Horace Heffner wrote: > 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. >
And that does not mean that we shouldn't think and consider those movements today, doesn't it? Even if Copernicus was probably talking about an apparent movement of the Sun, caused by the Earth's translation, and even if in Galileo's times the precision does not allowed them to detect those movements, that does not mean that we are not entitled today to consider a part of that movement as a real one, i.e. as a proper movement of the Sun. What I'm saying is this: even as early as in Copernicus times, the door was open, so to speak, for a consideration of the movements of the Sun as real(i.e. proper), but somehow in the course of history, that door was closed or forgotten, and we started to think about the Sun as fixed, for all practical purposes. And we still do this today, for all practical, cultural, and even scientific and astronomical purposes. That must and will change in the future; we should start to think about the movement of the Sun as a real one, in the same way as we consider today the movements of the Moon and Earth as proper. Mauro
