Galileo Galilei's Argument Analysis

Salviati’s thesis in the excerpts of Galileo Galilei’s Dialogue Concerning the Two Chief World Systems, the second day, states that all motion is relative, and diurnal motion is simply relative to the earth, with an emphasis on Copernican heliocentrism. Salviati argues with propositions set forth by Simplicio and Sagredo concerning three questions, one in which the earth is movable or immovable, the second is whether there is a chance in making it movable, and lastly regarding what motion would occur. Salviati’s arguments are concerning his observations of the terrestrial motions which involves the diurnal motions, which he uses to support the heliocentric conception of heavenly motions.
To support his thesis Salviati states that it would be irrational for the celestial sphere to rotate around the terrestrial globe when considering the velocity needed to make the other
Simplicio argues that the great motion is not emphasized or significant to other celestial bodies such as the sun, the moon, and how they rise and set, yet Salviati proposes that the characteristics mentioned would be meaningless without the earth. He argues that the changes occur simply in relation to the earth and are not in relation to the other heavenly bodies. In an argument about diurnal motion, Salviati states that Aristotle has no proof of this idea and that he simple states a reason without a valid demonstration on the topic of contrariety. Salviati poses his argument of the circular movement that the earth rotates from east to west and how the heavenly bodies move from west to east, creates circular motions that would be contrary to each other. Simplicio posed the argument on diurnal motion that is based upon Aristotelian theory, it is that circular motions are not contrary to one another, which he also argues that opposites cannot be defined as