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The Sothic cycle or Canicular period is a period of 1,461
Egyptian civil years of 365 days each or 1,460
Julian years averaging 365¼ days each. During a Sothic cycle, the 365-day year loses enough time that the start of its year once again coincides with the
heliacal rising
The heliacal rising ( ) or star rise of a star occurs annually, or the similar phenomenon of a planet, when it first becomes visible above the eastern horizon at dawn just before sunrise (thus becoming "the morning star") after a complete orbit of ...
of the star
Sirius
Sirius is the list of brightest stars, brightest star in the night sky. Its name is derived from the Ancient Greek language, Greek word , or , meaning 'glowing' or 'scorching'. The star is designated α Canis Majoris, Latinisation ...
( egy,
spdt or , 'Triangle'; grc-gre, Σῶθις, ) on 19 July in the
Julian calendar
The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematicians and astronomers such as Sosigenes of Alexandr ...
.
[.] It is an important aspect of
Egyptology
Egyptology (from ''Egypt'' and Greek , '' -logia''; ar, علم المصريات) is the study of ancient Egyptian history, language, literature, religion, architecture and art from the 5th millennium BC until the end of its native religious ...
, particularly with regard to reconstructions of the
Egyptian calendar
The ancient Egyptian calendar – a civil calendar – was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus an intercalary month of five epagomenal days treated as outside of the year proper. Eac ...
and its history.
Astronomical records of this displacement may have been responsible for the later establishment of the more accurate
Julian and
Alexandrian calendars.
Mechanics
The
ancient Egyptian
civil year
Generally speaking, a calendar year begins on the New Year's Day of the given calendar system and ends on the day before the following New Year's Day, and thus consists of a whole number of days. A year can also be measured by starting on any ...
, its holidays, and religious records reflect its apparent establishment at a point when the
return
Return may refer to:
In business, economics, and finance
* Return on investment (ROI), the financial gain after an expense.
* Rate of return, the financial term for the profit or loss derived from an investment
* Tax return, a blank document or t ...
of the bright star
Sirius
Sirius is the list of brightest stars, brightest star in the night sky. Its name is derived from the Ancient Greek language, Greek word , or , meaning 'glowing' or 'scorching'. The star is designated α Canis Majoris, Latinisation ...
to the night sky was considered to herald the annual
flooding of the Nile
The flooding of the Nile has been an important natural cycle in Egypt since Ancient Egypt, ancient times. It is celebrated by Egyptians as an annual holiday for two weeks starting August 15, known as ''Wafaa El-Nil''. It is also celebrated in the ...
.
[ However, because the civil calendar was exactly 365 days long and did not incorporate ]leap year
A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) added to keep the calendar year synchronized with the astronomical year or s ...
s until 22 BCE, its months "wandered" backwards through the solar year
A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky of a celestial body of the Solar System such as the Earth, completing a full cycle of seasons; for example, the time fro ...
at the rate of about one day in every four years. This almost exactly corresponded to its displacement against the Sothic year as well. (The Sothic year is about a minute longer than a Julian year.)[.] The sidereal year
A sidereal year (, ; ), also called a sidereal orbital period, is the time that Earth or another planetary body takes to orbit the Sun once with respect to the fixed stars.
Hence, for Earth, it is also the time taken for the Sun to return to the ...
of 365.25636 days is only valid for stars on the ecliptic
The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...
(the apparent path of the Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
across the sky) and having no proper motion
Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...
, whereas Sirius's displacement ~40° below the ecliptic, its proper motion, and the wobbling of the celestial equator
The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. This plane of reference bases the equatorial coordinate system. In other words, the celestial equator is an abstract projectio ...
cause the period between its heliacal rising
The heliacal rising ( ) or star rise of a star occurs annually, or the similar phenomenon of a planet, when it first becomes visible above the eastern horizon at dawn just before sunrise (thus becoming "the morning star") after a complete orbit of ...
s to be almost exactly 365.25 days long instead. This steady loss of one relative day every four years over the course of the 365-day calendar meant that the "wandering" day would return to its original place relative to the solar and Sothic year after precisely 1461 Egyptian civil years or 1460 Julian years.[
]
Discovery
This calendar cycle was well known in antiquity. Censorinus described it in his book ''De Die Natale'', in CE 238, and stated that the cycle had renewed 100 years earlier on the 12th of August. In the ninth century, Syncellus epitomized the Sothic Cycle in the "Old Egyptian Chronicle." Isaac Cullimore, an early Egyptologist and member of the Royal Society, published a discourse on it in 1833 in which he was the first to suggest that Censorinus had fudged the terminus date, and that it was more likely to fall in CE 136. He also computed the likely date of its invention as being around 1600 BCE.
In 1904, seven decades after Cullimore, Eduard Meyer
Eduard Meyer (25 January 1855 – 31 August 1930) was a German historian. He was the brother of Celticist Kuno Meyer (1858–1919).
Biography
Meyer was born in Hamburg and educated at the Gelehrtenschule des Johanneums and later at the univer ...
carefully combed known Egyptian inscriptions and written materials to find any mention of the calendar dates when Sirius rose at dawn. He found six of them, on which the dates of much of conventional Egyptian chronology
The majority of Egyptologists agree on the outline and many details of the chronology of Ancient Egypt. This scholarly consensus is the so-called Conventional Egyptian chronology, which places the beginning of the Old Kingdom in the 27th centur ...
are based. A heliacal rise of Sirius was recorded by Censorinus
Censorinus was a Roman grammarian and miscellaneous writer from the 3rd century AD.
Biography
He was the author of a lost work ''De Accentibus'' and of an extant treatise ''De Die Natali'', written in 238, and dedicated to his patron Quintus ...
as having happened on the Egyptian New Year's Day between 139 CE and 142 CE.
The record itself actually refers to 21 July 140 CE, but astronomical calculation definitely dates the heliacal rising at 20 July 139 CE, Julian. This correlates the Egyptian calendar to the Julian calendar
The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematicians and astronomers such as Sosigenes of Alexandr ...
. A Julian leap day occurs in 140 CE, and so the new year on 1 Thoth
Thoth (; from grc-koi, Θώθ ''Thṓth'', borrowed from cop, Ⲑⲱⲟⲩⲧ ''Thōout'', Egyptian: ', the reflex of " eis like the Ibis") is an ancient Egyptian deity. In art, he was often depicted as a man with the head of an ibis or a ...
is 20 July in 139 CE but it is 19 July for 140–142 CE. Thus Meyer Meyer may refer to:
People
*Meyer (surname), listing people so named
* Meyer (name), a list of people and fictional characters with the name
Companies
* Meyer Burger, a Swiss mechanical engineering company
* Meyer Corporation
* Meyer Sound Labo ...
was able to compare the Egyptian civil calendar date on which Sirius was observed rising heliacally to the Julian calendar date on which Sirius ''ought'' to have risen, count the number of intercalary days needed, and determine how many years were between the beginning of a cycle and the observation.
To calculate a date astronomically, one also needs to know the place of observation, since the latitude of the observation changes the day when the heliacal rising of Sirius can be seen, and mislocating an observation can potentially throw off the resulting chronology by several decades.[ Official observations are known to have been made at Heliopolis (or ]Memphis
Memphis most commonly refers to:
* Memphis, Egypt, a former capital of ancient Egypt
* Memphis, Tennessee, a major American city
Memphis may also refer to:
Places United States
* Memphis, Alabama
* Memphis, Florida
* Memphis, Indiana
* Memp ...
, near Cairo
Cairo ( ; ar, القاهرة, al-Qāhirah, ) is the capital of Egypt and its largest city, home to 10 million people. It is also part of the largest urban agglomeration in Africa, the Arab world and the Middle East: The Greater Cairo metro ...
), Thebes, and Elephantine
Elephantine ( ; ; arz, جزيرة الفنتين; el, Ἐλεφαντίνη ''Elephantíne''; , ) is an island on the Nile, forming part of the city of Aswan in Upper Egypt. The archaeological sites on the island were inscribed on the UNESCO ...
(near Aswan
Aswan (, also ; ar, أسوان, ʾAswān ; cop, Ⲥⲟⲩⲁⲛ ) is a city in Southern Egypt, and is the capital of the Aswan Governorate.
Aswan is a busy market and tourist centre located just north of the Aswan Dam on the east bank of the ...
),[ with the rising of Sirius observed at Cairo about 8 days after it is seen at Aswan.]
Meyer concluded that the Egyptian civil calendar was created in 4241 BCE.[Meyer, Eduard, ''Aegyptische Chronologie'', Berlin, Verlag der Königliche Akadamie der Wissenschaften (1904), Ch. I, p.41]
/ref>[Breasted, James Henry, ''A History of the Ancient Egyptians'', New York, Charles Scribner's Sons (1908), Ch. II, p.15]
(" e calendar year of 365 days was introduced in 4241 B.C., the earliest fixed date in the history of the world as known to us."), citing Meyer. Recent scholarship, however, has discredited that claim. Most scholars either move the observation upon which he based this forward by one cycle of Sirius, to 19 July 2781 BCE, or reject the assumption that the document on which Meyer relied indicates a rise of Sirius at all.
Chronological interpretation
Three specific observations of the heliacal rise of Sirius are extremely important for Egyptian chronology. The first is the aforementioned ivory tablet from the reign of Djer which supposedly indicates the beginning of a Sothic cycle, the rising of Sirius on the same day as the new year. If this does indicate the beginning of a Sothic cycle, it must date to about 17 July 2773 BCE.[ However, this date is too late for Djer's reign, so many scholars believe that it indicates a correlation between the rising of Sirius and the Egyptian ''lunar'' calendar, instead of the solar Egyptian civil calendar, which would render the tablet essentially devoid of chronological value.][
Gautschy ''et al''. (2017) claimed that a newly discovered Sothis date from the Old Kingdom and a subsequent astronomic study confirms the Sothic cycle model.
The second observation is clearly a reference to a heliacal rising, and is believed to date to the seventh year of ]Senusret III
Khakaure Senusret III (also written as Senwosret III or the hellenised form, Sesostris III) was a pharaoh of Egypt. He ruled from 1878 BC to 1839 BC during a time of great power and prosperity, and was the fifth king of the Twelfth Dynasty of the ...
. This observation was almost certainly made at Itj-Tawy
Itjtawy (full Egyptian name ''Amenemhat-itj-tawy'' — "Amenemhat, Seizer of the Two Lands"), is the name of the royal city founded as a new capital by Twelfth Dynasty Egyptian King Amenemhat I, who ruled from approximately 1991 BC to 1962 BC, ...
, the Twelfth Dynasty capital, which would date the Twelfth Dynasty from 1963 to 1786 BCE.[ The Ramses or Turin Papyrus Canon says 213 years (1991–1778 BCE), ]Parker Parker may refer to:
Persons
* Parker (given name)
* Parker (surname)
Places Place names in the United States
*Parker, Arizona
*Parker, Colorado
* Parker, Florida
* Parker, Idaho
* Parker, Kansas
* Parker, Missouri
* Parker, North Carolina
*Park ...
reduces it to 206 years (1991–1785 BCE), based on 17 July 1872 BCE as the Sothic date (120th year of 12th dynasty, a drift of 30 leap days). Prior to Parker's investigation of lunar dates, the 12th dynasty was placed as 213 years of 2007–1794 BCE interpreting the date 21 July 1888 BCE as the 120th year, and then for 2003–1790 BCE interpreting the date 20 July 1884 BCE as the 120th year.
The third observation was in the reign of Amenhotep I
Amenhotep I () ( egy, jmn-ḥtp(w) /jaˌmanuwˈħatpaw/ "Amun is satisfied"; Amarna cuneiform ''a-ma-an-ha-at-pe'' or ''-at-pa''), Amenôthes I, or Amenophis I, (,) from Ancient Greek Ἀμένωφις ,Dodson & Hilton (2004) p.126 additionally ...
, and, assuming it was made in Thebes, dates his reign between 1525 and 1504 BCE. If made in Memphis, Heliopolis, or some other Delta site instead, as a minority of scholars still argue, the entire chronology of the 18th Dynasty needs to be extended some 20 years.[
]
Observational procedure and precession
The Sothic cycle is a specific example of two cycles of differing length interacting to cycle together, here called a tertiary cycle. This is mathematically defined by the formula or half the harmonic mean
In mathematics, the harmonic mean is one of several kinds of average, and in particular, one of the Pythagorean means. It is sometimes appropriate for situations when the average rate is desired.
The harmonic mean can be expressed as the recipro ...
. In the case of the Sothic cycle the two cycles are the Egyptian civil year and the Sothic year.
The Sothic year is the length of time for the star Sirius to visually return to the same position in relation to the sun. Star years measured in this way vary due to axial precession
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In particu ...
, the movement of the Earth's axis in relation to the sun.
The length of time for a star to make a yearly path can be marked when it rises to a defined altitude above a local horizon at the time of sunrise. This altitude does not have to be the altitude of first possible visibility, nor the exact position observed. Throughout the year the star will rise to whatever altitude was chosen near the horizon approximately four minutes earlier each successive sunrise. Eventually the star will return to the same relative location at sunrise, regardless of the altitude chosen. This length of time can be called an ''observational year''. Stars that reside close to the ecliptic or the ecliptic meridian will – on average – exhibit observational years close to the sidereal year of 365.2564 days. The ecliptic and the meridian cut the sky into four quadrants. The axis of the earth wobbles around slowly moving the observer and changing the observation of the event. If the axis swings the observer closer to the event its observational year will be shortened. Likewise, the observational year can be lengthened when the axis swings away from the observer. This depends upon which quadrant of the sky the phenomenon is observed.
The Sothic year is remarkable because its average duration happened to have been nearly exactly 365.25 days, in the early before the unification of Egypt. The slow rate of change from this value is also of note. If observations and records could have been maintained during predynastic times the Sothic rise would optimally return to the same calendar day after 1461 calendar years. This value would drop to about 1456 calendar years by the Middle Kingdom. The value 1461 could also be maintained if the date of the Sothic rise were artificially maintained by moving the feast in celebration of this event one day every fourth year instead of rarely adjusting it according to observation.
It has been noticed, and the Sothic cycle confirms, that Sirius does not move retrograde across the sky, like other stars, a phenomenon widely known as the precession of the equinox
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In particu ...
:
:Sirius remains about the same distance from the equinoxes – and so from the solstices – throughout these many centuries, despite precession. — J.Z. Buchwald (2003)
For the same reason, the heliacal rising or zenith of Sirius does not slip through the calendar at the precession rate of about one day per 71.6 years as other stars do, but much slower. This remarkable stability within the solar year may be one reason that the Egyptians used it as a basis for their calendar. The coincidence of a heliacal rising of Sirius and the New Year reported by Censorinus occurred about 20 July, that is a month ''after'' the summer solstice.
Problems and criticisms
Determining the date of a heliacal rise of Sirius has been shown to be difficult, especially considering the need to know the exact latitude of the observation.[ Another problem is that because the Egyptian calendar loses one day every four years, a heliacal rise will take place on the same day for four years in a row, and any observation of that rise can date to any of those four years, making the observation imprecise.][
A number of criticisms have been levelled against the reliability of dating by the Sothic cycle. Some are serious enough to be considered problematic. Firstly, none of the astronomical observations have dates that mention the specific pharaoh in whose reign they were observed, forcing Egyptologists to supply that information on the basis of a certain amount of informed speculation. Secondly, there is no information regarding the nature of the civil calendar throughout the course of Egyptian history, forcing Egyptologists to assume that it existed unchanged for thousands of years; the Egyptians would only have needed to carry out one calendar reform in a few thousand years for these calculations to be worthless. Other criticisms are not considered as problematic, e.g. there is no extant mention of the Sothic cycle in ancient Egyptian writing, which may simply be a result of it either being so obvious to Egyptians that it didn't merit mention, or to relevant texts being destroyed over time or still awaiting discovery.
]Marc Van de Mieroop
Marc Van de Mieroop (b. 22 October 1956) is a noted Belgians, Belgian Assyriology, Assyriologist and Egyptology, Egyptologist who has been full professor of Ancient Near Eastern history at Columbia University since 1996.
Biography
Born in Bel ...
, in his discussion of chronology and dating, does not mention the Sothic cycle at all, and asserts that the bulk of historians nowadays would consider that it is not possible to put forward exact dates earlier than the 8th century BCE.
Some have recently claimed that the Theran eruption marks the beginning of the Eighteenth Dynasty, due to Theran ash and pumice discovered in the ruins of Avaris
Avaris (; Egyptian: ḥw.t wꜥr.t, sometimes ''hut-waret''; grc, Αὔαρις, Auaris; el, Άβαρις, Ávaris; ar, حوّارة, Hawwara) was the Hyksos capital of Egypt located at the modern site of Tell el-Dab'a in the northeastern r ...
, in layers that mark the end of the Hyksos era. Because the evidence of dendrochronologists indicates the eruption took place in 1626 BCE, this has been taken to indicate that dating by the Sothic cycle is off by 50–80 years at the outset of the 18th Dynasty. Claims that the Thera eruption is described on the ''Tempest Stele
The Tempest Stele (alt. Storm Stele) was erected by pharaoh Ahmose I early in the 18th Dynasty of Egypt, . The stele describes a great storm striking Egypt during this time, destroying tombs, temples and pyramids in the Theban region and the w ...
'' of Ahmose I
Ahmose I ( egy, jꜥḥ ms(j .w), reconstructed /ʔaʕaħ'maːsjə/ ( MK), Egyptological pronunciation ''Ahmose'', sometimes written as ''Amosis'' or ''Aahmes'', meaning "Iah (the Moon) is born") was a pharaoh
Pharaoh (, ; Egyptian: ...
have been disputed by writers such as Peter James.
See also
*Chronology of the ancient Near East
The chronology of the ancient Near East is a framework of dates for various events, rulers and dynasties. Historical inscriptions and texts customarily record events in terms of a succession of officials or rulers: "in the year X of king Y". Com ...
Notes
References
External links
*
{{DEFAULTSORT:Sothic Cycle
Egyptian calendar
Chronology
Egyptology
Units of time