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== Basis of the cycle ==

== Basis of the cycle ==

The star called [[Sirius]], or the "Dog Star," is the brightest [[star]] in the southern or [[tropic]]al [[sky]] at night. [[Manetho]], in the third century [[BC]], caught multiple mentions of the phrase ''peret Sopdet'', or literally, "rising of Sirius," in the documents that he examined. ''Sopdet'' is the Egyptian word for "Sirius." The [[Greek]] word is ''Sothis''.

The star called [[Sirius]], or the "Dog Star," is the brightest [[star]] in the southern or [[tropic]]al [[sky]] at night. [[Manetho]], in the third century BC, caught multiple mentions of the phrase ''peret Sopdet'', or literally, "rising of Sirius," in the documents that he examined. ''Sopdet'' is the Egyptian word for "Sirius." The [[Greek]] word is ''Sothis''.

Richard Lepsius, in 1858,<ref>Lepsius, Richard. ''In Königsbuch der Alten Ägypter''. Berlin:Besser, 1858. Cited in Mackey, ''op. cit.''</ref> first suggested that the phrase ''peret Sopdet'' referred to a regular [[Astronomical dating|astronomical event]].<ref name=Mackey/>Meyer, in 1904,<ref name=Meyer>Meyer, Eduard. ''Ägyptische Chronologie''. Berlin: Akademie der Wissenschaften, 1904. Cited in Mackey, ''op. cit.''</ref> constructed a long-range calendar based on the following observations:

Richard Lepsius, in 1858,<ref>Lepsius, Richard. ''In Königsbuch der Alten Ägypter''. Berlin:Besser, 1858. Cited in Mackey, ''op. cit.''</ref> first suggested that the phrase ''peret Sopdet'' referred to a regular [[Astronomical dating|astronomical event]].<ref name=Mackey/>Meyer, in 1904,<ref name=Meyer>Meyer, Eduard. ''Ägyptische Chronologie''. Berlin: Akademie der Wissenschaften, 1904. Cited in Mackey, ''op. cit.''</ref> constructed a long-range calendar based on the following observations:

# This year made no attempt to synchronize with the [[moon]] and, by gaining a day every four years, maintained no synchrony with the [[sun]], either.

# This year made no attempt to synchronize with the [[moon]] and, by gaining a day every four years, maintained no synchrony with the [[sun]], either.

Meyer calculated that Sirius would make a [[heliacal rising]] (that is, first be visible shortly before dawn during any given year) on the Egyptian [[New Year's Day]] every 1,460 years--that is to say, four times 365 years, at which time the calendar would realign with the seasons. Meyer then assumed that the Egyptians used this extended calendar as their actual civil calendar. Finally, he fixed the most recent "rising of Sothis" as having occurred in [[AD]] 140. He based this fixation entirely on a writing by [[Censorinus]], who allegedly had written that a heliacal rising of Sirius did fall on the Egyptian New Year in that year.

Meyer calculated that Sirius would make a [[heliacal rising]] (that is, first be visible shortly before dawn during any given year) on the Egyptian [[New Year's Day]] every 1,460 years--that is to say, four times 365 years, at which time the calendar would realign with the seasons. Meyer then assumed that the Egyptians used this extended calendar as their actual civil calendar. Finally, he fixed the most recent "rising of Sothis" as having occurred in AD 140. He based this fixation entirely on a writing by [[Censorinus]], who allegedly had written that a heliacal rising of Sirius did fall on the Egyptian New Year in that 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.<ref name=Mackey/> Meyer then supposed that 2780 BC occurred in Manetho's Fourth Dynasty, and that the Sothic calendar was already in use at the time. On that basis, he concluded that the year 4240 BC saw the invention of the Sothic calendar and was also the oldest fixed date in recorded human history.<ref name=Mackey/>

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.<ref name=Mackey/> Meyer then supposed that 2780 BC occurred in Manetho's Fourth Dynasty, and that the Sothic calendar was already in use at the time. On that basis, he concluded that the year 4240 BC saw the invention of the Sothic calendar and was also the oldest fixed date in recorded human history.<ref name=Mackey/>