Heritage Ireland are proud to present a "live" webcast of the winter solstice at Newgrange. The live stream will begin at 8.30 am on 21st and 22nd December 2007.
Thanks to nwhyte.
More at Crooked Timber here.
Newgrange is a clock. The shaft leading out to the roof box is precisely aligned so that on the morning of the Winter Solstice the first light of day will run directly into the middle of the tomb. Or, at least, it was precisely so aligned. It is so old that changes in the Earth’s orbit have affected its operation. When it was built, the sun would have struck the back wall of the chamber, rather than the floor, and the light would have remained in the chamber for about four minutes longer than it does now. It was very accurate. The people who built Newgrange knew what they were doing.