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The awaited return of the most obvious seasonal signal
The "brilliant" sectors of the sky
An assembly of sacred images

Figures portrayed
by stars in the night,
by nature "dramatic" figures

Why make reference to
seasonal stars.
Measuring time in "moons"

When lunar imagery is combined
with stellar imagery to compose a "mythical cinema"

The human condition
and its development
in the collective memory


French version


Sun and Moon: a problem couple

The lunar month (MN, Min, Men: Moon) lasts an average of 29 ½ days (29.530588). The Sun completes its cycle, the Year (annual = anulus or ring) in an average of 365 ¼ days (365.24220).
But these 365 ¼ days are not a multiple of the 29 ½ of the lunar month.

What happens? The solar year does not contain a simple whole number of lunar months, neither 12 nor 13. We would need an additional 11 (more precisely 10.875) days in order to have a total of 13 moons. Problematic!

This is a serious problem because the Solar Cycle is the Seasonal Cycle. It is marked by
  • a high point of short nights, the Summer Solstice (June 21);
  • and a low point of long nights, the Winter Solstice (December 21).
The Solstices are separated by two intermediate key-moments where the length of the night equals that of the day.
  • These are the Autumnal Equinox (September 22)
  • and the Vernal Equinox (March 20).

Because this cycle of seasons corresponds to differences in the amount of sunlight we receive at various moments, it is one of the fundamental features of Life on Earth.

When the "moons" roam through the seasons

The succession of "moons" occurs independently of this solar cycle of seasons and its corresponding changes in Nature. The pure lunar calendar is "vague". If we use seasonal circumstances to assign names to lunar months (e.g. a month close to the Vernal Equinox could be called the "Moon of the Bear’s Awakening"), the resulting series of 12 lunar months would end before the solar year was finished. If we continue the next lunar year without taking into account this difference, the lunar year will have an advance on the real season. In 36 lunar years the first month of the new lunar year will have made a complete tour and be back to the proper starting position, a sort of Rip Van Winkle trick.

Obviously this was not an acceptable solution, neither for the hunters and gatherers nor for subsequent farmers. Humanity’s vital activities needed months (and names for those months) that corresponded to precise and identical weather conditions and seasonal activities (accompanied by rites) year after year.

The invention of the first calendars, which brought lunar and solar cycles back into harmony, signaled the first mental epoch of humanity.

How did humans solve the problem? How, according to the Egyptian expression, did they "bring back together what was growing further apart"?

The "embolism" of the Thirteenth Moon

The fact that lunar cycles fall behind solar cycles by some 11 days means that in three (solar) years the difference adds up to about 30 days. And that would be the right moment to add a thirteenth month to the preceding 12 months.
This insertion of days in the calendar (Greek: "embolismos"), resets the appearances/disappearances of the Moon in "harmony" with the seasons (and Harmonia becomes a mythical figure).

This Thirteenth Moon is the twin of the previous month:

"This year (which ends in the month of Ulûlu) is too short and so the next month will be considered as the second Ulûlu"

(Babylonian text of Hammurabi)

A victory of human thought. This union of celestial cycles that govern life on Earth was the result of human calculations, and is probably represented on the proto-Egyptian "Narmer Palette".

Experience has shown that to obtain a somewhat durable " Harmonia", two additional lunar months have to be added during a cycle of five years.
The importance of these insertions of Thirteenth Moons is that the process imposes the notion of multiyear cycles. And the End of a Cycle and Entry into a New Time should be marked by pilgrimages on land or at sea (Delphic Cycle, Delian Cycle, etc), an evident source of unforgettable sacred images in our collective consciousness.

Throughout the millennia each culture persistently concentrated research on finding increasingly precise multiyear cycles.

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