Galileo Galilei made several groundbreaking discoveries that fundamentally changed our understanding of the cosmos:
- Craters and mountains on the Moon : Galileo observed that the Moon's surface was rough and mountainous, not smooth and perfect as previously believed. He estimated the heights of lunar mountains by measuring the shadows they cast
- Phases of Venus : He discovered that Venus exhibited phases similar to the Moon, which could only be explained if Venus orbited the Sun, not the Earth. This challenged the geocentric model of the universe
- Jupiter’s moons : Galileo discovered four moons orbiting Jupiter-Io, Europa, Ganymede, and Callisto (now called the Galilean moons). This was the first observation of celestial bodies orbiting something other than Earth, undermining the Earth-centered universe idea
- Stars of the Milky Way : He showed that the Milky Way was composed of countless individual stars, rather than being a nebulous cloud
- Sunspots : Galileo observed dark spots on the Sun, proving that the Sun itself was not perfect and unchanging, and that it rotated
- Other contributions : He improved the telescope, invented an early microscope and a thermometer precursor, and made important advances in physics such as the law of falling bodies, inertia, and projectile motion
These discoveries supported the Copernican heliocentric model, which placed the Sun at the center of the solar system, and challenged the prevailing Aristotelian geocentric view. Galileo’s work laid the foundation for modern astronomy and the scientific method
