lew@ihuxr.UUCP (07/15/83)
This is a followup to an article which appeared in net.misc and net.religion as part of the "Earth Centered Universe" discussion. cca!charlie stated that, "According to relativity theory ... there is no prefered frame of reference. This means that a stationary earth (the universe spins around it) is as valid a model as any other." The first statement is a misconception. Both special and general relativity give special status to inertial frames. The special theory only deals with a flat space-time (globally inertial frames) and the general theory shows how to patch together LOCALLY inertial frames into a curved global frame. This is accomplished independently of any special coordinate system. Each coordinate system has a different metric from which it is possible to calculate the physical (i.e. invariant) properties of the space. It's true that an earth-centered coordinate system is as good as any other (in general relativity) but this does not constitute a "model". The model is provided by the theory of general relativity itself. Lew Mammel, Jr. ihuxr!lew
gwyn%brl-vld@sri-unix.UUCP (07/29/83)
From: Doug Gwyn (VLD/VMB) <gwyn@brl-vld> The main point of General Relativity was that coordinates are completely an artifice, and physical phenomena do not know or care about coordinates. The exact mathematical expression of this principle encompasses more than just inertial frames... According to this interpretation, relativity DOES have something to say about an Earth-centered universe: "Go right ahead, but you're being silly."