How We See The Sky. A Naked-eye Tour Of Day & Night

Descripción

How we see the sky. A naked-eye tour of day & night, by Thomas Hockey. Ed. The University of Chicago Press, 2011. Size 23 x 15 cm. Condition: New. 240

Why does the world need this book? Why should you want to know about what lies between the pages of this book? These are the questions I will try to answer in this brief introduction.

First: Look around you. Up to half of everything you see is sky. The sky literally surrounds us. Even "The fool on the hill sees the sun going down / And the eyes in his head see the world spinning 'round" (The Fool on the Hill, The Beatles, 1967). Yet few of us know much more about the sky than that.

I think that this is a shame. For the sky is universal. Imagine yourself magically transported to a bar stool in some far-off land. You do not know the local language or customs, much less the cuisine. Nevertheless, there is one thing that you do have in common with the stranger seated beside you. You both have lived your lives under much the same sky.

Yet there is a difference: The more attuned you are to modern, Western society, the less likely you are to know about your sky. As I sat in the "ger" (yurt) of a family living on the Mongolian steppe, supping on kindly offered cheese and yogurt, I routinely asked the same question. I knew that the door of their nomadic house always faced south. My question was, simply, how do you know where south is? The answer was always the same. They just "know". I was asking a question so obvious, that it was as if someone had asked me how I know one plus two equals three, or how I know how to spell my own name. This knowledge is so quintessential to who they are that my Mongolian hosts can no longer recount the steps that led toward acquiring it.

Today's ignorance about the sky throughout much of the rest of the world was not always the status quo. While we like to think of ourselves, the present generation of humans, as well educated compared to our ancestors, there is much that we are becoming less and less knowledgeable about. Note that I am not thinking about obsolete technology, say, how to make the best whale-oil lamp; I mean fundamental knowledge about our environment. I am pondering the understanding of our own sky: what we see there, how what we see changes, and how it affects us.

I am interested in the astronomy accessible to everybody, without sophisticated instruments. It is the astronomy of the naked eye; you do not need a telescope to
engage in it. (Everything described in this book I have seen with my own eyes.)

I do not refer to any sort of secret knowledge from the past. That is largely the stuff of graphic novels. Since people have become literate, we have been able to archive information. This assures that what we have learned about the sky is preserved. Moreover, thanks to modern science, there are specialists who know more about the heavens than our predecessors even dreamed of learning. Still, I maintain that the corporate sky knowledge of the rest of us is less than that of the average Roman citizen two thousand years ago.

There are obvious reasons for this. For the aforementioned Roman, astronomy was practical. It was good for business. If you were in charge of shipping grain from Rome to Carthage, then (as now) it would be important to know two things: when the deal was to happen and where Carthage is. Before clocks, timekeeping was done almost exclusively by watching changes in the sky. Even more recently, the sky was a vital source of data for mariners navigating the seas. (For some, it still is.) The information provided us by the sky is so important to modern society that we have replaced many functions of the skies with technologies more under our control.

At the same time, the sky is less accessible to us. This may sound strange. However, the average shepherd had a much better view of the sky than us. Not only was his horizon unimpeded by construction, but the darkness of the sky was total in the absence of artificial illumination. More important, that shepherd simply spent more time under the night sky. He did not share our indoor lifestyle. Plus there was little else to do during the dark of night besides look up at the stars. (TV reception was poor in the year one.) Our shepherd of the past, as intelligent as we are today, paid good attention to what he saw above. Eventually he recognized patterns. He and his brethren were among the first astronomers.

I will go so far as to say that astronomy was the first science. This sounds jingoistic, considering that I am an astronomer. But hear me out: I think this because astronomy began as the simplest science.

Do I mean that astrophysics is somehow simpler than, say, microbiology? No. However, science is an act of formulating theories. Two things are of great help in making the observations necessary to create predictive theories. These are repetition and regularity. The repetitions and regularity of the lights in the sky made it easier for our forebears to construct theories about them than did the more complicated patterns exhibited among, for example, flora and fauna (or other more complex phenomena of our terrestrial world). And so science was launched.

Today's professional astronomers have transcended simple observation of the sky with the unaided eye. They are interested in the physical nature of the universe and the forces at work there. They have been enormously successful at their work. Our standard textbooks now are filled with insight about distant worlds and galaxies. To make room for this new knowledge, chapters about what the sky actually looks like from the earth have been abridged. (This phenomenon parallels the decline in physical geography content within the social science curriculum.) What a nineteenth-century student might have spent a semester studying, today's counterpart breezes through in a few weeks. In the century before last, we did not even know that we lived in a galaxy of stars. Yet we were much more familiar with the sky and its cycles.

Those days of old are gone. We are so removed from the sky, and other realms of nature, that often we are not cognizant of ways in which they still affect our lives. Speaking more broadly, a lot of our culture continues to draw upon the sky by way of language, myth, and metaphor. To understand ourselves, I believe that the sky still matters. For when early people looked up at, and thought about, the sky, they really were trying to answer what is perhaps the most human question of all: Where am I? What is my place in the universe? So are we.

Chapter 1 discusses the astronomical sky in and of itself. What is its apparent shape and extent? How do we describe its population of stars?

In chapter 2 we develop a means by which we can communicate with one another about locations and apparent motions in the sky. We follow the seemingly moving stars in the sky throughout the night. Our reference is the horizon, where the earth and sky meet.

Chapter 3 introduces the concept of the celestial sphere to our cast of characters. The idea of a celestial sphere makes it easier for us to describe—not just our sky—but the sky as it is at different places on the earth. Also, we address changes in the sky that take place, not just over one night, but over the course of the year.

Long-term changes in the appearance of the stars are the subject of chapter 4. We conclude our examination of the stars with a discussion of how to get the most out of our human vision while sky watching.

From the stars we move on to the sun in chapter 5. The apparent motion of the sun in the sky is our principal timekeeper.

Moreover, the sun presents us with the gift of seasons, the topic of chapter 6. By understanding the annual apparent behavior of the sun, we humans have maximized its use in agriculture and for light and warmth. In the process we created civilization.

In chapter 7 we take a trip around the world to see how the seasons affect different peoples. We introduce "heliacal rising," historically the most important sky phenomenon that you have never heard of!

Chapter 8 treats the moon. We mark our calendar by the moon. Calendars are everywhere, and they are not always the same.

Analogies of the moon's apparent motion with that of the sun are explored in chapter 9.

Yes, but what do the sun and moon really look like? In chapter 10 we step back and examine the features visible on these famous disks.

Chapter 11 is about eclipses. We need both the sun and the moon to produce this comparatively rare phenomenon. At the same time, eclipses are so exciting that they deserve a chapter all to themselves.

In chapter 12 we "put" the planets in the sky, thereby completing our list of the objects regularly seen there. However, we also add a few ephemeral sights, to
conclude the book.

(All descriptions of the sky herein are geocentric. They are based on an imaginary stationary earth. Until five hundred years ago, everybody assumed that geocentricism conformed to reality. We now know that the solar system is heliocentric—nearly centered upon the sun. I will use a bit of heliocentric jargon when discussing the sun; I think that it will be easy to tell which "centrism" I am using at any given time.)

CONTENTS
Preface
Introduction
1- Bowl of Night
2- This Big or Wheel Keeps Rolling
3- A Globe of Stars
4- Of Precession, Planispheres, and Patience
5- The King of Day
6- Solstices, Equinoxes, and More
7- Around the World with the Sun
8- Many Moons
9- Living Month to Month
10- Facing Up to the Moon (and the Sun, Too)
11- Eclipses
12- Placing Planets
Notes
Recommended Reading
Index

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