Understanding Our Universe (Third Edition)

Book Preface

You may wonder why it is a good idea to take a general-education science course. Scientists, including astronomers, have a specific approach to understanding new information. Astronomers “understand” when they can make
correct predictions about what will happen next. Astronomers “know” when an idea has been tested dozens or even hundreds of times and the idea has stood the test of time.

There are two fundamental goals to keep in mind as you take this course. The first is to understand some basic physical concepts and become familiar with the night sky. The second is to learn to think like a scientist and learn to use the scientific method, or process of science, to answer questions in this course and make decisions about science and technology in your life. We have written the third edition of Understanding Our Universe with these two goals in mind.
Throughout this book, we emphasize the content of astronomy (the masses of the planets, the compositions of stellar atmospheres) as well as how we know what we know. The scientific method is a valuable tool that you can carry with you, and use, for the rest of your life.
The most effective way to learn something is to “do” it. Whether playing an instrument or a sport or becoming a good cook, reading “how” can only take you so far. The same is true of learning astronomy. The following tools in each chapter help you “do” as you learn:
• Active Learning Figures open each chapter and ask you to “do” science by setting up an experiment and then making either a prediction or an observation and recording the results. We hope you find that the “answer” isn’t the most important part of the activity. Rather, we want the experience of thinking about a physical phenomenon and predicting what will happen next to become a natural way for you to apply your knowledge and understand new concepts.

•  To promote active reading, Check Your Understanding questions have been placed at the end of each section of a chapter. These questions act as “speed bumps” so that you will pause and check your comprehension of the material prior to moving on to the next section. These, and the questions and problems at the end of each chapter, are a great way to check whether you have a basic understanding of the material.
•  Reading Astronomy News sections toward the end of each chapter include a news article or press release with questions to help you make sense of how the science is presented. As a citizen of the world, recognizing what is credible and questioning what is not are important skills. You make judgments about science, distinguishing between good science and pseudoscience, in order to make decisions in the grocery store, pharmacy, car dealership, and voting booth. You base these decisions on the presentation of information you receive through the media, which is very different from the presentation of information in class. The goal of Reading Astronomy News is to help you build your scientific literacy and your ability to challenge what you hear elsewhere.
•  At the very end of each chapter, an Exploration activity shows you how to use the concepts and skills you learned in an interactive way. About half of the book’s Explorations ask you to use animations and simulations found on the Digital Resources Page on the Student Site, while the others are hands-on, paper-and-pencil activities that use everyday objects such as ice cubes or balloons.
We believe that the learn-by-doing approach not only helps you better understand the material but also makes the material more interesting and, perhaps, fun.

As you learn any new subject, one of the stumbling blocks is often the language of the subject itself. This can be jargon—
the specialized words unique to that subject—for example, supernova or Cepheid variable. But it can also be ordinary words that are used in a special way. As an example, the common word inflation usually applies to balloons or tires in everyday life, but economists use it very differently, and astronomers use it differently still. Throughout the book, we have included Vocabulary Alerts that point out the astronomical uses of common words to help you recognize how those terms are used by astronomers.
In learning science, there is another potential language issue. The language of science is mathematics, and it can be as challenging to learn as any other language. The math. To learn about nature, you will also need to speak its language. We don’t want the language of math to obscure the concepts, so we have placed this book’s mathematics in Working It Out boxes to make it clear when we are beginning and ending a mathematical argument, so that you can spend time with the concepts in the chapter text and then revisit the mathematics to study the formal language of the argument. Read through a Working It Out box once, then cover the worked example with a piece of paper, and work through the example until you can do it on your own. When you can do this, you will have learned a bit of the language of science. We want you to be comfortable reading, hearing, and speaking the language of science, and we provide you with tools to make it easier.
In addition to learning the language of astronomy, visualizing a process or phenomenon will help you reach a deeper understanding. In addition to the illustrations in the book, many physical concepts are further explained in a series of short Astronomy in Action videos, AstroTour animations, and new Interactive Simulations available in the ebook, Coursepack, and on the Student Site. The videos feature one of the authors (and several students) demonstrating physical concepts at work. Each animation is a brief tutorial on a concept or process in the chapter. The simulations allow you to explore topics such as Moon phases, Kepler’s laws, and the Hertzsprung-Russell diagram. Your instructor might assign the videos and animations to you or you might choose to watch them on your own to create a better picture of each concept in your mind.

Astronomy gives us a sense of perspective that no other field of study offers. The universe is vast, fascinating, and beautiful, filled with a wealth of objects that, surprisingly, can be understood using only a handful of principles. By the end of this book, you will have gained a sense of your place in the universe—both how incredibly small and insignificant you are and how incredibly unique and important you are.
Sincerely,
Stacy Palen
Laura Kay
George Bl