On Jan 31, 2006, at 12:22 PM, doctor_gabby_savy wrote:
Well, it was jumping to another set of questions from the one being discussed. We can only answer so many questions at a time, but here goes:
1) vernal equinox occurs once a year when day and night lengths are equal and when the sun rises at true east.
The vernal equinox is the time closest to the equinocial point (where earth cross the celestial equator). This actually contains a number of fallacies, namely the equal day and night myth. Different things occur at different latitudes.
Well exact equality its not a critical assumption of my consclusion. But they are near their most equal at VE, right?
IIRC it is usually within a couple of days at the equator and differing dates further from the equinox as you move away from the equator. For example, day and night are always equal at equator (correct?).
No, just close to the equinox. Keep in mind the equinox is a defined from the center of the sun and that when the sun rises, this is defined by the rising edge of the orb. However on the actual day of the equinox the point which describes the center of the sun above the horizon for 12 hours.
This is an important point, as the sun actually does take up a certain angle--actually one of my ancestors used this fact to first calculate the period of Venus (no pun intended). And in artic circle at Solstices its either long nights or long days. Approaching the VE days lengthen and nights shorten. At some point they are equal. And that occurs around VE. Thus around VE all lattitudes have near equal day and nights, right?
Nearly.
Much of this can be explained in a few moments with a globe and a light bulb, it's much more difficult to explain in words.
Also you need to understand that the sun is a lousy timekeeper, thus astronomers use the "equation of time". Some days it's more than 24 hours, other days it's less.
Understood. I was trying to keep it simple. Its not a critical assumption of my consclusion.
2) "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.
Yeah, approximately. This is caused by the obliquity of the
ecliptic. It changes over time.
Understood. I was trying to keep it simple. Its not a critical assumption of my consclusion.
3) Even with precession of the equinox, from an earth view, the sun will always rise at due east at the vernal equinox, thus the precession does not effect orientations of buildings to true east or the path of the sun relative to buildings (from a year of observations starting at the vernal equinox.)
Yes, it's just that the constellation the sun is in at any moment will change over time. Eventually sun will enter aquarius at this time.
In tropical right? Western astrologers are the ones tooting "age of acquarius"
In Jyotish, IIRC, it will occur around 2400 CE.
Thus, in sideral, sun at VE will always at cusp of Aries and Pisces.
4) The precession - the postion of the sun at vernal equinox -- travels through each constellation about every 26000/12 = 2160 years.n In 60 BC, the sun at vernal equinox was just on the cusp of Aires moving into Pisces. Around 2100, the the postion of the sun at vernal equinox will move from Pisces to Aquarius (aka the "age of aquarius").
Yes, sidereally.
No tropically, see above. Precession causes sun to retreat tropically I believe.
I'm not familiar enough with tropical system to say.
5) The sun annually transits 360 degree , a full "circle" around the constellations. Each month roughly corresponds to the suns position in each constallation.
No. Different constellations have different widths. This only works if you arbitrarily place a 12 x 30 degree gripd on the sky. Then, again, keep in min. the sun does not move at a constant rate (thus the equation of time) so even that is not exact. Also consider as did Kepler, the orbits are not perfect circles.
Understood. I was trying to keep it simple. Its not a critical assumption of my consclusion.
6) In summer months, the hemisphere one habitats is closer to the sun (due to its 23.5 degree tilt -- relative to its "eleptic" path around the sun). Thus in summer it is warmer and days are longer. In Winter the hemisphere is further from the sun, thus its colder and days are shorter. At the equinoxes, matched longitudes in each hemishperes are the same distance from the sun. Day and night are each 12 hours.
No. Long story.
I would like to hear it. Meanwhile I am sure we agree that summer is warmer than winter. Which is the relevant point for my train of logic.
7) The precession - the postion of the sun at vernal equinox -- travels to its opposite constallation every 13000 years. In 13000 years, the postion of the sun at vernal equinox will be in Virgo, 180 degrees from its present position in Pisces.
Approximately.
Yes. Every thing here is approximate.
8) When the sun is in virgo, around September, the tilt of the earth relative to its path around the sun gives fall weather for the northern hemisphere, and spring weather in the southern hemisphere.
Yeah...
So you agree that in 13000 years, tropical sun is in virgo, aka around september? I would have to calculate it, I am not very interested in tropical astrology.
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