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Astronomy is returning to Callanish on the Isle of Lewis, midway through the island’s two week Hebridean Dark Skies Festival, 5,000 years after the stone circle was built to observe the heavens.
On Thursday February 17, Stephen Mackintosh of Highland Astronomy hosts a stargazing event at Calanais Visitor Centre, by the ring of standing stones erected 2,000 years before Stonehenge, most likely as an astronomical observatory.
‘The most attractive explanation,’ writes Patrick Ashmore, who excavated Calanais, on the Historic Environment Scotland website, ‘is that every 18.6 years, the moon skims especially low over the southern hills. It seems to dance along them, like a great god visiting the Earth. Knowledge and prediction of this heavenly event gave earthly authority to those who watched the skies.’
The Neolithic monument, shaped like a cross with avenues leading to the central circle, was likely constructed around 3000 to 2900 BCE, and was rediscovered in the 19th century buried deep in peat, which accumulates in the area at one foot per century.
Australian researchers found statistical proof in 2016 that the oldest great circles in Britain – at Callanish and one in the village of Stenness on the Isle of Orkney – lined up with the movements of the Sun and the Moon.
The team at the University of Adelaide discovered the sites shared astronomical and landscape cues also found at smaller Bronze Age sites built more than 1,500 years later, on the nearby islands of Coll, Tiree, and Mull.
These cues include the fact that the water occurred in the south, and that the northern horizon was the closest, while the southern horizon was the most distant. The highest points of the horizon were marked by distinct mountains or hills, and the summer and winter solstitial Sun and standstill Moon tended to rise out of, and set into, these high points.
Using 3D landscape reconstructions, they calculated the likelihood of the monuments being astronomical was above 97.87 per cent for Stenness, and 97.87 per cent for Callanish. The evidence suggests that 5,000 years ago, the ancient people of Scotland managed to weave the sky and the land together in their stone circles to reflect the complex movements of the lunar and solar cycles.
If you visit at just the right time (every 18.61 years) you will see the moon rising above a symbolic point in a ridge called the Old Woman of the Moors (Cailleach na Mointich), said to represent a sleeping woman, before passing perfectly between the stones some hours later.
Tour guide Margaret R. Curtis saw this awe-inspiring display in 1987, and described it: ‘For three minutes…the moon was captured in an artificial frame of megaliths, and the cold grey pillars of stone were bathed in a golden glow… Like a lighthouse beam, the moonlight stretched down along the avenue towards us and caught us in its light.’
Catherine Heymans, Astronomer Royal for Scotland, said: ‘I’m delighted to join the 2022 Dark Skies Festival in celebration of one of the Hebrides’ most famous natural resources – its pristine dark view into the wilderness that is our Universe. With music, art, theatre, comedy and science there is something for everyone to enjoy whilst we wait for the Sun to set and the clouds to clear, to stargaze out into the cosmos.’
Festival director Andrew Eaton-Lewis said: ‘Even if the weather is against us, we’ll be offering another packed line-up of indoor events, exploring astronomy, the night sky, and our relationship with darkness.’