Sundials are "those instruments, either fixed or portable, which determine the divisions of the day (Latin: dies) by the motion of the shadow of some object on which the sun's rays fall. It must have been one of the earliest applications of a knowledge of the apparent motion of the sun; though for a long time men would probably be satisfied with the division into morning and afternoon as marked by sun-rise, sun-set and the greates elevation."
The first known mentioning of sundials occurs in a Babylonian compendium which is thought to date from 1,000 B.C.: the two Mul.Apin tablets. Here, one finds details on the varying length of the shadow of a gnomon (vertical rod) over the year. Other early references to a sundial can be found in the Bible, e.g., Isaiah 38:8:
- 8 Behold, I will bring again the shadow of the degrees, which is gone down in the sun dial of Ahaz, ten degrees backward. So the sun returned ten degrees, by which degrees it was gone down.
Conservative Bible Project (KJV) It isn't sure whether there was an artifact which was build as a sundial, or whether perhaps the stairs of a temple was used this way. So modern translations may phrase this verse differently:
- I will make the shadow cast by the sun go back the ten steps it has gone down on the stairway of Ahaz.'" So the sunlight went back the ten steps it had gone down. (NIV)