My Top 10 Space Moments By areade Period: 300 BCE to Oct 9, 2019 My Top 10 Space Moments 200 BCE Aristarchus proposes a heliocentric (Sun-centered) model of the universe 1520 Ferdinand Magellan observes Magellanic clouds, which are galaxies 1543 Nicholas Copernicus publishes a paper that represents the heliocentric model 1600 Giordano Bruno is burnt at the stake for promoting the heliocentric model 1609 Kepler publishes Astronomia Nova, explaining the motion of the planets 1632 Galileo publishes his Dialogue on Two World Systems, which argues for the heliocentric model 1687 Issac Newton publishes Principia Mathematica in which explains the law of universal gravity 1781 William Herschel discovers Uranus 1846 John Couch Adams discovers Neptune 1927 Georges Lemaitre proposes the Big Bang Theory 1929 Edwin Hubble discovers evidence of an expanding universe