Sir Isaac Newton is renowned for his foundational contributions to physics, particularly his laws of motion and universal gravitation. His work, primarily outlined in "Philosophiæ Naturalis Principia Mathematica" published in 1687, laid the groundwork for classical mechanics. Newton's three laws of motion describe the relationship between a body and the forces acting upon it, while his law of universal gravitation explains how masses attract each other with a force proportional to their masses and inversely proportional to the square of the distance between them. His discoveries revolutionized the scientific understanding of the physical universe.