The gnomon is one of the oldest astronomical instruments, which is a vertical pole. The shadow it casts on the surface of the earth makes it possible to determine the direction to the north. According to the time, which corresponds to noon local time, its shadow from the sun, which is at the southern point and at the upper culmination of its activity, is directed to the north and has a minimum length on this day. According to scientists it was the gnomon that became the prototype of the sundial.
Gnomon
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