HOAE General Science Practice Test 2026 – Complete Exam Prep Resource

Planets travel in closed, oval-shaped paths called ellipses, not circles. This is captured by Kepler's first law, which states that planets orbit the Sun in ellipses with the Sun at one focus. Johannes Kepler deduced this from careful observations and measurements, showing that the actual orbital shapes match ellipses rather than perfect circles. While Copernicus proposed a Sun-centered model and Galileo supported heliocentrism with observations, the specific claim about elliptical orbits comes from Kepler. Newton later explained why gravity leads to such elliptical paths, but the law describing the orbital shape itself is Kepler’s.