For thousands of years it was believed that our Universe was finite. In 1920, the Great Debate, also called the Shapley-Curtis Debate, took place in Washington, where Shapley argued that our Milky Way was the only galaxy in the Universe and Curtis argued that there were many other galaxies in the Universe but none of the opponents he had none. concrete evidence to prove the respective theories. However, in 1929 Edwin Hubble provided observational evidence from which he concluded that there were millions of galaxies in the Universe besides our Milky Way. And in the process of discovery, he also discovered that our Galaxy was actually expanding! The public formation of the Great Debate influenced how ideas were presented and ultimately led to the trajectory of the Debate. This article explains why Shapley believed there was only one galaxy and how Edwin Hubble proved him wrong with his discovery of the expanding Universe. From this discovery we realized that at a certain point in the past our Universe was very small, probably a tiny dot, then after the Big Bang it started to expand. This was a great discovery, which changed the history of Physics. In the end, the article also discusses whether our Universe will continue to expand or is there a limit? Expansion of the Universe First, it is important to understand what we mean by Expansion of the Universe. It means that galaxies outside our own are moving away from us and the more distant ones are moving even faster. It therefore means that no matter where we are, all the other galaxies are moving away from us. And if this continued, after a while these galaxies would expand infinitely. We still have very little knowledge of the other... half of the paper... Will the universe expand forever?" http://wmap.gsfc.nasa.gov/universe/uni_shape.html The Sloan Digital Sky Survey (SDSS) “The Expanding Universe” http://skyserver.sdss.org/dr1/en/astro/universe/universe. asp The General Education Astronomy Source (GEAS) (2006) “The Shapley-Curtis Debate – What is ours place in the Universe?” New Mexico State University http://astronomy.nmsu.edu/geas/lectures/lecture27/slide01.html Zabludoff .(2012) “A Great Debate: Shapley vs. Curtis and the Scale of the Universe (1920)". University of Arizona http://atropos.as.arizona.edu/aiz/teaching/a250/shapley_curtis.html Cary Sneider, “1929: Edwin Hubble Discovers that the Universe is expanding,” Carnegie Institute for Science http://cosmology. carnegiescience.edu/timeline/1929 Swara Ravindranath, “Edwin Powell Hubble,” March 2009, pp. 211-213 http://simplelink.library.utoronto.ca /url.cfm/416978