Lunation Calendar

There's usually one fully sunlit moon per month. Yesterday a second full moon appeared before July ceded our days to August.

Full Moons of July 2015

An occasional extra full moon is a function of the astronomical regularity of lunation and the papally decreed Gregorian Calendar introduced by Pope Gregory XIII in 1582.

Lunation - One lunar cycle with average duration of 29.53 days.

Our word moon comes from the Old English word mona.

"Even the word month is likely derived from the word moon and an Indo-European word, mê, which means to measure."
— Howard Markel

By measuring diurnality from the dark new moon to the sunlit full moon, our ancestors developed monthly calendars. Religious rituals like the Christian Easter were dutifully computed and observed around predictable lunar cycles. The Islamic calendar is purely lunar. The Christian Gregorian calendar is quasi-lunar.

Widely adopted, the Gregorian calendar has 12 months in a year. By comparison there are 12.37 lunations per year.

365.24 days/year ÷ 29.53 days/lunation = 12.37 lunations/year

The Gregorian calendar has exactly 12 months in a year, so an accumulation of .37 lunations occurs each Gregorian year. The accumulations of fractional lunations beyond the counting number 12, accounts for the occasional extra moon in a year.

An extra moon, whether considered over the time frame of a year, or over a season, or over a month, is colloquially called a blue moon to signify its rarity.

The blue moon isn't really an extra moon or blue in color, rather it follows as a side effect from a human construct of time - the Gregorian calendar.

Moon and Antelao

Image: Marcella Giulia

“Her antiquity in preceding and surviving succeeding tellurian generations: her nocturnal predominance: her satellitic dependence: her luminary reflection: her constancy under all her phases, rising and setting by her appointed times, waxing and waning: the forced invariability of her aspect: her indeterminate response to inaffirmative interrogation: her potency over effluent and refluent waters: her power to enamour, to mortify, to invest with beauty, to render insane, to incite to and aid delinquency: the tranquil inscrutability of her visage: the terribility of her isolated dominant resplendent propinquity: her omens of tempest and of calm: the stimulation of her light, her motion and her presence: the admonition of her craters, her arid seas, her silence: her splendour, when visible: her attraction, when invisible.”
― James Joyce, Ulysses

REFERENCES

• Astronomy Photo of the Day: 7/31/15 — Antelao Moon, Posted By Jaime Trosperon 31 July 2015.
• Blue Moon, Wikipedia.
• Science Diction: The Origin Of The Word ‘Moon’, Science Friday, 20 January 2012.

June of Every Calendar

In one full rotation of the earth, we observe the appearance and disappearance of sunlight. The diurnal cycle of the earth is one of many reoccurring patterns by which we experience time. We also experience time by witnessing seasonal changes and by observing life cycles.

Physicists and cosmologists have long puzzled over the nature of time.

Turning the calendar page of June, I am struck by the artificiality of time. In Snake River Overlook, I write of Ansel Adams' photograph of the Snake River flowing south past the Tetons that it's the:

"June of every calendar"

The Tetons and the Snake River, 1942.
Ansel Adams, 1902 – 1984

The subject, quality of light, and composition of Adams' grand image strikes a universal chord. Like the predictable cycles of sunlight, or the predictable ticks of a metronome, Adam's dramatic image is memorable enough to become popular iconography.

“Green was the silence, wet was the light, the month of June trembled like a butterfly.” ― Pablo Neruda, 1904 – 1973.

Like clocks, calendars are a relatively recent invention that give us analogs to diurnal and seasonal events. We mark time by calendars. Calendars and clocks name and objectify what we can sense with less precision. Clocks and calendars allow us to attend to time and arrive at appointments at the appointed time.

Time is like months rendered in panels. Which panel is June? Is it the panel behind, the panel ahead, or both?

Pine Trees (ink on six folded screens)
Hasegawa Tōhaku, 1539 - 1610

Time is a voyage of moments. Moments are neither discrete or continuous. It is time that affords us the distance to mark milestones, but perhaps more urgently, it is time that gives us the space for discovery.

“The real voyage of discovery consists not in seeking new landscapes, but in having new eyes.” ― Marcel Proust