Literature Review
A fascinating element of ancient Egyptian astronomy that was gradually adopted into Greco-Roman astrological practice is the decan. The decans were thirty-six individual stars or small constellations that rose and set at different times of the year, acting as a means of telling time throughout the night for the ancient Egyptians.
They were eventually incorporated into the Babylonian zodiac by Hellenistic scholars, astrologers, and priests in Alexandria and beyond. Three decans were assigned to each of the twelve zodiacal signs. Because of their incorporation into an astrological system, they were seen as relevant astrological elements alongside the planets, the constellations, and the zodiac. As hour-markers, the star or constellation that made up each decan was seen as a lesser protective god, akin to a daimon.
Eventually, their protector god role became medical in nature. In the Hermetic tradition that flourished in Alexandria, the decans were each assigned to the different parts of the body and were believed to have a say in the healing or decline of each of their given parts. In an attempt to influence health and as an alternative to the often-frightening medical practices of the day, there is evidence of a technical tradition that involved amulets constructed to act in cosmic sympathy with the each of the individual decans. The purpose of this paper is to review, synthesize, and contextualize the existent research on the decans, from their use as an astronomical hour-marker in pre-Hellenistic Egypt, up until the late Roman era. While it is impossible to provide an in-depth analysis of each distinct period or iteration of the decans (and is not the goal of the work to begin with), the purpose is to unify the often-disjointed research of the topic into one centralized location. In addition to this, context will be provided to allow for the framework of a timeline to be laid.
ALTHOUGH classical (Greek and Latin) sources tend to characterize Egypt as a culture with substantial astronomical (and astrological) knowledge, the actual Egyptian sources are much less obvious in this sense. This fact has led some scholars to say that Egypt has no place in the history of mathematical astronomy (Neugebauer 1975, 559). However, things are more complicated, and several important points have to be kept in mind (Quack 2016). First, in many cases, astronomical phenomena are integrated as parts of religious conceptions (von Lieven 2000). That makes them much more difficult to decode and often gives rise to suspicion by the historian of science.
Second, our record of preserved Egyptian texts is seriously distorted in favor of material from tomb contexts, but pure astronomical texts are not among the most likely candidates to be found there. As soon as material from settlements is available in substantial numbers (especially for the Greco-Roman period), astronomical texts tend to be present. Third, many of the sources are remnants of the practice without indicating the theory behind them, for example, lists of stars. This means that many of our overall conclusions are based on inference.
lt can be assumed that some basic astronomical facts were known in Egypt from very early times, especially those directly relevant for timekeeping. Tue Egyptian calendar is, unlike most other ancient cultures’, not primarily based on the moon. Rather it has uniformly 365 days (without any intercalary days), divided into three seasons each of four months, with 30 days per month, and at the end of the year five special days outside Originalveröffentlichung in: P.T. Keyser, J. Scarborough (Hrsg.), The Oxford Handbook of Science and Medicine in the Classical World, Oxford 2018, S. 61-70; Online-Veröffentlichung auf Propylaeum-DOK (2022), DOI: https://doi.org/10.11588/propylaeumdok.00005336 62
1.2 ANCIENT SCIENTIFIC TRADITIONS BEYOND GREECE AND ROME of the normal structure. This is the closest fixed-length approximation to the actual year-length possible and likely based on astronomical observations of either the sun or the stars. lt can be debated to what degree there was originally a lunar calendar in use in Egypt. For as far back as we have sufficient documentation, the civil calendar is dominant, although there is a lunar cycle, beginning on the day of the moon’s invisibility, and used for some aspects of religious life ( especially temple service and a few festivals). Since there is no continuous count of years, and the lunar months are kept in close relation to their civil counterparts, it is not really justified to speak of a genuine lunar calendar. The waxing and waning of the moon was conceptualized as gods entering and leaving the celestial eye (von Lieven 2000, 127-132). Since the lunar cycle had relevance for some religious feasts, it was observed in the temples and served, from the later Middle Kingdom (about 1850 BCE) onward, as the organizing principle for temple service (with change of staff always on the second day of the lunar cycle).
While for the older periods it is probable that it was based on actual observation, at least for the Greco-Roman period there were schematic 25-year cycles that worked well to keep the lunar cycle in line with the no intercalated Egyptian year of 365 days. A famous example of a schema is Papyrus Carlsberg 9 (for the interpretation, see Depuydt 1998b), but there is good documentation that slightly different methods were also in circulation (Lippert 2009; Bennet 2008). Those schemes specify how 29- and 30-day lunar months should follow each other, and when there would be a “big year” containing 13 lunar months. Celestial regions and stars play a substantial part already in the oldest corpora of religious texts preserved from ancient Egypt (Krauss 1997; Wallin 2002), but their location and identification with our star terminology is fraught with difficulties.
The most important stars and constellations were Orion (connected with Osiris, the god who was killed by his brother), Sirius (connected with his sister and wife Isis), and the Big Dipper (connected with the murderer Seth). Sirius (called Sothis in Egyptian) had a special role because its heliacal rising coincided with the ideal Egyptian New Year day that was linked with the onset of the Nile inundation. lt is likely that the specific phenomena of its appearance (like radiance, and in later periods planetary positions) were used for divinatory purposes, although unequivocal documentation exists only for the Roman period (Quack, forthcoming, a).
1.3 STAR CLOCKS AND DECANS
oldest explicitly astronomical monuments from Egypt are star clocks, attested by more than 20 copies, mainly on the inner side of coffin lids from the Eleventh and Twelfth Dynasties (ca 2050-1900 BCE) (Neugebauer and Parker 1960; Quack, forthcoming, a). They indicate, in principle, for each 10-day interval of the year a sequence of 12 stars (or parts of constellations), with each star moving up one position in the tabl
per interval. lt is generally assumed that a significant astronomical position of the star (most probably its rising in the east) indicates the onset of a new hour of the night. Tue “hours” are rather short hours of about 40 minutes, so that a change by one “hour” for a star every 10 days corresponds more or less to astronomical reality. These stars ( or parts of constellations) have a long history and still appear in some astrological treatises of classical antiquity.
They are commonly called decans (as they are in Greek and Latin texts), while the Egyptian designation is baktiu “those connected with work”-the “work” being the indication of the hours; often they are simply labeled in the texts as “stars” without further specification. Tue images seen in the sky by the Egyptians differ significantly from our modern tradition (mainly derived from Mesopotamia and Greece), and the identification of most of the Egyptian constellations is fraught with difficulties (a recent proposal is in Lull and Belmonte 2006). Observing the hours of the night was important mainly for the performance of some religious rituals.
There are two basic types of the oldest star clocks, with some differences in the actual choice of decans and a divergent starting point. lt is likely that this does not reflect different dates of invention (as supposed earlier by Neugebauer and Parker 1960 ); rather, both structures are equally schematic, with the one putting the heliacal rising of Sirius in the middle of the table, the other putting Sirius as the last regular star in the top line.
A different type of star clock is constituted by the “Ramesside star clocks” (Neugebauer and Parker 1964; Leitz 1995, 117-287; Depuydt 1998a). They are only attested in three royal tombs of the 11th century BCE, but thought by astronomical considerations (especially the rising date ofSirius) to go back to the 15th century BCE.
They are also based on stellar position but show several refinements. Tue individual tables are no longer for 10 but for 15 days, which makes them more suitable for fixed hours of 60 minutes. 1hey use the culmination as principal marker of hourly changes but allow also other positions, Which are defined in terms of human anatomy (like “left eye” or “right ear”) and probably refer to a human statue set up directly opposite the observer as a marker of the meridian; so these would indicate positions of the star more or less distant from precise culmination. Only attested on one single monument from the 4th century BCE is a type of stellar clock that divides the night only into three parts, based on the movements of the Big Dipper (Neugebauer and Parker 1969, 49-52). Tue actual engraving shows serious corruption.
1.4 The Book of Nut
Nut was acknowledged as the mother of five gods: Osiris, Isis, Seth, Nephthys, and Horus the Elder. In one myth documented by Plutarch in his essays on Isis and Osiris, the sun god cursed Nut, preventing her from giving birth to children on any day of the year. In order to circumvent the curse so that Nut would be able to give birth, Thoth won a game against the Moon and created five extra days of the year, during which Nut could give birth. The first to be born was the god Osiris.6 Nut’s association with Osiris was an important theme in the funerary culture of ancient Egypt. Because the deceased was usually associated with Osiris, Nut can be seen as the mother who offers protection to the deceased. In the Pyramid Texts, her role as the mother of Osiris is emphasized. In Pyramid Text 26 from the tomb of Merenre, 7 the sky goddess is referred to as mother of Osiris the King, who “has spread herself over [the Osiris]” and “protected [the Osiris] from everything bad, in her name of [‘Great
Protectress’].” 8 She is indirectly mentioned again regarding her maternal role in Pyramid Text 336 from the tomb of Merenre, which describes the deceased as “the Osiris” who is “firstborn of his mother.”9 Complementing her motherly and protective qualities in texts, Egyptian funerary iconography focused on her protective nature and her relationship with the deceased. Through depictions of her in tombs and on coffins, the body of the deceased would remain protected for eternity. As a protective deity, Nut appeared on coffins in two poses. As early as the New Kingdom and continuing on to later periods, a kneeling figure of Nut with outstretched wings could be found on the exterior of anthropoid coffin lids, underneath the modelled arms of the coffin,
A second form of representation of the goddess Nut could be found on the interior of the coffin lid. In this form, she was usually depicted as an outstretched frontal figure, with hands and feet extended toward either end of the coffin. Although references to Nut appeared in Pyramid Texts in the Old Kingdom and in the Coffin texts of the Middle Kingdom, the image of Nut on the underside of a coffin lid was not developed until the New Kingdom.11 For example, the sarcophagus of Merenptah from Dynasty 19 contains a
These images focus on Nut’s role as goddess of the night sky, as representations of the stars are present in some form on each coffin. On the coffins of Merenptah and Peftjauneith, the body of the figure of Nut is covered with stars.
On the coffin of Hornedjitef, depictions of planets, constellations, and decans are along either side of Nut’s body, which represent the stars in the night sky.
On the coffins, the constellations are represented by the twelve figures of the Greek zodiac. The figures of Nut on the underside of the coffin lids also reflect the Osirian theme of protection for the deceased, provided by Osiris’ mother, Nut. A coffin lid was the logical location for the figure of Nut because it would allow for her to cover and protect the body of the deceased, which rested just under the lid inside the coffins
https://digitalcommons.memphis.edu/cgi/viewcontent.cgi?article=2035&context=etd
most complex composition concerning celestial phenomena is constituted by the “fundamentals of the course of the stars” (von Lieven 2007), also known under the name Book of Nut. This composition is attested in three monumental versions (13th, 12th, and 6th centuries BCE) as well as a number of papyri of the Roman period (2nd century CE), plus an excerpt of a short passage attested in some tombs of the Twenty-Sixth Dynasty 64 ANCIENT SCIENTIFIC TRADITIONS BEYOND GREECE AND ROME (Regen 2015); another short extract is attested on the ceiling of the temple of Athribis in the Ptolemaic period. Two of those papyri (Papyrus Carlsberg 1 and ia) contain not only the basic text but also a translation into a more recent form of Egyptian, plus a commentary (not identical in the two sources).
The monumental versions (and one papyrus with hieroglyphic writing) also show a picture of the sky goddess (Nut) lifted into the air by her father (Shu); the demotic papyri describe this image without drawing it. The first part consists of relatively short texts accompanying parts of the drawing. The first section of this part describes phenomena of the sun, especially its rising in the morning; the redness in the morning is equated to hemorrhage during a birth. This is followed by a short description of the outer parts of the sky where the sun does not shine. A substantial section treats the stars, especially the decans. They are pressed into a schematic template where each decan spends, after its heliacal rising, the first So days in the eastern part of the sky, then his culmination serves, for 120 days, to indicate nightly hours, and afterward, he spends 90 days in the western part of the sky, before being invisible for 70 days. This is obviously not to be taken as numerically exact, and it works with a rounded year-length of 360 days (neglecting the final five days of the Egyptian year outside normal calendrical structure) in order to keep the calendar dates simple. Still, it shows that the Egyptian decans should be located in a celestial belt south of the ecliptic (Neugebauer and Parker 1960, 97-100). The description of the cycle of the sun is resumed, this time focusing more on sunset and night, but continuing until sunrise. lt is explained how the stars are following the sun. Finally, there is a section about the migratory birds which are understood as the souls of men, coming from the north to feed on the herbs of Egypt. The second part of the composition is contained in only one of the monumental versions, separated from the first part by passages about a shadow clock and a water clock, whereas the papyrus texts continue directly after the first part. The general style of the second part is more mythological than the first one, and there are longer connected texts. The disappearance of the stars is conceptualized as their consumption by a mother sow, their stay below the horizon as a purification. After the treatment of the stars, a section on the moon follows where the phases are mainly explained as interactions between different deities, for example, Horus and Seth. The final preserved section was understood as treating the moon and the planets by von Lieven (2007, 107-119, 190-201; 2012, 12of.), while Leitz (2008/2009, 17-19) preferred to see it as another treatment of exclusively the moon
https://archiv.ub.uni-heidelberg.de/propylaeumdok/5336/1/Quack_Astronomy_in_Ancient_Egypt_2018.pdf
This system was not always in use and was preceded by one based on the lunar cycles instead of stellar motion.6 In the previous system, each new month began at the point in which the “old moon” – the moon that had just completed its cycle from waxing to full to waning – became invisible. This created twelve months in the early Egyptian year, divided into three equal seasons – Ahktet (inundation), Peret (growth), and Shemu (harvest). A thirteenth month was intercalated if Sirius’ heliacal rising occurred within the last eleven days of the month, keeping the calendar linked to the seasons. This occurred once every two or three years.7 For the purpose of timekeeping, this system only lasted until 3000 B.C., but it carried on as a means of scheduling seasonal festivals until the end of pagan Egypt.8 The decanal timekeeping system was introduced in the 3rd millennium, probably for administrative reasons. This new civil calendar kept the number of months to 12 like its predecessor, but instead of inserting an entire extra month depending on the rising of Sirius, the Egyptians added the five epagomenal days to each year.9
natural length of the year. While 365 days is a very close estimate of the true length of the year (i.e. the amount of time it takes for the earth to complete a full rotation around the sun), it is not exact. In reality, the year is just under 365 and 1/4 days long. Scholars believed that the Egyptians were aware of this information from the beginning, but did not change the decan system to accompany it until the reign of Ptolemy III in 238 B.C.E , where a sixth epagomenal day was added every four years.10 For the thousands of years before this official correction (which wasn’t necessarily honoured by the locals), the Egyptian calendar was a wandering one, falling out of synchronization with the natural year length at a rate of approximately one day per four years. The use of decans as nightly hour markers was probably introduced around the same time as the implementation of the 365-day civil calendar.11 They allowed for the year to be easily broken into thirty-six ten-day “weeks.” However, because of the wandering calendar, eventually the decans used to represent each hour of the night would shift and the whole system would have to be adjusted. There is only evidence of one attempt at correcting for the wandering, occurring in the Twelfth Dynasty.12 By 1786 B.C.E., a system based on the decans transiting the meridian (passing through the highest point of the sky) instead of their heliacal rising was introduced.13 The Egyptians also began to make use of water clocks for improved accuracy.14 Despite the introduction of new systems for practical purposes, the decans as symbolic hour markers remained widespread in Egypt, and their civil calendric system
1.5 Decans and Egyptian Religion:
An Integral Connection That astronomical observation was intertwined with Egyptian religious culture is well established within scholarship, and can be seen in both the primary material and the archaeological evidence. Many temples were astronomically oriented, built in such a way to 15 mimic the alignment of the heavens.42 Egyptian religion is fraught with associations between the sun and the Pharaohs, the moon and the religious calendar, and the wanderings of the stars and the deities that were worshipped. There was little, if any, distinction between the observation of objects in the sky (what we would consider “scientific”) and religious symbolism and tradition. The Book of Nut, one of the most important astronomical texts that survives from pre-Hellenistic Egypt, does not make any sort of differentiation between celestial observation for the sake of scientific or mathematic inquiry, and celestial observation as a valid and practiced way to worship their sky deities. The decans, as facets of Egyptian astronomy, were no exception to this idea. Their associations in celestial diagrams with individual deities exhibits this. They all interacted within a system governed and protected by the goddess Nut, whose outstretched body formed the backdrop of the night sky for the stars (including the decans) to pass through as she birthed
Recorded in Egyptian star clocks was qualitative and used in a religious context to assist in funerary setting, decorating coffins as a way of assisting the dead through their journey to the Duat. Neugebauer states that, “Egypt has no place in a work on the history of mathematical astronomy.”
Egyptians, the stars were “the shining ones”— the eternal spirits of lesser gods (after the Sun and Moon). Thus, it is not an unreasonable assumption that following the motion of the stars was a religious devotion rather than a scientific procedure.” Neugebauer and Parker tell us that the deities that the decans embodied were seen as living phenomena in the sky, “children of Horus.” Their motion throughout the sky during the year was symbolic of the process of birth, life, and death in a way that was visible to all – this, Von Bomhard states, is the meaning behind the Egyptian word for the decans, which they translated as “the living.”
Where more scientific approaches would have processed the decanal system as an indication of some cycle of rotation, the Egyptian priests and astronomers grounded the motions within the context most understandable to them – the gods and the Duat.
The star clocks, decan lists, and any texts
A Work for Eternity (London: Periplus, 1999), 51. 16 concerning the decans were first and foremost religious. For modern astronomers to assume some greater scientific basis for the decanal system is to remove the Egyptian sources from their context and deny them their original purpose as sacred.46 The associations of decans with their deities becomes more important in later Egyptian religion, especially as they become associated with the Babylonian zodiac and are taken up by Hellenistic culture in various ways, as we will
attests to the importance of these systems as funerary symbols. The decan systems were not calculated, rigorous time markers akin to the modern clock.47 The diagonal and transit star charts fell out of synchronization relatively quickly, and this was not missed by the Egyptians. If the decan systems were to be used for their day-to-day utility, the issue of their wandering would have been remedied for accuracy. Instead, the star charts we find are calibrated for specific moments in time. This is because the clock was predominately used by the dead contained within the tomb or coffin. The decan that rose each hour was a symbolic guide to allow the journey to the Duat to be made by the dead. This is what much of the scholarship regarding the decans in Egyptian astronomy has concluded: they were based in the actual risings and settings of specific stars and constellations, but their primary context was religious. They were not necessarily important for the sake of scientific or mathematic inquiry. However, while we would see these two as distinct, mutually exclusive reasons to observe the stars, the Egyptians melded these concepts together, and religion and astronomy were wed in a way that would not
References :
https://archiv.ub.uni-heidelberg.de/propylaeumdok/5336/1/Quack_Astronomy_in_Ancient_Egypt_2018.pdf
https://digitalcommons.memphis.edu/cgi/viewcontent.cgi?article=2035&context=etd