In physics, the force of attraction between two objects is gravitational force. Isaac Newton's law of universal gravitation defines the concept of gravitational force, stating that a gravitational attraction exists between all objects.
Newton's law asserts that the strength of gravitational force between any two objects depends on their sizes. In other words, the larger the object, the stronger the gravitational attraction. Therefore, large bodies such as planets and moons are attracted together by a tremendous amount of gravitational force. The amount of force is measured in newtons, which is calculated by multiplying a universal constant, known as G, by the product of the two object's masses, and then dividing by the square of the distance between the objects.