Isaac Newton helped develop the principles of modern physics, including the laws of motion, and is cred as one of the great minds of the 17th-century Scientific Revolution. In 1687, Newton published his most acclaimed work, 'Philosophiae Naturalis Principia Mathematica' ('Mathematical Principles of Natural Philosophy'), which has been called the single most influential book on physics. Newton's theory of gravity states that two objects attract each other with a force of gravitational attraction that's proportional to their masses and inversely proportional to the square of the distance between their centers. Isaac Newton was a physicist and mathematician who developed the principles of modern physics, including the laws of motion and is cred as one of the great minds of the 17th-century Scientific Revolution. In 1687, he published his most acclaimed work, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), which has been called the single most influential book on physics. In 1705, he was knighted by Queen Anne of England, making him Sir Isaac Newton.