Rerturn to Archeoastronomy Index Page

Blake Learmonth

Background and Rationale

Ask middle school students about Astronomy, and most will describe a science with telescopes, planets, stars and distant galaxies, a modern high tech science. Most would be surprised to find out that Astronomy is probably the oldest of the sciences, possibly the origin of observational science, and that in many societies it predates written history by thousands of years.¹ Equally surprising, would be the concept that Astronomy can be done with simple instruments (or none at all) and that it has very down to earth, practical applications. Fewer still would be aware of astronomy’s deeply spiritual connections.

Modern urban people seem out of touch with the natural world and the cosmos around them. At some level, that is not too strange. If a person buys food at a grocery store that imports off- season fruits and vegetables from the other hemisphere, travels from an air-conditioned house to an air-conditioned office in an air-conditioned car, the natural cycles around him have little effect on his daily routines. In today’s light-polluted world it takes a well-publicized event like an eclipse or a comet’s appearance to get people to look up, and then, in urban areas at least, they don’t see much.

Students in my classes, 6th and 8th graders, are at least as out of touch as their adult contemporaries. As part of a mapping unit that my students were working on last spring, students were required to know their cardinal directions and place them with reasonable accuracy on a map of our school. While the maps were being created I was frequently asked for help identifying directions. I would prefer that my students work things out rather than just tricking me into just giving them the answer, so I often answer questions with questions. My first reaction question to their direction question was, "Where does the Sun come up?" Several of them gave the right verbal response, "east," and some could draw the compass rose with the directions in the right relation to each other, but very few could point the right direction. I should mention that this took place in Albuquerque, New Mexico, a city with frequent clear weather, where the sun rises over a 10,000-ft mountain range. The view of the mountains is seldom obscured by dense vegetation or tall buildings. In the winter months, at least, these students are often traveling to school while the Sun is rising over the mountains; it is part of their daily experience.

In addition to lack of knowledge, Middle school kids harbor some serious misconceptions about some pretty basic astronomical ideas.² Snider cites an Israeli study from the late 1970s, replicated in San Francisco in the 1980s which indicated that the majority of elementary students and 25% of eighth graders were unclear as to what it meant when people said the Earth was "round." Many who agreed that the Earth had a spherical shape believed that we lived on a flat spot either on or in the sphere. The misconceptions that the phases of the Moon are caused by the shadow of the Earth and that seasons are caused by being closer to or farther from the sun, persist into adulthood. As teachers, we have to watch out for the belief that some ideas are so basic that "everybody knows" them. In teaching an American history lesson to eighth graders, during my first year as a teacher, I was pleased that most of them could state that a "Tory" was someone loyal to the British king. My bubble was burst however when my teaching partner discovered that most of them had no concept of what "loyal" meant.

Some concepts important to studying astronomy are very difficult for children who have not mastered abstract thought. Being able to think in three dimensions, for example, is hard for many adults. Many astronomy lessons require the student to change back and forth between a standing-on-Earth point of view and an out-in-space or "God’s eye" view, which is simply beyond the capability of most 11-14 year olds. The solution seems to be to involve students in first hand observation. (See lesson recommendations below.)

Unit Goals

One of the goals of this teaching unit is to make students aware of the astronomical phenomena that take place around them on a daily or seasonal basis. This awareness will be encouraged through both casual and formal observation. Since careful observation is at the root of all science, this practice can be justified on several levels: Experiencing the kind of observation that led to the science of astronomy, establishing a connection with the natural world by experiencing cycles first hand, and establishing or reinforcing a connection with Southwestern Native culture by emphasizing the long history of naked eye astronomy in this region. Studying ancient astronomy will also provide an opportunity for students to compare and contrast ancient and modern astronomy as well as notice the similarities and differences between the early astronomy of variety of cultures.

Additionally, activities should provide concrete role playing type opportunities where students can act out astronomical situations that are difficult to conceptualize, as well as the opportunity to build tools for making scientific astronomical observations.

Why Study Astronomy?

Ignorance may be bliss, but knowledge is power. An ignorant individual is totally at the mercy of apparently unknowable forces around him. Such an individual is also at the mercy of less ignorant individuals. For ancient people ignorance and survival were mutually exclusive. A person living in the natural world is confronted by astronomy; ignorance is very hard to maintain. The Sun, the Moon, the visible planet, and the stars rise and set everyday. Long before any kind of systematic study of the heavens existed, people had to notice day-to-day changes. Since natural phenomena like seasons affect all living things, members of even the most primitive societies benefit from being able to predict natural cycles. There is a right time to hunt for certain animals, a right time to gather certain plants. In agricultural societies timing becomes even more important. Conveniently, the sky provides the clocks and calendars to help people know the best time and, possibly more importantly, to anticipate or predict the best time. All that is required is careful observation.

To the ignorant, prediction has a magical, supernatural aspect, and those with the ability to predict are relatively more powerful than those who live from surprise to surprise. The job of Astronomer seems to have evolved from groups valuing individuals who could predict celestial cycles and events. According to John North in The Norton History of Astronomy and Cosmology, "Astronomy has always been allied with religion--in the first place, one suspects, because both were concerned with the same objects. The Sun, moon, and stars were divinities in many societies."³ I question the "always" in North’s statement. It seems that science and religion have had an adversarial relationship in western society for the last 500 years or so, but recent European history aside, astronomy has been valued by a wide variety of societies for its ability to predict natural occurrences and thereby schedule human activities in spiritual or practical harmony with natural cycles. For me it has been important to keep in mind that the disconnect between science and religion, spiritual and practical is a modern European phenomenon. To this day, in Southwest Pueblo societies, the pueblo astronomer is a religious figure, a "priest," who assures that his people, "perform the proper ceremony at the proper time."⁴ The observations that the priest makes are no less systematic or "scientific" than the observations made by people thought of as scientists by the non-Pueblo society. An activity like planting crops has both a spiritual "proper time" and a practical "proper time" that coincide and can be determined from astronomical observation. Getting the time right has, for many societies, both practical and religious implications.

Archaeoastronomy, Ancient Astronomy

If there is any idea that is consistent about ancient people and astronomy, it is that all ancient people were aware of sky, both the day sky and the night sky. They created rock art all over the world, they built structures that were either shrines or actual observatories, they created stories to explain celestial events, and they deified celestial objects. However, once the basic similarities are established, the details lead in a thousand directions. Additionally, while many of the astronomical practices which will be described below have contributed to, or evolved into, modern astronomy, others, like past and present Southwestern, Native American astronomy, exist actively independent of any interaction with non-native astronomy.

Ancient Europeans: the "Henge Builders"

The debate about the meaning of various British henges, Stonehenge, Woodhenge, and many others constructed over 2 or 3 millennia, all over the British Isles, fills literally hundreds of volumes, not to mention dozens of Internet sites. The debate itself brings up a very important aspect of Archaeoastronomy, the tendency to project modern ideas onto ancient cultures. Historian Stuart Piggott put it this way:

Scientists studying the various stone, earth and wood circles of Britain have been obsessed with alignments of various stones or posts with various astronomic events. Scientists have descended on these, and other, sites with video cameras, surveying equipment, and computers, none of which ancient astronomers would have had at their disposal. All of the technology applied to Stonehenge has not led to agreement among scientists about how it worked, though most seem to agree that the henge sites do function at some level as either observatories or shrines. To add to the confusion many of the sites have been rebuilt, not by modern archaeologists, but by a long succession of ancient people who used the sites. Their purpose may have evolved as well. "There were really several Stonehenges. Like a cathedral, it was built and rebuilt on the same spot over a span of two thousand years," using different building materials. "Successive construction work...destroyed much evidence that would allow us to trace astronomical alignments with confidence."⁶

Whether the alignments work or not, the high banked ditches and lentil topped stones (found only in the later versions at Stonehenge) form an artificial horizon that could have been useful in predicting events as common as solstices or as rare as solar eclipses.⁷

Egyptians and Babylonians

The Egyptians and Babylonians were sky watchers too. Having written languages and systems of numbers, they developed systems for recording events in the skies. Both developed calendars, and kept track of days, and divided the day into hours. The 365-day year is an Egyptian creation as is the 24-hour day. Dividing the hours into 60 minutes and again into 60 seconds comes from the Babylonians. Egyptians used star observations to determine their seasons, which were not solstice based. Egyptians had only three seasons, ‘flood’, ‘emergence’, and ‘low water’ or, ‘harvest,’ based on the flooding of the Nile and indicated by the helical rising of Sirius. (the first sighting of Sirius on the eastern horizon after its winter period of invisibility, in mid July) ⁸ The Ancient Egyptians also had three ten-day weeks in each month, which has no astronomical connection. In text books, Egyptians are often given credit for being great astronomers in the modern sense of the word, but:

Roman records considered any one living in Egypt to be Egyptian, so Greeks like Ptolomy, "the greatest astronomer of antiquity,"¹⁰ who lived in Alexandria, are referred to as Egyptians. Roman records also credit Egyptians with having invented things that were really borrowed from other cultures. The zodiac, for example, with several of the same constellations we use today, is found in Egyptian temples, but also in earlier Babylonian records.

Babylonian/Mesopotamian astronomical records span several centuries before and around the BC/AD transition. Modern astronomers relate to the Mesopotamians because they far exceeded the Egyptians in using mathematics. "All those sciences in the modern world that make use of mathematical methods are indebted to the astronomers of Babylon, from the last five or six centuries before the Christian era."¹¹ Among their accomplishments was the development of the sexagesimal, base 60, number system, which forms the basis for our time keeping and angle measuring systems today. Their oldest literature, the Gilgamesh epic "Has hints of ritual observing of the Sun, moon, and planets over distant peaks,"¹² a practice which seems to be the basis for observational astronomy in many cultures.

Over centuries of observation and recording events Babylonians began to see patterns in the recurrence of celestial events, and became able to predict events such as eclipses. Many of their predictions came directly from the data and a fairly accurate calendar. If an event happened over and over at a given interval, it was reasonable to predict that it is going to happen again at the same interval. There was no need to understand the why. Some Mesopotamian religions thought that certain numbers were important and meaningful, so it is possible that the numbers were seen as the actual cause of an event. Babylonian religion also connected astronomical events with earthly events. With huge astronomic records and huge historical records, Babylonians produced lists of omens, 7000 all together, many of them relating to the planet Venus, which predicted all manner of events. These omens were not exactly astrology, which was really a later Greek development. Babylonians had fallen into a very popular logical fallacy, post hoc, ergo propter hoc -- after this, therefore caused by this. And they had the records to prove it.

In a trend appreciated by modern scientists as a breakthrough, Babylonians made the transition between just observing events, and developing mathematical rules that exactly predicted the results. They had, for example, rules for calculating the rising and setting time of the moon in relation to its phase. Between the use of long record keeping and sophisticated mathematics, Babylonians became very good at predicting astronomical events.

Mesoamerican

Like the Babylonians and the Egyptians, The Mayans had written language, a system of numbers and mathematics. They kept extensive records of both historical and astronomical events. Unfortunately, most of these records were destroyed by the Spanish in the early 16th century, in the clash of religions that inevitably followed European invasion of Native American cultures. Although the loss of the majority of Mesoamerican written records to religious chauvinism has certainly limited, and possibly skewed, our knowledge of their society, continuing progress has been made in interpreting the surviving documents. As well as surviving documents, there are surviving people, descendants of the Maya, from whom ethnographic information may be gleaned.

We know, for example, that Mayans produced a variety of calendars, and that the calendars were based on astronomy. From studying Mayan documents and monuments:

There were basically three Mayan calendars. One roughly equivalent to our 365 day solar calendar, one referred to as the "vague" calendar with 360 days, and a religious calendar of 260 days, which is referred to as an almanac because it also contains records and predictions of eclipses and other astronomical events. These included some that could not possibly have been observed by the Mayans or any of their neighbors, but that could have been predicted mathematically.

There are Mayan records of horizon watching, and when the horizon was obscured by jungle, the Mayans built structures to observe solar events at least. At Uaxactún in what is now Guatemala a pyramid faces east, providing a view of three small temples that form an artificial eastern horizon. An observer standing on the center of the steps of the pyramid at sunrise on the day of the summer solstice sees the sunrise aligned with the left temple. If the procedure is repeated at either equinox the sun rises centered in the middle temple. At winter solstice the sun aligns with the right temple.

Mayans also observed, recorded and predicted the behavior of the visible planets and stars; they particularly focused on the movements of Venus which are said to have dictated the time for ritual warfare.

Southwestern Native Astronomy

In contrast to the Maya, the Southwestern Pueblo People, both modern and prehistoric, have not kept written records (Until very recently their languages have not been written.) There is no indication that they use(d) mathematics, or even arithmetic, beyond relatively short counts.¹⁴ Despite these facts, Pueblo people have a long tradition of observing and using astronomical events. For Pueblo people the spiritual world and the world of astronomy coincide. The reasons for doing astronomy are spiritual. It might be reasonable to say that all actions in the Pueblo world are spiritual. When one combines this idea with a view of the cosmos as interactive, the job of astronomer takes on a very different character from the job of astronomers in the outside world. Westerners study astronomy to try to understand the cosmos, pueblo people already understand the cosmos and do astronomy to stay in harmony with the order of the universe.

Staying in harmony has requirements. "Nature functions with the active cooperation of mankind, who must perform the proper ceremony at the proper time to ensure the regulation of order."¹⁵ Furthermore, the method for knowing the proper time and the proper ceremony must also be correct. For example, most Pueblo groups do sun watching in order to anticipate ceremonies around the winter and summer solstices; the responsibility usually falls on a "Sun Priest," who could just get out an almanac and look up the exact time of the solstice and announce it to the people in time for them to prepare for the ceremony. To an outsider this would seem fine, but for order to be maintained, the Sun Priest must obtain the information in the proper way. The proper way is to observe the sunrise or sunset from a certain spot, possibly marking your observations in some way, until the moment is right to announce the ceremony. It seems that the process is critically important. In a Zuni story recorded in the 1960s , a woman tries to seduce Pequin, the Zuni sun priest.

Later in the story, the woman kills the Sun Priest, and he is proven right when the Sun doesn’t come up until a new Pequin is found.

The idea that astronomical rituals are performed to assure the continuation of life as it has been, is not unique to the Zuni. When asked why ancient Britons would build Stonehenge, Alison Jolly replied, "Anyone who has lived through an English winter can see the point; to make the sun come back."¹⁷ For the Chumash of California, "The winter solstice was the most critical moment of all because of the possibility (If the people did not take the correct ceremonial actions) that he sun might choose not to come back."¹⁸

Careful observation of the Sun, Moon, and stars also reinforces the Pueblo view of a cosmic duality. The Hopi universe, for example, is made up of two worlds, an upper and a lower. The two worlds are balancing opposites. When it is day in the upper world, it is night in the lower world; as stars set in our world they rise in the other, summer is winter...¹⁹ Ceremonies help insure that the Sun, which is personified and deified along with other celestial objects, will make harmonious transitions to and from the other world at the proper time.

The Mechanics of Pueblo Astronomy (Sunwatching and some basic astronomy)

Since pueblo astronomy is tied up with ceremonial schedules, celestial objects, which exhibit repeating cycles throughout the year, are most commonly observed. Since instruments are not commonly used, these cycles must be observable with the naked eye. From an earthbound point of view, the Sun, the Moon, and the stars all go around the Earth rising in the east and setting in the west. (Caused by the eastward spin of the Earth) Days are counted by the rising or setting of the sun, which is pretty hard to miss. But, unless one is paying attention, some of the other celestial motions are not so hard to miss. Still from an earthbound point of view, the point of sunrise (or sunset) on the horizon changes from day to day with the seasons. At the spring (vernal) equinox, when day and night are of equal length, the sun rises to the east (March.21). From that day until the summer solstice, June 21, the day gets longer, the night shorter, and the sun rise moves north along the horizon. At first the movement north is quite rapid, easily visible. As the year progresses toward the summer solstice, the day to day movement of sunrise slows to the point of being imperceptible. The sun seems to stand still, which is what solstice means, "sun stands still." With practice and careful observation, a sun watcher can both mark and anticipate the solstice. No fancy equipment is needed. World wide, ancient and modern people use the two methods used by Pueblo Sun Priests. The first is horizon watching. Sun priests selected a spot, usually near the pueblo, with a good view of the eastern horizon. It is important that the horizon is not smooth; there must be details for reference points. (See figure 1) From his watching point, the sun priest watches for the first gleam of sunlight every morning, noting its location relative to features on the horizon. At first, all the sun priest would be able to do would be to note the solstice having passed. He would notice that the Sun’s northward movement had stopped, seeming to stand still for a few days. The Sun would then be seen to move south, at which point the Sun priest could announce that the solstice had passed. As the sun moves south along the horizon, it passes the same points as it did on its way north. If a count had been kept, tying knots in a cord or scratching lines on a calendar stick, the priest would know how many days it had taken for the sun to make the round trip from a particular landmark to the " Sun’s Summer House" and back (let’s say 20 days, for example). The natural assumption would be that it took half of the days each way, so the solstice would be the middle day in the count. The next year, with a good memory or some sort of record, the Sun priest would know that when the sun passed the horizon marker, solstice would be in 10 days. Assuming the sun priest has chosen a good place from which to watch, the same procedure works for winter solstice, only the directions are reversed. Similarly, sunset also works, but is much harder to view, since the observer is blinded by the sun right up to the moment that the last gleam needs to be observed. Topography often dictates the choice of the sun watching procedure.( See Figure 1)

In the Zuni oral tradition, the story is that it took the first Pequin eight years to get the solstice right, Which may or may not be intended to be taken literally. It may just indicate that it was important to get it right and that it took a long time. Eight and other multiples of four are important ritual numbers for Pueblo people.²⁰ The second method for Sun watching involves using features of either natural or man made structures to project sunlight on a wall so that the approach of the solstice can be anticipated and then confirmed. For this to work, placement of the opening and the distance to the wall have to be within certain limits. The alignment to the Sun also has to be right (but there are several different alignments that work). The ideal situation is to have a small opening in a wall that has an unobstructed view of the rising or setting Sun and an inside wall one or two meters from that opening onto which light can be projected. The sunbeam entering the opening acts like a lever, projecting a spot of light on the opposite wall which pivots on the fulcrum of the opening as the Sun moves. The position of the spot of light at sunrise (or sunset) can be marked on the wall. Unfortunately, there are two aspects of the light projection system that work against each other. If the opening in the outside wall and the wall onto which the light is projected are very close, the spot of light will have very crisp edges, which is good for accurate observations. However, the shorter lever arm of the sunbeam means that the spot will move only a very short distance, too short for daily changes to be apparent. Light projected on a more distant wall will have more apparent movement, but the resolution deteriorates, the edges of the spot become fuzzy. For naked eye observation, the projected spot needs to move at least .5 cm per day in the period about two weeks before the solstice. If the site meets these criteria it can be used to predict the solstices within a day.

Apparent alignments of buildings used by prehistoric pueblo people have led to the inference that, like their descendants, early residents of the southwest used structures for astronomical purposes. There are many sites in the Chaco Canyon area of New Mexico and elsewhere in the Four Corners area where interesting things happen at important astronomical times. There are certainly places that could have been astronomic observatories.

One particularly interesting prehistoric pueblo site is Pueblo Bonito in Chaco Canyon, which has features that make both types of sun watching possible. Pueblo Bonito is a large multi-story structure with several hundred rooms and many round ceremonial Kiva spaces. It also contains several corner windows or doors, which are uncommon in ancient Pueblo architecture. For winter solstice anticipation, one of these openings in particular, gives a good view of the southeastern horizon which has features allowing for good sunrise watching until the end of October. At that time the sun starts to move on to a relatively featureless part of the horizon. About the same time as horizon watching becomes difficult, the opening projects a beam of light into the room which moves noticeably northward as the solstice approaches. The light patch moves an average of 3 cm per day; with wall markers, the beam’s horizontal motion could be used to anticipate the winter solstice within a day.²¹ The beam continues across the wall until the winter solstice when, "the sunbeam neatly throws a square patch of light into the corner of the room.²² (I should mention that a small west facing window in my house projects a rectangular patch of light onto the opposite wall of my living room, which aligns very nicely with the corner of the room at summer solstice sunset. Until very recently my living room had not functioned as an observatory.)

Moon Watching

Pueblo people observe the moon, particularly the phases of the moon, in order to schedule ceremonial and agricultural activities, (See "Moon Phases" below) and to establish a measurable length of time shorter than a season but longer than a day. The "moon" = "month" concept is certainly in line with the origin of the word "month" in English. Pueblo "months" also come from lunar phase cycles.(The Jewish and Islamic calendars are similarly lunar cycle based.) "For most pueblos, the month usually begins at the first sighting of the first visible crescent -- the observable "new" moon,"²³ which sets the length of pueblo months at about 30 days. Ten months per year is most common, but numbers of months from 6 to 14 are historically reported.²⁴ There are two important concepts that contribute to the controversy. Because of the Pueblo concept of duality, the names of the first five or six months of the year are sometimes recycled for the second half. Also, and this is a problem for all calendars, the 29.5 day lunar phase cycle doesn’t fit evenly into the 365.25 day solar year. The discrepancy leads to the need to create intercalation, "leap" periods, to compensate. It would be very easy for an outsider to confuse the intercalation periods with real months.

Moon Phases

The daily change in appearance of the Moon from fully lit to completely dark and all of the steps in between, are the "phases" of the Moon. Contrary to very commonly held misconceptions, the shadow of the Earth on the Moon has nothing to do with the phases. Because the Moon’s orbit around the Earth is tilted about 5 degrees from the Earth’s orbit around the Sun, the Moon very seldom passes through the Earth’s shadow. Phases are caused by the Sun’s light hitting the Moon from the side from our point of view. Imagine someone sitting next to a lamp in a dark room. If you are facing them, the half of their face toward the lamp will be brightly lit; the other side will be shadowed. Observe the "first quarter" Moon about two weeks after the new Moon. It will be in the southern sky at sunset. If you face the Moon, the right side of your head and the right side of the Moon will be lit by the Sun. A person facing you would see half of your face lit by the Sun in just the same way that you see half of the Moon’s face lit by the Sun. At full Moon, the Moon rises at sunset and its entire face is lit by the Sun (it always is fully lit, but you are observing at a different angle each day, so the fully lit part faces a different direction from your point of view.) Again, a person standing between you and the Sun sees you the same way you see the Moon, one "face" in full sunlight. The "third quarter" Moon is high in the southern sky at sunrise. As you face the Moon, its left side will be lit and a person facing you will see your face lit on the left side. In both cases the side toward the Sun is lit. Lastly, at the new Moon you probably won’t be able to see the Moon at all, since the Moon is more or less between you and the Sun all day. Both the brightness of the Sun and the fact that the shadow side of the Moon is facing you make the moon nearly impossible to see. A few days after the new Moon, just after sunset in the western sky, something really interesting occurs; the Moon, still lit mostly on the side away from you, appears dark, although a glimmer of sunlight may be showing on the right edge, but the dark side of the Moon is lit by Earth glow, the Sun’s light reflected off of the Earth. Someone standing on the dark side of the Moon would experience a "full Earth." None of the previous words, even if I had stated them perfectly, would be a thousandth as effective for making this concept clear as really doing the observation. You may also be surprised, as I was, how often the Moon is visible during the day. (See Moon phase activities below.)

Observational Methods and "Tools"

As various cultures carried out astronomical observations, they developed methods and tools to make the process easier. The earliest "tools" were natural; as indicated above, many people used--and still use-- horizon landmarks to mark the position of the sun, moon, and stars. The Moon’s phases were, and are, also observed. The information obtained was and is used to track and predict celestial events and to time ceremonial and practical events. Tools that followed seem to fall into two groups: time measuring tools, and position measuring tools. Time measuring tools included calendars and sundials,( as well as other shadow clocks). Position measuring devices were used both to locate objects in the sky and to use objects in the sky to locate one’s self on the Earth.

If one pounds a stick or pole into the ground, a shadow will be cast. The shadow casting pole is called a gnomon. Observing the shadow will allow a person to notice several things. Hourly (continuously), the shadow will change direction and length. From day to day, the sunrise and sunset angle of the shadow will change, as will the length of the shadow at mid day. Gnomons were used by many ancient people and are still used in modern sundials. Observing seasonal changes in a gnomon’s shadow allows solstice prediction and also establishes a yearly calendar.

Gnomons can also be used to establish directions.²⁵ (See gnomon activity below.) In the simplest use, the shadow of a vertical gnomon points north at noon (when its shadow is shortest.) for latitudes north of the Tropic of Cancer. The east-west line can be established by connecting the end points of equal length shadows. Malville and Putnam suggest that the prehistoric pueblo people may have used gnomons to precisely align their buildings.²⁶

Astrolabes

Any instrument used to measure altitudes above the horizon can be called an astrolabe. Planispheric astrolabes combine the ability to measure angles with star charts for specific locations, which allow the time to be determined as well as allowing a number of other observations to be made. There is an excellent web site devoted to astrolabes that can be found at: http://myhouse.com/mc/planet/astrodir/astrolab.htm. Many navigational instruments, including sextants and quadrants evolved from astrolabes which were developed thousands of years ago by Greek and Islamic scholars. The astrolabes that students will construct will be simple sighting and angle measuring tools. (See astrolabe lesson below, and figure 3.)

Lesson and Activity Suggestions

Target grades: 6-8

Sun and Moon Watching:

Focusing Activity:

Talk with students about the historical precedence for making basic astronomical observations. Emphasize whichever cultural history or histories are appropriate to your locale. In any case, students should know that people have been observing the sky for millennia. They might enjoy a challenge, "Most kids a thousand years ago, with no telescopes, computers or television, knew more about what was happening in the sky than you do."

Each period will keep a Moon and Sun watching log, including the local rising and setting time, the phase of the Moon (by description and drawing), and the position of the first glimmer of sunlight on the Eastern horizon. The teacher will create forms for posting the information, and find a suitable location for sun watching. The instructions should include dire warnings in as many languages as necessary, instructing students not to look directly at the sun! After Astrolabe lesson has been done (See below) students can also record the azimuth, the number of degrees along the horizon, of the rising sun, as well as its altitude at noon.

University Of Texas, Austin McDonald Observatory’s Star Date Radio Report:

Students will be required to listen to University Of Texas, Austin, McDonald Observatory’s Star Date radio report on National Public Radio (7:00 PM daily in Albuquerque) or access their web site, http://stardate.utexas.edu/radio/s_

radioscript.html, to post in their science journals and report back to their classes. All of these responsibilities will be rotated among the students, so that every student won’t have to watch the sun and moon or report on Star Date every day.

Regular Lessons:

Lesson One: Introduction to Astronomy Through Children’s Books

Goals:

Use low reading level, high interest children’s books to introduce the subject of astronomy and to introduce astronomy vocabulary. To encourage peer teaching.

Objectives:

In groups of four, students will review children's books on astronomy. Students will report to the class what they liked and didn’t like about the books they reviewed as well as three pieces of information that they think were important. Each group will also add 5 astronomy words to a class vocabulary list (which will be combined with lists from the other 5 classes).

With teacher guidance, students should acquire basic information about the structure of the solar system, particularly the Sun-Earth-Moon system. They should become comfortable with the idea that their universe extends far beyond the solar system. They may acquire some information on different cultural outlooks on astronomy.

Background:

I was astounded at the number of children's books on astronomy in my local branch library. Most are graphically vivid and exciting, and as far as I could tell most were free of obvious misinformation. If this is typical, it should be fairly easy to assemble a fairly large collection of books to be reviewed. If books on local Native American astronomy or ancient astronomy are in the collection, try to get them as a contrast to modern "Western" astronomy.

This class is the anticipatory set for the unit, and as such has no anticipatory set of its own. My guess is that with a pile of Astronomy books on a table the problem will be to get the kids to stop looking at the books long enough to give instructions.

Instruction:

Students should be placed in groups of 3-5, using whatever group selection and role assignment scheme is typical in your classroom. Let the students know that they are starting a unit on astronomy and that you would like them to look at the books on the tables for about 5 minutes. After 5 minutes have students brainstorm what they think astronomy will be about. Use a web or list on the board to record their ideas. Pass out or describe the following assignment:

Compile the vocabulary list from all classes and distribute to students. Use crosswords, word searches, and other vocabulary games to increase vocabulary knowledge.

Materials:

25-35 children’s astronomy books, some duplicates would be okay. (In the Southwest, Native American astronomy stories can be included for cultural reference.)

Lesson Two, Angles:

(Could be a cooperative lesson taught with the math teacher if students are in "teams" or "families.")

Goals:

To make students aware of angles. To acquaint students with tools for measuring angles.

Objectives:

Students will observe and measure angles. They will be able to identify 45^o, 90^o angles, and 360^o of a circle.

Background:

Babylonians came up with the idea of dividing the year and the circle into 360 parts. The degrees of the circle correspond closely to days of the Earth’s orbit around the Sun. Like time, Babylonians with their number system based on 60, divided each degree into 60 minutes and each minute into 60 seconds for very precise measurements of angles on very big circles.

Focusing Activity:

Students should have protractors. Distribute several cut out shapes to each table group. Shapes should include triangles, squares, rectangles, polygons, and circles. Let students manipulate them for five minutes. Suggest that students might "measure" them with their protractors, but don’t explain what "measure" means. After 5 minutes, ask what students think that an angle is. Allow the discussion to go on until a reasonable answer is obtained.

Instruction: Measuring Angles

Talk briefly about Babylonians. (See background above.) Ask if any of your students are skateboarders, dancers, or ice skaters. If so, ask what a "360" is, a full circle spin. Explain that the name comes from the 360^o in a circle. Have students look at their protractors, most will have half circle 180^o protractors. Using either a giant protractor on the board or a clear one and an overhead projector, demonstrate measuring some angles. You may want to talk about acute, sharp angles less than 90^o and obtuse, open angles greater than 90^o. Be sure that you measure some 90^o angles and some 45^o angles. (90o angles are important in astronomy, 90^o separate the cardinal directions, the equator and the poles, and the horizon to the zenith, and 45^o angles are common in everyday activities.)

Practice:

Create or acquire a work sheet on measuring angles; or use the shapes from earlier in the activities. Have the students measure a variety of angles using their protractors.

Assessment:

Within the groups, have students exchange and correct the papers. Let them know not to be too picky, that the idea is to get within a few degrees of the correct angle. Precision will become more important as they practice and measure real angles in astronomy. The mission of the group is to make sure everyone at their table knows how to measure angles.

Lesson Three: Shadows and Gnomons

Goals:

To allow students to experience the way shadows are cast and see what the shadows can tell us about the movement of the light source or the shadow casting object.

Objectives:

Students will construct small shadow casting instruments and experiment with positioning them relative to light sources.

Materials:

Per student, one piece of Per table, either a flashlight or a foam core, table lamp with no shade
0 cm x 10cm x 5mm
one toothpick
protractors

Shadow Activities: (See figure 2.)

Here are two activities that can run simultaneously so that only half as many lamps and flashlights will be needed, and a third separate activity.

Activity One:

Students construct squares with cardinal directions indicated on them as pictured in figure 2. A tooth pick should be stuck in the center as close to vertical as possible.

Students will experiment with aiming a flashlight at the toothpick gnomon from different angles, changing both vertical and horizontal position, and recording how the shadow changes as the light source moves. The observations can be very freeform, or students can be provided with a list of angles of the light, and be required to record shadow length and angle for each.

Extension:

Have students prop up the north edge of the gnomon platform about 20^o_. Observe the changes in the shadows.

Activity Two:

In this version the light source, a small table lamp with no shade stays still and the gnomon platform moves around it. It is important that the platform continues to be pointed in the same direction while it moves around the light.

Extension:

At first, the gnomon platform should remain flat on the table as it "orbits" the lamp. Once the effects have been observed in one plane, students can try raising and tilting the platform.

Activity Three:

Find a large unshaded area outside. Have students bring in poles, broomsticks dowels, 2x4s, pipes, rebar, pretty much any thing tall and straight will work. Place the poles vertically, scattered around the area. Visit the area frequently with students to observe shadows. Use the gnomon shadows to establish the cardinal directions.

Lesson Four: Astrolabes

Background:

Both the Project ASTRO Universe at Your Fingertips, (sec J. page 9-19), and Astronomy For All Ages, (pages 35-38) have excellent plans and activities to make and experiment with astrolabes. A web search on "making an Astrolabe" will also yield reproducible patterns for making simple angle measuring astrolabes.

(http://myhouse.com/mc/planet/astrodir/astrolab.htm) is an excellent site for astrolabe history and for information on a variety of types of astrolabes. The site creator also offers fairly sophisticated astrolabes custom made for your location.

Goals:

To acquaint students with an ancient astronomical instrument, the astrolabe and its usefulness for measuring angles to objects both on the earth and in the sky. Also to introduce safe solar observation techniques. To create a tool that can be used in later activities.

Objectives:

Students will construct simple astrolabes from easily obtainable materials. Students will use their astrolabes to make a number of horizontal and vertical angle measurements. Students will use their astrolabes to measure angular heights and angular separations of various objects around the school and on the horizon.

Materials:

Either: copied or printed astrolabe protractor from one of the sources mentioned above and a stiff material like card stock, cardboard, thin plywood, or foam core, and suitable glue for mounting reproduced protractor

Or: a plastic student protractor

And: a smooth plastic straw, tape or glue to attach the straw to the protractor, strong thread or thin string, a washer, nut or fishing weight, and an 1/8 inch or smaller drill bit (for putting a hole in the plastic protractor).(see figure 3)

Activities:

Use the astrolabes outside of the classroom to measure the angular height of a variety of objects. Sight through the straw and read the angle off of the protractor.

To measure the angle of the Sun, aim the astrolabe straw at the Sun without looking at the Sun. Put your hand or a paper in the shadow of the astrolabe and adjust the angle until there is a small round dot of sunlight passing through the straw and hitting your hand or the paper. Read the angle off of the protractor.

Evaluation:

Check as students are doing their observations or give a specific list of objects to measure

Lesson Five:

Using the Astrolabe to Prove that the Earth’s Surface is Curved

Goals:

To allow students to experience the curvature of the Earth directly, using the astrolabes that they created in the previous lesson as a tool. Students should convince themselves and each other that their observations indicate that at least the part of the Earth around Albuquerque, NM is not flat.

Objectives:

On a field trip, students will measure the vertical angle of the sight line from the top of Sandia Peak, east of Albuquerque New Mexico to the top of Mt. Taylor, about 110 km away, using an astrolabe. They may also just get a feel for the curvature of the Earth from the way the horizon looks from a high mountain point of view. Students will brainstorm possible implications of the angle that they observe. Hopefully students can reach a consensus about the shape of the Earth.

Background:

Middle school students still have problems rationalizing the conflict between their daily observation that the world around them is more or less flat, with being told over and over by their teachers that it is "round." The word "round" may well be part of the problem. I try very hard to use the word "spherical," but find that neither my sixth nor eighth grade students are really comfortable with the word "spherical." I usually end up saying, "round, like a ball." This field trip will help students experience the sphericalness of the Earth directly.

Activity:

Aside from physically transporting the students to the top of the mountain, this is really a very straight forward lesson. Students will be shown a western horizon profile as seen from Sandia Peak (10,400ft, 3800 m.); Mt. Taylor (11,300 ft, 4130 m) is a very prominent, cone shaped volcano, and is hard to miss.

Their assignment is to sight the top of Mt. Taylor through the straw of their astrolabes and record the angle compared to the ground, which is the sight line when the weighted string passes by the 0^o mark on the astrolabe’s protractor. (This may take some explanation if you are using a plastic protractor for the degree scale of your astrolabe, since straight down is 0^o on an astrolabe, but is 90^o on most protractors. Subtracting 90 from the number on the protractor will give the degrees of altitude relative to the horizon) What should stimulate controversy among the students is that while Mt. Taylor is higher in altitude than Sandia Peak the sighting angle will actually be negative, down several degrees below the place where the horizon would be if the Earth were flat. Students with quarter circle astrolabes will have to flip them around backwards, looking through them opposite direction they use sighting stars, which will again emphasize the downward angle of their sighting.

At the next class opportunity encourage, the discussion as to why Mt. Taylor seems "down" from Sandia Peak. Get students to diagram their explanations. Possibly a debate format would work if the class seems to be dividing up into a "flat Earth" group and a "curved Earth" group.

Lesson Five: Acting Out a Year in the Life of the Earth:

Goals:

By modeling the actions of the Sun-Earth-Moon system students can get a feel for how the seasons work, what causes the phases of the Moon, and why we see different stars at different times of year.

Objectives:

Students will create a room sized map of the constellations on a large roll of black bulletin board paper, create papier-mâché Earth and Moon "heads," and act out a year of the Earth orbiting the Sun. The system will be stopped at various points for a tour guide style narration of the sights. (and for the actors to get aligned correctly to simulate the Earth’s tilt on its axis)

Focusing Activity:

In class reading of Sun and Moon stories from a variety of cultures.

Materials: large roll of Black paper
white chalk
very large balloons for Earth and Moon forms (globes would of course work too.
papier-mâché supplies: water, wheat paste, and newspaper.
very bright light source
darkened room

Activities:

Each period will create a section of the zodiac equal to two months of calendar time.
Earth and Moon heads will be created or Earth and Moon globes located.
Earth and Moon actors will be elected
Several "tour guides" will be selected. and given their scripts. These scripts could also be generated by students researching a particular section of the zodiac as a research project.

The completed zodiac will be attached to the outer walls of the classroom at about table height.

A very bright light source will be pointed at the "Earth" and "Moon" as they orbit.

The "tour guides" will narrate at least the following events:

The Summer and Winter Solstices. At Summer Solstice the North Pole tips toward the light source about 23^o. At Winter Solstice the North Pole tips away from the light source about 23^o. The Vernal Equinox, 90^o counter clockwise from the Winter Solstice, the Earth Tilts back toward the Winter Solstice point. The Autumnal Equinox, 90^o past the Summer Solstice the Earth still tilts toward the Winter Solstice point. At any point, the Moon’s phases can be demonstrated. Remember, the Moon’s orbit is very slow compared to the Earth’s spin, about 1/27 as fast.

Lesson sketches:

Sundial Activity: Use gnomon activities with the "field of poles" to spin off into building sundials. There are good patterns in The Universe at Your Fingertips and Astronomy for All Ages.

Field Trip to an Observatory: On Friday evenings, during the school year, the University of New Mexico observatory is open to the public. There are several telescopes set up and usually several friendly helpful UNM astronomy students to guide kids. I’ve taken as many as 100 students, but smaller groups on successive weeks works better.

Field Trip to an Ancient Native American Archeological Site where Astronomers and Archaeologists believe astronomical observations were made. Chaco Canyon is a great place to visit but it is a long way from almost anywhere.

Bring a Planetarium to School: Most cities have museums or organizations with inflatable mobile planetariums. If you teach middle school, make sure they know that you need them to do their activity 6 times in a row.

Start a Sun and Moon Watching Tradition: Set up a location for making sunrise observations. Have kids design a structure to help with observations. The gnomon field might give them some ideas. Have kids write a secular ceremony to welcome the Sun. Consult with religious people to avoid stepping on any one’s traditions. Maybe a "Sunrise Club."

Notes

1John North, The Norton History of Astronomy and Cosmology, (London: W.W. Norton & Co., 1995) xxii.