As a family we have a yearly tradition of heading out for a longish walk on Christmas Eve. We usually park up somewhere remote in the van, make some bacon rolls then head out along a forest trail or up a local hill. This year we decided to see if we could catch the setting Sun at Clava Cairns, a beautiful bronze age site located only a mile or so from Culloden battlefield near Inverness.
During my astronomy outreach I’ve given quite a few talks referencing Clava Cairns in relation to the fascinating subject of ancient astronomy. Often wild speculations are made about many prehistoric sites, in particular Stonehenge, with dubious claims of alignments to stellar constellations or complex planetary cycles. But one thing is almost universally agreed by archaeologists and astronomers alike, that many of these ancient structures were configured to mark the passage of the solar year.
In Clava’s case, both main passage cairns have mid winter setting sun alignments facing towards the south west, such that for several days either end of the shortest day, the light from the setting Sun will shine down the central passage and light up the interior of the structure.
Of course it’s one thing to read second hand accounts of this phenomena, and quite another to experience them first hand. As luck would have it, when we approached the site around 3.30pm the Sun was clearly visible and just setting in the south west, allowing us to witness this amazing spectacle and to capture some photographs.
From inside the north east cairn, closest to the main entrance of the site, the passage was already brightly washed over with sunlight. I was curious to determine if the sun’s position was low enough to light the passage when it was originally covered over (several thousand years ago), so crouched down within the passage to take some of my shots. Sure enough, the rays of the Sun could be directly sighted down the camera lens.
The motivation for the astronomical alignment of these structures is still the topic of heated debate amongst historians and archaeologists, but one thing residents of the north of Scotland can appreciate first hand is the depressingly short days and long hard winters we experience at this time of year. Some sort of large scale and perhaps communal confirmation that the south westerly extreme of the winter sunset (and its associated low midday elevation) had been reached would have been very reassuring to early agricultural societies.
It’s this concept of the Sun both halting its low elevation in the south at midday and the most southern extreme of its setting and rising positions that gives rise to the word Solstice – ‘sol ‘ sistere’ meaning Sun standstill. The reverse applies during mid summer when the sun rises and sets at its most extreme positions to the north of east and west, and reaches its highest elevation at midday.
There are some researchers who go much further, and point to alignments between the stones at Clava Cairns with the Celtic cross quarter days and the more complex dynamics of major and minor lunar standstills. Whilst these may be true it should also be remembered that it only takes two points to make a straight line! As ever we need to be cautious with our wish to believe, and back everything up, where possible, with evidence.