Equations of time, elliptical orbits of the earth and solar alignments were the subject of intense discussions in a Co Galway garden yesterday when Ireland's largest sundial was unveiled.
The clock-cum-calendar was designed by Jenny Beale and her husband, Dr Colin Brown, at Brigit's Garden - run by the couple as a non-profit charity in Roscahill, beyond Moycullen.
Master of ceremonies for the unveiling was ornithologist, artist and environmentalist Gordon D'Arcy, who noted sundials were the oldest existing piece of scientific instrumentation.
Even as a qualified mathematician and scientist, he found himself "completely bewildered" by the complexity. The "gnomon", which casts the shadow, was made from bog oak by sculptor Ronnie Graham and its precise position towards the southern end of the circle was carefully calculated using an Ordnance Survey 1:50,000 map and a global positioning system (GPS) satellite receiver.
Describing the project's genesis, Dr Colin Brown paid tribute to Maire Ní Chionna of Galway County Council, who spent many nights out on location with distance-measuring instruments.
Also involved was artist Mick Wilkins, who carved the lettering on the dial and set in stone the three faces of Saint Brigit after whom the garden is named.
Whereas a normal sundial tells the time from the shadow's position as it moves clockwise around a dial marked with hours, the date can also be ascertained from the shadow's length, Dr Brown explained. In winter, the sun is low in the sky and the shadow is long, while it shortens with summer.
The final design accounts for many complexities, with colour-coded times, dates and months linked by figure-of-eight curves or "petals" of successive "analemmas". The garden is open daily from spring to the end of September and its managers intend to use the sundial for educational projects with younger visitors.