A British mathematician and physicist who lived from 1643 - 1727. Newton made major advances in the studies of optics, mathematics, astronomy, and physics, most of which were published in his two major works, Opticks and Principia. Among other innovations, he constructed the first reflecting telescope (now known as a Newtonian style telescope), invented integral calculus, and postulated a Universal Law of Gravity. Newton’s First Law: Objects in motion stay in motion, and objects at rest stay at rest, unless acted upon by an outside force. Newton’s Second Law: For every action, there is an equal and opposite reaction. Newton’s Third Law: The force exerted on an object and the acceleration of the object are directly proportional. The constant of proportionality is the mass of the object. Newton’s Law of Gravity:The gravitational force exerted on one object by another object is proportional to the product of the masses of the two objects and inversely proportional to the square of the distance between them. The constant of proportionality is the Universal Gravitational Constant, G.