Sothic dating

The Sothic cycle is the extended calendar that the Egyptologist Eduard Meyer invented in 1904 in an attempt to standardize the dates given on Egyptian documents (carved in stone or written on papyrus) and produce a unified chronology of ancient Egypt.The star called Sirius, or the "Dog Star," is the brightest star in the southern or tropical sky at night.The second observation is clearly a reference to a helical rise, and is believed to date to the seventh year of Senusret III.

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Sothic dating

The most significant advance made in the study of ancient Egyptian chronology in recent years is the repudiation by Neugebauer and others of an astronomical origin for the Egyptian civil calendar and , as a corollary, the elimination of the so-called Sothic Cycle as a factor in dating the earliest periods of Egyptian History.

For the fixing in time of the Egyptian Middle Kingdom and the periods preceding it, the key date is the seventh year of the reign of King Sesostris III of the Twelfth Dynasty.

The Sothic cycle or Canicular period is a period of 1461 ancient Egyptian years (of 365 days each) or 1460 Julian years (averaging 365.25 days each).

During a Sothic cycle, the 365-day year loses enough time that the start of the year once again coincides with the heliacal rising of the star Sirius (called Sothis in Greek; a single year between heliacal risings of Sothis is a Sothic year).

Because Sirius is not on the ecliptic, the wobbling of the celestial equator and hence of the horizon at the latitude of Egypt causes the Sothic year to be slightly smaller.

Indeed, it is almost exactly 365.25 days long, the average number of days in a Julian year.Projecting backward (and assuming that Censorinus was correct and that Meyer understood him correctly), Meyer calculated prior Sothic years as having occurred in 1320 BC, 2780 BC, and 4240 BC.Meyer then supposed that 2780 BC occurred in Manetho's Fourth Dynasty, and that the Sothic calendar was already in use at the time.If this does indicate the beginning of a Sothic cycle, it must date to about 2773 BC.However, this date is too early for Djer's reign, so many scholars believe that it indicates a correlation between the rising of Sothis and the lunar calendar, instead of the solar calendar, which would render the tablet essentially devoid of chronological value.A heliacal rise of Sirius was recorded by Censorinus as having happened on the Egyptian new year's day, between 139 and 142 AD This correlates the Egyptian calendar to the Julian calendar.

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