The Sun Comes Down Only at the Salstice

Four thousand years ago, there was people in ireland who had a sufficient understanding of astronomy to be able to build this giant tomb. And what it's doing is in whether the sun is actually coming back or not. People are always racking their brains about why did they want this thousand years ago? What did they do? What rituals did they perform? Why does the sun come down here only only at the salstice? My guess is, folkin parania, i reckond to the people in irelands, four thousand years ago. New grange, to them, was like the most important scientific centre that they had available to em.