Egyptian astronomy started inprehistoric times, in thePredynastic Period. In the 5th millennium BCE, the stone circles atNabta Playa may have made use of astronomical alignments. By the time the historicalDynastic Period began in the 3rd millennium BCE, the 365 day period of theEgyptian calendar was already in use, and the observation ofstars was important in determining the annual flooding of theNile.
TheEgyptian pyramids were carefully aligned towards thepole star,[citation needed] and the temple ofAmun-Re atKarnak was aligned on the rising of themidwinter Sun.[citation needed]Astronomy played a considerable part in fixing the dates ofreligious festivals and determining the hours of night, and templeastrologers were especially adept at watching the stars and observing theconjunctions and risings of theSun,Moon, andplanets, as well as thelunar phases.
InPtolemaic Egypt, the Egyptian tradition merged withGreek astronomy andBabylonian astronomy, with the city ofAlexandria inLower Egypt becoming the centre of scientific activity across theHellenistic world.Roman Egypt produced the greatest astronomer of the era,Ptolemy (90–168 CE). His works on astronomy, including theAlmagest, became the most influential books in the history of Western astronomy. Following theMuslim conquest of Egypt, the region came to bedominated by Arabic culture andIslamic astronomy.
The astronomerIbn Yunus (c. 950–1009) observed theSun's position for many years using a largeastrolabe, and his observations oneclipses were still used centuries later. In 1006,Ali ibn Ridwan observed theSN 1006, asupernova regarded as the brightest stellar event inrecorded history, and left the most detailed description of it. In the 14th century,Najm al-Din al-Misri wrote a treatise describing over 100 different types of scientific and astronomical instruments, many of which he invented himself.
Egyptian astronomy dates back to prehistoric times. The presence ofstone circles atNabta Playa inUpper Egypt from the5th millennium BCE show the importance ofastronomy to the religious life ofancient Egypt, even in the prehistoric period. The annualflooding of the Nile meant that theheliacal risings, or first visible appearances ofstars atdawn, were of special interest in determining when this might occur. The 365 day period of theEgyptian calendar was already in use at the beginning ofEgyptian history. Theconstellation system used among theEgyptians also appears to have been essentially of native origin. Archaeological evidence has linked fractal geometry designs among Sub-Saharan African cultures with Egyptian cosmological signs.[2]
The precise orientation of theEgyptian pyramids serves as a lasting demonstration of the high degree of technical skill attained in the3rd millennium BCE. It has been shown[where?] the pyramids were aligned towards thepole star, which, because of theprecession of the equinoxes, was at that timeThuban, a faint star in the constellation ofDraco.[3] Evaluation of the site of the temple ofAmun-Re atKarnak, taking into account the change over time of theobliquity of the ecliptic, has shown that the Great Temple was aligned on the rising of themidwinter Sun.[4] 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 inreligious matters for fixing the dates of festivals and determining the hours of thenight. The titles of several temple books are preserved recording the movements and phases of theSun,Moon andstars. The rising ofSirius (Egyptian:Sopdet,Greek:Sothis) at the beginning of the inundation was a particularly important point to fix in the yearly calendar.[5] One of the most important Egyptian astronomical texts was theBook of Nut, going back to theMiddle Kingdom or earlier.
For Ancient Egyptians, the death of a king had a strong connection to the stars. They believed once a king was deceased, their soul would rise to the heavens and become a star.[6] ThePyramid Texts describe the king ascending and becoming theMorning Star among the Imperishable Stars of past kings.[7]
Beginning with the9th Dynasty, ancient Egyptians produced 'Diagonal star tables', which were usually painted on the inside surface of wooden coffin lids.[8] This practice continued until the12th dynasty.[9] These 'Diagonal star tables' or star charts are also known as 'diagonal star clocks'. In the past they have also been known as 'star calendars', or 'decanal clocks'.[10] These star charts featuring the paintings of Egyptian deities,decans, constellations, and star observations are also found on the ceilings of tombs and temples.
From the tables of stars on the ceiling of the tombs ofRameses VI andRameses 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 thepole star passed over the middle of his head. On the different days of the year each hour was determined by a fixed starculminating 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.[5]
Macrobius Ambrosius Theodosius (floruit 395–423 CE) attributed the planetary theory where theEarth rotates on its axis and the interior planetsMercury andVenus revolvearound the Sun which in turn revolves around the Earth, to the ancient Egyptians. He called it the "Egyptian System", and stated that "it did not escape the skill of theEgyptians", though there is no other evidence it was known in ancient Egypt.[11][12]: 512
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Writing in theRoman 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 ahorologium (ὡρολόγιον) in his hand, and apalm (φοίνιξ), the symbols of astrology. He must know by heart theHermetic 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.[13]
The astrologer's instruments (horologium andpalm) are aplumb line and sighting instrument. They have been identified with two inscribed objects in theBerlin Museum; a short handle from which a plumb line was hung, and a palm branch with a sight-slit in the broader end. In the Ancient Egyptian language they were referred to as themerkhet andbay respectively. The palm branch was held close to the eye, the plumb line in the other hand – perhaps at arm's length.[5][a]
FollowingAlexander the Great's conquests and the foundation ofPtolemaic Egypt, the native Egyptian tradition of astronomy had merged withGreek astronomy as well asBabylonian astronomy. The city ofAlexandria inLower Egypt became the centre of scientific activity throughout theHellenistic civilization. The greatest Alexandrian astronomer of this era was the Greek,Eratosthenes (c. 276–195 BCE), who calculated the size of theEarth, providing an estimate for the circumference of the Earth.
Following theRoman conquest of Egypt, the region once again became the centre of scientific activity throughout theRoman Empire. The greatest astronomer of this era was theHellenic Egyptian,Claudius Ptolemy (90–168 CE). Originating from theThebaid region ofUpper Egypt, he worked at Alexandria and wrote works on astronomy including theAlmagest, thePlanetary Hypotheses, and theTetrabiblos, as well as theHandy Tables, theCanobic Inscription, and other works unrelated to astronomy.
Ptolemy'sAlmagest (originally titledThe Mathematical Syntaxis) 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 idea, theequant.
A few mathematicians oflate Antiquity wrote commentaries on theAlmagest, includingPappus of Alexandria as well asTheon of Alexandria and his daughterHypatia. Ptolemaic astronomy became standard in medieval western European andIslamic astronomy until it was displaced byMaraghan,heliocentric, andTychonic systems by the 16th century.
Following theMuslim conquest of Egypt, The region came to bedominated by Arabic culture. It was ruled by theRashidun,Umayyad andAbbasid Caliphates up until the 10th century, when theFatimids founded their ownCaliphate centred around the city ofCairo in Egypt. The region once again became a centre of scientific activity, competing withBaghdad for intellectual dominance in themedieval Islamic world. By the 13th century, the city of Cairo eventually overtook Baghdad as the intellectual center of the Islamic world.[citation needed]
Ibn Yunus (c. 950–1009) observed more than 10,000 entries for the Sun's position for many years using a largeastrolabe with a diameter of nearly 1.4 meters. His observations oneclipses were still used centuries later inSimon Newcomb's investigations on the motion of the Moon, while his other observations inspiredLaplace'sObliquity of the Ecliptic andInequalities of Jupiter and Saturn.[clarification needed (not the title of any work by Laplace)][citation needed] In 1006,Ali ibn Ridwan observed thesupernova of 1006, regarded as the brightest stellar event in recorded history, and left the most detailed description of the temporary star. He says that the object was two to three times as large as the disc ofVenus and about one-quarter the brightness of theMoon, and that the star was low on the southern horizon.[15]
Theastrolabicquadrant was invented inEgypt in the 11th century or 12th century, and later known in Europe as the "Quadrans Vetus" (Old Quadrant).[16]: 333 In 14th centuryEgypt, Najm al-Din al-Misri (c. 1325) wrote a treatise describing over 100 different types of scientific and astronomical instruments, many of which he invented himself.[17]
One or more of the preceding sentences incorporates text from a publication now in thepublic domain: Griffith, Francis Llewellyn (1911). "Ancient Egypt". InChisholm, Hugh (ed.).Encyclopædia Britannica. Vol. 9 (11th ed.). Cambridge University Press. pp. 39–80.
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