Misplaced Pages

Revision as of 20:56, 14 June 2009

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.

Ancient Egypt

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.

Greco-Roman Egypt

Writing in the Roman era, Clement of Alexandria gives some idea of the importance of astronomical observations to the sacred rites:

And after the Singer advances the Astrologer (ὡροσκόπος), with a horologium (ὡρολόγιον) in his hand, and a palm (φοίνιξ), the symbols of astrology. He must know by heart the Hermetic astrological books, which are four in number. Of these, one is about the arrangement of the fixed stars that are visible; one on the positions of the sun and moon and five planets; one on the conjunctions and phases of the sun and moon; and one concerns their risings.

The Astrologer's instruments (horologium and palm) are a plumb line and sighting instrument. They have been identified with two inscribed objects in the Berlin Museum; a short handle from which a plumb line was hung, and a palm branch with a sight-slit in the broader end. The latter was held close to the eye, the former in the other hand, perhaps at arms length. The "Hermetic" books which Clement refers to are the Egyptian theological texts, which probably have nothing to do with Hellenistic Hermetism.

Following Alexander the Great's conquests and the foundation of Ptolemaic Egypt, the native Egyptian tradition of astronomy had merged with Greek astronomy as well as Babylonian astronomy. The city of Alexandria in Lower Egypt became the centre of scientific activity throughout the Hellenistic civilization. The greatest Alexandrian astronomer of this era was the Greek, Eratosthenes (c. 276-195 BCE), who calculated the size of the Earth, providing a value for the Earth radius.

Following the Roman conquest of Egypt, the region once again became the centre of scientific activity throughout the Roman Empire. The greatest astronomer of this era was the Hellenized Egyptian, Ptolemy (90-168 CE). Originating from the Thebaid region of Upper Egypt, he worked at Alexandria and wrote works on astronomy including the Almagest, the Planetary Hypotheses, and the Tetrabiblos, as well as the Handy Tables, the Canobic Inscription, and other minor works. The Almagest is one of the most influential books in the history of Western astronomy. In this book, Ptolemy explained how to predict the behavior of the planets with the introduction of a new mathematical tool, the equant. A few mathematicians of late Antiquity wrote commentaries on the Almagest, including Pappus of Alexandria as well as Theon of Alexandria and his daughter Hypatia. Ptolemaic astronomy became standard in medieval western European and Islamic astronomy until it was displaced by Maraghan, heliocentric and Tychonic systems by the 16th century.

Arabic Egypt

Notes

1. Ruggles, C.L.N. (2005), Ancient Astronomy, pages 354-355. ABC-Clio. ISBN 1-85109-477-6.
2. Krupp, E.C. (1988). "Light in the Temples", in C.L.N. Ruggles: Records in Stone: Papers in Memory of Alexander Thom. CUP, 473-499. ISBN 0-521-33381-4.
3. Clement of Alexandria, Stromata, vi. 4
4. O Neugebauer, Egyptian Planetary Texts, Transactions, American Philosophical Society, Vol. 32, Part 2, 1942, Page 237.

See also

• Ancient Egypt
• Archaeoastronomy
• Babylonian astronomy
• Dendera zodiac
• Egyptian astrology
• Egyptian calendar
• Egyptian mathematics
• Greek astronomy
• History of astronomy
• Islamic astronomy
• Nabta Playa
• Sothic cycle

 This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. {{cite encyclopedia}}: Missing or empty |title= (help)

• Ancient astronomy
• Ancient Egyptian society
• History of astronomy