Final answer:
Galileo's discoveries revolutionized astronomy by challenging prevailing ideas, emphasizing observation, and paving the way for modern scientific methodology.
Step-by-step explanation:
Galileo's discoveries were the most important ones in astronomy because they revolutionized our understanding of the universe and paved the way for modern scientific methodology. His use of the telescope allowed him to make groundbreaking observations, such as the discovery of moons orbiting Jupiter and the details of sunspots, that contradicted the prevailing ancient ideas and religious beliefs. Galileo's emphasis on observation and empirical evidence over logical argument challenged the authority of the time, leading to his persecution by the Inquisition.
However, the repeated verification of his work by others after his death and the eventual acceptance of his ideas by the church and scientific communities solidified the significance of his discoveries.