The main image shows the beautiful twin spirals of kerb stone 67 (K67) at Newgrange, one of just three lavishly decorated kerb stones (out of 97!) that encircle the 5,200-year-old monument like a giant belt.
The spiral is dominant in the megalithic art of Brú na Bóinne, and the triple spiral (triskele) is found only at Newgrange (on K1 and in the chamber - third image) and no other Irish monument. What does the spiral represent? We cannot know with any certainty, but it may relate to the seasonal movement of the sun from solstice to solstice. At the latitude of Newgrange (53° 41' north), there is a huge variation in the height of the sun's daily apex in the sky between summer and winter.
The movement of the sun from solstice to solstice. (Image credit)
Looking at the diagram, we see that the sun creates a sort-of "half spiral" in the sky as it rises in the east and sets in the west each day over a six-month period between the solstices. It moves in a series of growing (between winter and summer) and contracting (between summer and winter) arcs in the sky. If we imagine that these arcs are completed beneath the horizon, what we really have is a spiral!
The fascinating thing about the conjoined spirals of K67 is that they are both "clockwise" spirals – i.e. they can both be seen to wind outwards from the centre in a clockwise direction. This SUGGESTS (note: we cannot be sure about any of this) that the spirals may represent the growth of the sun in the sky AFTER winter solstice, in other words, in the days and weeks following its spectacular illumination of the inner chamber of Newgrange.
The triple spiral (triskele) carving on a stone inside the chamber of Newgrange. Get your own print or mounted print of this image here.
The mythology of Newgrange suggests that it was built by The Dagda, a chief of the Tuatha Dé Danann, the prehistoric gods, and it was he who controlled the weather and the harvest. He made love with Bóinn (goddess of the Boyne) at Newgrange and in order to allow this to happen, they made the sun stand still in the sky.
Thither came by chance the Dagda
into the house of famous Elcmaire:
he fell to importuning the woman:
he brought her to the birth in a single day.
It was then they made the sun stand still
to the end of nine months – strange the tale –
warming the noble ether
in the roof of the perfect firmament.
(From the Metrical Dindshenchas).
This would appear to be a mythological depiction of the midwinter illumination of the interior of Newgrange (Síd in Broga), because that occurs at the time of winter solstice, when the sun is "standing still" (i.e. not moving on the horizon from day to day). Amazing stuff.