The Winter Solstice is an astronomical phenomenon that marks the shortest day and the longest night of the year. In the Northern Hemisphere, the Winter Solstice occurs on 21 or 22 December, when the sun shines directly over the tropic of Capricorn. At sunrise on the shortest day of the year, for 17 minutes, direct sunlight can enter the Newgrange monument, not through the doorway, but through the specially contrived small opening above the entrance known as the ‘roof box’, to illuminate the Chamber.