Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site rochester.UUCP Path: utzoo!linus!philabs!seismo!rochester!FtG From: FtG@rochester.UUCP Newsgroups: net.physics Subject: Re: Circumnavigation Message-ID: <1981@rochester.UUCP> Date: Fri, 17-Jun-83 12:36:19 EDT Article-I.D.: rocheste.1981 Posted: Fri Jun 17 12:36:19 1983 Date-Received: Sat, 18-Jun-83 22:46:44 EDT References: <2183@sri-arpa.UUCP> Organization: University of Rochester Lines: 12 I believe Sagan was referring to circumnavigating the KNOWN universe, which is a small fraction of the entire universe. The diameter of the known universe is taken to be a fixed constant and those objects currently within the diameter but receding away will eventually become "unknown". (The combination of inverse square and red-shift puts an upper limit on what we can "see", even with the very best [radio] telescope possible due to quantum mech. effects.) This diameter, in light years, depends on your choice of Hubble constant,.... etc. FtG @ rochester