Winter solstice occurs when the earth's semi-axis tilts farthest from the sun. This occurs twice with the planet earth each year. When the northern hemisphere is tilted farthest from the sun, which occurs on approximately December 20th to 22nd each year, the northern hemisphere's winter begins. When the southern hemisphere is tilted farthest from the sun, which occurs on approximately June 20th to June 22nd each year, the southern hemisphere's winter begins. The maximum axial tilt of the earth is reached when the northern or southern winter solstices occur. When one hemisphere experiences summer solstice, the other hemisphere experiences winter solstice.
The word solstice is derived from Latin, meaning 'sun stands still' and was chosen because during a solstice the sun appears to remain still in its position in the sky.
Although the solstice is marked by a whole day on the calendar, it's actually just the brief moment when the sun is exactly over the Tropic of Capricorn that the event occurs.
When winter solstice occurs in the southern hemisphere it experiences its longest night and shortest day of the year. The opposite is true when the summer solstice occurs, and the southern hemisphere experiences its longest day and night.
Meteorologists consider the first day of winter to be Dec. 1, but ask an astronomer — or just about anyone else — and they'll likely answer that the winter solstice marks the start of the season. There are two ways to look at it: meteorological seasons and astronomical seasons. Meteorological seasons are based on the annual temperature cycle, explains NOAA, while astronomical seasons are based on the position of the Earth in relation to the sun.
When winter solstice occurs in the northern hemisphere it experiences its shortest day and longest night of the year. The opposite is true when the summer solstice occurs, and the northern hemisphere experiences its longest day and shortest night.
Since 1793, the full moon has only occurred on the winter solstice 10 times, according to the Farmer's Almanac. The last one was in 2010, which was also a lunar eclipse! The next full moon on a winter solstice won't be until 2094.
For days before and after the winter solstice occurs, the sun appears to stand still in the sky at its noon-time elevation.
Some confuse the solstice with the equinox. Both occur twice a year, but the equinox occurs when the sun is directly above the equator, day and night are equal in length, and the equinox marks the beginnings of fall and spring, depending on the hemisphere.
Since Christ wasn't issued a birth certificate, there's no record of the date when he was supposed to have been born. Meanwhile, humans have been celebrating the winter solstice throughout history — the Romans had their feast of Saturnalia, early German and Nordic pagans had their yuletide celebrations. Even Stonehenge has connections to the solstice. But eventually Christian leaders, endeavoring to attract pagans to their faith, added Christian meaning to these traditional festivals. Many Christmas customs, like the Christmas tree, can be directly traced to solstice celebrations.
Stonehenge, in Wiltshire, England is a popular spot during winter and summer solstice in the northern hemisphere. Newgrange in Ireland is another monument dating back thousands of years that appears to have been built in alignment with the solstice.
The winter solstice is also referred to as Midwinter, the Longest Night, and Yule.
Solstices have been used throughout history to time many important events each year, including the sowing of seeds for crops, mating of animals, harvesting of crops, and monitoring the reserves of winter food.
The actual moment that the solstice occurs cannot be observed by amateurs because the sun moves so slowly that astronomical data tracking must be used to pinpoint the actual moment of the solstice.
During the winter solstice the sun appears to be at its lowest point in the sky.
Following the winter solstice the days begin to become longer while the nights begin to shorten.
Following the winter solstice the temperatures become colder. In the northern hemisphere the coldest months are December, January and February, while in the summer hemisphere the coldest months are June, July, and August.
During the solstice, whether it is summer or winter solstice, the sun isn't moving - it's actually the earth tilting to and away from the sun.
Although winter solstice marks the beginning of the astrological winter, the coldest winter days are yet to come, often not for a month or even two in some years.