Ancient stone monuments may have been used for mysterious night-time ceremonies, archaeologists believe, after finding that some rock carvings only appear in moonlight.
Traditionally Neolithic structures were believed to align with the movements of the Sun, with the huge Wiltshire circle of Stonehenge lining up perfectly with the summer solstice.
But a new investigation of the stone age engraved panel Hendraburnick Quoit in Cornwall by Dr Andy Jones, found nearly 10 times the number of markings when viewed in moonlight or very low sunlight from the south east.
They also discovered that pieces of quartz had been deliberately smashed up around the site which would have glowed in the dark under moonlight, or firelight, creating a gentle luminescence.
Dr Jones, of the Cornwall Archaeological Unit said: “I think the new marks show that this site was used at night and it is likely that other megalithic sites were as well.
“We were aware there were some cup and ring marks on the rocks but we were there on a sunny afternoon and noticed it was casting shadows on others which nobody had seen before.
“When we went out to some imaging at night, when the camera flashed we suddenly saw more and more art, which suggested that it was meant to be seen at night and in the moonlight.
“Then when you think about the quartz smashed around, which would have caused flashes and luminescence, suddenly you see that these images would have emerged out of the dark.
“Stonehenge does have markings, and I think that many more would be found at sites across the country if people were to look at them in different light.”
Hendraburnick Quoit is a large propped ‘axe-shaped’ stone that was set upon a low platform of slates on Hendraburnick Down, near Davidstow. Dr Jones believes it was dragged up from the valley below to act as a ritual marker for a sacred site in the Late Neolithic or Early Bronze Age, around 2,500BC.
Previous studies had recorded 13 cup marks on the rocks but Dr Jones and colleague Thomas Goskar found 105 engravings when he started to look under new light, making it the most highly decorated and complex example of rock art in southern England.
Writing in the archaeology journal Time and Mine, and Dr Jones and Mr Goskar conlcude: “As in many cultures where darkness is associated with the supernatural and the heightening of senses , it is possible that some activities at Hendraburnick Quoit may have been undertaken at night.
“Quartz has luminescent properties and reflects both moonlight and firelight
“Given that human eye perceives colour and shade quite differently at night than by daylight and the art would have been visible in moonlit conditions, the smashed quartz at Hendraburnick could have been used as part of night time activity on the site in order to ‘release’ the luminescent properties of the quartz around the monument and ‘reveal’ the art in a particular way.
“After the ritual, the broken pieces, once they had fallen on the ground, could have effectively formed a wider platform or arc which would have continued to glisten around it in the moonlight, and thereby added to the ‘aura’ of the site.”
Smashed up quartz pieces discovered at the Early Bronze Age cairn at Olcote near Calanais, on the Isles of Lewis are thought to be linked with funerary and lunar rites.
The new research was published in the archaeology journal Time and Mind.