Gravitation — from Newton’s apple to Earth’s mass
From Newton’s apple to Earth’s mass — follow gravity from the 1/r² law through Cavendish’s experiment to the precise value of g.
Article 1 — How Newton reached the 1/r² law
Article 2 — How Cavendish measured G
Article 3 — Earth mass, the value of g, and its variation with altitude
From Articles 1 and 2, we now have both pieces of the puzzle: