Galileo's commentary using 21st century tools

"Now what is said here of Jupiter is to be understood of Saturn and Mars also. In Saturn these retrogressions are somewhat more frequent than in Jupiter, because its motion is slower than Jupiter's, so that the Earth overtakes it in a shorter time. In Mars they are rarer, its motion being faster than that of Jupiter, so that the Earth spends more time in catching up with it. Next, as to Venus and Mercury, whose circles are included within that of the Earth, stoppings and retrograde motions appear in them also, due not to any motion that really exists in them, but to the annual motion of the Earth. This is acutely demonstrated by Copernicus . . .

You see, gentlemen, with what ease and simplicity the annual motion -- if made by the Earth -- lends itself to supplying reasons for the apparent anomalies which are observed in the movements of the five planets. . . . It removes them all and reduces these movements to equable and regular motions; and it was Nicholas Copernicus who first clarified for us the reasons for this marvelous effect." 1632, Dialogue Concerning the Two Chief World Systems

http://apod.nasa.gov/apod/ap011220.html

The inner planetary retrogrades have a number of differences which Galileo does not pick up on but are now easily accessible with additional graphics. The plotting of the motions of the inner planets which include retrogrades also incorporate the annual orbital motion of the field of the background stars due to the annual motion of the Earth along the line of the planet's orbital motion.

http://www.youtube.com/watch?feature...&v=MdFrE7hWj0A

http://www.youtube.com/watch?v=eeQwY...cYaW1okcYgB1NR

The motion of Elnath,Castor and Pollux in the first graphic has no daily rotational component but strictly a consequence seen in the second animated graphic as stars are seen to disappear behind the glare of the Sun due to the Earth's orbital motion.

The motion of Venus and Mercury against the background stars,first in the direction opposite their apparent motion as they swerve out from behind the Sun and then with the motion of field of the background stars leads to a number of conclusions which alter Galileo's commentary.

1 - The annual apparent motion of the background field of stars is a consequence of the Earth's annual motion.

2 - The apparent retrograde motion of Venus and Mercury is due to their annual motion around the Sun rather than any input supplied by the Earth's orbital motion.

The changing perspective between the orbital motion of the Earth and the interior planets has minimal impact on why the inner planets display retrograde motion as opposed to the major input of the Earth's motion in the apparent retrogrades of the outer planets.

There is no peer review involved,just enough effort and talent to work through details and enjoy conclusions.