I would recommend you get a copy of "Practical Astronomy with your Pocket Calculator" which you can get used real cheap. One of the important concepts to grok in celestial mechanics is *frames of reference*. For example, there are horizon coordinates, equatorial coordinates, ecliptic coordinates, Galactic coordinates, etc. All are *different* frames of reference. While precession will tell you how the satellites appear and change in regards to the background of "fixed" stars, it's really a different frame of reference than when your talking about where the sun is in the sky related to earths horizon. In that regard the important thing is the earths orbit around the sun, which is an ellipse, not a circle. Therefore the important thing is it's eccentricity and it's eccentric anomalies. These are how you'll really calculate the suns positions, rise/set times, etc.
For example, you could learn how to calculate the actual position of the sun, sunrises and sunsets, etc. and it would then become clear that these orbital dynamics are what will determine the position of the sun from the reference point of the earths horizon. Yes the background of the stars does change over time, but only when you include them in your frame of reference. On Jan 30, 2006, at 11:52 PM, doctor_gabby_savy wrote: > --- In FairfieldLife@yahoogroups.com, gullible fool <[EMAIL PROTECTED]> > wrote: > >> >> >> >>> It will be for quite some time. It won't be in 13000 >>> years. >>> >> >> How's 8000 years? Is that enough proof? Link to here >> and change "maximum year" to 9999 and "yearly >> increment" to 100 and you will find that the vernal >> equinox in 9900 will be on March 21st. >> >> http://aom.giss.nasa.gov/srvernal.html >> > > Um, not really. My reading of the very first line of the site is that > March 21 as vernal equinox is a fixed input, a core assumption of the > model. Thats fine for 100-200 year spans, which is what I suspect the > model is used for. Its not fine for 13000 years out. > > > "For the six Atmosphere-Ocean Model simulations (C089, C090, C091, > C092, C093, C094) used by this current web site, all years have > exactly 365 days and vernal equinox always occurs on March 21, hour > 0." > > > >>> You are confusing precession with >>> nutation >>> >> >> I have been an astronomy buff for 38 years and am not >> confused easily. I leave it to those who know little >> about the subject to be confused. >> > > Ok fine. So asking a second time, as a learned bright guy with 38 year > experience in astronomy, how exactly do you define precession of the > equinox? > > I define it as follows: > > >>> "Precesion of the equinox" means that the position >>> of the sun at the >>> vernal equinox, relative to the constallations, >>> "retreats" one degree >>> every 72 years, making a full cycle around the >>> zodiac of 12 >>> constellations every 26000 years. Vernal equinox >>> occurs once a year >>> when day and night lengths are equal and when the >>> sun rises at true east. >>> > > What parts of my definition do you disagree with? > > > > >> --- doctor_gabby_savy <[EMAIL PROTECTED]> >> wrote: >> >> >>> --- In FairfieldLife@yahoogroups.com, gullible fool >>> <[EMAIL PROTECTED]> wrote: >>> >>>> >>>> >>>> >>>>> Well I will bet you a quart of soma that in >>>>> >>> 13000 >>> >>>>> years the vernal >>>>> equinox will be in "September". Lets meet then >>>>> >>> and >>> >>>>> see. >>>>> >>>> >>>> No. The sun moves from its lowest point in the sky >>>> relative to the earth to its highest point in the >>>> >>> sky >>> >>>> relative to the earth in six months, from the >>>> >>> winter >>> >>>> solstice day to the summer solstice day. Half-way >>>> through the six months, the sun crosses the >>>> >>> mid-point >>> >>>> (celestial equator) on its journey northward and >>>> >>> that >>> >>>> crossing of the mid-point is what the vernal >>>> >>> equinox >>> >>>> is. The vernal equinox will always be in March in >>>> >>> the >>> >>>> northern hemisphere and in September in the >>>> >>> southern >>> >>>> hemisphere. >>>> >>> >>> It will be for quite some time. It won't be in 13000 >>> years. >>> >>> >>>> That won't change because of the earth's >>>> minor wobbling. >>>> >>> >>> >>> The 26000 year cycle of the precession of equinox >>> can hardly be termed >>> minor wobbling. You are confusing precession with >>> nutation. How >>> exactly do you define precession of the equinox? >>> >>> I define it as follows: >>> >>> "Precesion of the equinox" means that the position >>> of the sun at the >>> vernal equinox, relative to the constallations, >>> "retreats" one degree >>> every 72 years, making a full cycle around the >>> zodiac of 12 >>> constellations every 26000 years. Vernal equinox >>> occurs once a year >>> when day and night lengths are equal and when the >>> sun rises at true east. >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> ------------------------ Yahoo! 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