Winter Solstice

In astronomy, the solstice is either of the two times a year when the Sun is at its greatest distance from the celestial equator, the great circle on the celestial sphere that is on the same plane as the earth's equator.

In the Northern Hemisphere, the winter solstice occurs either December 21 or 22, when the sun shines directly over the tropic of Capricorn; the summer solstice occurs either June 21 or 22, when the sun shines directly over the tropic of Cancer.

In the Southern Hemisphere, the winter and summer solstices are reversed.

Longest Night of the Year:
The winter solstice marks the shortest day and the longest night of the year.

The sun appears at its lowest point in the sky, and its noontime elevation appears to be the same for several days before and after the solstice. Hence the origin of the word solstice, which comes from Latin solstitium, from sol, “sun” and -stitium, “a stoppage.” Following the winter solstice, the days begin to grow longer and the nights shorter.