Science and Invention


How long have sundials been in use?

Sundials, which indicate the time of day by the shadow cast by a stick, pin, or other object, usually on a horizontal plate, have been in use since before the sixth century B.C., when both the ancient Chinese and Egyptians used the device to tell time. Sundials proved to be a fairly accurate indicator of the passage of time. But it has its problems: A sundial can be difficult to read, the markings have to be adjusted according to latitude, and the readings differ with the seasons. They remain popular as garden ornaments today.


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