Isaac Newton

Sir Isaac Newton transformed our understanding of the universe more profoundly than perhaps any other individual in history. His Philosophiæ Naturalis Principia Mathematica (1687) established the laws of motion and universal gravitation that governed physics for over two centuries. Newton's interest in astronomy began at Cambridge, where he developed calculus and began his experiments with light and optics. In 1668, he built the first practical reflecting telescope — the Newtonian reflector — solving the chromatic aberration that plagued refracting telescopes. This design remains widely used by amateur astronomers today. The Principia showed that the same force causing an apple to fall also keeps the Moon in orbit and the planets on their paths. His law of universal gravitation unified terrestrial and celestial mechanics for the first time, explaining Kepler's laws from first principles. Newton also explained the tides, the precession of the equinoxes, and the orbits of comets. Despite his genius, Newton was famously difficult. His bitter rivalry with Leibniz over calculus and his disputes with Robert Hooke over optics were legendary. He served as Warden of the Royal Mint and President of the Royal Society.

• Law of Universal Gravitation — unified terrestrial and celestial mechanics • Three Laws of Motion — foundation of classical mechanics • Built the first practical reflecting telescope (1668) • Demonstrated that white light is composed of a spectrum of colors • Co-invented calculus, essential for celestial mechanics • Explained Kepler's laws from gravitational first principles