On Oct 12, 2009, at 6:13 AM, Mauro Lacy wrote:
Horace Heffner wrote:
...
...
I really don't think that is possible. There is indeed a slight
apparent retrograde motion of the stars, and it is at an inclination
to the ecliptic. (The poles of the earth's rotation don't match the
poles of the ecliptic.) It amounts to a yearly revolution. It occurs
in the reverse order of the signs (astrological solar houses), i.e.
is retrograde. It is merely an aspect of the earth rotating around
the sun in the ecliptic. It is due to the earth midheaven (or nadir
etc.) at any location rotating, with respect to the fixed sky,
roughly an extra 4 minutes every solar day, i.e 24 solar hours. This
makes the stars seem to be located behind where they were the prior
day, which is an illusion due to the rotation of the earth around the
sun. The sun is off position (with respect to the fixed stars) 4
minutes a day due to the earth moving forward in its orbit. At
midnight different stars are at the midheaven, and the old stars
appear to move about 1 degree of arc retrograde, i.e. (4 m/(24 h*60
m))*360 degrees = 1 degree. In one siderial day the earth rotates
360 degrees with respect to the fixed stars. In one solar day the
sun rotates 360 degrees with respect to the sun. Since the earth
advances about 1 degree in its orbit, the siderial day is about 4
minutes shorter than the solar day.
Now extrapolate that to a movement of the Sun that is not apparent,
i.e.
that is not caused by the translation of the Earth around the Sun, but
by the own translation of the Sun, and you'll see what I mean.
The issue is what Galileo meant. What he meant is clear even from
the translation.
I don't know what "own translation of the sun" means. Within the
precision of Galileo's time, the solar system moved as a unit. The
movement of the solar system through the galaxy was not detectible.
The movement of the near stars due to the parallax from the earth's
orbit as baseline was not even known.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
