Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site mordor.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!lll-crg!mordor!@S1-A.ARPA:KFL@mit-mc.arpa From: @S1-A.ARPA:KFL@mit-mc.arpa Newsgroups: net.space Subject: SPACE Digest V5 #240 Message-ID: <3121@mordor.UUCP> Date: Tue, 20-Aug-85 21:41:35 EDT Article-I.D.: mordor.3121 Posted: Tue Aug 20 21:41:35 1985 Date-Received: Fri, 23-Aug-85 07:14:31 EDT Sender: daemon@mordor.UUCP Organization: S-1 Project, LLNL Lines: 17 From: Keith F. LynchI think that that formula for axial tilt as a function of time is an approximation only valid for a certain period, since it is a cubic equation and the way the tilt really varies is more like a sine wave. No finite polynomial can approximate a sine wave over an arbitrarily large interval (I thought you No-Such-Agency folks knew all about non-polynomial functions, etc). Note that what is being measured is the tilt between the plane of the ecliptic and the plane of the Earth's equator. It is not the ecliptic that is moving, but the equator, or rather the projection into space of the equator (the equator stays at about the same place on the ground). Where does one find equations like that? I have been looking for such things... ...Keith