Neolithic Monuments in Northeastern Europe Threatened

Archaeogeodesy Study Results
for Three Major Neolithic Complexes

ArchaeoBlog, an archaeology web log by James Q. Jacobs

Introduction    |    Monument Complexes    |    Results    |    Conclusions    |    Site Data    |    References
Continuing Entries:     2006.03.19    |    2006.04.24    |     2006.09.09    |    2007.01.22

When obliquity equaled precisely 24 degrees, at Avebury
the summer solstice sunset pointed precisely to Newgrange.



2006.03.09 - The Hill of Tara and Thornborough Henges have become new foci in the ancient sites preservation struggle. The ancient geodetic significance of Neolithic monuments is not considered in decision making related to development and ensuing site destruction. These massive ancient monuments, a focus of my archaeogeodesy studies for some time, have been part of human heritage for 5,000 years. I've given them renewed attention because they are threatened.  Also, I obtained GPS readings for several Tara features. Herein, I present some findings related to the Neolithic complexes at Tara, Newgrange, and Avebury.

Archaeogeodesy, as a new and developing area of scientific inquiry, illustrates how decisions impacting ancient monuments are made before science develops the tools required to fully study and understand what is being destroyed. The classic example of this dilemna is the burning of the Mayan codices due to religious paradigms; the texts were considered false religion. Today, from three surviving books, the codices are known to be scientific, in fact, the most advanced astronomical texts from that time. From my archaeological viewpoint, an ancient book written on the earth, a geodetic codex, is being destroyed in our time. Our prevailing 'scientific' paradigm is the sum, to a large degree, of beliefs in our time, reflecting ignorance of the past and of the purpose of the Neolithic monuments. What has changed is the scale of the codex being burned.

Professor George Eogan at Rath Lugh National Monument, Hill of Tara.

Monument Complexes Considered

This discussion focuses on three complexes; Avebury, Newgrange, and Tara. The two complexes in Ireland are positioned, from the Avebury complex, at a distance equaling one one-hundredth of earth's circumference (CIR/100). Table 1 presents the coordinates used for the sites. The three complexes and the features considered are:

  1. Avebury Complex
    • Avebury Henge, 470 m in diameter, one of the four 'giant' henges, with the largest known stone circle at 331.6 m, plus two 103.6 m stone circles
    • Windmill Hill Henge, dating to 3300 BCE, 365 m in diameter outer elliptical ditch and embankment circle with inner circles, type-site and largest 'causewayed camp' and type-site for 'Windmill Hill culture' pottery
    • Silbury Hill, the highest Neolithic mound at 40 m, 500 m in circumference
    • The Sanctuary, on Overton Hill six concentric rings of timber uprights stood before two concentric megalithic rings. The West Kenneth Stone Avenue, parallel rows of menhirs connected The Sanctuary and Avebury
  2. Bend on the Boyne Complex
    • Newgrange Stone Circle, 103.6 m in diameter and containing Newgrange Tumulus dated to 3200 BCE, 80m in diameter
    • Knowth Tumulus dated to at least 3100 BCE, 84 m in diameter, two passaged chambers, with 18 surrounding smaller mounds, the greatest concentration of megalithic engraving occurs here, one quarter of all Europe's neolithic art
    • Dowth Tumulus
    • Newgrange Henge A, 140 m in diameter
    • Dowth Henge, 165 m in diameter, one of the largest henges in Ireland
  3. Tara Complex
    • Rath Righ and the Forradh, the concentric features of the Hill of Tara
    • Graine Henge

The complexes, built and altered over many centuries, are immense arrays of monuments with many more features than the ones listed above. Their relationships are therefore complex. Future refinements in method, especially more accurate GPS and survey data for the locations, will slightly alter the results presented (article now reflects some new GPS data, as noted below). At the same time, it is important to consider the scale of the earth and the limitations of the architects of their arrangement. One one-hundredth of circumference is 400 km and changes of several meters are relatively insignificant in relation to this arc, and especially so relative to the size of the earth.

Download a small Excel applet, Neolithic Calc, to examine site relationships.


Avebury latitude


A fundamental site variable is geodetic properties of the location. Avebury is today centered at a latitude equaling 1/7th of circumference, 51.428609 degrees. Precisely 360/7 equals 51.4285714 degrees, a slight error still within the henge. From Avebury, at latitude CIR/7, the site-to-site bearing to Tara complex is also CIR/7. Another consideration is local latitude to longitude ratio. Windmill Hill (pictured) is situated where the equal-degree latitude to longitude ratio is 8:5, or 1.60:1.0. These are not haphazard placements.

From Windmill Hill to Graine Henge, the arc equals one one-hundredth circumference, 3.5885° or 0.009968 CIR. From Windmill Hill to Newgrange the arc equals 3.5886° or 0.009968 CIR. The arc distances between the Irish and British site features considered herein ranges from 3.576° (Windmill Hill to Dowth) to 3.608° (Avebury to Newgrange). In fractions of circumference, the range is from CIR/99.77 to CIR/100.66.

Graine Henge is not the largest nor the central feature at Tara. Like Windmill Hill, the Hill of Tara is crowned by concentric features, the immense Rath Righ henge encircling the central hill fort, the Forradh or King's Seat, a mound surrounded by two embankment and ditch rings. Rath Righ also encloses Cormaic hill fort and a passage mound, Mound of the Hostages. The center-to-center arc distance from Windmill Hill to Rath Righ equals 3.5855° and, while not precisely CIR/100, numerous circular earthen features mark the surrounding landscape.

The angle 3.59758° has astronomical significance. In 10,000 days, there are 366.01 lunar orbits, and in 10,000 rotations there are 365.01 lunar orbits. This most significant intercalation of these three periods are products of the three fundamental astronomical motions, earth rotation and lunar and solar orbits. The difference between lunar orbit motion per 100 days and per 100 earth rotations is 3.59758° or CIR/100.06, equal to the distances from the Tara complex and from the Newgrange complex to the Avebury complex. Multiplying degrees of lunar orbit motion per rotation and per day each times 10,000 results in nearly 360 of difference. Mean lunar orbit per rotation (R27) equals 13.1404 and, at this latitude, CIR/100 equals about 1,314,040 ft.

I noted several other relationships.  Rath Righ and Newgrange Henge A form a 3:4:5 triangle, with a 15 km hypotenuse and the two sides within 200 m of precise. From Newgrange to Graine Henge, the arc distance and the degrees longitude difference are near equal, 0.13876° and 0.13827° respectively (1.0:0.9963, a 34 m E-W displacement from precise).

2006.03.09 - Conclusions

Given the preliminary results, I conclude that a complete examination of these relationships is warranted, one including more monuments and features, with accurate GPS readings or survey coordinates for all the monuments in a single global system. Precise GPS and survey data may reveal far more relationships than are currently apparent, especially considering the number of archaeological placemarks near to and in the viewscape surrounding the Hill of Tara. Considering the relationships presented by just the few, major geodetic placemarks herein, the possibility of archaeometrology and encoded information in the complex array around Tara Hill needs to be assessed. Hopefully this landscape codex will be understood and the Neolithic qualities and features of the landscape preserved to the degree possible.

My computations continue, and I will post more findings soon. But enough for the moment. I don't want to give away the location of that pot of gold buried by Leprechauns in a field of four-leaf clover at the end of a rainbow.

Continuing Entries

Datum Updates: March 19, 2006.

After determining more accurate coordinates for Avebury, Silbury Hill and Windmill Hill, I determined their site-to-site relationships (updated/reflected in results discussed above). Additionally, the Avebury to Silbury Hill arc equals 0.01307° (0.00100 R27), 1/1000th of lunar orbit per earth rotation. The Windmill Hill to Silbury Hill arc equals 0.02900° or 1/1000 of earth orbit per full moon period (0.00100 S29). These two arc distances and the placement of the three monuments presents precise fractions of astrogeodetic modules based on the three fundamental cosmic motions. The fundamental astronomy, the modules, and notation are further explained in the Archaeogeodesy series.

GPS Updates: April 24, 2006.

The Newgrange coordinate has been updated with a GPS reading for the center of Newgrange Mound. The results above now reflect this change. Knowth Mound, Dowth Mound, and Dowth Henges GPS coordinates were also obtained. The arc from Knowth Mound to Windmill Hill equals 3.60006° or CIR/99.9985, an excess of only 6.1 m. And the distance from Knowth to Newgrange equals 1/1000 of earth's diameter, therefore the distance from Newgrange to Windmill Hill is 314.19 (100 pi) times that from Newgrange to Knowth. From Avebury to Dowth Henge equals 3.59647 degrees.

Research Update: Sept. 9, 2006.

Once in a while I get a whim and follow it. And advancing technology and new interactive online information processing capabilities are seemingly having a synergistic effect on research. I found myself flying around in the Thornborough Moor vicinity thanks to Google Earth, this after noting a possible lunar major alignment of two of the Thornborough henges (more on this soon in a Thornborough page). I aligned the henges and tilted down, then followed the line to the NW horizon, and then onward until serendipitously flying over the highest point on the Isle, Ben Nevis. I rotated back, aligned the display to Thornborough and flew back, over Ben Nevis, directly over the many Thornborough Moor henges and, continuing with the whim, onward with curiousity. I arrived at Mont Blanc, the highest point in Western Europe.

Hovering in cyberspace above Mont Blanc, another whim came to mind. I wanted to know if the Newgrange and Avebury complexes aligned on the highest point in Western Europe. Of course, they do! GPS coordinates for Mont Blanc confirm the obvious line. A line from Knowth and Newgrange passes between Avebury and Silbury Hill over the Sanctuary, where the respective bearings angles sum 179.98 degrees. Also, the Sanctuary arc distance from Mont Blanc is precisely 8.0° (CIR/45).

Next whim, check the illumination angles. Given Newgrange's well-known winter solstice passage illumination, winter solstice was the obvious suspect. At Avebury the bearing of 130.82° to Mont Blanc matches the winter solstice angle during the Neolithic occupation period. Using Victor Reijs' GeoAstro calculator (in Neolithic Calc), Avebury's winter solstice angle was 130.82° given epoch -3300 and altitude 0.0. Avebury's summer solstice sunset, in the direction of Newgrange (bearing 49.29° W. of N.) was 49.29° given epoch -2700 and altitude 0.0. This date concurs with radiocarbon dating of Avebury and Newgrange. From Windmill Hill the bearing is 49.33° to Newgrange and Knowth.

It goes like this, right? Observation, pattern, hypothesis, prediction, test, observe...the cycle repeats... until finally, formulate hypothesis if supportable. As these intriguing relationships mount in number and predictions are confirmed, so also concerns with formulating hypotheses become more pressing. In light of current findings, "major monuments may evidence ancient geodetic placemarking" seems a reasonable idea to subject to testing. Of course, that's only possible if the sites survive modern developments.

Research Update: Jan. 22, 2007.

Once in a while I get a whim and follow it. And interactive online discourse enabled me to follow this one. The updated ArchaeoGeodesy embeds Victor Reijs' GeoAstro, a declinations calculator. Victor and I dialogue archaeocosmology and fundamental astronomy from years back. His interest in celestial alignments and his critique of my more cartographic approach to ancient monuments led to embedding GeoAstro in Neolithic Calc and in archaeogeodesy.xls. This useful synergy resulted in a new finding.

I'm getting to the whim. To celebrate the 20th anniversary of defining and quantifying the astrogeodetic modules used in my archaeogeodesy studies, I updated ArchaeoGeodesy with v2007.01.11, complete with an eclipse calculator. As I final-checked the worksheets, I noticed the GeoAstro output for obliquity angle was quite near 24 degrees. Here's the whim. I thought, "What if the Ancients used the obliquity angle as a temporal benchmark." I did not check immediately—busy with family, monumental politics, repairing the calendar, anniversaries and all.

The Neolithic Thornborough landscape has been horribly wasted by gravel quarries, with mining intruding upon the monuments, not unlike Woodhenge at Cahokia. Quarry expansion plans may destroy the Thornborough landscape further. Many henges in Europe, like earthworks in North America, are simply gone forever. So many pages of the book burning at once these days, it's fueling global warming! So I turned attention to updating the Thornborough page, to provide more information for that preservation struggle.

I set the site variables to Thornborough South, Ben Nevis, and Devil's Arrow, adjusted the epoch to -2758.325 to set obliquity to 24 degrees, and set the altitude to 0.0 degrees. Thus, the illumination declinations present the level horizon position of the center of the sun and moon when obliquity equaled 24 degrees. The result was a very accurate match between Thornborough South lunar major extrema and the bearings to Ben Nevis. A collegue expressed doubt, plus there is no Neolithic monument on Ben Nevis. So I checked a second alignment, Avebury and Newgrange of course.

Avebury and Newgrange have something striking in common. They have three megalthic stone circles of the same diameter, one surrounding the Newgrange passage tumulus, two within the earthwork and large stone circle at Avebury. The Avebury to Newgrange bearing accurately matches the summer solstice sunset bearing using the same settings. Meanwhile, Victor has been improving the declination calculation tools. With his new formulations, the Avebury to Newgrange alignment is a perfect match.

At Avebury, when obliquity equaled precisely 24 degrees,
the level summer solstice sunset pointed precisely to Newgrange.

Other questions collegues raised include "Why 0.0 altitude?" and "Why the center of the celestial sphere?" In geometry, why level is an easy question to answer. That is how the math is accomplished, using perpendicular axis and planes. Level is the natural, local geodetic reference also, and determinable with water. It is gravity referenced. To the question regarding pointing at the center of the object, I had to reply, "Well, when you point at something...." Hence, again the center of gravity is the reference.

If this discovery proves to be a temporal benchmark built into the Neolithic complex (and more widely, like Egypt, etc.) the implications are considerable. I will be giving this finding further scrutiny and will report later. I'm hoping that the 24 degrees obliquity angle will prove to be a temporal reference for the placement/arrangement of the monuments, a key to a very large door in the dark halls of prehistoric science. I'm going to open that door now, expecting the illumination will end a period of darkness. Caution, synergy at work!

I should also mention something perhaps not trivial or coincidence. Silbury Hill and Marlborough Mound, the two tallest European mounds, are only 100 m from due east-west of each other, and they are spaced 1/4,800th of circumference apart. The two tallest menhirs in the British Isle, Rudston Monolith and Devils Arrow, are more precisely an east-west line. The arc distance from Devils Arrow to Thornborough Center equals 1/2,400th of circumference. There comes a point when hypothesis testing simply gives way to just reading the book.

Additional Coordinates: Sept. 30, 2007

Google Earth has updated the aerial imagery for the Bend of the Boyne area. New coordinates and site codes follow below. The three Boyne passage mounds have lunar minor alignments (within a few meters of accuracy) given 24 degree obliquity and zero altitude:

Bearing knotu - newtu = 124.780°
knotu lunar minor = 124.371°
Bearing newtu - dowtu = 58.547°
newtu lunar minor = 58.720°

Knowth tumulus is pictured in the following image.

Discourse: Collected discussion group postings.
March 2006 April 2006

Neolithic Monument Locations

Table 1. The site coordinates are available in the Excel file, neolithic_calc.xls, and in a
Google Earth placemark file created with Neolithic Calc v2006.9.09 site codes.
Coordinate Source
Rath Righ - Forradh
GPS 7m Megalithomania
Mound of the Hostages
GPS 9m Megalithomania
Graine Henge
GPS 5m Megalithomania
Newgrange Henge A
map-scaled 1:50,000
Newgrange Henge P
map-scaled 1:50,000
Newgrange Mound
GPS Reijs
Knowth Mound
GPS Reijs
Dowth Mound
GPS Reijs
Dowth Henge
GPS Reijs
Windmill Hill
51.428609 1:5,000
51.442086 1:5,000
Silbury Hill
51.415710 1:5,000
The Sanctuary
51.411125 1:5,000
Mont Blanc

2007.10.04 - Google Earth updates the Bend of the Boyne. The new aerial imagery is quite high resolution. Download the Google Earth placemarks file, boyne.kmz, or use the coordinates to locate a monument. The following coordinates were determined in Google Earth on Sept. 30, 2007.

Dowth Henge Q
Dowth Tumulus
Knowth Tumulus
Newgrange Tumulus
Newgrange A
Newgrange B
Newgrange M


Newgrange N
Newgrange R
Newgrange S
Newgrange T
Newgrange V

2008.02.22 - Winter Solstice and Long Barrows. The arc distance between West Kennet Long Barrow and East Kennet Long Barrow accurately presents the value of days per lunar orbit. The Avebury to Silbury Hill arc presents days per lunar anomalistic period.

2008.11.23 - The zenith angle of lunar major at Newgrange A was 24 degrees when obliquity was 24 degrees.

History of this Study

The Archaeogeodesy Pages introduce the topic to readers unfamiliar with the research. I still maintain a secretive attitude about most of my study results, mostly because gold diggers still loot sites. But ignorance also threatens sites. My dilemna is finding a proper balance. I first wrote of findings in personal communications beginning in 1987. In 1991 I distributed to several colleagues Earth Commensurate Units based on fundamental astronomic motions and I noted the geofractional distance 1/100 of circumference for the Tikal to Chichen Itza arc, and likewise for other arcs. That year I also noted the Chaco Meridian in the American Southwest and the Maya Meridian centered on Tikal, Guatemala. I then concluded,

"That there is a site-to-site ordered array of monuments in both North and South America is no longer doubtful! That astronomically commensurate scaling was utilized in both monument size and site-to-site spacing seems evident."

It was not until thereafter, in Nov. 1991, that I turned to Old World monuments to assess the same possibilities. I quickly discovered that the Avebury and Newgrange complexes were CIR/100 apart. To my surprise, I also noted that the Newgrange to Cheops distance was CIR/10 (one-tenth of earth's circumference).

In 1998, I published the Archaeogeodesy Pages on the WWW. In 2000 I wrote The Possible Geodetic Properties and Relationships of Neolithic Monuments of the British Isles, Preliminary Results. During that study, analysis of the geodetic properties of site latitudes revealed the CIR/7 latitude position of Avebury. I added Tara to the study thereafter.  My research is ongoing.  Please contribute GPS readings.

References and Further Readings

  • British Archaeology 82, Carrowmaore - tombs for hunters
  • Burl, Aubrey, 1976. The Stone Circles of the British Isles.
  • Burl, Aubrey, 1979. Prehistoric Avebury.
  • Cleal, Rosamund 2002. Great Sites; Windmill Hill, British Archaeology 67.
  • Gray, H 1935. The Avebury Excavations, 1908-1922, Archaeologia vol 84:99-126.
  • Pitts, M and A Whittle 1992. The Development and Date of Avebury, Proceedings of the Prehistoric Society vol 58:203-212.
  • Rose, Mark 2004. Tara Threatened. Archaeology, April 8, 2004.
  • Ruggles, C L N and A W R Whittle 1981. Astronomy and Society in Britain during the Period 4000-1500 BC, BAR Series vol 88.
  • Smith, Isobel F 1965. Windmill Hill and Avebury: excavations by Alexander Keiller, 1925-1939.
  • Whittle, Alasdair 1993. The Neolithic of the Avebury Area: Sequence, Environment, Settlement and Monuments, Oxford Journal of Archaeology 12:29-53.
  • Brú na Bóinne WHS Research Framework Consultation Draft

Aerial photographs of Newgrange, Knowth, & Dowth   |   Ancient Monument Placemarks

Downloads: Excel: neolithic_calc.xls   |   archaeogeodesy.xls   |   Google Earth neolithic_calc.kmz

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