Apart from observing the Avebury landscape from aesthetic and purely visual perspectives (see the ‘Selected Visual Observations’ pages), the investigators also looked at aspects of the monuments and topography from more analytical angles – specifically concerning sightlines, new solar astronomy at Avebury, and simulacra.
Sightlines within the core Avebury Complex landscape were examined in order to revisit and confirm by direct field observations findings made by one of the investigators several years prior to the Landscape and Perception project. These sightlines allow exploration of the relationships between the Avebury monuments and between the monuments and the surrounding topography, the ‘lie of the land’. (This work is to some extent preliminary, and would be extended if a larger project can be resourced.)
The study focused on Silbury Hill, standing as it does fairly central within the core landscape. The great mound acts like the hub of a wheel whose rim is formed by the nearest surrounding major monuments, some possibly contemporary with the mound, and others earlier. When viewed from each of these monuments the profile of Silbury Hill is intersected by the distant skyline between the flat summit and the weathered ledge.
Viewed from West Kennet Long Barrow, the skyline to the north is formed by Windmill Hill, and this intersects the profile of Silbury Hill at about the same height as the weathered ledge. This observation is possible only from the western tip of the long barrow, and it is significant that this part was an extension that had been added onto the barrow – perhaps around the time Silbury was being built. This sightline provides a visual connection between one of the oldest monuments, West Kennet long barrow, and the ancestral Windmill Hill, and associates these sites with the awesome "new" monument of Silbury in between.
Observations of Silbury made at other times from the other key monumental sites in the heart of the complex, namely, East Kennet long barrow, the Sanctuary, Avebury henge, and another great long barrow to the west confirmed that in each case the skyline passed behind the profile of the great mound somewhere between the flat summit and the weathered ledge.
At Avebury henge, the viewing position was taken to be where the tallest stone had stood, a now-destroyed feature that had been called the Obelisk and which had stood in the southern half of the great, outer, circle.
Only the top segment of Silbury is visible from the henge, visually wedged between the distant horizon and the foreground slope of Waden Hill. A very tight, precise sightline, so precise, in fact, that just before harvest time the height of the cereal crop on Waden Hill blocks it. This must always have been the case, for it is known from pollen analysis that cereals were grown there in Neolithic times. It is tempting to suspect that this relates to the fact that an early phase of the major part of the structure at Silbury appears to have been started at harvest time, suggesting that it was connected with harvest celebrations and rituals – the Stone Age forerunners of Lughnasa and Lammas – and perhaps the fecundity of the Earth in general.
What could the significance have been of this top segment of the mound? Looking eastwards from the top of Silbury around the times of Lughnasa and Beltane (early August and early May respectively, when the sun rises from the same part of the horizon) the far skyline is visible just over the top of nearby Waden Hill. The sun can be seen rising from it. If the viewpoint is then immediately moved lower down to the east-facing part of the Silbury ledge, then the distant horizon appears to drop behind the bulk of Waden Hill's looming ridge, and the sun is seen to rise, again, over this a few minutes later. So Silbury appears to have been built exactly tall enough to separate the near and distant eastern skylines, and thus facilitate a symbolic "double sunrise" at ceremonially important times of the year.
What appears to be a further, even more dramatic piece of ritual showmanship can also be experienced by an observer on the summit of Silbury at these times: a glow of light can be seen stretching away to the western horizon from the tip of Silbury's shadow cast by the rising sun. This is a refractive effect known as a "glory" created in the dewdrops in the fields below. The psychological effect of this phenomenon is to make one feel as if Silbury Hill is blessing the land. [PLEASE NOTE: due to careless damage, it is now strictly forbidden to climb Silbury Hill.]
It is reasonable to speculate, therefore, that Silbury Hill stands just where it does and to the height that it does in order to be able to facilitate the north-south visual link between West Kennet long barrow and Windmill Hill, the demands of the "double sunrise" effect to the east, and to enable the skyline association to be visible from the key monument sites all around. If so, it is a staggering display of Stone Age sacred geography co-ordinating built monuments with natural topography and astronomy.
Interpretation is always a risky business, but it seems reasonable to see Silbury Hill in terms of acting as intermediary between the fecundity of the Earth and the source of life, the sun – considered to be a goddess, Sunna, in early northern Europe. Perhaps the great mound symbolised the Earth Mother herself.
The Silbury ‘Sunroll’
A “sunroll” is the visual illusion of a setting sun rolling down a hill slope when viewed from a certain location, a backsight (there is a sun rising counterpart to the phenomenon as well). Except in equatorial regions, the sun doesn’t drop vertically to its setting position on the horizon but follows a sloping path down to its setting point, the angle of the path depending on the latitude. When the path’s angle matches that of a hill slope, we have a sunroll. Archaeoastronomer George Currie calculated that a sunroll should be visible at Avebury – specifically down the north-eastern slope of Silbury Hill as viewed from a point in the Palisades (see Introductory). Viewing from the identified point in the Palisades, on-site researchers Pete Glastonbury and Steve Marshall confirmed Currie’s calculations with a sighting of the sunroll on May 15, 2009 (Marshall et al., 2010). The sun’s setting position moved northward until the summer solstice (June 21), and then returned southward to provide another optimum roll on July25th. Marshall, Glastonbury and the investigators, with others, witnessed the roll on July 25, 2009.
A simulacrum is the accidental, chance, resemblance of one thing, typically anthropomorphic or zoomorphic, in another’s shape, such as a face or figure in the clouds, the gnarled bark of a tree or in rocky crags. It has been widely noted that a number of the standing stones at Avebury have resemblances to animal heads, human faces, gargoyle-like configurations, etc. Conservative opinion dismisses these simulacra as due to weathering, but while one must always be on guard for reading too much into the forms of rocks, some of the shapes are pretty fundamental to the stones, and if we can see the likenesses today, presumably so could the Neolithic people who strained and struggled to select and erect them. Indeed, without the weathering they might have been even more noticeable. With these simulacra, are we glimpsing the lost gods of the Stone Age, the pantheon of Avebury? Here are a select few the investigators have noted.