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Christmas Day 2021 - The Turning of the Tide, some Lunar Observations

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Howl at the Moon

Irish Marine Wildlife log

The Turning of the Tide - Bob Mould


The Tides of Life: How our lifespan is linked to the diurnal turning of the tides - the ebb and flow of life, from ebb tide to full tide to ebb tide again

Shakespeare had this to say about the ebb and flow of life:
"There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
On such a full sea are we now afloat,
And we must take the current when it serves,
Or lose our ventures."
[Brutus to Cassius in the Shakespearean drama "Julius Caesar"]

Many years ago, in Dún Chaoin, the village in West Kerry where I lived, an old woman said to me on my 33rd birthday - "Tá tu ar barr an taoide anois, a buachall! Ach cogair! Ni fada go mbeidh an taoide ag casaadh!" [ "You are at high water noiw, my boy! But be wary! It won't be long before the tide turns again!"]

Máire was a close relative of the famous Peig Sayers, the Blasket Island story teller whose oral story-telling was written down in "Peig. A Schéil Féin" [ Peig Sayers: Reflections of an Old Woman]. All the Blasket Islanders at that time spoke beautiful Homeric Gaelic [Irish language] which was both poetic and full of metaphors as above, mostly derived from nature and the sea and the turning of the tides and the seasons. But this particular mention of my age and co-relation with the height of the tide has always left a deep impression on me and how closely connected our lifespan is in relation to the periods of the tides.

                              The Rule of Twelfths and our Lifespan 

The Rule of Twelfths for tidal periods, in areas with tidal sine curves with regular diurnal or semi-diurnal tides, goes as follows:
Low Water (Slack water)
*1st hr. of flood - 1/12 of strength (flow or height)
2nd hr. of flood - 2/12   
3rd hr. of flood - 3/12
4th hr. of flood - 3/12
5th hr. of flood - 2/12 
6th hr. of flood - 1/12
High Water (slack water)
1st hr. of ebb - 1/12
2nd hr. of ebb - 2/ 12
3rd hr. of ebb - 3/12
4th hr. of ebb - 3/12
5th hr. of ebb - 2/12
6th hr. of ebb - 1/12
Low Water (slack water)
[* 1 hr. segments for areas with semi-diurnal tides (two high water and two low water per day) and 2 hr. segments for areas with diurnal tides (one high water and one low water per day)].

Some Tidal facts and other items of Celestial Interest

The Rule of Twelfths can also be used to calculate approximately the duration of daylight for any given day from one solstice to another, if one knows the times of sunrise and sunset at either end.
The Rule of Twelfths assumes that the tides are semi-diurnal or diurnal, corresponding to the sine curve (which is not always the case at different locations on the earth, depending on the local geography and bathymetry) and also that the time between high water and low water is 6 hrs. But this is not always the case and the ebb period between high water and low water can be "stretched", with the result that the flood tide is usually stronger than the ebb tide and also the times of the tides vary every day.
"Spring Tides" ["King Tides"] occur at new moon and full moon when the tides "spring forth" and the term has nothing to do with the seasonal expression of Springtime - apart from the fact that it is also the time when animals and plants "spring forth". New Moons occur when the moon is aligned directly between the earth and the sun and full moons occur when the earth lies directly between the moon and the sun. During these periods the gravitational pull of both the sun and  the moon acting together cause the tides to bulge on the surface of the ocean facing them, which results in either your boat hanging off the quay wall if you have not allowed enough slack on your mooring ropes for the drop of the tide or bringing your bucket and spade with you to the beach to build sandcastles and finding no sand but only seawater on a full Spring tide.
Our moon was formed about 4.5 billion years ago from dust and debris that coalesced after a large Mar's sized celestial body hit the proto-earth a glancing blow, tilting it 23.5 degrees, thus eventually creating our seasons. Life on earth, from the beginning, is the result of an incredible amount of coincidences and random "goldilocks" experiences like the above celestial collision.

The normal duration of the tidal cycle from low water to high water and back to low water again is 12 hrs. and 25.2 minutes which is half a lunar day, a full lunar day is thus 24 hrs. and 50.4 minutes. This is due to the fact that the moon is orbiting the earth in the same direction as the earth is rotating on its axis and the time of moonrise is consequently 50.4 minutes later every day.

Due to the elliptical orbit of the moon around the earth it exerts its greatest gravitational pull on the earth at "perigee" when it is closest to the earth in its orbit and the least gravitational pull at "apogee" when it is furthest away. Further more, if the phase of  the moon at full or new moon coincides with "perigee" we get a "super moon". The closest the moon gets to the earth at "perigee" is 360,000 km. / 224,000 miles and the furthest away it gets is 405,000 km / 251,655 miles. These are not vast distances ( I have bigger mileage on the odometer of my car!) and so it is easy to see how the moon exerts such influence on the earth and all of its inhabitants. This is particularly so in the intertidal zones where the lunar cycle has a major influence on all marine organisms. Many of the marine animals and organisms of the intertidal zone have adjusted their life cycles and physiology in sync with the daily and monthly tidal movements and as this zone is the original birthplace of the ancestors of all terrestrial animals on earth there are still traces of this daily and / or monthly synchronization in the physiology of lots of existing terrestrial animals, including ourselves.

The moon, and the full moon in particular, also exerts a great influence on human beings  who are composed of about 60% water overall, with some organs like the brain, heart, lings, kidneys and muscles containing over 70% water. The word "lunatic" comes from the Latin word - "luna" - for the moon, and the extra pull of gravity from a new or full moon in particular may influence our brain causing mood swings like aggressiveness, unpredictability, sleeplessness etc and may also affect the delicate balance of the fluid behind our eardrums causing a feeling of imbalance..

The period of the full moon, know as the "white moon cycle" is regarded as a fertile period by horticulturists and farmers for sowing and it has been shown in a Japanese study that many women ovulate at full moon and that there may be remnants of a moon menstruation synchronization from our distant evolutionary past. The female menstrual cycle for a  mature female is almost exactly the same length as a lunar month (29.5 days) which may point back to the fact of a common marine ancestry for all animals, including humans.

All of this makes for a very interesting comparison when comparing the complete period of the tidal cycle to one's own lifespan.

Life Expectancy given "High Water" at 33 yrs. of age, as per Máire.

If we take Máire's expression re "Barr an Taoide" at face value (which seems like a fair proposition!) then a man of 33 yrs. is at the height of his tide, so to speak. Using this as a reference point we can now re-tabulate the Rule of Twelfths for a human lifespan but taking into account that the period from high water to low water is "stretched" by an unknown amount (t) but not greater than 1/12.
Here is the sine curve of our lifespan plus (t) for H.W. at 33yrs. as per Máire, and H.W. at 35 yrs. which some may think is more appropriate!
                                          Low water [Birth]
H.W. at  33yrs                                     H.W. at 35 yrs.
1st hr. of flood - 2.75 yrs.                     1st hr. of flood - 2.91 yrs.
2nd hr. of flood - 8.25 yrs.                    2nd hr. of flood - 8.751 yrs. 
3rd hr. of flood 16.50 yrs.                     3rd hr. of flood - 17.502 yrs.
4th hr. of flood - 26.75 yrs.                   4th hr. of flood - 26.253 yrs.
5th hr. of flood 30.25 yrs.                     5th hr. of flood - 32.087 yrs.
6th hr. of flood 33.00 yrs                      6th hr. of flood - 35.004 yrs.
                                     High Tide - Barr an Taoide!
1st hr. of ebb - 35.75 yrs.                     1st hr. of ebb - 37.921 yrs.
2nd hr. of ebb - 41.25 yrs.                    2nd hr. of ebb - 43.755 yrs.
3rd hr. of ebb - 49.50 yrs.                     3rd hr. of ebb - 52.506 yrs.
4th hr. of ebb - 57.75 yrs.                     4th hr. of ebb - 61.257 yrs.
5th hr. of ebb - 63.25 yrs.                     5th hr. of ebb - 67.091 hrs.
6th hr. of ebb - 66.00 yrs.                     6th hr. of ebb - 70.925 yrs.
+ (t) (2.75 yrs.) - 68.75 yrs.                   + (t) ( 2.917) - 72. 925 yrs.
                                     Low Water  [Death!]

Either of these two results may seem a little at odds with official 2021 figures in Ireland for life expectancy which are 78.4 yrs. for men and 82.8 yrs. for women [ Life Expectancy - CSO - Central Statistics Office, Ireland] but in western societies most people approaching or over 70 yrs. are often under some form of life-saving medication or have undergone some form of life-saving or life enhancing operation in order to artificially extend and enhance their natural lifespan. Whether this is morally justifiable in a world that is over populated and where life expectancy is far from uniform between so called "developed economies" and "third world" countries is highly debatable.
Interestingly, if you take the country with the highest overall life expectancy which is Japan at 85 yrs. combined (men and women) life expectancy, and the Central African Republic with lowest combined life expectancy at 53 yrs,, the average median life expectancy age between the two extremes comes to 69 yrs. which is almost exactly the result of our calculations by the Rule of Twelfths using Maire's data of "Barr an Taoide"!
Of course, there are naturally long-lived exceptions to predicted life expectancy tables and statistics, just as we have exceptions and higher than expected storm  and tidal surges in our oceans, which are not predicted in our tide tables..

You can interpolate these figures based on the data that you input. Just as you have to know the time of sunrise and sunset at each different solstice to calculate the duration of daylight on any given day, so too in this case if you do not accept Máire's interpretation of the time of your own maximum high water (33yrs.) you can invent your own personal maximus and then you can calculate the approximate time of your own personal demise based on the Rule of Twelfths.

One thing is for sure. You will never think of the ebb and flow of the tide again without thinking of your own mortality, and possibly calculating your own predestined demise, and sadly, whatever the outcome of your calculations, you will never be able to turn back the tide and you can never cheat death!


                                Twenty Years A-Growing by Maurice O'Sullivan

Calculating the span of a man's life also seems to have been a preoccupation of Blasket island writers as expressed by this four-line poem which gives the title to Maurice O'Sullivan's wonderful book about his childhood on the Great Blasket Island.
"Fice blian ag fás.
Fice blian faoi bhláth,
Fice blian ag cromadh,
Fice blian ar meathlú     "
His uncle asks the young Maurice:
"Did you never hear how the life of a man is divided?"
"Twenty years a-growing,
Twenty years in blossom,
Twenty years a-stooping,
Twenty years declining".

The four fold division of man's lifespan by the Blasket Islanders seems to be based loosely on the turning of the four seasons (rather than the tides) of Spring, Summer, Autumn and Winter, although the period a-stooping from age 40yrs. to 60 yrs. and "declining" from age 60 yrs. to 80 yrs. seems a bit excessive, even if compensated for by extra longevity! In the spoken Gaelic of the Blasket Islanders there  was no single word for the age 40 yrs., 60 yrs.  and 80 yrs. and instead of using the numerals "daichead" (40), "seasca" (60) and "ochtó" (80) when referring to age they said "dha ficid blian", "trí ficid blian", "ceithre ficid blian " meaning literally "twice twenty years", "three times twenty years", "four times twenty years". Blasket Islanders literally thought in four seasonal lifetime cycles of twenty years each, rather than in linear annual years.

Blasket islanders did normally live to a ripe old age, if not cut down by some disease or accident - like a drowning or falling off a cliff - and despite, or possibly because of their simple diet, they often lived into their eighties like the O' Dalaigh man who refused to leave his home on the Inish [Inish Vickillaun - one of the outer Blasket islands] when his family moved back to the main island of the Great Blasket and he stayed on the island well into his eighties, only provisioned with " a goat, a bag of flour and a stack of turf" for the winter months.

Perhaps he knew that his allotted "Twenty years declining" was coming to an end and despite what he would do, or where he would go, he would not be able to turn back the tide.

We started these musings on the turning of the tide and life with a quotation from Shakespeare and perhaps it would be fitting to end with "Requiem" by the Scottish writer Robert Louis Stevenson [1850 - 1894] written on his gravestone in his new home overlooking the sea in Mount Vaea, Samoa where he spent the last four years of his life -

"Under the wide and starry sky,
Dig the grave and let me lie.
Glad did I live and gladly die,
And I laid me down with a will.

This be the verse you grave for me:
Here he lies where he longed to be;
Home is the sailor, home from the sea,
And the hunter home from the hill""

Log of the Whale Watching Tour Boat M.V. "Blasket Princess"

Christmas Day, 2021        Captain Whales Galore

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