Newgrange sun trap may be only 50 years old,

robp

Trapping the winter solstice sun at Newgrange in Co Meath is not a 5,000-year-old phenomenon, but a 50-year-old “construct”, according to a former State archaeologist.

Our Stone Age ancestors were not as clever as we thought, and the significance of Newgrange as a “Hiberno-Roman” cult site in the late Iron Age has been deliberately underplayed, Michael Gibbons, co-author of a paper on the subject, argues.

Newgrange’s alignment, which captures the rising sun during the winter solstice period around December 21st, has made it one of the world’s best known megalithic tombs.

If skies are clear during sunrises from December 19th to 23rd, a narrow beam of light penetrates its “roof-box”, reaches the chamber floor and extends gradually to illuminate the entire chamber over 1 7-minute period – marking new life at the turn of the year.

However, in an article published in archaeological journal Emania, Mr Gibbons and his brother Myles take issue with the excavation and reconstruction work carried out on the passage tomb half a century ago by the late Prof Michael O’Kelly, including the famous “roof box” for trapping the sunlight – said to be 5,000 years old.

Mr Gibbons, an independent archaeologist based in Connemara, is a former co-director of the Office of Public Works (OPW) national sites and monuments record office.

http://www.irishtimes.com/news/ireland/irish-news/newgrange-sun-trap-may-be-only-50-years-old-says-archaeologist-1.2913483

Wibbs

Well the white pebble facade is a complete farce. Only possible with concrete. The entrance is more about tourist access. That said I recall reading a book on the excavation and the roof box looked legit. Even if the roof box was a fabrication the alignment was clearly purposeful(like others in the area). The neglect of the structure's importance to later cultures has been sidelined alright. There's a passage in a Greek text(IIRC) which fans of Stonehenge reckon fits that site, but is far more fitting for Newgrange.

eeguy

I don't really understand.

Is there no record before 1967 of the roofbox?

Wibbs

Some of the old pre dig photos seem to show the top of it, there is certainly another lintel stone set further back.

Tabnabs

Has Prof George Eogan commented on this? He's surely a man in the know when it comes to passage tombs

Tabnabs

From the OPW:

recedite

It smacks of self-publicity, is he launching a new book or something?

Even if part of the roof had fallen in and was refitted, it would make no difference to the original alignment and structure of the tomb.

And whatever it was used for in celtic times may be just as irrelevant to its pre-celtic original use as the current usage.

And anyway, the light concept is not all that clever. You could just make up a mobile template out of wood or wicker basket materials, and keep moving it around during the last week or two in December to get the alignment right. Then build the permanent structure later on.
A couple of years ago at this time of year I drew a slanted line with a black marker on a window reveal of the house. Along the line of the shadow cast by the sun hitting the roof overhang. Its interesting to see the angle of the shadow change throughout the year, relative to the black line. Interesting and slightly amusing, but not all that clever.
Go out and draw your own line somewhere over the next few days if the sun come out!

Cianmcliam

recedite wrote: »

It smacks of self-publicity, is he launching a new book or something?

Even if part of the roof had fallen in and was refitted, it would make no difference to the original alignment and structure of the tomb.

And whatever it was used for in celtic times may be just as irrelevant to its pre-celtic original use as the current usage.

And anyway, the light concept is not all that clever. You could just make up a mobile template out of wood or wicker basket materials, and keep moving it around during the last week or two in December to get the alignment right. Then build the permanent structure later on.
A couple of years ago at this time of year I drew a slanted line with a black marker on a window reveal of the house. Along the line of the shadow cast by the sun hitting the roof overhang. Its interesting to see the angle of the shadow change throughout the year, relative to the black line. Interesting and slightly amusing, but not all that clever.
Go out and draw your own line somewhere over the next few days if the sun come out!

But there's a twist at Newgrange that makes it ingenious, the passage slopes upwards 2m so the slit of the roofbox is level with the floor of the chamber. Yet, there's a bend in the passage so you can't see the line of the floor from the roofbox (I've tried). So to check the roofbox was at just the critical height to allow the beam get through the bend and onto the floor was a master stroke of engineering. It is not like a simple opening to allow light in. A couple of inches out and nothing would happen. You only get a few good mornings on the worst time of year for watching the sun on the horizon, even slight cloud will reduce the effect to make it barely visible, as happened us when we viewed it a few years ago. Only when the sun passed through a tiny sliver of cloud was it visible on the floor.

slowburner

First, there is no evidence whatsoever to suggest the Prof O’Kelly “fabricated” the roof box with its decorated lintel as it has been visible and recorded photographically since at least the 1930s...
To suggest that “it has not a shred of authenticity” and is somehow a “construct” or figment of Prof O’Kelly’s imagination is nonsense.

http://www.irishtimes.com/opinion/letters/newgrange-the-archaeological-evidence-1.2916654

recedite

Cianmcliam wrote: »

But there's a twist at Newgrange that makes it ingenious, the passage slopes upwards 2m so the slit of the roofbox is level with the floor of the chamber. Yet, there's a bend in the passage so you can't see the line of the floor from the roofbox (I've tried)...

Light still travels in a straight line. There are only two variables to design into it; the verticle axis and the horizontal. The slanted shadow line angling down from the roofbox represents the vertical. The horizontal could be checked with a piece of string at any time, just to make sure the bend in the passage was enough to restrict a wide slit of light down to a more narrow beam.

Cianmcliam

recedite wrote: »

Light still travels in a straight line. There are only two variables to design into it; the verticle axis and the horizontal. The slanted shadow line angling down from the roofbox represents the vertical. The horizontal could be checked with a piece of string at any time, just to make sure the bend in the passage was enough to restrict a wide slit of light down to a more narrow beam.

You can make it sound easy on paper, but you still have to build it with giant rocks, each of the capstones perched on just the right number of corbels, none of which are a standard size, allow for settling and movement when the cairn is piled on top and all without the beam of light as a reference. Most impressive of all, for those who witness it, the beam of light from the roofbox hits the floor exactly at the junction of the passage and chamber and stretches across the chamber floor, right to the back of the chamber in 3,200BC. It doesn't appear in the passage until the sun rises higher and the beam retreats from the chamber down the passage. At the time of construction this would happen precisely at the moment the first limb of the sun appears above the horizon. That is precision engineering at a time when the most sophisticated engineering tool was probably the plumb bob or the gnomon.

I've been to passage tombs in Brittany, Wales, Portugal and Spain and none have anything approaching such an intricate feature.

recedite

I agree its "state of the art" for its type. But I wouldn't assume every aspect of the finished structure was designed from the start. Even a modern building often ends up different to the architects plans and spec.
Starting off with a vaguely designed perishable structure, and then adding more durable materials over many years it would be possible to build up a finished structure that accomplished the "intricate" features described.
Perhaps one interesting aspect would be to explore the amount of "tweakability" that was designed into Newgrange. For example could the roof box have been resting on a sandy mortar and smaller stones so that it could be adjusted afterwards by lowering it to get the angle of the light right? The lintel stone seems not so large that it could not be jacked up a bit, using wooden levers if needs be.

The entire roof box could have been added in after the main structure. That's how Canadians put the windows in their log cabins. First they built a windowless log cabin, then cut out windows wherever they needed them.

Could the curve of the passageway have been tweaked during construction? How easy would it be to raise or lower the floor level inside? By tweaking these things after construction, they could have adjusted the travel of the light beam around the floor.

Cianmcliam

It almost certainly was tweaked before the mound was completed around it. In fact they retained the mound of stones on each side by covering the slopes with rolled out turf so the entrance could be finished. The passage though was like that from the start, the stones that line it were slotted into a pair of pre-cut trenches and there's no evidence they ever moved stones once they were placed into these trenches. The spoil heaps from the trenches were still outside the passage so this was well thought out in advance and they moved on once the passage was in place.

The chamber floor was on the original surface level, though there are accounts that it may have been paved or cobbled originally.

Whether it was placed in perfect position in the first attempt or tweaked meticulously during the construction wouldn't lessen the achievement of getting it to work, either way it shows a unique and remarkable concept being created for the first time.

slowburner

This critical examination of the Newgrange roof-box controversy provides a well structured, informative, and authoritative rebuttal of recent claims by Michael Gibbons. Highly recommended, and written by one of the most valued contributors to this forum.

https://blog.shadowsandstone.com/2016/12/27/raising-the-roof-comments-on-the-recent-newgrange-roofbox-controversy/