circular orbits with elliptical ones & described velocities of planets. Today we know them as: 1) Planetary orbits are ellipses with the Sun as one of the foci (top magenta ellipse) 2) A line from Sun to planet sweeps out equal areas in equal time periods (middle ellipse) 3) The square of the 🧵2/

planet’s orbital period (or year) is proportional to the cube of the semi-major axis (shown as the horizontal arrow in bottom ellipse). But, I find it fascinating- & important to note- that he came to these laws exploring mystical ideas about music, geometry & congruence with physical phenomena. 🧵3