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Video lecture for this chapter
Hello, explorer! You are about to start a journey that will take you to the farthest reaches of space and the innermost depths of matter and from the earliest beginning of time to the future billions of years from now. Introductory astronomy classes have the daunting task of introducing students to the wonders of the entire universe in one short course, often just one semester or one quarter long. Though the places and events you will encounter will sometimes be mind-boggling, I hope you will find it such a fascinating experience that you will want to learn more about those places in another course or in your own free time in the library or in your backyard with binoculars or telescope (or even better, at star parties on a mountain far from the city lights with your local astronomy club).
The first part of this chapter takes you on a tour of the universe in space and time to give you some context---``set the stage and introduce the characters'', some familiar and others quite obscure but still vital to the play. It is like a travel brochure you read before your vacation trip. One word of warning: a lot of numbers and facts are presented in the first section but do not try to memorize them. What is important is to get a sense of the relative scale of things.
In grade school you probably memorized a lot of facts about the planets and stars and when you were older you wondered, ``but how do they know that?'' In the following chapters you will learn how astronomers measure the distances, sizes, and ages of these objects and determine what they are like and what makes them appear the way they do. This textbook emphasizes the techniques and process astronomers use to find out about the universe around us and the unifying principles operating ``behind the scenes''. Facts will be given as examples of what is found when those techniques are used or as examples of a particular effect of a physical principle in operation.
The second part of the chapter presents a brief description of the philosophy and method of science and the role astronomy plays in our attempts to understand the universe scientifically. At the end is a discussion of the non-science often confused with astronomy called astrology. Vocabulary terms in the text are set in boldface to help you find them.
last updated: November 26, 2021