The path to our current understanding of the Universe was not easy or always in the same direction. Sometimes our path would splinter in two (geocentric versus heliocentric); sometimes it would converge (Newton’s Clockwork Universe); and sometimes it would break off in several unending directions (the modern cosmologies). But to construct the path astronomers would have to debate the theories suggested by their observations. The keystone debate for our modern times was the Shapley-Curtis debate of 1920. In the debate, the structure of galaxies was debated. Shapley envisioned a universe of one galaxy, while Curtis envisioned a universe of many galaxies. Which one had the evidence on their side? That is a question you must answer after reviewing the data and their theories.
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Professor Howard Astronomy Musings 
Curtis won the debate because his points were more accurate than those of Shapley. Curtis received support from the scientific community for his research which debunked most of the findings of Shapley’s research. Curtis’s observation about the universe being 10 kpc was accurate when compared to prior information. Curtis also observed that there were many galaxies within our universe which was proven to be correct. Shapley stood by his position that there was only one galaxy in our universe which was later proved to be incorrect. Curtis’s observation that the sun was near the center of our universe might been an incorrect piece of his debate material, but his accurate information outweighed his inaccurate information and thus he won the debate. Shapley noted that our sun was not the center of our galaxy which was proven to be an accurate statement by prior information.
The Shapley-Curtis debate took place in Washington D.C. in 1920. It was a historically significant exchange of findings, theories and ideas that provided a lot of new insights to the way our galaxy was thought to be composed. Despite it being such a significant debate, it wasn’t sufficiently publicized or attended. There wasn’t a definite winner since it wasn’t so much a “debate” in the modern sense of the word, so much as a presentation and exchange of ideas from each party. Based on the findings and evidence used by each scientist and what history has proven to be right many decades later, it can be said that the outcome was a draw between both Shapley and Curtis. Each one was right about certain points. Shapley was correct about the use of Cepheid variables as a form of measuring distance and was also correct about the size of the galaxy and the sun’s location within it. On the other hand, Curtis was correct about the universe being composed of many galaxies. The evidence backs both individuals’ views on these points, which is why we can conclude that both were correct to some extent.
After looking it all over, both Shapley and Curtis had the right ideas. When it comes down to who had the best evidence, it was Shapley. Curtis was only right on the locations of spiral nebulae. Shapley got it right when he said that the sun was away from the center of the Milky Way. He was also closer to the actual diameter of the Milky Way than Curtis. He said that it was 300,000 light years across, when the actual diameter is 100,000 light years. So, in the end, Shapley got more of the key points correct than Shapley.