The last article looked at the second register up of engraved stone R8 (eighth on the right) in the corridor of Gavrinis cairn, 4Km east of Loqmariaquer, which appears to count the 19 years of the Metonic period and mark the 18th year which, plus a little bit, marks the ending of a given of the Saros eclipse period relative to a starting eclipse. Below this register, the first appears to show how the moon's orbit sits on top of the ecliptic (the sun's path within the year) so that every lunar orbit over 18.618 years sweeps out a different range of angles on the horizon at moon rise (or set in the west) according as to which part of the ecliptic it is curently sitting on: it can be above, below or on the ecliptic. When on the ecliptic, it can eclipse the sun or be eclipsed by the earth's shadow and the moon moves so quickly that when the sun is sitting at one of the two crossing points of the moon's orbit, these eclipses are highly likely (even if not visible).
It is therefore true that the Saros period, which is the dominant synchronicity regarding eclipses, is punctuated by actual eclipses which can only occur when the sun is sitting on a lunar node. But the cause of the eclipses, the nodes' locations (opposite each other) on the ecliptic, are forever on the move so as to "orbit" the earth in the 18.618 years of the Draconic period, travelling backwards relative to the planets and sun (i.e. retrograde). The first register of Gavrinis stone R8 appears to provide an explanation about how the moon's orbit sits upon the ecliptic in a variable way that leads to the 18 year saros period within which very similar eclipses recur, delineated in register two.
Register one of R8 is one of the most memorable images of Gavrinis, appearing to show three serpentine lines rising upwards, between lines that limit and demark them.
On the left is a common symbol for counting astronomical periods, a line or monolith with concentric bands. The arrow heads, sitting point down, are symbols of angles and it seems the custom at Carnac for such arrows to indicate specific multiple square geometries and their diagonals. Afour-square suggests, by its diagonal, the first arrowhead, this diagonal similarly angled to the median line of the central of three serpents, shown red as being the equinoctal mean of the sun's extremes in the year. If so then the serpent of the red line does not move except over thousands of years (due to precession).
The left hand serpent (with a blue median) is clearly an opposed sinusoidal-like wave, and the blue line is angled according to the triple square diagonal and left hand serpent median line. The right hand serpent has the opposite character, in phase with the solar serpent, and its vertical median line (coloured green like the triple square) probably borrows from the meaning of triple squares as time-factored structures. The base of a triple square is commonly associated with the eclipse year in length, relative to the (blue) diagonal which would then be the solar year in length.
This motif of serpents therefore appears to express in art
- the opposing nature of the lunar orbit and solar "orbit", causing the moon to peak where the sun's path is on the other side the celestial equator (the red median line).
- the additive nature of the lunar orbit and solar "orbit", causing the moon to peak where the sun's path is on the same side the celestial equator (the red median line).
Today one might introduce the Saros cycle by saying that the lunar nodes move causing eclipses to occur twice within a period less than a year until after 36 + 2 = 38, there have been 223 lunar months, just one lunar year of 12 months short of the Metonic period of 19 solar years. , R8 may have been viewed in the light of the fact that the lunar maxima occur at the extremes of the sun's path to north and south whilst instead the nodes are wherever the moon is known to be travelling on the ecliptic. The search for the mechanism of eclipses is a search for where the moon is not riding above or below the sun's path, but sitting exactly upon it, a circumstance of crossing the sun's path rather than exceeding it or not, on the horizon.
One has to learn to deduce the node's invisible location by studying the location of the moon relative to the ecliptic. Without any sky pointing technologies of measurement, the megalithic horizon event of the moons's rising or setting can indicate whether it is sitting on the ecliptic, if one knows
- which point of the ecliptic the moon should be sitting on (using a lunar simulator) and
- which point of the ecliptic is rising when the moon actually rises (using the circumpolar stars).
If the two points exactly correspond, then the moon is on one of its two nodes.