Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site pucc-i Path: utzoo!watmath!clyde!burl!hou3c!hocda!houxm!ihnp4!inuxc!pur-ee!CS-Mordred!Pucc-H:Pucc-I:ags From: ags@pucc-i (Seaman) Newsgroups: net.ai Subject: Re: Four color... Message-ID: <209@pucc-i> Date: Fri, 17-Feb-84 16:19:17 EST Article-I.D.: pucc-i.209 Posted: Fri Feb 17 16:19:17 1984 Date-Received: Mon, 20-Feb-84 06:54:37 EST References: <5540@uiucdcs.UUCP> <1290@mit-eddie.UUCP> Organization: Purdue University Computing Center Lines: 17 > I had thought that 4 color planar had been proved, but that > the "conjectures" of 5 colors for a sphere and 7 for a torus > were still waiting. (Those numbers are right, aren't they?) The sphere problem is equivalent to a plane problem. Just prick a whole in the middle of one of the regions and flatten it into a plane. Therefore 4 colors are sufficient for a sphere. Seven colors were known to be necessary and sufficient on a torus, long before the four-color proof was found for the planar case. -- Dave Seaman ..!pur-ee!pucc-i:ags "Against people who give vent to their loquacity by extraneous bombastic circumlocution."