Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!houxm!houxz!vax135!floyd!cmcl2!seismo!hao!hplabs!sdcrdcf!sdcsvax!dcdwest!ittvax!decvax!mcnc!ecsvax!dgary From: dgary@ecsvax.UUCP Newsgroups: net.physics,net.astro.expert Subject: pulsing quasars and the like Message-ID: <2631@ecsvax.UUCP> Date: Fri, 1-Jun-84 20:02:43 EDT Article-I.D.: ecsvax.2631 Posted: Fri Jun 1 20:02:43 1984 Date-Received: Tue, 5-Jun-84 19:37:59 EDT Lines: 30 For some time I have been reading about rapidly pulsing objects and how this puts an upper limit on their size. That is, since no signal can propagate faster than light, the period of oscillation of a body cannot be less than the light transit time. I'm confused by this, and I offer a thought experiment to explain why. Imagine an immense pool of water with a couple of flags at either end. Suppose I disturb the water in the center of the pool so that waves cause the flags to move up and down. A distant observer can see that the flags are moving almost in unison. Can this user then infer that the pool is of a certain limited size? Or, more to the point, imagine a spherical body in space light years across. A signal travelling at less than c but consisting of high-frequency pulses travels from the center of the body and reaches the perimeter 'simultaneously' in all directions, causing said perimeter to pulsate in unison. I'm not suggesting a mechanism, just asking if this isn't somehow possible. If we're talking about objects more or less at rest with respect to us, I don't see how simulaneity considerations really enter into it. So, does the period of pulsation really place an upper limit on size?? Confusedly, D Gary Grady Duke University Computation Center, Durham, NC 27706 (919) 684-4146 USENET: {decvax,ihnp4,akgua,etc.}!mcnc!ecsvax!dgary