rincipia (taking a year and a half to be written) opened by stating the three laws of motion that have immortalized Newton, in millions of textbooks, thoughtful minds worldwide can reitterate these laws verbatium. These laws have truly changed how the "modern man" looks at the world around us:

1. (Law of inertia): A body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an external force.

2. A force acting on a body gives it an acceleration which is in the direction of the force and has magnitude inversely proportional to the mass of the body: .

3. Whenever a body exerts a force on another body, the latter exerts a force of equal magnitude and opposite direction on the former.

The second book of Principia talked about Newton's own philosophy, explaining new scientific ways that would come to replace current realms of thought, such as Cartesianism. Four Laws that would describe Newton's new scientific method were outlined within this book:

(1) We are to admit no more causes of natural things such as are both true and sufficient to explain their appearances.

(2) The same natural effects must be assigned to the same causes.

(3) Qualities of bodies are to be esteemed as universal.

(4) Propositions deduced from observation of phenomena should be viewed as accurate until other phenomena contradict them. (Weisstien)

These rules revolutionized scientific thought, allowed previously unsolvable problems to be understood, and with this second book came through applications on how these rules could be used in the sciences.

Book Three of Principia showed applications of the previously explained, and even and in-depth look at ocean tides and their reliance on lunar motion. To explain his thoughts on universal gravitation, Saturn was observed to slow down as it passed Jupiter. Through Newton's various scientific connections, he was able to prove that this had been observed, and with his equations, he could prove why it occured also. He was also proven by finding that the earth was actually not a perfect sphere, which disproved current Cartesianism thought.