Sir Isaac Newton is known for his theory of gravity. He formulated the law of universal gravitation, which describes the gravitational force that attracts two bodies toward each other based on their masses and the distance between them. This groundbreaking concept was articulated in Newton's work "Philosophiæ Naturalis Principia Mathematica," published in 1687. Newton’s insights laid the foundation for classical mechanics and transformed our understanding of motion and celestial phenomena. His gravitational theory explains not just earthly objects but also the orbits of planets and the behavior of objects in space, profoundly influencing physics and mathematics for centuries.