Isaac Newton (4 January 1643–31 March 1727, Gregorian calendar) was an English mathematician and natural philosopher whose writings established major foundations of classical mechanics. A central figure of the Scientific Revolution, he formulated laws of motion and universal gravitation, developed calculus independently of Gottfried Wilhelm Leibniz, and investigated the composition of white light. His principal scientific books were Philosophiæ Naturalis Principia Mathematica (1687) and Opticks (1704). His activities also included alchemy, biblical scholarship, and administration of the English coinage. (newtonproject.ox.ac.uk)
Early life and Cambridge career
Newton was born at Woolsthorpe, Lincolnshire, after his father’s death. His birth was recorded as 25 December 1642 under the Julian calendar then used in England; this corresponds to 4 January 1643 in the Gregorian calendar. Following his mother’s remarriage, he spent part of his childhood in his maternal grandmother’s care. He attended school in Grantham and entered Trinity College, Cambridge, in 1661. (newtonproject.ox.ac.uk)
After receiving his bachelor’s degree in 1665, Newton returned to Lincolnshire during plague-related interruptions at Cambridge. In 1665–1666 he developed important ideas in mathematics, gravitation, and optics, although these investigations required substantial later development. He became a fellow of Trinity in 1667 and succeeded Isaac Barrow as Lucasian Professor of Mathematics in 1669. His early lectures concentrated on optical questions rather than exclusively on pure mathematics. (newtonproject.ox.ac.uk)
Mathematics and calculus
Newton’s calculus treated quantities as generated by continuous change. He called changing quantities “fluents” and their rates of change “fluxions,” concepts corresponding broadly to functions and derivatives. His methods connected the determination of instantaneous rates with the inverse problem of finding accumulated quantities, now expressed through integration. These investigations provided techniques for tangents, areas, and problems involving motion. Much of his early work circulated in manuscripts before publication. (newtonproject.ox.ac.uk)
Newton also extended the binomial theorem beyond nonnegative integer exponents and investigated power series. He developed methods for approximating roots of equations, associated with what is now called Newton’s method. These contributions extended the computational resources available to seventeenth-century mathematicians. (explore.trin.cam.ac.uk)
Gottfried Wilhelm Leibniz independently developed calculus during the 1670s and published an account in 1684. A prolonged priority dispute subsequently divided their supporters. Newton’s earlier manuscripts establish the chronology of his discoveries, but Leibniz’s independent development is also recognized; the history is not accurately described as one mathematician simply copying the other. (newtonproject.ox.ac.uk)
Motion and universal gravitation
The Principia, published in Latin in 1687, presented a mathematical system for terrestrial and celestial motion. Edmond Halley’s visit to Newton in 1684 encouraged the investigations that developed into the book. It combined mathematical demonstrations with applications to observed astronomical phenomena. (newtonproject.ox.ac.uk)
Newton’s three laws of motion describe inertia, the relationship between force and changes in momentum, and equal and opposite forces between interacting bodies. In modern notation, the second law is commonly written for a body of constant mass. The third law concerns forces acting on different bodies, rather than two forces cancelling on the same body. (www1.grc.nasa.gov)
His theory of gravitation made attraction universal: every particle of matter attracts every other. For two point masses, the force is proportional to their masses and inversely proportional to the square of their separation. This supplied a common explanation for falling bodies near Earth and the orbital motion of the Moon and planets. Newton demonstrated how the inverse-square relationship accounted for the planetary regularities established by Johannes Kepler. (cdaweb.gsfc.nasa.gov)
Light and optical instruments
Newton’s research in optics established that white light is a mixture of differently coloured components. His prism experiments distinguished the separation of existing colours from the idea that glass creates colour by modifying otherwise homogeneous light. The components differ in their refraction, explaining their separation into a spectrum. (newtonproject.ox.ac.uk)
He also built the first practical reflecting telescope, using a mirror rather than a large objective lens to collect light. Opticks organized his experimental investigations and included successive sets of “Queries” addressing broader questions about light, matter, and natural processes. These queries offered research questions and speculative possibilities rather than presenting every proposal as an established result. (explore.trin.cam.ac.uk)
Alchemy and religious scholarship
Newton devoted approximately thirty years to alchemy, often termed “chymistry” in his period. His surviving writings and transcriptions on the subject amount to about a million words. This work formed a substantial, largely private component of his intellectual activity alongside his better-known mathematical investigations. (newton.dlib.indiana.edu)
His studies of Christianity included biblical interpretation, prophecy, chronology, and early church history. He privately rejected the orthodox doctrine of the Trinity. These positions were not generally disclosed publicly during his lifetime, and his theological manuscripts document interests substantially broader than his published scientific books. (newtonproject.ox.ac.uk)
Public offices and final years
Newton became Warden of the Royal Mint in 1696 and Master in 1699, remaining Master until his death. He participated in the major silver recoinage, investigated coin clipping and counterfeiting, and emphasized accuracy in coin weight and metallic fineness. His Mint career involved sustained administrative responsibilities rather than merely an honorary appointment. (royalmintmuseum.org.uk)
He was elected president of the Royal Society in 1703 and knighted in 1705. Newton died on 20 March 1727 under the Julian calendar—31 March in the Gregorian calendar—and was buried in Westminster Abbey. His surviving notebooks, correspondence, and annotated publications record the development of his work through experiments, calculations, exchanges with others, and repeated revision. (fitzmuseum.cam.ac.uk)