Researchers at the Nottingham Trent University have gathered new evidence that a 4000-year-old monolith was aligned to be an astronomical marker. The 2.2 meter high monument, located at a ridge called Gardom's Edge in the Peak District National Park (Derbyshire, England), has a striking, right-angled triangular shape that slants up towards geographic south. The orientation and inclination of the slope is aligned to the altitude of the Sun at mid-summer. The researchers believe that the monolith was set in place to give symbolic meaning to the location through the changing seasonal illuminations. Dr Daniel Brown presented the findings at the National Astronomy Meeting in Manchester.
     The researchers have carried out a microtopography survey of the surface surrounding the monolith. Their findings indicate the presence of packing stones around its base, evidence that the pillar was placed carefully in position. They have also carried out 3-D modelling of illumination of the stone through the seasons, adapting for changes in Earth's tilt to the ecliptic plane over four millennia. The landscape surrounding the stone harbors many ancient monuments such as Bronze Age roundhouses, a late Neolithic enclosure, and other traces of a long lasting human occupation. The researchers believe that the stone is also late Neolithic, set in place around 2000 BCE.
     "Through our survey, we have found a higher density of packing stones on one side, supporting the case that the stone has been orientated intentionally," said Dr Brown.
The 3-D modelling showed that the slanted side of the stone would remain in permanent shadow during the winter, while it would have been illuminated only in the morning and afternoon during most of the summer. At midsummer, the sun would have lit the stone brightly all day. The researchers are currently backing up the model by gathering contemporary photographic evidence of the stone.
     "The stone would have been an ideal marker for a social arena for seasonal gatherings," said Dr Brown. "It's not a sundial in the sense that people would have used it to determine an exact time. We think that it was set in position to give a symbolic meaning to its location, a bit like the way that some religious buildings are aligned in a specific direction for symbolic reasons."
     The monolith's triangular shape and flat, north-facing side are just some of the reasons scientists think it was positioned to mark changing seasons. "The use of shadow casting in monuments of this period is quite rare in the British Isles," said Dr Brown. "But there are some examples including New Grange, Ireland, and some Clava cairns in the north-east of Scotland that have been proposed to include the intentional use of shadows. Both are associated to burial sites using the symbolism of a cyclic light and shadow display to represent eternity. Given the proximity of the Neolithic enclosure and possible ritual importance of this site, the Gardom's Edge monolith could be another such example."
     The researchers hope that the new evidence will support the case for a wider archaeological survey of the site.

Edited from ScienceDaily, MSNBC (27 March 2012), Past Horizons (3 April 2012)