Per numbered titles: 1 Newtonian gravity 2 Quantum mechanics of charged particles 3 Classical electrodynamics of point particles They explicitly mention the

Per numbered titles: 1 Newtonian gravity 2 Quantum mechanics of charged particles 3 Classical electrodynamics of point particles They explicitly mention they use point particles. Problem in 1 Newtonian gravity is especially egregious example. They model planets(!) as material points and see how they come infinitely close to each other. The author does mention these problems are pure math unrelated to reality.