The following article is part of a biography of Sir Isaac Newton, the English mathematician and scientist, author of the Principia. It portrays the years after Newton's birth in 1642, his education, as well as his early scientific contributions, before the writing of his main work, the Principia Mathematica, in 1685. Overview of Newton's Life Sir Isaac Newton is known for many scientific findings. Some of these discoveries include the laws of motion, the theory of gravity, and basic calculus. Although Newton was predominantly known for his discoveries in mathematics and physics, he also put much effort and study into chemistry, biblical history and optics. One of Newton's most famous writing was the Principia where he described some of his major findings of time, physics, mathematics and calculus. Although his theories soon became universal, he faced much opposition with some of his early theories. Specifically, his theory of gravity faced criticism from leading scientists such as Christiaan Huygens and Leibniz. After a few years of debate, Newton's concept of gravity became universally accepted as he became the dominant figure in the European continent. Birth and education Isaac Newton was born on Christmas Day, 25 December 1642 Old Style (which was 4 January 1643 on the Gregorian calendar, which is now used) at Woolsthorpe Manor in Woolsthorpe-by-Colsterworth, a hamlet in the county of Lincolnshire. (At the time of Newton's birth, England had not adopted the Gregorian calendar and therefore his date of birth was recorded as 25 December, according to the Julian calendar.) Newton was born three months after the death of his father, a prosperous farmer also named Isaac Newton. His father was described as a "wild and extravagant man". Born prematurely, young Isaac was a small child; his mother Hannah Ayscough reportedly said that he could have fit inside a quart mug. When Newton was three, his mother remarried and went to live with her new husband, the Reverend Barnabus Smith, leaving her son in the care of his maternal grandmother, Margery Ayscough. The young Isaac disliked his stepfather and held some enmity towards his mother for marrying him, as revealed by this entry in a list of sins committed up to the age of 19: "Threatening my father and mother to burn them and the house over them." Later on his mother returned after her husband died. From age 12 to age 16, Newton resided with William Clarke,