Unit One: Investigating Motions of the Sky
4. Exploring an Archaeoastronomy Site
High atop a barren ridge along the crest of the Bighorn Mountains in north-central Wyoming lies an ancient stone circle: the Bighorn Medicine Wheel. Its not a perfect circle, but it has a pile of stones or cairn at its center, with a dozen or so lines of stones running straight from the center to the rim, like spokes of a bicycle wheel. Half a dozen stone cairns are located on or just outside the wheel's "rim," each connected to the center by one of the stone "spokes." Each of the cairns, including the hub, are hollow, so that one could stand or sit in the middle of the cairn, or place an offering or sacred object there. Built by Native Americans centuries ago, its original use and meaning are not known. Some have suggested that the wheel is an ancient observatory used to mark the changes of the seasons. Others have suggested that it's meaning is purely symbolic and religious. Still others have thought it is a mixture of both. One way to test whether or not it is an observatory is to visit the Wheel, sit in the various cairns for a number of nights scattered through the year, and sight along the stone spokes to see if they coincide with any significant astronomical alignments such as the winter solstice sunset, or seasonal moonrises. Aside from the fact that such an on-site study would be time-consuming and physically rigorous, the Wheel is currently protected and surrounded by a very high fence. With modern sky simulators like Starry Night, however, it is possible to make an astronomical study of the Wheel without leaving your home or school. In this Doing Science, you will test the astronomical interpretation of the Wheel (or other structure of your choice, like Stonehenge) by looking for significant astronomical alignments that correspond with structural elements.
Find the location (latitude and Longitude) of the Wheel (or alternate structure) and the most accurate map or plan that you can. A place to start for the Bighorn Medicine Wheel is: http://solar-center.stanford.edu/AO/bighorn.html
Other places to look are in books on ancient astronomy (there are several good ones). A small, but unlabeled map of the Wheel is in J. A. Eddy (1974) Science, vol. 184, pp 1035-1043, a reference commonly found in school libraries.
- Make a large digital or paper copy of the map, orient it properly, and pick a sighting location—such as one of the cairns. Draw lines from the sighting location along linear elements of the Wheel, like spokes, that you think are potentially significant.
- Use a protractor or software-measuring tool to measure the azimuths of each of your lines. Make a table with your lines and measurements.
- Enter the position of the Wheel into Starry Night and look for astronomical events that correspond with each of your measured azimuths. Events to test include solstice sunrises and sunsets, rising or setting points of bright stars, moonrises, etc. Note any significant alignments on your table.
As you search for information and pictures of the Wheel, you will likely find alignments suggested by other investigators. If you do, test them! Other researchers can make mistakes or may overlook something. Remember, there is no consensus as to the meaning of the Wheel, so any astronomical significance or lack thereof that you can support with observations can be as valid as anyone else's.
- Make a poster or PowerPoint showing the map of the Wheel (or alternate structure), the sighting location(s) you have chosen, the structural alignments you think are significant, and screen captures of any astronomical events that you think coincide with the alignments. Write a summary of your observations, including a claim about the significance or non-significance of the Wheel as an ancient observatory.
- There are a few dozen "medicine wheels" in central United States and Canada that were made by Native American tribes that had contact with each other, and may have had similar reasons for building the wheels. Find maps of several of those other wheels, test for astronomical alignments, and see if you can find any similarities or common patterns to the wheels that might provide additional clues as to the purpose of these structures. (If you chose to do Stonehenge, you can do the same extended comparison using some of the dozens of other stone circles found in the British Isles.)