Universal Law of Gravitation

From true

Newton suggested that all objects (both terrestrial and celestial objects) obey the same law of gravitation. They are all attracted to each other, and the attraction depends only on the mass of each object and the distance between the objects.

where F is the force of attraction between two objects,

M is the mass of one of the objects,

m is the mass of the other object,

r is the distance between the objects, and

G is the constant of proportionality which makes the units come out right

Key idea: G can only be determined by experimental measurement. It is called a universal constant because it is believed that anyone who uses the same units will get the same number for G wherever they are in the universe.