Explorations: An Introduction to Astronomy, Updated, 3/e
Tom Arny
ISBN: 0072465700 Copyright year: 2004
Preface
Preface
When I began writing Explorations: An Introduction to Astronomy, many people
asked me why I was writing an astronomy book. Much of my motivation comes from
wanting to share my own sense of wonderment about the Universe. I hope that in an
astronomy course, students can get some sense of where they fit in the astronomical
Universe—a sense of location in the cosmic landscape. I also hope that students will
come away from such a course with a sense of the richness of the Universe.When we
look around us on our own planet,we see incredible biodiversity. So, too, when we look
at the heavens,we see incredible astrodiversity. Stars, moons, and planets are as strange,
colorful, and wonderful as tropical butterflies. Finally, I hope that students will gain
some appreciation of the methods by which such tiny beings as we are have learned so
much about the Universe. Those methods are not just laboratory techniques. Far more
important is the process of learning: the steps by which we go from observation to
hypothesis and then on to what we hope is understanding.
But why write your own astronomy book when so many already exist? Most of the
current books have so much material that they are impossible to get through in a single
semester, and much material is omitted. I therefore decided that my first goal was to
make a book that was short.However, as I worked at it, I kept finding things that I didn’t
want to leave out, material such as calendars and the history of astronomy. But how
could I write a short book and still include such topics? The solution was to organize
the book so that instructors and students could omit the unwanted sections without
interrupting the flow of ideas. Thus, I placed a number of topics such as time keeping
and exo-biology into Essays that may be easily skipped. I also tried to make the book
short by limiting its scope. Rather than covering everything, I have tried to focus on
only what at the time seemed to me the most important ideas.
Another goal I set myself was to give simple explanations of why things happen. Such
explanations generally involve physical principles that are unfamiliar to nonscience students.
However, many even very complicated physical ideas can be appreciated, if not
fully understood, by appeal to analogy or to similarities with everyday phenomena. For
example, diffraction effects can be seen by looking at a bright light through a lock of
your hair pulled over your eyes or through glasses that you have foggedwith your breath.
By tying physical principles to everyday observations,many of the more abstract and remote
ideas become more familiar. Thus, I have used analogies heavily throughout the
book, and I have designed the illustrations to make those analogies more concrete.
An additional aim throughout this text is to explain how astronomers know the
many curious things they have learned about our Universe. Such explanations often
require mathematics, and so I have included it wherever it is crucial to understanding
a method of measurement, as in the use of the modified form of Kepler’s third law to
determine a star’s mass or in Wien’s law to measure its temperature. However, because
math is so intimidating to so many students, I have tried to begin these discussions by
introducing the essence of the calculations in everyday language. Thus, if the student
or instructor chooses to omit the math, it will not prevent an understanding of the
basic idea involved. For example,Wien’s law relates the temperature of a hot object to
its color by a mathematical law. However, the consequences of the law can be seen in
everyday life when we estimate how hot an electric stove burner is by the color it glows.
Similarly, I have tried to work through the math problems step by step, explaining that
terms must be cross-multiplied, and so forth.
As a final goal, I have set many of the modern discoveries in their historical context.
I want to demonstrate that science is a dynamic process and that it is subject to controversy.
Ideas are often not immediately accepted, and to appreciate those that scientists
finally settle on, it helps to understand the arguments for and against them, as well
as the train of reasoning that leads to the “accepted” answer. On this point, I must digress
and reveal my own amazement (and naiveté) at how many widely accepted ideas
have such flimsy underpinnings and how many widely quoted values for astronomical
quantities are very imperfectly known.
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2004 McGraw-Hill Higher Education