This photographic study lends support to the proposal that the cairns at Newgrange and Loughcrew were built by a sophisticated society with a keen interest in tracking and recording the movements of the sun. When viewed in this light, the cairns and their enclosed passages take on a new significance and can be seen as purpose-built structures. They still work well as Calendars but have lost some of their usefulness due to the recent change in climatic conditions and, in the case of Newgrange, a change in the obliquity of the ecliptic. Nevertheless, they can be, and probably were, used to precisely define major events in the sun's yearly and four-yearly cycle. The immense engineering work involved in their construction and the precision of their orientation to the sun on important days in the sun's cycle, suggest that this ability to understand the world around them was of immense importance to the society 5,000 years ago.

Ground Plan of Newgrange

The decoration plays an important, though different, role in both sites. In Newgrange the decoration on the kerbstone in front of the passage announces the purpose of the cairn. The phenomenon of reversal of movement is graphically illustrated. This mimics the reversal of movement of the sun at the time of the winter solstice. This spiral ornamentation is then repeated in other areas throughout the site. The construction features of Newgrange provide the ideal environment in which to study the minute movement of the sun when it is at visual standstill. For the society which built it, Newgrange could have provided the earliest possible evidence that the sun had begun to reverse its movement along the eastern horizon, bringing with this change the promise of another growing season and the lengthening of daylight hours. This naturally occurring phenomenon is celebrated in the unique ornamentation found at the site.

The spectacular ornamentation found deep inside Cairn T has a different purpose. The symbols engraved on the backstone in general reflect universal representations of the sun and are similar to those produced by other early societies. However, the decoration in Cairn T has a precise functional purpose rather than a decorative one. As the sun shines directly onto the symbols engraved on the backstone they act not just as primitive representations of the sun, but as devices precisely positioned to measure solar movement. By so doing at a time of the year when the sun is moving at its greatest rate, minor
variations in the yearly cycle of the sun are disclosed.

There can be little doubt but that these two sites, if not all passage cairns, were sophisticated structures built to measure the sun's movement by a society which possessed considerable engineering skill. Why they expended so much effort for this purpose can not be easily explained. These two structures continue to work as designed after 5,000 years and must rank as one of early society's most remarkable achievements.

The sites of Newgrange and Loughcrew are within a one hour drive from Dublin . An excellent guided tour is available at Newgrange however there are no guides at Loughcrew. A key to Cairn T is available on request from the local curator. A flashlamp is a useful accessory in Cairn T while there is a considerable walk and climb involved to get to the cairn from the nearby car park.

Light Years Ago is available in hardback and in softback editions and is published by Black Cat Press. For further information and any comments you might have contact Light Years Ago .

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All images are copyright Tim O'Brien and Black Cat Press. No image can be reproduced without the prior permission from Tim O'Brien

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