“We cannot teach people anything; we can only help them discover it within themselves.” — Galileo Galilei
Italian astronomer Galileo Galilei observed what he believed to be a "fixed star” on this day in 1612 — but what he saw that luminous night was no star at all — in fact, Galileo had discovered a planet 17 times the size of Earth. This would be history’s first recorded observation of Neptune, the eighth and outermost planet in our solar system. Considered to the “father of modern physics”, Galileo made this finding while inspecting the four large moons of Jupiter, all of which are now named in his honor — the Galilean moons are individually known as Io, Europa, Ganymede, and Callisto. While scientists and astronomers are still arguing whether Galileo officially discovered Neptune, the analyses of the skies detailed in his notebooks confirm he was the first to record a sighting of the massive planet.