Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site mordor.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!ut-sally!mordor!@S1-A.ARPA,@MIT-MC:pduff%ti-eg.csnet@csnet-relay.arpa From: @S1-A.ARPA,@MIT-MC:pduff%ti-eg.csnet@csnet-relay.arpa Newsgroups: net.space Subject: questions about the theory of relativity Message-ID: <1786@mordor.UUCP> Date: Tue, 14-May-85 05:49:29 EDT Article-I.D.: mordor.1786 Posted: Tue May 14 05:49:29 1985 Date-Received: Thu, 16-May-85 06:32:08 EDT Sender: daemon@mordor.UUCP Lines: 49 From: Patrick_Duff While space-digest is answering questions from people who have always been bothered by some aspect of the theory of relativity, I have a few which have been puzzling me for some time. Is it theoretically possible to create a device which, after being "locked" onto an object (e.g., the Earth), could always tell you your velocity relative to that object (even after a period of near-light speed travel, various maneuvers, etc.)? I'm not talking about a computer which would perform calculations based upon a history file of past accelerations, but rather a "device" which reacts to the accelerations it experiences. What about a "clock" which would always tell you the time & date on the other object? It seems to me that if you can make either one you can make the other one as well; they are *almost* the same device, aren't they? If these devices are possible, would they require lots of mass (as massive as a planet, perhaps?) to achieve reasonable accuracy over inter-stellar distances, or could they be something more like a wrist-watch? An early science fiction book (\Skylark/ by E. E. Doc Smith) had another interesting device which was something like a compass; where-ever you were in the universe, it would point at whatever you had "locked" it onto (the farther away you were from the object, the longer it took the needle to stop moving, or the more power you had to feed it, or something like that; at one point the characters in the story measured this to find out not only the direction, but also the approximate distance to the object). In science fiction stories, the ease with which ships travel through time without traveling through space has always bothered me. If you could exchange one of the three space axes for a time axis (such as inside the event horizon of a black hole?), travel along it, and then rotate back, then to move 1 second you would have to travel approximately 186,000 miles. Am I missing something here? Also, what difference would it make whether you traveled that distance at a slow speed (.001 c) or a fast speed (.999 c)? Does such travel avoid any cause/effect paradoxes? After all, you would be staying within the cause/effect light-cone, wouldn't you? Finally (for now anyway), I have heard it said that Einstein's theory of relativity could be replaced by a quantum theory of gravity. I'm unconvinced; it seems to me that they concern fundamentally different aspects of the universe. regards, Patrick Patrick S. Duff, ***CR 5621*** pduff.ti-eg@csnet-relay 5049 Walker Dr. #91103 214/480-1659 (work) The Colony, TX 75056-1120 214/370-5363 (home) (a suburb of Dallas, TX)