This past Christmas was the second year running that no member of the public was admitted to Newgrange. Only a tiny number live to go back five millennia in time. Pre-pandemic, a lottery would permit a handful to live the dawn on any given December 21: The magical and mythical winter solstice. For the rest of us, the Brú na Boinne experience is not quite so moving – a tour guide’s old-school torch mimics the sun lighting up the chamber. Yet one cannot but experience it all and wonder how, over 5,000 years ago, primitive man knew so much about…