What are the Newtonian principles?
Isaac Newton, in his book, Principa Mathematica ("Mathematical Principles") codified the findings of Galileo from a generation earlier in developing the Three Laws of Motion. The first enunciated the concept of inertia, where matter at rest stays at rest, matter in motion stays in motion at a constant velocity when not acted upon by a force. The second law, the foundation of Classical Physics, defines a force as the product of a mass (the quantity of inertia matter possesses or that matter's resistance to acceleration) and an acceleration, in the famous formula F=ma. Finally, the third law observes that for every action, there is an equal and opposite reaction. These principles enabled Newton to derive the law of Universal Gravitation, precisely calculate planetary and Lunar motions, and study the nature of light. To quantify these observations, he independently derived the branch of Mathematics known as Calculus, as did his German contemporary Leibniz.
Newton conceived an overall description of the universe that remained absolute for 100 years. Only in the late 1800's did Newton's schema require alteration with the study of atomic particles, when velocities approached the speed of light, and when quantum effects regarding energy and matter were discovered.