Egyptian Astronomy - Ancient Egypt

Ancient Egypt

Egyptian astronomy begins in prehistoric times. The presence of stone circles at Nabta Playa dating from the 5th millennium BCE show the importance of astronomy to the religious life of ancient Egypt even in the prehistoric period. The annual flooding of the Nile meant that the heliacal risings, or first visible appearances of stars at dawn, was of special interest in determining when this might occur, and it is no surprise that the 365 day period of the Egyptian calendar was already in use at the beginning of Egyptian history. The constellation system used among the Egyptians also appears to have been essentially of native origin.

The precise orientation of the Egyptian pyramids affords a lasting demonstration of the high degree of technical skill in watching the heavens attained in the 3rd millennium BCE. It has been shown the Pyramids were aligned towards the pole star, which, because of the precession of the equinoxes, was at that time Thuban, a faint star in the constellation of Draco. Evaluation of the site of the temple of Amun-Re at Karnak, taking into account the change over time of the obliquity of the ecliptic, has shown that the Great Temple was aligned on the rising of the midwinter sun. The length of the corridor down which sunlight would travel would have limited illumination at other times of the year.

Astronomy played a considerable part in religious matters for fixing the dates of festivals and determining the hours of the night. The titles of several temple books are preserved recording the movements and phases of the sun, moon and stars. The rising of Sirius (Egyptian: Sopdet, Greek: Sothis) at the beginning of the inundation was a particularly important point to fix in the yearly calendar.

From the tables of stars on the ceiling of the tombs of Rameses VI and Rameses IX it seems that for fixing the hours of the night a man seated on the ground faced the Astrologer in such a position that the line of observation of the pole star passed over the middle of his head. On the different days of the year each hour was determined by a fixed star culminating or nearly culminating in it, and the position of these stars at the time is given in the tables as in the centre, on the left eye, on the right shoulder, etc. According to the texts, in founding or rebuilding temples the north axis was determined by the same apparatus, and we may conclude that it was the usual one for astronomical observations. In careful hands it might give results of a high degree of accuracy.

Macrobius Ambrosius Theodosius (floruit AD 395–423) attributed the planetary theory where the Earth rotates on its axis and the interior planets Mercury and Venus revolve around the Sun which in turn revolves around the Earth, to the ancient Egyptians. He named it the "Egyptian System," and stated that "it did not escape the skill of the Egyptians," though there is no other evidence it was known in ancient Egypt.