Newton's law of universal gravitation describes gravity as a force by stating that every particle attracts every other particle in the universe with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between their centers of mass.
This is a general physical law derived from empirical observations by what Isaac Newton called inductive reasoning.[4] It is a part of classical mechanics and was formulated in Newton's work PhilosophiƦ Naturalis Principia Mathematica (Latin for 'Mathematical Principles of Natural Philosophy' (the Principia)), first published on 5 July 1687.
The equation for universal gravitation thus takes the form:
where F is the gravitational force acting between two objects, m1 and m2 are the masses of the objects, r is the distance between the centers of their masses, and G is the gravitational constant.
The force of gravity between to objects is proportional to their masses and inversely proportional to the square of distance between them. The constant of this proportionality is big G.
Direct Proportionality to Mass : If you double the mass of one object, the gravitational force between them will double. If you double the mass of both objects, the gravitational force will increase four times.
Inverse Square Proportionality to Distance : This is a key concept. If you double the distance between two objects, the gravitational force decreases by a factor of four. If you triple the distance, the force decreases by a factor of nine.
