Any two masses in the universe attract each other with a force which is i) directly proportional to the product of the masses, ii) inversely proportional to the square of the distance between their centres. F=GmM/r² where G= universal gravitational constant. m and M are the masses of two bodies. r = distance between them. * Larger the masses , greater is the force between them. * Larger the distance , smaller is the force. * If the distance is halved , force increases 4 times. * If the distance is doubled, force becomes one-fourth. * The force is not effected with any medium between the masses.