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Cultures > Mississippians

:: 900 AD - 1500 AD

Cultural Background | Surviving


Keeping Time
Woodhenge served as a calendar to chart the summer and winter solstices, and the spring and fall equinox.

The solstice occurs when the sun is the farthest from the equator. This happens two times a year, once in the summer and once in the winter. The summer solstice is the longest day of the year and the winter solstice is the shortest day of the year in the northern hemisphere.

The equinox occurs when the sun crosses the equator. The equator is an imaginary line around the Earth that is the same distance from the North and South Poles. It divides the Earth into the northern and southern hemispheres. When this happens, the length of the day and night are equal. This also happens twice a year.

The Mississippians were aware of the movements of celestial bodies in the heavens, especially the Sun. They were also aware that everything ran in cycles of time. For that reason they invented celestial calendars such as Woodhenge, which marked significant horizontal astronomical events.

Woodhenge is a solar horizon calendar that enabled the Mississippians to track the sun's movement as a way of determining important dates. Over a period of 100 years, five of these calendars were built. The first circle consisted of 24 posts. The diameter of the circle was 240 feet. The second circle had 36 posts. The diameter of that circle was 408 feet. The third circle, which was most completely excavated, had 48 posts. The diameter of the circle was 410 feet. The fourth partially excavated, would have had 60 posts. The diameter of its circle was 440 feet. The last Woodhenge was only an arc consisting of 12 posts. The diameter of the circle was 440 feet. The posts were made of red cedar, which was regarded as sacred wood. They were 15-20 inches in diameter and stood about 20 feet tall. The Woodhenge monument was a link to the heavens above and the earth below.

The Mississippians knew that the position of the Earth changed throughout the year as the Earth revolved around the sun. During the winter, the days are short and the sun is low in the sky. The sun does not rise exactly in the east, but instead rises just south of east and sets just south of west. Thus, the days are shorter, starting at December 21st, which is the winter solstice and the shortest day of the year.

Each subsequent day the sun rises higher in the sky until it reaches the point where it is in the sky for 12 hours. Everyone in the world will experience an equal day and equal night. This is called the spring equinox, March 21st, when the sun rises exactly east and sets exactly west.

As the revolution period continues, the Earth reaches its highest path in the sky. This is the summer solstice, June 21st, and the longest day of the year. The Sun now rises to the north of east and sets north of west. After the summer solstice, the Sun follows a lower path through the sky, until it reaches the point where it is in the sky for exactly 12 hours again, the Fall Equinox. It continues its cycle until it reaches the lowest path again at the winter solstice. The position of the sun can be observed from the horizon.

The Mississippians carefully observed the placement of the rising sun from Monks Mound, located due north. The shadow plot lined up with specific poles on the Woodhenge circle. This signaled the time to begin preparing for planting and harvesting. Everyone watched as the sun slowly rose. The sun priest, who was standing on top of the center pole, led the people in chants
and songs.

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See images of Woodhenge. [enlarge]

Learn more about the lunar cycle, the solar cycle, and keeping time.

Learn more about Woodhenge at Cahokia Mounds State Historic Site.


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