Table of contents The Milky Way Is All There Is Space is standing still The Universe is 6 000 Years old Our Solar System Has Only Six Planets 10 Planet Vulcan Exists 12 Stars Are Made of Iron 14 Everything in the Universe is visible 16 The Moon Was Once Part of Earth 18 Saturn is the only Planet with Rings 20 Pluto is a Planet 22 The Outer Solar System Is Empty 24 Our Sun is the Only Star with Planets 26 Fact Sheet 28 Glossary 30 For More Information 31 Index 32 About the Author 32
Busted The Milky Way Is All There is In the early 1900s no one knew supporters had no proof of that how vast the universe really was Then Edwin Hubble made the first But that changed in 1920 That of two key discoveries that busted year American astronomer Harlow Shapley's hypothesis Shapley accurately measured Earth's In 1919 Hubble worked at the galaxy the Milky Way According to Mt Wilson Observatory in California his calculations it was 100 000 The observatory's 100 inch Hooker light years across He and many Telescope was the biggest telescope other astronomers argued that was of its day With it Hubble took it The Milky Way was the universe thousands of photographs of spiral Other astronomers disagreed nebulae over time On October 4 Heber Curtis thought Earth's galaxy 1924 he was comparing photos was one of many But he and his of the Andromeda Nebula He discovered a Cepheid variable A Cepheid is the one kind of star Scientists astronomers use to accurately continue to study measure distance Shapley had used the Milky Way a Cepheid to make his calculations in 1920 Using the Cepheid in Andromeda Hubble discovered it was 900 000 light years away Andromeda was outside our galaxy way outside of it Later astronomers found Hubble's new number was
The Andromeda Galaxy Andromeda was actually more than twice that distance from number is likely to increase too New technologies and research methods may reveal even more Earth But Hubble's discovery still busted Shapley's theory Hubble galaxies also discovered Andromeda itself was a galaxy The Milky Way was not the only galaxy in the universe Now fewer than 100 years later 2 54 million scientists know there are at least 100 billion galaxies out there That Distance in light years from Earth to the Andromeda galaxy THE SHAPLEY CURTIS DEBATE On April 26 1920 astronomers Harlow Shapley and Heber Curtis held a debate in Washington DC They argued about the size of the universe Shapley argued the universe ended at the limits In 1920 Shapley measured the Milky Way to be 100 000 light years wide Four years later Hubble found a star in Andromeda that was nine times farther away than Shapley thought This proved Andromeda was outside Earth's galaxy and the universe was much bigger than previously thought of Earth s galaxy Curtis argued the Milky Way was one of many island universes Astronomers now call this the Great
