Optical Telescope (Galileo's Refractor)

Galileo’s Refractor was the first instrument to directly challenge the geocentric view of the cosmos, providing the initial observational evidence for the Copernican model. By magnifying objects 20×, it revealed Jupiter’s four largest moons—now called the Galilean moons—and detailed lunar craters and Saturn’s rings, fundamentally shifting astronomy. Over 400 years later, even modern telescopes with 10-meter mirrors acknowledge Galileo’s design as the template for all subsequent optical astronomy.