By engaging with all the videos within this series, you will effectively complete a full undergraduate course in astronomy, equipping yourself with the knowledge and skills necessary to navigate the night sky with confidence, learning all the basics and many advanced topics! In this session, we explore the significant contributions of Galileo Galilei to the advancement of the heliocentric model and the broader development of modern science. Despite Kepler discovering that planets, including Earth, move around the Sun in elliptical orbits, his works were often overlooked due to their complexity. His observations with the telescope in 1609 revealed: 1. The Moon had valleys and mountains, contradicting the Aristotelian idea of celestial perfection. 2. The Sun had sunspots, indicating it too was not a perfect, immutable sphere. 3. The Milky Way consisted of many stars invisible to the naked eye, challenging Scriptural interpretations. 4. 5. Venus exhibited phases similar to the Moon, proving it orbited the Sun. These observations were compiled in his influential book, “The Starry Messenger,” published in 1610, which he used to gain favor with the Medici family and spread his findings. While under house arrest, Galileo wrote further on the motion of objects, works that later influenced Isaac Newton. His daughter, Sister Maria Celeste, played a crucial role in assisting him during this period. Galileo’s unwavering commitment to evidence-based science and his method of observation and experimentation, rather than reliance on accepted dogma, solidifies his legacy as the father of modern science. His efforts to propagate the heliocentric model, despite facing significant opposition, helped lay the groundwork for future scientific advancements.