How can a wood or stone henge be used to track the seasons? Here’s a short video I shot up at Abriachan Forest today where I explain some of the possibilities.
*Abriachan Forest is a Dark Sky Discovery site and one of the best public locations for accessing dark skies in the Highlands.
Look out for a special Star Stories online event for the Winter Solstice.
Changing position of Sunrise from a fixed location over a year
The changing position of Sunrise throughout a year from a fixed location. The further north or south of the equator we live the more extreme our seasonal changes and the bigger shifts we perceive in the sunrise or sunset position during the year. In such harsh and changing seasons it would also have been the more important for ancient cultures to mark the seasons.
Using the landscape to mark the seasons like this is called a horizon calendar. But what if your horizons are flat and featureless, or you require more accuracy, or you’re a powerful priest and wish to theatricise important changes in time?
Then ‘perhaps’ you construct an artificial horizon by placing large stones to mark the progress of the Sun – a henge.
Photo Credit: Zaid Alabbdi
In view of recent developments my contribution to this years Inverness Science Festival will be a free live streamed talk. Please visit my Highland Astronomy facebook page for more details:
Astronomer Stephen Mackintosh will take you back in time to discover how our distant ancestors used the Sun, Moon and stars to track the progress of time and the seasons. Looking at ancient monuments connected to the night sky, we’ll go on a tour of Egypt, Central America, southern England and back home to Scotland where some of the finest concentrations of neolithic structures exist anywhere in Europe, not least the wonderful Clava Cairns. Plus advice on sky watching and naked eye observing you can put into practice yourself.
Note: this event is free and will be live streamed online as part of the Inverness Science Festival’s adjusted programme.
Stephen Mackintosh’s blog: modulouniverse.com
Image by Callanish Digital Design: callanishdigitaldesign.com
The main henge posts are now in place. Markers and smaller posts for the Celtic cross quarter days still to be added.
More progress on the wood henge and Celtic calendar up at Abriachan Forest, with the main posts for the meridian, equinoxes and solstice rise and set positions now in place.
Not quite finished yet. Abriachan plan to sow seeds for next few weeks and let the ground within the perimeter settle.
Descriptive marks for the main posts and small posts for the Celtic Cross Quarter days Imbolc, Lammas, Samhain and Beltane will be added later.
In addition to tracking the Sun and measuring the solar year, we can use the henge during the stargazing programme to record the rising of new seasonal constellations in the East and rough measurements of the transit altitudes (due south) and azimuth positions of the stars.
We also had a great kick off to the Star Stories program last night with ancient astronomy learning, storytelling and activities for the young ones.
The next event will be Nov 23rd with guest astronomer and author Steve Owens (aka Dark Sky Man). Booking links will go up shortly.
I had a fun afternoon surveying the markers in preparation for the final Wood Henge up at Abriachan Forest.
The final construction will mark the meridian from north to south, the equinoxes, mid summer and mid winter rising and setting positions of the Sun. Between the main solstice posts we’ll eventually place markers for the ancient cross quarter days, or Celtic Wheel of Time.
A simple henge like this can track the solar year, lunar rising positions and the changing constellations in the night sky.
With Abriachan Community
Looking south west from inside the north east cairn at Clava
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.
Sun rays striking the winter solstice aligned passage.
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.
My daughter Violet standing in the sunlight directed down the main passage of the north east cairn.
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.
The two main passage cairns at Clava have south westerly mid winter sunset alignments.
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.
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