On Oct 11, 2009, at 5:36 PM, Mauro Lacy wrote:
Horace Heffner wrote:
On Oct 11, 2009, at 4:38 PM, Mauro Lacy wrote:
"The third motion in inclination is consequently required. This
also is
a yearly revolution, but it occurs in the reverse order of the
signs,
that is, in the direction opposite to that of the motion of the
center.
The above just talks about the apparent slight daily apparent
retrograde motion of the stars due to the difference in the sidereal
day (23 h 56 m 4.1 s) vs the solar day. This is merely an aspect of
the earth rotating around the sun in the ecliptic. See:
http://scienceworld.wolfram.com/astronomy/SiderealDay.html
The apparent motion of the stars is thus in the opposite direction of
the sun's motion, because at the same solar time very day the earth
has rotated a an extra 4 minutes so the overhead position has
advanced relative to the stars - making the stars appear to move
retrograde (backwards in relation to the sun's movement.)
This is just a ramification of the earth moving in the ecliptic.
These two motions are opposite in direction and nearly equal in
period.
The result is that the earth’s axis and equator, the largest of the
parallels of latitude on it, face almost the same portion of the
heavens, just as if they remained motionless.
This says that the plane of the earth's motion (the ecliptic) is
almost fixed in relation to the fixed stars, and thus so are the
poles of the ecliptic. This is just a non-geocentric description of
the plane of the ecliptic.
Meanwhile the sun
seems to
move through the obliquity of the ecliptic with the motion of the
earth’s center, as though this were the center of the universe. Only
remember that, in relation to the sphere of the fixed stars, the
distance between the sun and the earth vanishes from our sight
forthwith."
To me this just means: the sun appears to move on the ecliptic
because the earth moves around the sun in the plane of the ecliptic,
and the stars do not appear to move because the distance to the sun
is miniscule in comparison to the distance to the stars.
That's only the last part of it. I recommend you to read it again.
It is
also convenient to read the previous passages also.
Best regards,
Mauro
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
