Wednesday, July 09, 2014

Archeoastrotronomy: Finding Directions by the Sun

Solar method of Determining Cardinal Points
Finding cardinal points (the directions of north, south, east, and west) can be done by using the sun.  One simple method is to watch the sun rise or set, which would tell you which direction was east or west. Therefore, north and south would be perpendicular to the east-west axis. This is one way to find geographical north.

 The U.S. Army suggests using a more precise method in determining the cardinal directions. Place a tall stick upright on level ground. (On a sundial, this upright stick would be the gnomon.) Mark the shadow that forms from the sun striking the gnomon. Place a line perpendicular at the tip of this shadow. This marks the western direction, but is not precisely west.

 Then wait at least ten or more minutes, and mark the tip of the new shadow formed by the gnomon. For greater accuracy, wait again for another ten minutes, and then mark that shadow tip as well. Draw a straight line between these three points. This becomes the east-west line. To find the north-south line, stand with the direction of west on your left. Now you are facing north. This north-south line bisects the east-west axis at right angles. (For telling time, the crossing of the two axis is the noon line.) 

 Because finding directions was a sacred obligation for the ancient Egyptians, they did more precise measurements. To them, the Land of the Dead, where the Soul goes, laid in the west. Therefore their tombs including The Pyramids would have an entrance facing west. The ancient Egyptians probably used one of their obelisks as a gnomon. By tracking the shadows formed at the solstices and equinoxes, the ancient Egyptians could construct a more accurate basis for the north-south and east-west lines. Moreover, the obelisk, acting as the gnomon, would cast a moving shadow throughout the day. When this shadow was marked each hour, the radii of a circle were formed. In this manner, directions such as northwest could also be determined.

Finding the cardinal directions requires you to observe the movement of the sun. For accuracy, a stick and patience are needed. By using the stick as a gnomon, you can mark the various shadows formed as the sun moves across the sky. In this manner, you can determine the actual directions. With repeated observations throughout the year, a precise line for each direction could be constructed for religious purposes.
The sun moves north and south of east and west as the seasons progress and thus only marks true or exact east and west for a small portion of the year. 

 Works Used.
Aveni, Anthony, “People and the Sky,” Thames & Hudson: N.Y, 2008.
 Duke, Dennis, “Four Lost Episodes in Ancient Solar Theory,” Florida State University, 2008,, .
 Magli, Giulio, “Mysteries and Discoveries of Archaeoastronomy,” Copernicus Books: N.Y., 2009.
 ----, “Methods of Finding Cardinal Points,” World Mysteries, 2004,, .

No comments: