Talk on complexities of megalithic sites


ARCHAEOLOGY, astronomy and mathematics all converge when it comes to Ireland’s megalithic tombs. The prehistoric architects of monuments such as Newgrange took great care in building and aligning these structures, leaving many questions to be answered by modern-day researchers.

The complexities of these sites were discussed yesterday at the Brú na Bóinne visitor centre where the Office of Public Works hosted two Maths Week talks by Dr Frank Prendergast of Dublin Institute of Technology.

Dr Prendergast is based in the College of Engineering and the Built Environment but his main role is as an archaeoastronomer. He studies these early sites to try to identify hidden mathematical complexity in their construction and orientation or alignments with the stars or our sun.

“We are dealing with a huge number of sites,” he told students from O’Carolan College in Nobber, Co Meath, and Gormanston College in Gormanston, Co Meath, who attended his talk yesterday afternoon. There are at least 1,500 but only 20 or so are the famous passage tombs as at Newgrange, Dowth and Knowth.

“I look at these sites from an astronomical perspective,” he said after the talk.

He talked about the history of these sites with the portal, court and passage tombs dating back to between 3,500 BC and 2,500 BC. The Bronze Age wedge tombs were somewhat later, about 2,200, he said.

He published a research paper this year on the “Lismullin Enclosure”, an important early Iron Age site revealed as construction got under way on the M3 motorway across Co Meath. Dating back to between 450 BC and 350 BC, Lismullin is a hugely important site given its complexity, he said.

It was assembled with extreme care and did not feature tombs. “Lismullin is now regarded by archaeologists as a pagan ritual site,” Dr Prendergast said.

Maths puzzle

Pi is the number of times the diameter of a circle will divide into the circumference or edge of a circle. Every time, for every circle it is always the same. It is an amazing number that starts with 3.14152 and appears to go on forever. Although in schools 22/7 was often used (before calculators) as an approximation, it cannot be expressed as one whole number divided by another.

This seriously disturbed the ancient Greeks and numbers such as these are called irrational numbers. However, pi crops up in all sorts of places in nature.

Three tennis balls fit snugly into a cylindrical tube. Which do you think is the longer, the length of the tube or the circumference?

There was an error in yesterday’s puzzle, which should have stated that five guests didn’t show rather than four. As given, the puzzle worked out at 14.45 people.

All details, methodology and solutions on

Solution:Despite appearances, the circumference is longer than the length.

Maths Week continues until next weekend.