-I.D.: brl-smok.1825 Posted: Fri Mar 14 18:37:41 1986 Date-Received: Mon, 17-Mar-86 04:16:15 EST References: <368@ihnet.UUCP> <2057@jhunix.UUCP> <2874@sjuvax.UUCP> <446@3comvax.UUCP> Reply-To: gwyn@brl.ARPA Distribution: net Organization: Ballistic Research Lab (BRL) Lines: 59 Xref: watmath net.physics:3944 net.origins:2958 In article <446@3comvax.UUCP> michaelm@3comvax.UUCP (Michael McNeil) writes: >Come on, people! It isn't just the misspelling, it isn't just the >strong language (whether you call it name-calling or not) -- Karl's >argument is completely wrong! Einstein's theory of general relativity >was published more than seventy years ago (1915) -- and it certainly >*does* allow non-inertial reference frames! Only Einstein's *special* >relativity (1905) is restricted in its application to inertial frames. The idea that centrifugal force can be explained by the inductive effect of all matter in the universe is known as Mach's principle. This principle appears to be necessary for any theory that claims that there is no absolute motion. Einstein originally supported Mach's principle and tried to deduce it from general relativity, but in later years he became less convinced of its necessity. The concepts of "absolute", "relative", and "motion" are more subtle than they appear, it turns out. Because of the emphasis on teaching the special theory of relativity, far too much emphasis is placed on so-called "inertial frames" of reference. From a more general viewpoint, one has an inertial frame (locally) whenever the metric is diagonal. It is not always possible to diagonalize the metric by a differentiable change of coordinates, let alone one corresponding to a "motion"; this observation has led to attempts to extend general relativity using a more general notion of metric. > 39.2. Metric Theories of Gravity > > Two lines of argument narrow attention to a restricted class > of gravitation theories, called *metric theories*. It should be noted that Einstein and other early workers in relativity theory determined that the general theory was incomplete, and attempted to extend it in various ways. Some of these attempts generalized the idea of metric, but the most successful theories were formulated in terms of the affine connection of the tangent bundle, with metric introduced only comparatively late in the formal development of the theories, as a derived notion or as an independent-but-related notion. My favorite formulation of the general theory, Schr"odinger's, introduces the metric purely as shorthand for an entity that can be produced from the affinity field. The emphasis on metric has its origins in the Gauss/Riemann development of differential geometry; related concepts have spread throughout linear mathematics. The main complaint I have against Misner/Thorne/ Wheeler is that the book does not adequately prepare one for understanding or investigating the more general theory, which does not track the usual development of differential geometry. The "pure affine" field theory yields a number of interesting symmetries beyond those of general relativity. These are expected to correspond to physical laws other than the gravitational field equations. This was the motivating idea behind the "unified field theory" program pursued by Einstein and others, which has almost universally been called a failure by textbooks. If one compares the structure of theories such as Einstein/Straus/Kaufman with present-day non-Abelian gauge field theories, it becomes apparent that Einstein as usual knew what he was doing and was simply ahead of his time.