On Sep 19, 6:12*pm, Sam Wormley wrote:
oriel36 wrote:
The approaching Equinox represents the product of two separate motions
- daily rotation which causes the day and night cycle and the slow
orbital turning of the Earth which brings the *rotational axis in line
with the solar radiation/orbital shadow boundary and causes variations
in the daylight/darkness cycle at all points North and South of the
Equator -

* *Many definition will say the equinox occurs when the sun crosses the
* *celestial equator, but the correct definition is when the apparent
* *longitude of the sun is 0° or 180°.


No offence Sam,about 500 years on from Copernicus,the least we can do
is explain the Equinox event in terms of the motions of the
Earth.Trust me,this is a major modification to the explanation for
seasonal variations in daylight/darkness with the added insight that
the daily rotational and orbital motions combine to generate the
variations in the natural noon cycle.



* *As Paul Schlyter pointed out on the 19th of last March, the difference
* *between the two is just a few tens of seconds at most, which most would
* *not notice.

* -Sam

This is the 21st century Sam and it is about time somebody actually
noticed that the Earth orbits the Sun in a specific way.The orbital
motion of the planet is slowly turning to the central Sun and is about
to split the rotational poles thereby generating global symmetry in
terms of daylight/darkness.For astronomers,the Equinoxes should far
more interesting than the hemispherical seasonal solstices but as yet
it requires astronomers to appreciate this.

Go ahead and celebrate your geocentric view of the Sun crossing the Ra/
Dec celestial Equator and be proud of it,I still have to find people
who have the aptitude and the dignity to approach the modification for
seasonal explanations using the motions of the Earth arising from the
original explanation of Copernicus -

"To this circle, which goes through the middle of the signs, and to
its plane, the equator and the earth's axis must be understood to have
a variable inclination. For if they stayed at a constant angle, and
were affected exclusively by the motion of the centre, no inequality
of days and nights would be observed. On the contrary,it day or the
day of equal daylight and darkness, or summer or winter, or whatever
the character of the season, it would remain identical and
unchanged." Copernicus

It is when the unequal natural noon cycles require an explanation that
the modification becomes apparent,specifically isolating orbital
motion and determining that a location slowly changes through 360
degrees with respect to the Sun in the absence of daily rotation.Your
colleagues are so focused on referencing daily rotational and annual
orbital motion off the astrological Ra/Dec framework that they cannot
see the subtle motion within a motion as a location slowly turns
through 360 degrees with respect to the central Sun or maybe it is
just that they do not want to see this 100% geometric and
observational certainty.

I am not surprised that you express the Equinox in geocentric terms
but it would be much better to see an attempt at explaining it in
terms of the motion of the Earth.