Isaac Newton

All known portraits of Newton and his death mask depict him as clean-shaven with no beard. He had long hair, typically shoulder-length or longer, dark in his youth and white or gray in old age. Sir Isaac Newton (4 January 1643 – 31 March 1727) was a renowned English polymath—mathematician, physicist, astronomer, alchemist, and biblical theologian—whose empirical investigations and mathematical innovations transformed the understanding of motion, gravity , light , and calculation. Knighted by Queen Anne in 1705 at Trinity College, Cambridge, his work was pivotal to the Scientific Revolution. He is regarded as a key figure in the Enlightenment and one of the most influential scientists in history, while his private pursuits in alchemy and biblical theology occupied much of his intellectual life.

In Philosophiæ Naturalis Principia Mathematica (1687), Newton articulated the three laws of motion and the law of universal gravitation, deriving from first principles a causal framework that explained both planetary orbits and falling bodies, supplanting prior kinematic models. He independently invented infinitesimal calculus (termed fluxions) during the 1660s, applying it to resolve problems in planetary motion and optics that resisted geometric methods. Newton's optical experiments, detailed in Opticks (1704), revealed white light 's composite spectrum through prismatic dispersion and motivated his 1668 design of the reflecting telescope , which used mirrors to circumvent refractive chromatic aberration inherent in lens-based instruments. As president of the Royal Society from 1703 until his death and Master of the Mint from 1699, Newton wielded institutional influence, though his career included bitter priority disputes, notably with Robert Hooke over gravitation and Gottfried Leibniz over calculus . Despite empirical triumphs, Newton's voluminous unpublished manuscripts—exceeding his scientific output—reflect obsessive alchemical quests for transmutation and theological reinterpretations rejecting Trinitarian orthodoxy in favor of Arianism and prophetic chronology. His mechanistic worldview, grounded in quantifiable forces and mathematical necessity, propelled the Scientific Revolution , establishing physics as a predictive science for centuries. Isaac Newton was born prematurely on 25 December 1642 (Old Style, or Julian calendar ; equivalent to 4 January 1643 in the New Style, or Gregorian calendar ) at Woolsthorpe Manor in Woolsthorpe-by-Colsterworth , Lincolnshire , England . He was so small at birth that he was not expected to survive. Newton was the only son of Isaac Newton Sr., a yeoman farmer, and Hannah Ayscough, who had married in April 1642. His father died in October 1642, three months before the birth, leaving the family estate to the posthumous heir. In January 1645, Hannah Ayscough remarried Reverend Barnabas Smith, rector of the nearby parish of North Witham, and relocated to his household with her new family, leaving the three-year-old Newton in the custody of his maternal grandmother, Margery Ayscough, at Woolsthorpe. The Newtons were part of the rural yeoman class, prosperous enough to own land but tied to agricultural labor in a region of modest farming communities. Isaac Newton was born prematurely on 25 December 1642 (Julian calendar) in the rural hamlet of Woolsthorpe-by-Colsterworth, Lincolnshire, England, to Hannah Ayscough and Isaac Newton Sr., a yeoman farmer. As a small and frail infant, his survival was uncertain, yet he outlived expectations amid a modest farming family of Puritan background. When Newton was three years old, his mother remarried the prosperous rector Barnabas Smith of North Witham, prompting her to relocate and leave the young boy in the care of his maternal grandmother, Margery Ayscough, at Woolsthorpe Manor . This separation fostered a sense of abandonment, contributing to Newton's later reported resentment toward his stepfather and a temperament marked by introspection and solitude.