2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/135330We present a natural proof of Kepler's law of ellipses in the spirit of Euclidean geometry. Moreover we discuss two existing Euclidean geometric proofs, one by Feynman in hist Lost Lecture from 1964 and the other by Newton in the Principia of 1687.12 pagesSymplectic GeometryHistory and Overviewtext