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coi

2011/12/15 tijlan <jbotijlan@gmail.com>:
> There are two kinds of south: geological south and magnetic south. The
> geological one represents the point where the planet's axis of
> rotation meets its surface, also called the south pole. 

The axis of rotation also shifts depending on kinetic conditions.

The terrestrial (map) poles are almost fixed to the Earth, but they may 
shift with regard to horizontal tectonic motions:
http://www.iers.org/nn_10968/IERS/EN/DataProducts/ITRS/itrs.html?__nnn=true

There are also celestial poles.

There are therefore at least four kinds of south: celestial south, south of 
a map, "south" (or rather a negative pole) of rotation, south of magnetic 
field.

1. Celestial south
According to the International Astronomical Union, 
http://www.iau.org/static/resolutions/IAU2000_French.pdf
the celestial poles are defined depending on the Earth's revolution around 
the sun (Nos. B1.7 + B1.3 for the Celestial Intermediate Pole). 

2. South of a map
The terrestrial poles are defined depending on the Celestial Intermediate 
Pole (No. B1.8 for the International Terrestrial Reference System).

3. Pole of rotation 
A positive pole ("north") of rotation is defined with so-called right-hand 
grip rule. 
http://en.wikipedia.org/wiki/File:Manoderecha.svg
"South", or rather a negative pole of rotation is the opposite side.
This definition is applied to asteroids and comets:
http://www2.keck.hawaii.edu/inst/people/conrad/research/pub/WGCCRE2009-preprint.pdf

4. South of magnetic field
South of magnetic field is rather complicated. 
A magnetic field is a vector field. 
The south pole of a magnet is the point to which line integrals of magnetic 
field point toward; the north pole of a magnet is the point from which line 
integrals of magnetic field point away.
The South Pole of the Earth is the north pole of a magnet that attracts the 
south pole of another magnet. 
A magnet may have more than two poles.
Some celestial bodies form very complicated magnetic fields. For example, 
the Sun forms a rotating magnetic field: 
http://en.wikipedia.org/wiki/File:Heliospheric-current-sheet.gif


The poles of 1, 2, 3 are defined as two ends of an axis, but the poles of 4 
are not necessarily on an axis. In other words, north and south of 1, 2, 3 
can be defined dependent on each other, or dependent on the definition of 
the axis; on the other hand, north(s) and south(s) of 4 should be defined 
independently.

mi'e guskant mu'o

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<div>coi</div><div><br></div><div>2011/12/15 tijlan &lt;jbotijlan@gmail.com=
&gt;:</div><div>&gt; There are two kinds of south: geological south and mag=
netic south. The</div><div>&gt; geological one represents the point where t=
he planet's axis of</div><div>&gt; rotation meets its surface, also called =
the south pole.&nbsp;</div><div><br></div><div>The axis of rotation also sh=
ifts depending on kinetic conditions.</div><div><br></div><div>The terrestr=
ial (map) poles are almost fixed to the Earth, but they may shift with rega=
rd to horizontal tectonic motions:</div><div>http://www.iers.org/nn_10968/I=
ERS/EN/DataProducts/ITRS/itrs.html?__nnn=3Dtrue</div><div><br></div><div>Th=
ere are also celestial poles.</div><div><br></div><div>There are therefore =
at least four kinds of south: celestial south, south of a map, "south" (or =
rather a negative pole) of rotation, south of magnetic field.</div><div><br=
></div><div>1. Celestial south</div><div>According to the International Ast=
ronomical Union,&nbsp;</div><div>http://www.iau.org/static/resolutions/IAU2=
000_French.pdf</div><div>the celestial poles are defined depending on the E=
arth's revolution around the sun (Nos. B1.7 + B1.3 for the Celestial Interm=
ediate Pole).&nbsp;</div><div><br></div><div>2. South of a map</div><div>Th=
e terrestrial poles are defined depending on the Celestial Intermediate Pol=
e (No. B1.8 for the International Terrestrial Reference System).</div><div>=
<br></div><div>3. Pole of rotation&nbsp;</div><div>A positive pole ("north"=
) of rotation is defined with so-called right-hand grip rule.&nbsp;</div><d=
iv>http://en.wikipedia.org/wiki/File:Manoderecha.svg</div><div>"South", or =
rather a negative pole of rotation is the opposite side.</div><div>This def=
inition is applied to asteroids and comets:</div><div>http://www2.keck.hawa=
ii.edu/inst/people/conrad/research/pub/WGCCRE2009-preprint.pdf</div><div><b=
r></div><div>4. South of magnetic field</div><div>South of magnetic field i=
s rather complicated.&nbsp;</div><div>A magnetic field is a vector field.&n=
bsp;</div><div>The south pole of a magnet is the point to which line integr=
als of magnetic field point toward; the north pole of a magnet is the point=
 from which line integrals of magnetic field point away.</div><div>The Sout=
h Pole of the Earth is the north pole of a magnet that attracts the south p=
ole of another magnet.&nbsp;</div><div>A magnet may have more than two pole=
s.</div><div>Some celestial bodies form very complicated magnetic fields. F=
or example, the Sun forms a rotating magnetic field: http://en.wikipedia.or=
g/wiki/File:Heliospheric-current-sheet.gif</div><div><br></div><div><br></d=
iv><div>The poles of 1, 2, 3 are defined as two ends of an axis, but the po=
les of 4 are not necessarily on an axis. In other words, north and south of=
 1, 2, 3 can be defined dependent on each other, or dependent on the defini=
tion of the axis; on the other hand, north(s) and south(s) of 4 should be d=
efined independently.</div><div><br></div><div>mi'e guskant mu'o</div><div>=
<br></div>

<p></p>

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