Isaac Newton's theory of universal gravitation is a physical law describing the gravitational attraction between bodies with mass. It is apart of classical mechanics and was first formulated in Newton's work Philosophiae Naturalis Principia Mathematica, published in 1687. In modern language it states the following Every point mass attracts every other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses where • F is the magnitude of the gravitational force between the two point masses, • G is the gravitational constant, • m is the mass of the first point mass, • m is the mass of the second point mass, • r is the distance between the two point masses" -- Reference Wikipedia.org back to 27)