Discovery of the Expansion of the Universe

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For thousands of years it was believed that our Universe was finite. In 1920, The Great Debate, also called the Shapley-Curtis Debate happened 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 had any concrete evidence to prove their respective theories. However, in 1929 Edwin Hubble provided observational evidence from which he concluded that there was millions of galaxies in the Universe beside our Milky Way Galaxy. And in the process of discovering, he also found out that our Galaxy was in fact expanding! The public formation of the Great Debate influenced the ways ideas were presented and it ultimately lead to the trajectory of the Debate. This paper argues why Shapley believed that there is only one Galaxy and how Edwin Hubble proved him wrong with his discovery of the expanding Universe. From this discovery, we came to realize that at some point in the past, our Universe was very small, probably a tiny dot, then after the Big Bang, it started expanding. This was a big discovery, which changed the history of Physics. At the end, the paper also discusses - if our Universe will continue to expand or is there a limit?

Expansion of the Universe
Firstly, it is important to understand what we understand by the Expansion of the Universe. It means that the galaxies outside our own galaxy are moving away from us and the ones that are farther apart are moving even faster. Therefore it means that no matter where we are, all the other galaxies are moving away from us. And if it continues to do so, after a time, these galaxies would expand to infinity. We still have very little knowledge about the ot...

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... 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 our 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)”. The University of Arizona http://atropos.as.arizona.edu/aiz/teaching/a250/shapley_curtis.html Cary Sneider, “1929: Edwin Hubble Discovers the Universe is Expanding”, Carnegie Institute for Science http://cosmology.carnegiescience.edu/timeline/1929 Swara Ravindranath, "Edwin Powell Hubble", March 2009, pp. 211-213
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