A unique and enigmatic group of prehistoric stone monuments in mid-Ulster is helping archaeoastronomers learn more about the meaning and significance of astronomy in prehistoric Ireland and Britain. On Wednesday 9th April at the UK/Ireland National Astronomy Meeting in Dublin, Professor Clive Ruggles of the University of Leicester will describe his research on a number of distinctive and remarkably complex Bronze Age monuments, consisting of interrelated stone circles, rows, and cairns, which are located in an area centred around Counties Tyrone, Fermanagh, Derry and Donegal. He has discovered a number of apparently significant astronomical alignments amongst these mid-Ulster monuments, including some particularly spectacular ones relating to the Moon, and he will talk about how astronomers and archaeologists interpret such alignments.

Clive Ruggles is Professor of Archaeoastronomy and has had an interest in the mid-Ulster monuments ever since 1998, when he took up a one-year Senior Visiting Research Fellowship at the Institute of Irish Studies at Queen’s University, Belfast. Working with local archaeologists on both sides of the border, he set out to survey the monuments looking for evidence of astronomical alignments and other relationships between the monuments and the surrounding landscape.

“Archaeologists now believe that such visible links between monuments and the surrounding landscape and sky helped to symbolise the links between living people, their ancestors, and the cosmos as they perceived it”, says Professor Ruggles. “The builders were not ‘astronomers’ in the sense that we would mean it today, but celestial objects and cycles were important to them in keeping their own lives in harmony with their world. By studying astronomical alignments we can learn something of how people comprehended the world in the past.”

The discovery of the astronomical alignments did not come as a total surprise: these stone circles and rows, the best-know of which is Beaghmore in County Tyrone, are located in a region mid-way between other groups of broadly contemporary monuments known to have significant associations with the Moon – one in the south-west of Ireland and the other on the Hebridean Islands and the western mainland of Scotland. Some alignments relate to the Sun on the solstices (mid-summer’s day and mid-winter’s day) but overall Professor Ruggles’ results suggest that the mid-Ulster builders were more interested in the Moon. There is some evidence for two different traditions, very possibly dating from different times. One is associated with the wider tradition extending from Ireland to western Scotland, while the other is highly distinctive of this particular area. But how should they be interpreted?

“Great care is needed”, cautions Professor Ruggles. “Just because a monument is aligned in a direction that we would be tempted to interpret as astronomically significant, such as the direction of sunrise or sunset on one of the solstices, this might not have been intentional. Everything has to point somewhere and there might have been many different factors influencing an orientation. Even if we can convince ourselves that an astronomical alignment was intentional, this does not in itself help us to theorise about its possible meaning and significance to the people who built or used the monument. When astronomers and archaeologists weigh up their theories against the available evidence from their different academic backgrounds, they can come to spectacularly different conclusions.”

Many archaeoastronomers see repeated trends as the most acceptable evidence for intentional astronomical alignments. In some parts of Ireland and Britain there are distinctive local groups of conspicuous stone monuments that show remarkably consistent trends in design, orientation, and location in the landscape. Some of them – such as the Neolithic recumbent stone circles in Aberdeenshire and the Bronze Age short stone rows of Counties Cork and Kerry – show clear relationships with the Sun or Moon.

Archaeologists generally prefer to base their interpretations on a much wider range of evidence about a particular monument or place. From an archaeological perspective, it is not the mere existence of an intentional alignment that matters but its possible meaning and significance. That means taking into account case studies from a range of human societies, past and present.

“The need to reconcile these two different approaches becomes particularly clear when we are trying to interpret small groups of monuments such as the mid-Ulster ones”, says Professor Ruggles.