Here are some helpful sites.

• Newgrange Ireland - Megalithic Passage Tomb - World Heritage Site
• Good Pics!

• Shadowsandstone.com Photography by Ken Williams - powered by smugmug Two good interior pics.
• Good Stone Alignment Info suggests later standing stones were put in place on significant astronomical dates.
• http://www.nd.edu/~ikuijt/Ireland/Sites/jstahl/detail.htm —Good description with measurements.
• http://homepage.eircom.net/~archaeology/three/knowth.htm —Good astronomical analysis.

There appear to be three main types of construction stone. Small to enormous rounded slabs of local brown or brownish gray stone (sedimentary?) make up most of the structure. Dark basalt rectangular blocks and more irregular angular white quartz blocks were brought from further afield to face the front.

53°41′39.4″N, 6°28′36.6″W

• newgrange-init.inc
• newgrange.pov

An optimization heuristic should, from the current state of the system, change its state to one in a path to arriving at a solution. One method (gradient search) is to change the state incrementally toward one nearer the solution state, though this requires a means to measure the fitness of the current state and a similar means to measure candidate states. Another heuristic chooses the best among alternative available actions, though this requires a slightly different metric to measure the suitability of each candidate action.

An optimal construction process moves from the initial state to a desired solution using as few resources as possible.

To use an optimization process a solution is usually defined so the process can determine the best intermediate steps and when to stop. It is possible to optimize the behavior of parts of the system (stones in this case) without regard to the solution. So long as some kind of 'piling' behavior results, and the pile is constrained to staying within certain parameters, a solution may result implicitly.

This is how ants, bees, termites, and other social creatures build their structures. They do not work off of a predesigned master plan, but each worker behaves in such a way that a characteristic structure results. This is how I propose to model megalithic construction.

Using a particle system to model the construction of building should be much like modeling any other process this way. Instead of gravity, wind, and so on as motivational forces, there is another intentional motivational force. A stone rolls downhill because its properties interacting with its environment leaves it no other possibility. Another stone is placed into a wall for the same general reason, only the motivational forces are different. What are these intentional motivational forces?

1. Start with a landscape (turf particle system) strewn with a distribution of local stone.
2. Two quarries with facing stone can be modeled later, after construction of the mound.
3. Constrain the movement of each stone to respect physical laws such as gravity.

The solution is any configuration such that the solar passage will remain outlined by stone for millennia with all 'worker' forces removed.

Consider modelling one frame per day: 5 min = 7200 frames. At 1 frame/day, 7200 frames = 19.7 years. This is the time estimate for 300 workers at http://www.knowth.com/newgrange.htm. But, it seems more likely Newgrange was not constructed in its present form at the outset. Construction may have been more gradual and cyclic, with maintenance, renovation, and reconstruction continuing through the ages. These phases may have been determined simply by the distribution of stone in the area. Large slabs were found and used first, then with the larger slabs more difficult to locate, caretakers had to figure out what to do with the gradually decreasing size of stones brought to the site.

The motivational forces (workers) need not be modeled but it may be more pleasing to do so and to show them doing their thing. In one experiment, 3 workers moved a 1 tonne stone 15m across and 4 m up in 12 hours without mechanical aid.

• Turf, modeled as a mesh, a heightfield, or perhaps as blobs–the nodes must be editable within POV_Ray.
• Local Stone Slabs
• Stone Spalls split from an outcropping to the north? (Graywacke)
• 'Regular' Cairn Stone (Gravel Pit), natural angle of repose ~40º¹⁾
• Larger, Rounded Cairn Stone
• Granite (optional), modeled as slightly rounded rectangular block
• Quartz (optional)

It is likely the granite and quartz facing stones were cut at the quarry to reduce transportation costs. They may have been added well after construction of the mound. They can be modeled separately.

The finished structure includes the following unquarried and largely uncut stones, likely “collected from where they had been left lying about at the end of the Ice Age” [O'Kelly, 117].

• 97 kerbstones 1.7m to 4.5m long, 1.2m avg height above ground, ≥1 tonne. Most are greywacke except 2 brown carboniferous sandstone.
• 450 large slabs including 43 Passage orthostats 1.5m avg. height (2m+ max). Most are greywacke (average density 2.65 g/cc) except 2 sandstone, with their inner edges parially rounded-off, and infilled with flat spalls. One of the largest slabs was 4×1.8×0.5m, ~ 10 tonnes, the next ~8 tonnes.
• About 100 of these slabs are roof corbels

The covering cairn is about 200,000 tonnes of regular cairn stone, likely quarried from a gravel pit 750 m S of Newgrange and 46m below it, about 4 million 50-kg sacksfull. ”…water-rolled pebbles about 20cm across”²⁾

The time and location of the solstice sunrise has changed somewhat over 5,000 years.

* Use the Temporal Epoch Calculator by James Q. Jacobs spreadsheet.

Azimuth: 133°42' to 138°24', elevation 0°51' to 1°40'; declination -22°58' to -25°53' to illuminate the back wall of the rear recess with a 40cm beam originally, now narrowed to 17cm due to leaning othostats. —[Dr. John Patrick, quoted in O'Kelly, 124]

The neolithic population of the 50 km² (r = 4 km) Newgrange basin was about 1200, the same as today, and consisted of 200 6-person homesteads. [Frank Mitchell, 1976, 130]

At Behy/Glenulra, field walls about 150-200m apart enclose pasturage parcels up to 7ha.³⁾