Archaeoastronomy

ASTRONOMY SURVIVAL NOTEBOOK Archaeoastronomy SESSION THREE: ARCHAEOASTRONOMY Archaeoastronomy is the practical use of astronomy as it applies to early cultures. It is of interest to astronomers and archaeologists because it encompasses the study of astronomical principles employed in ancient works of architecture (sometimes referred to as astroarchaeology) as well as the practice of astronomy and methods of observations among ancient peoples. ORIGINS OF ASTRONOMY AND ASTRONOMICAL OBSERVATIONS The importance of astronomy to all ancient cultures stemmed from a practical need to establish a precise method for telling time, monitoring agricultural events, performing religious ceremonies, and regulating governmental activities. Early people discovered that the systematic progression of the seasons was matched to the rhythmic motions of the heavens, and that the sky was a far more accurate indicator of these cycles than making systematic observations of the weather. People realized that the movement of the sun across the sky could fix the day and its divisions, while the changing phases of the moon established the month ("moonth" in Old English). By observing the rising or setting of a specific star when near the sun (heliacal rising or setting), the year could be defined. And, because there were seven objects which moved against the starry background; five planets, the moon, and the sun, the popular notion of the week came to fore. Ancient cultures did not understand the true physical nature of these seven wanderers in the heavens, so it was only natural to deify them and to closely monitor their changing positions. Those individuals who became proficient in these tasks were able to wield enormous power with the populace and ruling infrastructures; so much so, that they were venerated as priests and allowed to exist as a separate, almost untouchable segment of society. They designed temples with astronomical alignments to track the extreme positions of the sun and the moon. In a sense, these structures acted as permanent calendars. Eventually, in the Middle East, a complex series of rules were devised to relate this celestial dance as an indicator of human destiny. The pseudoscience of astrology with its many different types of horoscopes was a direct result of this synthesis. THE ANCESTRAL PUEBLOANS OF THE CHACOAN PHENOMENON About 500 AD, Native Americans who lived in the upper Rio Grande, Colorado, and San Juan river basins of what is today, Utah, Colorado, Arizona, and New Mexico, began to abandon their nomadic existence for the richer rewards of a more stable and settled farming lifestyle. Instead of seasonal migrations from region to region, as hunters and gatherers, crops were planted on a regular basis to insure a more consistent and varied food supply. In good years, food surpluses were realized which helped sustain villages against times of famine. Collectively these people were known as the Ancestral Puebloans. The Navajo never knew the Ancestral Puebloans. When they migrated into the Four Corners region during the fifteenth century (1400s), they only discovered their silent ruins. The Ancestral Puebloans lived in harmony with nature, and as a result they were keen observers of the Earth and the heavens. Most of their waking hours were spent out-of-doors surrounded by an expansive azure sky and canyon walls. They could tell impending weather 69 ASTRONOMY SURVIVAL NOTEBOOK Archaeoastronomy changes by monitoring insect activity or wind direction. The rhythmic changes of the heavens set the tone for daily, monthly, and yearly calendrical cycles. Farming was difficult because rainfall was scarce, and what rain fell evaporated quickly in the dry desert air. Most of the annual precipitation came in short bursts, during thunderstorms that occurred mainly in the spring and summer months and averaged about 8.8 inches per year. Temperatures could range from well below zero on the coldest winter mornings to over 100 degrees F. on the hottest summer afternoons. The Ancestral Puebloans dwelled in family or clan units on mesa tops or in the many protective enclaves afforded by surrounding cliff walls. They built their pueblos (towns) and ceremonial structures from the abundant sandstone rock which was all around them. A distinctive feature of pueblo architecture was the kiva, a roofed ceremonial room, found usually below ground level, and almost always reserved for men. This may possibly be explained by the fact that Ancestral Puebloan society was matriarchal. Women held property rights, family names, and clan affiliations were passed down through the female. Divorce, Ancestral Puebloan style, was simply the wife putting the husband’s belongings outside of her pueblo. Men and boys had to have a place to congregate, and the kiva was thought to be used to that practical extent, as well as for religious ceremonies. Ancestral Puebloan men and women were short and lean. Average heights were about five feet, slightly higher for men and slightly lower for women. Weights were about 100 pounds. Life spans averaged under 30 years with men living longer than women. Arthritis and tooth decay were often contributing factors to an early death, as well as a high child mortality rate, especially in times of famine. EARLY CULTURES AND THE SKY A. What were the conditions which allowed ancient people to make good astronomical observations thousands of years ago? The culture had to possess a 1. Functioning language or some method of communication 2. Practical, working knowledge of mathematical principles 3. Sufficient longevity of its population to observe the repetition of cyclical events B. Early people probably did not understand the relationships in movements between the Earth, moon, and sun. They were, however, able to measure their positions and establish alignments which served as monitoring devices. C. Objects and observations of interest to early humans 1. Sun: Solstitial positions of the sun—June 21/December 21 a. The sun rises and sets at positions most north or south of east and west respectively. b. Noontime positions of the sun are highest and lowest for the year. c. Length of the day is longest or shortest for the year. 2. Moon: Major and minor standstill positions. These represent the extreme positions of moonrise and moonset along the horizon. They are created by the five degree inclination of the moon’s orbit to the plane of the ecliptic. 3. Helical rising of a star: The Egyptian’s first observations of Sirius before the rising sun overpowered it in the dawn sky pinpointed the beginning of their year and the annual flooding of the Nile River. 70 ASTRONOMY SURVIVAL NOTEBOOK Archaeoastronomy 4. Bright Stars or star clusters and their rising or transit positions signaled seasonal changes. The rising, setting, or transit positions of the Pleiades were used by the Aztecs in Mexico to establish calendrical cycles and the construction of cities. 5. Conjunctions (objects appear close together in the sky) and eclipses of the sun and of the moon. D. Methods of observation 1. Introduction 1) Menhir: Standing stones which were used as positional markers, usually associated with European megalithic sites. 2) Foresight: A distant mountain or conspicuous geographical feature which the sun rises or sets behind. 3) Backsight: The position from which the observations are conducted. 2. Stationary observer: The observer watches the changing position of the rising or setting sun against the features of a distant horizon. Stone circles or other isolated menhirs between the backsight and foresight could have been used as markers to indicate the extreme positions of the sun or moon or other religious and agricultural events. In this manner a calendar could have been established. The use of intervening menhirs in Native American observations did not usually occur. 3. Observer moves: Distinctive notches on hillsides located miles away from the observer could have been used as foresights. The observer would have positioned himself (at a backsight) so that each day the sun would have risen or set behind the same geographical point, such as a notch in a mountain range. Since the location of the sun would have shifted from one day to the next, the observer would have continuously changed his backsight location to keep the sun rising behind the same geographical location. He could have marked these changing positions with a series of stones. He would have easily noticed when the solstice occurred, marked by the most northerly or southerly rising positions of the sun, since afterwards, he would have been retracing his steps as the sun moved in the opposite direction. 4. Windows/Ports (small openings) and doorways, etc.: A building is designed in such a manner that hallways/doors/windows (ports) permit the passage of sunlight or moonlight into certain parts of the structure at certain key times of the year or when these objects are in certain key positions. The entire structures themselves or the alignment of ports create the markers which can be used to establish a yearly calendar. 5. Sun Daggers: The passage of sunlight through natural or worked rock formations creates a dagger-like image on another rock face at certain key times of the year. The most famous of these observatories is the sun dagger atop Fajada Butte in Chaco Culture National Historical Park in northern New Mexico. 71 ASTRONOMY SURVIVAL NOTEBOOK Archaeoastronomy NOTES 72 ASTRONOMY SURVIVAL NOTEBOOK Archaeoastronomy Date: _________________________________ 1. ____________________________________

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