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Archaeoastronomy Links Stone-Age Tomb Builders With Sun
Scientific research at the prehistoric Passage Tomb Cemetery at Loughcrew, one of Ireland's premier archaeological sites, is revealing new data on the astronomical orientations of the passage tombs and relationships in the way they are laid out.
Using techniques from the science of archaeoastronomy, this research has already identified significant astronomical orientations in the larger focal tombs and significant patterns in the relative orientations of the monuments.
Frank Prendergast of the Dublin Institute of Technology presented the results of his research to date at the UK/Ireland National Astronomy Meeting in Dublin on Wednesday 9 April.
"By examing the relationship between the landscape, the monuments and astronomy, we can complement existing archaeological knowledge and hopefully gain insight into how prehistoric communities might have perceived their place in the cosmos," says Frank Prendergast.
Loughcrew is a nationally important archaeological landscape located 70 km north-west of Dublin in County Meath. It is the site of one of the four major passage tomb cemeteries in Ireland and dates from the Middle Neolithic (3600-3100 BC) and later.
The principal type of monument is the passage tomb and some 30 of these survive in varying condition. Typically they consist of a circular cairn retained by a stone kerb.
The tomb lies within the cairn and may be roofed or unroofed. Megalithic art is often inscribed on some of the stones within the tomb.
Previous investigations by archeologists indicate that these monuments were landmarks on the Neolithic landscape, and the larger focal tombs and their smaller surrounding satellite tombs would have had a major impact on prehistoric communities and their ritual and ceremonial practices.
Frank Prendergast's investigations show that two of the largest focal tombs are oriented towards the rising Sun at the equinoxes. On these days, at dawn and for a period of some 20 minutes afterwards, the interior of the tombs are spectacularly illuminated by a shaft of sunlight.
At these times, the elaborate engravings on some of the stones within both chambers are clearly visible in the otherwise dark interior. Equinoctial orientations are not common and their interpretation is controversial.
It is well known that many such tombs found elsewhere in Ireland and beyond, such as at Newgrange, are oriented towards the direction of the rising Sun on the solstices. These are the days in December and June when the Sun's motion in the sky reaches a 'turning point'.
The direction of the rising Sun reaches its most northerly and southerly points on these dates and these are observable events. Our prehistoric ancestors would therefore not have required any advanced understanding or knowledge to pinpoint them.
By contrast, the equinoxes, which occur in late March and September, are midway between the solstices and are not obvious unique events: to locate them, an observer must track the total annual range of the Sun's rising direction and then divide it in half.
The question that immediately arises is, "Why would the tomb builders wish to do this?" Even more intriguingly at Loughcrew, there is a pattern of orientation between many of the smaller satellite tombs -- both towards each other and towards the two focal tombs.
UK/Ireland National Astronomy Meeting Web site
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