We deal in this book with the broad and burgeoning subject of pretelescopic astronomy. People around the world have been deeply interested in the sun, moon, and stars for millennia. Of central interest to historians are answers to the questions, "What did they know and when did they know it?" In this section, we discuss why we want to know the answers to these questions, and the means by which scholars have attempted to provide the answers.
What we know of ancient cultures stems from their writings, artifacts, representations, monuments, tombs, and even the organization of their cities. In one way or another, each of these cultural expressions demonstrates interest in an aspect of the heavens. The deciphering of Babylonian cuneiform and of Egyptian hieroglyphic writing and the decoding and interpretation of astronomical texts and tables are long-standing scholarly activities. The newer science of archaeoastronomy deals mainly with astronomical discoveries outside of the writings.
As a discipline, archaeoastronomy stems from the publication of J.N. Lockyer's Dawn of Astronomy in 1894. Working with little regard to the findings of archaeology, Lockyer attempted to date structures by purely astronomical criteria. With this approach, he at once illumined a fresh path for scientific exploration and incited such criticism that few dared to venture on that path again for more than half a century. The renaissance of the subject is more than a little due to the publication in 1968 of Stonehenge Decoded by Gerald Hawkins. This helped to draw popular attention to the astronomical practices of earlier cultures, and interest has continued to grow. As a science, where successful, it has had to be open to the contributions of many disciplines, as diverse as ancient poetry and quantitative mathematics.
An aspect of ancient astronomical study deals with trying to find solutions to astronomical and astrophysical problems from early data. Thus, the discovery that the bright star Sirius was once described as red, when it is now clearly white, may light up formerly obscure paths of stellar evolution. Early descriptions of the "seven sisters" may help us to find out something about long-term variability among the Pleiades star cluster, because the normal unaided human eye now detects only six stars. Records of ancient eclipses provide evidence of the length of the month (and the changing distance of the Moon) on the one hand, and of the length of the day (and the slowing of the Earth's rotation) on the other. Records of ancient supernovae provide dates of initial explosions, and thus ages, and when coupled with current measures of the angular sizes and rates of expansion, provide distances, and luminosities of these objects. Because supernovae are among the brightest single stars known, they provide "standard candles" for the determination of distances to remote galaxies, thus, aiding the determination of the size and age of the universe.
A branch of ancient astronomy, called "astroarchaeology" by Hawkins, deals with the application of astronomy to archaeological problems. The term has not achieved wide currency, but the aspect of archaeoastronomy it represents has not been ignored. The astronomical dating of structures (or complexes of structures) that may have incorporated astronomical alignments is an example of such application. The success of any such enterprise, depends, therefore, on the genuine astronomical intent of the builders. This question is still moot in many cases, but in others, the evidence for intent appears to be strong.
Most contemporary practitioners of archaeoastronomy seem to be interested in the subject for itself, in order to understand the astronomical activities of ancient cultures. Investigations of the use to which astronomy is put in the religious and social contexts of particular groups has produced still another area of contemporary study: ethnoastronomy.
It is difficult enough to work in a field such as the history of mathematical astronomy, as exemplified by the prolific work of the late great scholar Otto Neugebauer, in which the scholarly materials required to understand completely the ideas and workings of a culture are still undiscovered in the debris of destroyed cities or in caches of forgotten caves. It is even more difficult to recover ancient astronomy practices from the remnants of cultures that were systematically destroyed, as in post-Columbian Mesoamerica, or from cultures for which no written material at all is known, as in Stone Age Britain. Mesoamerican scholars and astronomers have long had mutual interest in studying eclipses and calendars, among other phenomena in which the Mayans and other peoples of the region had remarkably strong interest. Multidisciplinary scholars such as Anthony Aveni have done much to demonstrate astronomical alignments at Mesoamerican and South American sites. The study of megalithic Britain by the survey-engineer Alexander Thom and his son Archibald has helped to reveal the capabilities of the megalith builders. More recent archaeoastronomy has been characterized by close scrutiny of the uncertainties in the observational data and a strong emphasis on the limitations of measurements in the field due to various effects, such as parallax shifts, or the bending and dimming effects of the Earth's atmosphere, or the intrinsic motions of the stars. Much greater attention also is being paid to the archaeological and cultural contexts of the cultures. Measurements of great accuracy, investigations of the precision and accuracy of those measurements, and attention to context are in large part what distinguishes archaeoastron-omy from Lockyer's (1894/1973) early efforts. If we know, for example, that a certain group of people was interested in the " dark constellations" of the Milky Way, we should not limit our study of potential astronomical alignments of their geoglyphs or structures to the brightest objects in the sky or even to the brightest stars. As it continues to mature, archaeoastronomy can be regarded as an increasingly important component of ancient astronomy.
Whatever the emphasis, the end result of attention to detail of any of these approaches is a richer appreciation of the cultures that provide the data and of the advance of the arts and sciences that are needed to complete the study. In the present work, we try to consider evidence from all the approaches to ancient astronomy.
Aside from purely scholarly reasons for studying the subject, to seek an understanding of ancient astronomy is to encounter deep well-springs of religion, life-energizing forces of sex and eroticism, and, frequently, cosmic aspects of games and sports. In discovering the astronomy of the ancients, we also discover much about their cultures and their intellectual capabilities, accomplishments, and limitations, and in discovering these things, we discover much about ourselves.
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