You look at your PDA (Personal Digital Assistant) marveling at the versatility of the device, not knowing that our ancestors, without the digital technology to help, had mastered the art of time keeping by inventing Sundials,.
Sundials, which are the earliest known and ancient device for timekeeping were invented during the second millennium BC. China, Egypt and the Middle East produced fixed and mobile sundials during that period. To measure the time, these sundials used the height of the sun in the sky and the length of the shadow it produced.
Using horizontal or vertical shadow casters and the hollow of the bowl marked with hour lines were some of the important features of the various designs of sundials developed by Romans and Greeks. Using the altitude of the sun as a guideline to measure the time, the Romans also designed a portable ring and pillar dials.
In the first century AD, it was discovered that shadow casters set parallel to the axis of the Earth caused a shadow to fall in the same time and in the same direction during all the 365 days to make it more reliable.
In 1556, Johann Gebhart of Nuremberg designed an ivory diptych dial. During...
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