Sir Isaac Newton is known for his work on the law of gravity. In the late 17th century, he formulated the law of universal gravitation, which states that every mass attracts every other mass in the universe, and the strength of this attraction is proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This groundbreaking work was published in his seminal book, "Mathematical Principles of Natural Philosophy" (1687), where he also contributed significantly to calculus and laws of motion. Newton's insights laid the groundwork for classical mechanics and revolutionized our understanding of the physical world.