Sunlight warms up the passage and chamber of Cairn T atop the hill of Carnbane East at Loughcrew at dawn on the Spring Equinox. All of the carvings on the passage orthostats come alive, dancing to the tune of the waxing daylight.
A series of cleverly-positioned stones "shape" the sun's light into a square shape as it enters the chamber.
In the chamber, the sun's warm light penetrates into the rear, where it illuminates stones which appear to have etchings of the sun carved onto their surface.
This is the "Equinox Stone" in the rear of the chamber which receives direct sunlight on the equinoxes. In this photo, the stone is illuminated by indirect sunlight, after the beam has left the rear chamber.
By about 7.38am, when the above photo was taken, direct sunlight no longer strikes the back stone, instead illuminating stones just outside the rear recess.
The American author Martin Brennan believed the mound-builders were competent calendar makers. Is this carving an example of their skill in this area?
This stunning image showing sunlight on the Equinox Stone was taken by photographer Ken Williams on March 20th, 2007. Ken's beautiful images can be found on his website, Shadows and Stone.
Click here to see an RTE television news report of the Spring Equinox event 2007.