Why didn't astronomers before shapely realize how large the galaxy is?

Answer 1

Before Harlow Shapley’s work in the early 20th century, astronomers underestimated the size of the Milky Way galaxy due to limited observational data and a lack of understanding of its structure. They primarily viewed the galaxy as a collection of stars within a relatively small area, influenced by the bright band of the Milky Way visible from Earth. Shapley's research, particularly through the study of globular clusters and their distances, revealed the true scale of the galaxy, demonstrating that it was much larger than previously thought. This shift in perspective ultimately led to a more accurate understanding of our galaxy's vastness.