Passage tomb, older than Egypt's pyramids, is a place of astronomical, spiritual, and ceremonial importance.”Tourism Ireland

Tomorrow, Dec 22, is the winter solstice, which marks the shortest day and longest night of the year for those who live in the northern half of the planet. It is also the day when a ray of light illuminates the Newgrange passage tomb, a 5,000-year-old tomb in County Meath that is older than the pyramids of Giza in Egypt.

At dawn on the mornings surrounding the solstice a narrow beam of light enters the 62-foot long passage and lights the floor. It moves along the ground, from the window box until it lights the rear chamber. This Neolithic light show lasts 17 minutes.

Local expert Michael Fox told National Geographic, “Archaeologists have classified Newgrange as a passage tomb but it is more than that. ‘Ancient temple’ is a more fitting label: a place of astronomical, spiritual, and ceremonial importance.”

Beautiful lights outside Newgrange.

Beautiful lights outside Newgrange.

Professor MJ O’Kelly carried out excavations at Newgrange from 1962 to 1975 and became known as the father of “New Archaeology." It was O’Kelly who produced the first scientific dates for Newgrange and rediscovered the roof box, which guides the light into the chamber. On Dec 21, 1967 he was the first person to see the winter solstice display at Newgrange in thousands of years.

O’Kelly’s daughter told the BBC, “He found the roof box when uncovering the roof chamber but wondered about its purpose…My mother, who worked closely with him, suggested that it might be connected with the winter solstice. And that was how he discovered it."

In his notes O’Kelly recorded: “The effect is very dramatic as the direct light of the sun brightens and cast a glow of light all over the chamber. I can see parts of the roof and a reflected light shines right back into the back of the end chamber.”

His daughter, who experienced the solstice at Newgrange the following year, told the BBC, “Suddenly this shaft of light came into the chamber and hit the back wall. I remember being quietly moved – it was like someone was speaking to you from thousands of years before. I still see it like a picture before my inner eye – it was a golden light."

Inside Newgrange.

Inside Newgrange.

The 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. That makes the solar alignment at Newgrange very precise compared to similar phenomena at other passage graves in England and Scotland.

It is a marvel of early astronomy that never fails to amaze because Newgrange actually predates the great pyramid of Giza in Egypt by at least 500 years. Built sometime between 3100 and 2900BC, the famous passage tomb at Newgrange is estimated to be approximately 5,000 years old, even predating Stonehenge in Britain by 1,000 years.

Read more: 5,000-year-old Newgrange to be X-rayed to determine origin

The structure itself lay hidden beneath the earth for over 5,000 years due to mound slippage, which effectively preserved it, until its rediscovery in the late 17th century, when men looking for building stone came across what they thought was a cave.

Restored to its former glory the Newgrange mound is a solid structure that’s 250 feet across and 40 feet high, covering one acre of land. A tribute to its builders, the roof has remained essentially intact and waterproof for over 5,000 years.

Ground plan of Newgrange.

Ground plan of Newgrange.

Ancient carvings can be seen on many of the massive, kidney-shaped mound’s curbstones, including the triple-spiral design synonymous with Newgrange.

Close up of some of the kerb stones outside Newgrange.

Close up of some of the kerb stones outside Newgrange.

Every December Newgrange attracts major global attention. Newgrange is open to the public all year round and one of the nation’s most popular attractions. Newgrange opens its doors on the winter solstice to a select number of people who entry a free lottery. 

Almost fifty years after O'Kelly's discovery the winter solstice at Newgrange is a huge event. It attracts attention from all over the world and the lottery for places to be in the chamber during Solstice 2015 attracted 30, 452 entries. At the end of September 50 names were drawn from among all the entrants by local schoolchildren. These lucky few will gather for sunrise on the mornings between December 18 and 23 at the entrance.