The answer to the crossword for the term BY FORCE OF GRAVITY is NEWTON. Sir Isaac Newton was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who lived in the 17th century. He is best known for his laws of motion and universal gravitation, which form the foundation of classical mechanics. His work on gravity led him to conclude that it is a force of attraction between two objects that is proportional to their masses and inversely proportional to the square of the distance between them. This is now known as the law of universal gravitation.