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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