Isaac Newton proposed the law of universal gravitation in the late 17th century, specifically in his work "Philosophiæ Naturalis Principia Mathematica," published in 1687. This groundbreaking theory posits that every mass attracts every other mass in the universe, and the force of attraction is proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Newton’s work laid the foundations for classical physics and transformed our understanding of motion and celestial bodies, allowing for the prediction of planets’ movements and the mechanics governing objects both on Earth and in space.