Wednesday, December 16, 2009

New Grange and the Winter Solstice

How cool is this? AMAZING I SAY!

Newgrange (Irish: Sí an Bhrú) is a passage tomb of the Brú na Bóinne complex in County Meath. It is one of the most famous prehistoric sites in the world, and indeed the most famous of all Irish prehistoric sites. Newgrange was built in such a way that at dawn on the shortest day of the year, the winter solstice, a narrow beam of sunlight for a very short time illuminates the floor of the chamber at the end of the long passageway

The complex of Newgrange was originally built between c. 3100 and 2900 BC, meaning that it's aproximately 5,000 years old. According to Carbon-14 dates, it is more than 500 years older than the Great Pyramid of Giza in Egypt, and predatesStonehenge by about 1,000 years.

In the Neolithic period, Newgrange continued as a focus of some ceremonial activity. New monuments added to the site included a timber circle to the south-east of the main mound and a smaller timber circle to the west. The eastern timber circle consisted of five concentric rows of pits. The outer row contained wooden posts. The next row of pits had clay linings and was used to burn animal remains. The three inner rows of pits were dug to accept the animal remains. Within the circle were post and stake holes associated with Beaker pottery and flint flakes. The western timber circle consisted of two concentric rows of parallel postholes and pits defining a circle 20 m in diameter.

A concentric mound of clay was constructed around the southern and western sides of the mound and covered a structure consisting of two parallel lines of post and ditches that had been partly burnt. A free-standing circle of large stones was constructed encircling the mound. Near the entrance, 17 hearths were used to set fires. These structures at Newgrange are generally contemporary with a number of Henges known from the Boyne Valley, at Newgrange Site A, Newgrange Site O, Dowth Henge andMonknewtown Henge.

The Newgrange mound is 76m (250ft) across and 12m (40ft) high, and covers 0.4 hectares (one acre). Within the mound, a long passage, stretching approximately one third of the length of the mound, leads to a cruciform (cross-shaped) chamber. The passage itself is over 18m (60ft) long. The burial chamber has a corbelled roof which rises steeply upwards to a height of nearly 6m (20 ft). A tribute to its builders, the roof has remained essentially intact and waterproof for over 5,000 years.

Once a year, at the winter solstice, the rising sun shines directly along the long passage into the chamber for about 17 minutes and illuminates the chamber floor. This alignment is too precise to have occurred by chance. Professor M. J. O'Kelly was the first person in modern times to observe this event on December 21, 1967.

The sun enters the passage through a specially contrived opening, known as a roofbox, directly above the main entrance. Although solar alignments are not uncommon among passage graves, Newgrange is one of few to contain the additional roofbox feature (Cairn G at Carrowkeel Megalithic Cemetery is another). The alignment is such that although the roofbox is above the passage entrance, the light hits the floor of the inner chamber.

Today the first light enters about four minutes after sunrise, but calculations based on the precession of the Earth show that 5,000 years ago first light would have entered exactly at sunrise. The solar alignment at Newgrange is very precise compared to similar phenomena at other passage graves such as Dowth or Maes Howe in the Orkney islands, off the coast of Scotland.

Current-day visitors to Newgrange are treated to a re-enactment of this event through the use of electric lights situated within the tomb. The finale of a Newgrange tour results in every tour member standing inside the tomb where the tour guide then turns off the lights, and lights the light bulb simulating the sun as it would appear on the winter solstice. Anyone visiting the historic site can experience an approximation of the phenomenon any time of year, and is often the highlight of the tour. A lottery is held annually for "tickets" to be allowed into the tomb to view the actual event. The popularity of this event was the reason a lottery was introduced, and also why the lights were installed.

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