Heritage Discoveries: The Newgrange Solar Alignment

Newgrange is probably the best known monument in Ireland and one of the best known in the world. But it was not until 1967 that its most famous feature was rediscovered.

Newgrange with the roof box above the entrance and the decorated entrance kerbstone in the foreground. Image by Clemesnfranz.

The Newgrange Passage Tomb is one of a number of prehistoric tombs and other monuments that form the Brú na Bóinne UNESCO World Heritage Site. The megalithic passage tomb at Newgrange is one of the most elaborate examples of the 230 passage tombs known in Ireland. It consists of a stone built passage and chamber 24m long aligned with the entrance facing the south-east. The passage is built with large stone slabs called orthostats (standing stones) and is roofed with flat slabs. At the end of the long passage the three chambers are arranged in the shape of a cross, with one to either side of the passage and a third facing the entrance. The chambers have a corbelled roof that is about 6m high. Within the chambers there are four large stone objects shaped like basins.

The passage tomb is covered by an oval mound 85m in diameter and 11m high that is enclosed at the base by 97 stone kerbstones. Many of the stones in the passage and chambers and in the kerb are decorated with a style of incised abstract artwork, like that on the illustrated entrance kerbstone, known as passage tomb art. Radiocarbon dating of the tomb has placed its construction in the centuries before 3000 BC. Like most passage tombs Newgrange formed part of a group of tombs referred to as a cemetery. Newgrange has three smaller satellite passage tombs nearby and is relatively close to two other large passage tombs at Knowth and Dowth that also have small satellit tombs.

Much of what we know about Newgrange is because of the work of Michael J. O’Kelly, the Professor of Archaeology in University College Cork, who directed the excavations at Newgrange from 1962 to 1975. On the morning of the 21 December 1967, the day of the winter solstice, Prof. O’Kelly waited in the chamber at sunrise and witnessed a beam of light enter the chamber through the roof box, travel along the passage and light up the chamber.

The roof box above the entrance to the tomb was built over a gap in the first two roof stones of the passage and is covered by a decorated lintel stone. The box allows the sun to enter the tomb for about a week before and a week after the winter solstice. Astronomical calculations have indicated that the sun would originally have lit a triple spiral carved on back wall of the tomb. The significance of the solar alignement should not be underestimated as it indicates that stone age people had a sophisticated understanding of the natural world that was incorported into their architectural designs and religious beliefs.

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