Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbvax.BERKELEY.EDU Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!space From: JOSH@YKTVMH.BITNET ("Josh Knight") Newsgroups: net.space Subject: Clumping doesn't fix Olber's paradox Message-ID: <8603041333.AA12454@s1-b.arpa> Date: Mon, 3-Mar-86 20:46:46 EST Article-I.D.: s1-b.8603041333.AA12454 Posted: Mon Mar 3 20:46:46 1986 Date-Received: Fri, 7-Mar-86 04:03:07 EST Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 57 BH> Date: 26 Feb 86 19:55:07 GMT BH> From: hplabs!amdahl!drivax!holloway@ucbvax.berkeley.edu (Bruce Holloway) BH> Subject: Re: Olber's paradox BH> Another solution (maybe): All stellar objects tend to "clump" into BH> solar systems, galaxies, clusters, ad infinitum. So instead of spreading BH> evenly throughout the sky, we just see light from these collections, the BH> scope of said clumps depending on how far away the object(s) is/are. REM> From: Robert Elton Maas REM> Subject: Many solutions to olber's paradox!! (Keep an open mind!) REM> Of course! ...(material deleted)... REM> I should have thought of that myself, having workd REM> with Mandelbrot and Gosper and Farmwald and Moravec on fractal stuff REM> at SU-AI... Indeed, if the large-scale clumping of the Universe has REM> sufficiently small fractal dimension, then even in a static and REM> infinite-time Universe you see only a finite amount of light from any REM> point due to inverse-square diminuation and less than square REM> accumulation of stars. It sounds paradoxial, after all with infinite REM> time the density of light should increase linearily, exceeding any REM> given level, but actually in fractal universe with increasingly large REM> voids as you go out further you get an effect similar to a single REM> local cluster with emptiness beyond: most of the light that is emitted REM> goes out to fill the infinite void beyond, with the part that stays REM> local being buonded in intensity. From "The New Cosmos" by Albrecht Unsold (translated by W.H. McCrea, Springer-Verlag 1969, NY), p 328: H.W.M Olbers 1826 appears to have been one of the first astronomers to have considered a cosmological problem from an empirical standpoint. Olber's paradox asserts: Were the universe infinite in time and space and (more or less) uniformly filled with stars, then - in the absence of absorption - the whole sky would radiate with a brightness that would match the mean surface brightness of the stars, and thus about that of the surface of the sun. I don't think clumping, no matter what its statistical characteristics can avoid the paradox. Basically, if one extends one's line of sight far enough, one finds it ending up on a star, i.e. the entire surface is covered with star surface. At this point it is only surface brightness that matters. Olber's paradox is "why is the night sky dark" not "why is the sky not infinitely bright". I'm not as sure about my conclusion if one assumes one is at the center of the universe, but I tend not to make that assumption ;-). As an aside, it is interesting to note that in the early part of this century, an incorrect accounting for interstellar absorption caused many astronomers to believe our galaxy was a small elliptical one, rather than the large spiral it really is. Of course one of the artifacts of this error was to place the solar system near the center of the galaxy. Josh Knight IBM T.J. Watson Research Center josh@yktvmh.BITNET, josh.yktvmh@ibm-sj.arpa