The chart is largely symbolic and functional but does contain pictures of some significant groups of stars. ![]() The lower section contains pictures of star gods or demons. The chart was read from right to left and the pictures represent Mars (the boat and the bull), Orion with the three stars including the Sun and Moon, Sirius, Jupiter, Saturn, Mercury and Venus. The divisions in the top part of the chart represent decans. Babylonian and Egyptian astronomers were able to measure the altitude and lateral displacement of heavenly objects from a particularĭirection by using a Merkhet, thus giving the earliest ideas of turning, or angle. The other object is the rib of a palm leaf, split at one end to make a thin slit for a sight. It was developed around 600 BCE and uses a plumb line to obtain a true vertical, as in the picture. The Merkhet is one of the oldest known astronomical instruments. The square of the height of the gnomon and its shadow. To do this they constructed the "gnomon circle" whose radius was the square root of the sum of In contrast, the Hindus used the East - West direction, the rising and setting of the sun, to orient their "fire-altars" for religious practices. Today, a gnomon is the vertical rod or similar device that makes the shadow on a sundial.įor more about sundials go to Leo's article - Brief History of Time Measurement.Īt midday the shadow of a stick is shortest, and the civilisations of Mesopotamia, Egypt, and China took the North - South direction from this alignment. In Euclid Book II, where Euclid deals with the transformation of areas, the gnomon takes the form of an "L-shaped" area touching two adjacent sides of a parallelogram. The name gnomon comes from the Greek and refers to any L-shaped instrument, originally used to draw a right angle. The shadow cast from a shadow stick was used to observe the motion of the Sun and thus to tell time. ![]() The most ancient device found in all early civilisations, is a "shadow stick". Ancient Instruments and Measuring the Stars ![]() Some of the terms used in this article are described in more detail here. This is the first of three articles on the History of Trigonometry. Early Astronomy and the Beginnings of a Mathematical Science
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