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
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