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|Telling Time With the Sun
The sundial is the oldest known device for the measurement of time. Some time, way back in prehistoric times, some "cave man" noticed that the shadow of a cliff or a tree reached almost the same place every day when the sun was high in the heavens. It was easy to place a small stone at the point reached by the shadow. So now there were three points in the day-- sunrise, midday, and sunset. The next step was probably to trace the curve of the shadow and mark other spots upon it.
an early man drawing a curve to mark the traveling
The first recorded use of a sundial is in the Book of Isaiah, chapter 38, which dates back to about 700 B.C.
A sundial consists of the plane (dial place) and the gnomon (style). The dial face is divided into hours and sometimes half and quarter hours. The gnomon is a flat piece of metal set in the center of the dial. It points toward the North Pole in the Northern Hemisphere and toward the South Pole in the Southern Hemisphere. The upper edge of the gnomon must slant upward from the dial face at an angle equal to the latitude of the location of the sundial. However, as the following illustrations will show, as long as the correct "parts" are present, a sundial does not have to look anything at all like the one above in order to "do its job."
Richards Topical Encyclopedia New York: The
Richards Company, Inc., 1961
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This page was last updated on 08/10/2018.