Shadow of the Sun
Early man must have first tracked time by the daily changes of shadows through the trees. Once down from the trees and into the sun, he may have used sticks and purposely placed rocks for shadow “markers,” and may have carried a “special” shadow stick just for this purpose.
Early Egyptians had a stick with a crosspiece that was used to tell morning and then afternoon time by the Sun (Thothmes III period - 1500 BC). In this time of digital and “Atomic” clocks, there is something satisfying and basic about a timepiece linked directly to the warm, life-giving Sun.
One type of sundial is a Vertical Dial. A Vertical Dial is usually placed on a vertical surface (such as a wall) facing south or nearly south. The first Vertical Dials may have been scratched in the sides of cliffs or rocks (Bold, deep patterns that produced shadows). Vertical Dials are now found on the sides of buildings throughout the world. Many old town halls and clock towers in Europe have sundials on their exterior walls. A beautiful one
is on the SofusLies Auditorium at the University of Oslo.
Photo : Anne BruvoldAnother is on the Physics building at the University of Washington.
The gnomon (shadow stick) for a vertical sundial is on top. The latitude, and the number of degrees the wall deviates from true south, determines the hour-line spacing. After these basics are accounted for, the imagination is the limit on actual design. The gnomon could be a needle or a fish (or a whale?). The lines could be grooves, ridges, or boldly painted lines. A well-designed sundial can be beautiful, simple and instructive. It can be readily accessible to the public. The sundial and the sundial site can incorporate information on the earth’s orbit, seasons, etc…. It seems a natural gift for astronomy enthusiasts to give to the public…. And the BPAA Observatory does have a south- facing wall….
For further information:The North American Sundial Association, www.sundials.org The British Sundial Society, www.sundialsoc.org.uk Sundials: Their Theory and Construction, Albert E. Waugh (Dover Publications, 1973.)
Those interested in joining the BPAA Sundial Group or who have information concerning sundials theywould like to share, email me at firstname.lastname@example.org.