In: Physics
Henges may have been used for rituals or astronomical observation rather than day-to-day activity. That their ditches are located inside their banks indicates that they were not used for defence, and that the barrier of the earthworks was more likely symbolic than functional. Following arguments presented for Irish Iron Age enclosures, Barclay suggested that they are 'defensive': that the ditch and bank face something 'dangerous' inside the enclosure. He has also suggested that the considerable range of things surrounded by the earthworks, and the very long date range, are because henges were designed mainly to enclose pre-existing ceremonial sites that were seen as 'ritually charged' and therefore dangerous to people. It has been conjectured that whatever took place inside the enclosures was intended to be separate from the outside world and perhaps known only to select individuals or groups.
The alignment of henges is a contentious issue. Popular belief is that their entrances point towards certain heavenly bodies. But henge orientation is highly variable and may have been more determined by local topography than by desire for symbolic orientation. Statistical analysis showed that Class I henges have a slight tendency to have an entrance set in the north or north-east quarter. Class II henges generally have their axes aligned approximately south-east to north-west or north-east to south-west.
It has been suggested that the stone and timber structures sometimes built inside henges were used as solar declinometers to measure the position of the rising or setting sun. These structures do not appear in all henges and when they do, often they are considerably more recent than the henges. Thus, they are not necessarily connected with the henge's original function. It has been conjectured that they could have been used to synchronize a calendar to the solar cycle for purposes of planting crops or timing religious rituals. Some henges have poles, stones or entrances that indicate the position of the rising or setting sun during the equinoxes and solstices, while others appear to frame certain constellations. Additionally, many are placed so that nearby hills either mark or do not interfere with such observations. Finally, some henges appear to be placed at particular latitudes. For example, a number are placed at a latitude of 55 degrees north, where the same two markers can indicate the rising and setting sun for both the spring and autumn equinoxes. But as henges are present from the extreme north to the extreme south of Britain, their latitude could not have been of great importance.
Formalisation is commonly attributed to henges: indications of the builders' concerns to control the arrival at, entrance into, and movement within the enclosures. This was achieved by placing flanking stones or avenues at the entrances of some henges, or by dividing the internal space with timber circles. While some henges were the first monuments to be built in their areas, others were added to already important landscapes, especially the larger examples.
The concentric nature of many of the internal features, such as the five rings of postholes at Balfarg or the six at Woodhenge, may represent a finer distinction than the inside-out differences suggested by henge earthworks. The ordering of space and the circular movement suggested by the sometimes densely packed internal features indicates a sophisticated degree of spatial understanding.