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Illustrations JanetMoneymaker MarjieBassler Copyright2013GravitasPublications,Inc. Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem, ortransmitted,inanyformorbyanymea

Contents iii CHAPTER 1 EXPLORING THE COSMOS 1.1 1.2 1.3 1.4 1.5 Introduction Who Was the First Astronomer Famous Early Astronomers Astronomers Today Summary 2 3 5 8 9 1 CHAPTER 2 THE TELESCOPE 2.1 2

iv Contents CHAPTER 6 Earths Neighborhood 6.1 6.2 6.3 6.4 6.5 Introduction Our Solar Neighborhood Orbits Why Is Earth Special Summary 40 40 44 45 47 49 49 51 52 53 54 56 56 57 59 61 63 64 65 66 67 69

2 Focus On Elementary Astronomy 1.1 Introduction When you look up at the sky at night, what do you see If the sky is free of clouds and there are not too many lights around, you might see the Moon,

Chapter 1 Exploring The Cosmos 3 1.2 Who Was the First Astronomer Its hard to say who was the first astronomer. Many early people studied the planets and stars and even without modern tools discover

4 Focus On Elementary Astronomy Earth In other words, do we live in a Suncentered cosmos or an Earthcentered cosmos It appears, from simple observation, that we live in an Earthcentered cosmos. When

Chapter 1 Exploring The Cosmos 5 1.3 Famous Early Astronomers Nicolaus Copernicus was a famous astronomer who also thought that the Earth moved around the Sun. Copernicus was born in 1473 in the anc

6 Focus On Elementary Astronomy his hard work. Another 100 years passed before people took his ideas seriously. Another famous astronomer also changed the way we see the cosmos. His name was Tycho B

Chapter 1 Exploring The Cosmos Galileo Galilei was also a famous early astronomer. He was interested in trying to find out how the planets move. Galileo was born in 1564 in Pisa, Italy. He studied man

8 Focus On Elementary Astronomy 1.4 Astronomers Today Today, many scientists study the stars and planets. Astronomy is a science, and modern astronomers are scientists who use a variety of scientif

Chapter 1 Exploring The Cosmos physics are essential for understanding how the stars and planets move in space. Most importantly, astronomers must always be curious and willing to argue to defend thei