Direction of the Earth's axis tilt in the x-y ecliptic plane?

Stuart Levy wrote:
snip
The Earth's motion vector spends about half the year in the
northern hemisphere, about half in the southern, but the durations
aren't quite equal because of its elliptical orbit. So, in which
hemisphere does it spend more time?

Okay, the bonus round question. - If the winter solstice is at
ecliptic or solar longitude 270 degrees and the longitude of perihelion
(closest approach to the Sun) is about what - 283 degrees ), I would
guess that the southern hemisphere and south celestial pole are
pointing towards the Sun at perihelion.

In the ellipsis of a Keplerian orbit, the perihelion side of the
ellipsis is smaller and the aphelion side is larger.
http://en.wikipedia.org/wiki/Perihelion

So, I would guess that the northern hemisphere spends more time pointed
at the Sun than the southern hemisphere.

So, Mr. Trebek, I mean Stuart - - do I get the Jeopardy buzzer or the
bell?

- Canopus56

On 2006-03-20, canopus56 wrote:
SkySea wrote:
snip

Thanks to you and WIlliam H. Thanks for tips. So if I put the "North
Celestial Pole" (NCP) into a coordinate converter, the ecliptic
coordinates of the North Celestial Pole are at:

Ecliptic Long Eclipitc Lat
90 00 00.0 66 33 38.6

So, if at the spring equinox, the ecliptic longitude and latitude of
the Sun is:

Ecliptic Long Ecliptic Lat
00 00 00.0 00 00 00.0

The x-y axial orientation of the Earth's axis relative to the ecliptic
is
perpendicular to the direction of the Sun. (???)

But is the 90 degs ecliptic latitude in the direction of Earth's travel
in its orbit or tilted opposite the Earth's orbital direction of
travel?

The right ascension of the sun at the March equinox is by
definiton zero because that is the point you measure from.
If you were in space looking at the solar system from the
direction of the North ecliptic pole, the Earth would be
rotating on its axis in a counterclockwise direction and the
Earth would be revolving around the Sun in a counterclockwise
direction. The north pole of the Earth would be pointing toward
Ursa Minor. It would be turned toward the Sun in June and
turned away from the Sun in January. So depending on what
day of the year it is, the north pole would be facing the
direction of the Earth's movement around the sun, or at an
angle or facing away.

--
The night is just the shadow of the Earth.

On 2006-03-20, canopus56 wrote:

After playing around with the JPL Planetica
http://space.jpl.nasa.gov/ (Earth view from above, counterclockwise
orbit travel), I guess I've convinced myself that the x-y plane axial
orientation of the Earth's axis at the equinoxes is in the direction of
the Earth's travel in its orbit. If someone could confirm, it would
appreciated. - Canopus56

In September the North Pole is leaning in the direction of the Earth's
motion. In March it is leaning away.

--
The night is just the shadow of the Earth.

William Hamblen wrote:
snip
It would be turned toward the Sun in June and
turned away from the Sun in January.

And at the equinoxes in March and September, it would pointed in what
direction if viewed from above at the North Ecliptic Pole - ignoring
ecliptic latitude - and only discussing ecliptic longitude? -
Canopus56

On 2006-03-20, canopus56 wrote:

So, I would guess that the northern hemisphere spends more time pointed
at the Sun than the southern hemisphere.

The first day of Spring is March 20, 2006, and the first day of Autumn
is September 23, 2006, in the northern hemisphere. March 20 to September
23 is 186 days, which is more than half a year. During the spring and
summer the hemisphere is turned toward the sun.

--
The night is just the shadow of the Earth.

William Hamblen wrote:
On 2006-03-20, canopus56 wrote:


So, I would guess that the northern hemisphere spends more time pointed
at the Sun than the southern hemisphere.


The first day of Spring is March 20, 2006, and the first day of Autumn
is September 23, 2006, in the northern hemisphere. March 20 to September
23 is 186 days, which is more than half a year. During the spring and
summer the hemisphere is turned toward the sun.


This effect would be even more pronounced with a greater eccentricity
of the earth's orbit about the sun.

I suppose you have'nt noticed that your terms are entirely
hemispherical but then again I have never come across individuals who
explicitly love their quasi-geocentric creations.

To William

The Ptolemaic astronomers had cut planetary motion loose from the
stellar background,they created an Equant to account for the discrepany
which Kepler accounted for through an orbit that was neither perfectly
circular not displayed equable motion.

Anyone can enjoy the difference between Ptolemaic and Copernican
astronomies and the conclusions they drew for isolated orbital motion
free of the stellar background -

http://antwrp.gsfc.nasa.gov/apod/ima...2000_tezel.gif

No doubt your disgusting fables will have the ear of people here who
are indoctrinated into the Ra/Dec system but you certainly have no
support from the first heliocentrists such as Rheticus,the student of
Copernicus -

Rheticus



"With regard to the apparent motions of the Sun and Moon, it is perhaps
possible to deny what is said about the motion of the Earth, although I
do not see how the explanation of precession is to be transferred to
the sphere of the stars. But if anyone desires to look either to the
order and harmony of the system of the spheres, or to ease and elegance
and a complete explanation of the causes of the phenomena, by no other
hypotheses will he demonstrate more neatly and correctly the apparent
motions of the remaining planets. For all these phenomena appear to be
linked most nobly together, as by a golden chain; and each of the
planets, by its position and order and very inequality of its motion,
bears witness that the Earth moves. . . .

I sincerely cherish Ptolemy and his followers equally with my teacher,
since I have ever in mind and memory that sacred precept of Aristotle:
"We must esteem both parties but follow the more accurate." And yet
somehow I feel more inclined to the hypotheses of my teacher. This is
so perhaps partly because I am persuaded that now at last I have a more
accurate understanding of the delightful maxim which on account of its
weightiness and truth is attributed to Plato: "God ever geometrizes";
but partly because in my teacher's revival of astronomy I see, as the
saying is, with both eyes and as though a fog had lifted and the sky
were now clear, the force of that wise statement of Socrates in the
Phaedrus: "If I think any other man is able to see things that can
naturally be collected into one and divided into many, him I follow
after and 'walk in his footsteps as if he were a god.'" 1540, Narratio
Prima RHETICUS

oriel36 wrote:
I suppose you have'nt noticed that your terms are entirely
hemispherical but then again I have never come across individuals who
explicitly love their quasi-geocentric creations.



Equinox - March 20, 2006 18:26 UTC
Solstice - June 21, 2006 12:26 UTC
Equinox - Sept 23, 2006 04:03 UTC
Solstice - Dec 22, 2006 00:22 UTC

are independent of hemisphere.

Goodness me,most of humanity already know of climate imbalances while
you and your colleagues dither around with hemispherical variable axial
tilt to the Sun or orbital plane is Equinoxal descriptions.

Is there not one intelligent person here who can manage to keep the
orientations local and not give into the temptation of assigning
seasonal change to variable axial tilt -

http://www.diduknow.info/sun/images/high_low_sun.gif

It is not that difficult -

1 - Keep axial orientation fixed .No need to reference it off to the
Sun or orbital plane,it remains more or less fixed over an annual
orbit.

2 Seperate axial and orbital motions as independent motions. Do not
combine them as the above winter/summer graphic shows in terms of
sunrise/sunset.

3 - Attribute the change in seasons from the deviations occurs in bands
straddling the Equator rather than using hemispheres which split the
planet in two.

4 - Assign the correct mechanism for seasonal changes to a change in
orbital orientation against fixed axial rotation.The change in orbital
orientation is what generates the Equation of Time differential of the
natural unequal day .It is easy to appreceate the change in orbital
orientation by compltely ignoring axial motion and orientation and
concentrating on the behavior of the Earth's orbital shadow at 90
degrees to the Sun/Earth line -

http://www.mhhe.com/physsci/astronom...ages/04f15.jpg

5 - Anybody,I repeat anybody,who attributes seasons using the Ra/Dec
system presents a real obstacle for considering climate imbalances from
seasonal cyclical norms.Is this what you want ?.