Welcome to Elementary Astronomy

About the Author

Robert H. Gowdy is an Associate Professor of Physics at Virginia Commonwealth University (VCU) in Richmond, Virginia.  He earned a Ph.D. in Physics from Yale University in 1968 and does research in the area of General Relativity -- Einstein's theory of gravity.  He is best known for a large family of solutions of Einstein's field equations, which have come to be called "Gowdy Spacetimes."  These solutions have been used to test the "Cosmic Censorship Conjecture," which asserts that Naked singularities cannot develop from regular initial conditions (It passed the test.).  The solutions have also been used to validate computer simulations of Einstein's theory in extreme astrophysical situations such as collisions of black holes and neutron stars.  For a light-hearted introduction to these solutions, see "Gravitational Waves and Spherical Chickens." For a more technical discussion of the solutions, see "Gowdy Spacetimes."

Dr. Gowdy has been teaching a general education course in astronomy at VCU since 1978.  The course has changed format many times over the years, moving onto the World Wide Web in 1995, adopting peer instruction long before classroom response systems were available, and joining the Top Hat Marketplace in 2019.

About the Course

This course is intended to fulfill a general education science requirement.  Because astronomy makes use of all of the other sciences, it is an ideal topic for such a course.  You will learn a little philosophy of science, some Earth science, some physics, some chemistry, and some biology as we work our way through the solar system and discuss the search for life on other worlds.  You will also learn a great deal about how astronomers have discovered our place in the universe.

All of us tend to block ideas and concepts that we are not familiar with.  Our attention focuses instead on things that we know something about.  This course will increase the variety of things that you know something about and will help you to see what is out there.

Each of the chapters contains embedded questions such as this one:

Each question actually has several versions.  When you view a question, you will see just one of the versions, chosen at random.  Someone else viewing the same question may see another version.  There are always at least two versions and there can be as many as 16, all addressing the same topic.  Your instructor may assign these questions as homework and may give credit for attempting the questions as well as credit for correct answers.  If your instructor uses the question pack provided with this course, the questions embedded in the chapters cover most of the 427 possible topics that could appear on any exam.

In addition to the chapters, you will find that each chapter has a "preview" and a "review."  The preview is the chapter without the homework questions.  The review is only the homework questions.  Your instructor may choose to assign these pages in one of two ways:  (1) Preview pages to read ahead, chapters as homework, and reviews as self-tests after the homework is done. (2) Preview pages to read and review pages as homework, chapters assigned for review after the homework is done.

The way that Top Hat pages currently work, the version of a question that you see when you first look at a page for either homework or review, is the only version that you will ever see.  To see other versions,  get together with other students when you study.

In a descriptive course such as this one, it is important to adopt a good learning strategy.  I recommend that you test yourself constantly and never waste a wrong answer.  When your first answer to one of the embedded questions is wrong, do not just guess again or ask for the correct answer.  That is a waste of a wrong answer.  A wrong answer provides precious information:  It tells you what you do not know.  Questions are numbered by chapter and section so that you always know what the question is about.  Go back to the beginning of the section that the question is about and find the answer yourself before trying the question again.  In that way you learn the information in context and can connect it to other ideas.  The problem with just asking for the correct answer to a question is that you may never see that version of the question again.  Worse, you may see a version that looks like the one that you learned, but is not actually  the one that you think it is.

This course is only an introduction to a vast subject.  Fortunately, through the internet, you have access to all of human knowledge.  The ideas that you learn here can be keys to unlock that knowledge.  Use a search engine to find out more about the ideas and people that we discuss.  You will find, for example, that the astronomer Tycho Brahe, discussed in Chapter 3, was seriously weird.  You will also find that the more you know, the easier it is to remember what you know, so do not worry about filling your brain with things that will not be on the test.

Enjoy the journey.