Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site brl-tgr.ARPA Path: utzoo!linus!philabs!cmcl2!seismo!brl-tgr!wmartin From: wmartin@brl-tgr.ARPA (Will Martin ) Newsgroups: net.astro Subject: Re: StarDate: August 18 Message-ID: <4112@brl-tgr.ARPA> Date: Mon, 20-Aug-84 14:49:45 EDT Article-I.D.: brl-tgr.4112 Posted: Mon Aug 20 14:49:45 1984 Date-Received: Wed, 22-Aug-84 02:51:42 EDT References: <414@utastro.UUCP> Organization: Ballistics Research Lab Lines: 27 > In summer, our night sky is turned so that we face toward the center of our > own galaxy. The above quote caused me to begin wondering... Is this situation (that Earth is on the side of the Sun toward the galactic center during Northern Hemisphere summer) something that is pure chance, or is there a reason for it? Is this one of those variable astronomic phenomena that move in long cycles, like the pole star changing as the Earth's axis precesses? If so, do we just happen to be around when this is the case, and in 50,000 or 100,000 years our solar system will have rotated as a whole, and Earth will be on the galactic-center side of the Sun during Northern Hemisphere Winter instead of Summer? (That year-figure is a random guess; what is the actual cycle length, if this is true?) Or is this situation sort of "fixed" with respect to the galaxy? By the way, is there any force or influence that encourages the plane of the planetary orbits to fall in line with the galactic plane? Or is it random chance that our orbit plane is not at right angles to the galactic plane, or some other arbitrary angle? Please post any explanation or discussion. Thanks, Will Martin