Astronomy and Stonehenge: almost everyone has heard of this connection, so that Stonehenge is for us an almost obligatory starting point. Stonehenge belongs to an historical period, the Neolithic of Northern Europe, during which a great number of megalithic monuments were constructed. The most simple architectural unit of Megalithic people was the single standing stone, also called the menhir. Menhirs are found in isolated positions, or arranged in rows, in some cases numbering hundreds, as is the case in the famous alignments of Carnac in Brittany. Menhirs were also used to form stone circles, rectangles, and oval-shaped rings. The second architectural expression of megalithic building is the dolmen, a structure consisting of two standing stones supporting a huge lintel, normally used for burials. The dolmen principle was also utilised in building more complex tombs, the passage graves, comprising a corridor of standing stones roofed with huge slabs and ending in one or more chambers. In most cases these structures were covered by an earth mound. Another typical structure where the menhir is the fundamental unit is the so-called henge: a stone circle surrounded by a ditch enclosed in a bank earthwork. As Stonehenge indeed has its own ditch-bank enclosure. However, and contrary to the other henges, the stones of the circle are assembled in a special manner, which resembles a wooden construction which has been built in stone. The monument is located on the Salisbury Plain in Wiltshire, England. What we see today is what remains of a long process of successive stages of construction, and also of afterthoughts, because the disposition of some megaliths was changed during the centuries. The first monument was a big ditch-bank surrounded by pits – the so-called Aubrey holes - which perhaps contained timbers. In a second phase, the builders abandoned timber in favour of stone, and put in place relatively small megaliths, weighing 4-5 tons each. Many such stones however, of a quality called bluestone, were transported from as far away as 240 kilometres, from the Preseli Hills, Pembrokeshire, Wales. Already during this first megalithic phase, the stone ring had a north-eastern entrance, and a couple of monoliths located outside the entrance, of which only the so-called Heel Stone remains. With the later phase, the monument changed again. The decision was taken to bring to the site many enormous “sarsen” stones, of a type quarried some 40 kilometres to the north. These megaliths were erected accordingly to quite a complex architectural plan, based on a continuous circle ring enclosing a structure usually called horseshoe. It consists of five free standing trilithons arranged in a horseshoe shape; the symmetry axis is aligned with the northeast entrance axis. What inspired the design of this complex and unique structure? It is difficult to escape the idea that the Stonehenge outer stone circle was meant to suggest a sphere. The interpretation of the horseshoe is difficult, although clearly the idea of some kind of holy of holies comes to mind. There is however, no written evidence coming from the Neolithic, so that any discussion on what Stonehenge was used for or why it was constructed must remain, at least in part, speculative. In spite of this, some messages have undoubtedly been written at Stonehenge using the language of stars and stones, and we can use Archaeoastronomy to read them. In fact the original axis of the monument points – from the inside looking out – to the rising Sun at the summer solstice. The spectacle of the Sun rising at Stonehenge at midsummer is still quite awe-inspiring today. So Stonehenge is a crystal-clear example of an astronomically oriented building. But why? The solar cycle is naturally marked by the two solstices, and usually these two days, and in particular the winter solstice, were associated by ancient cultures with concepts of renewal and rebirth. Stonehenge in itself was not isolated, it was part of a “hub” of monuments - perhaps a Neolithic pilgrimage centre - some of which are still to be excavated. The approach to Stonehenge occurred along the Avenue, an ancient road made out of a parallel pair of ditches which comes from the nearby River Avon, and the horseshoe appears as the final section of a symbolic path, or the procession to a temple. Perhaps it was a place devoted to the ancestors and to the dead: Stonehenge, built in eternal stone, was connected to the west, where the Sun sets, and had a wooden counterpart, today nicknamed Woodhenge, towards the east, and the world of the living. The horizon to the west is flat so the axis of the monument is also oriented to the winter solstice sunset, from outside looking along the Avenue. Perhaps this was the primary orientation. The spectacle of the Sun disappearing amidst the ordered ensemble of giant stones at winter solstice is equally fascinating as that visible at the summer solstice. A connection of other Stonehenge megaliths, the so-called station-stones, with the extreme positions attained by the Moon at the horizon is also likely to be non-casual. In any case, it is important to put in evidence that Stonehenge was not a high-precision astronomical instrument, and even less a computer to predict eclipses, as claimed many times in the past. The fascinating astronomical information it carries on to us rather refers to the symbolic world of its builders.
