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Solar petroglyph illuminated by sunbeam at dawn on Spring Equinox
Backstone of Cairn T, Loughcrew. 2000 Martin Byrne


A.  Astronomical alignments;
B.  Astronomical references in Irish mythology:
C.  Kerbstone counting;
D.  Geographical alignments and geomancy;
E.  Acoustic properties of megalithic monuments.


This programme would scientifically investigate the controversial question of astronomical design in Irish megalithic sites from the Mesolithic, Neolithic and later periods. The progarmme has three proposed goals:

  1. To develop and field-test a methodology and a user-friendly software application for the scientific investigation of astronomical alignments at megalithic sites. This would involve the use of hand-held GPS (Global Positioning System) technology and (gyro-)theodolites for site surveys, followed by the use (and/or development and testing) of an integrated 3d GIS (Geographical Information System) mapping software application.

    The GIS application would be loaded with (a) an accurate 3-dimensional map of the area under investigation, (b) the precise geographical co-ordinates of particular monuments obtained by GPS, and (c) the precise azimuth windows of particular passages and of alignments between locally inter-visible monuments, obtained by theodolite measurements during the site survey. Once this information was entered into the database, the software would then generate, for specified map co-ordinates and azimuths, point-of-view images displaying the accurate relation of celestial events (such as Solsticial and Equinoctial sunrise and sunset, major and minor lunar standstills, helicacal rising of major constellations, etc. ) calibrated for the relevant time period with GPSU and/or other astronomical software) to the actual contours of the locally visible horizon as seen by an observer at a particular site.

  2. To apply this methodology and software application to the thorough investigation of a selected group of Irish megalithic complexes. The area proposed for our first study is the Brú na Bóinne area including the UNESCO World Heritage site, with a focus on the 40 known and/or suspected astronomical alignments identified in our draft map of the Boyne Valley.

    Other megalithic complexes which the Institute is keen to investigate include Knocknarea / Carrowmore in Co. Sligo (with 30 surviving passage mounds and 30 others destroyed or ruined), Loughcrew in Co. Westmeath (with approximately 30 passage mounds and cairns), and Carrowkeel in County Sligo.

  3. To determine once and for all whether astronomical orientation is or is not a common feature of the architectural and artistic design of Irish megalithic sites.

If the results of this research programme were to confirm the astronomical design hypothesis, they would be widely disseminated to the Irish archaeological community so as to protect and further study this feature during future restoration work.


The objective of this programme would be to carry out a systematic search for astronomical references in Irish mythological texts and related local folklore. Click here for details.


The objective of this programme would be to investigate the hypothesis that builders of the megalithic monuments used counting to anticipate significant astronomical events, and included facilities for such counting in the design of the monuments themselves. Astronomers like Hawkins and Hoyle believe that the 56 Aubrey holes in Stonehenge were designed to track the lunar nodal cycle, which is associated with lunar standstills and eclipses. Similarly, the 127 kerbstones at Knowth may have been a device for counting tropical moons; 127 is the number of tropical moons in half a lunar nodal cycle. Knowledge of the rhythm of heavenly cycles would have given neolithic people a way to anticipate and confirm the periodic sighting of heavenly bodies along alignments. Click here for details.


The objective of this programme would be to determine what scientific correlation, if any, might exist between measurable local variations or anomalies in the Earth's magnetic field.and the unusual qualities which the theories of geomancy and the related practice of dowsing ascribe to some megalithic sites and other features of a landscape. Click here for details.


The objective of this programme would be to investigate the acoustic properties of megalithic monuments, including the Helmholtz resonance phenomenon which has been found to occur when music is perfomed in some chambered cairns. Helmholtz resonance is the scientific name for the hollow type of sound created by blowing a stream of air across the top of an empty bottle, which has been recorded in cairns in Scotland. If many chambered cairns have this characteristic, it is possible that they were also designed for the ritual performance of music.Click here for details.


Please email your comments to Michael O'Callaghan at or contact him at this address.



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Updated 25 May 2001
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