In the early morning of December 21 each year, the light from the rising sun aligns perfectly with the "roof-box" opening of the Newgrange neolithic passage tomb, travels up the 19m corridor and enters the watertight central chamber where it illuminates it completely.
Is the solstice on the same day every year?
This year marks a very special anniversary.
Ireland's Ancient East, in conjuction with Ripplecom, will stream the solstice around the world to a potenial audience of millions. The monument is carefully positioned so that on the day of the winter solstice, the sun sets through a gap in the stones. It represents the exact moment when the Northern Hemisphere is tilted at its furthest point away from the sun.
It would make sense that the shortest day of the year would also be the coldest, but that's actually a bit of a misnomer. The sunrise will occur at 7:16 a.m. and, then, the sun will reach the spot right above the Tropic of Capricorn at 11:27 a.m.
It sure is, and has been for centuries.
Here's everything you need to know about the December solstice, the day the sun "stands still".
The word "Yule" - used to describe the Christmas season - is believed to have come from the Norse word "jol" which referred to the winter solstice festival. And that's why, for millennia, humans have celebrated the solstice-for the return of the sun that it marks.
The summer solstice happens in June. Now every year on the winter solstice people flock from across the globe to Newgrange in County Meath, to feel closer to their ancestors and catch a glimpse of their ancient Ireland's engineering expertise.
Stonehenge is an ancient monument in England that is often mentioned in the same breath as the winter solstice.