The winter solstice also known as
midwinter occurs when one of the Earth's poles has its maximum tilt away from
the Sun. It happens twice yearly, once in each hemisphere. For that hemisphere,
the winter solstice is the day with the shortest period of daylight and longest
night of the year, when the Sun is at its lowest daily maximum elevation in the
sky. At the pole, there is continuous darkness or twilight around the winter
solstice. Its opposite is the summer solstice. Also, the sun goes 90 degrees
below the horizon at solar midnight to the nadir.
History
The solstice may have been a
special moment of the annual cycle for some cultures even during neolithic
times. Astronomical events were often used to guide activities, such as the mating
of animals, the sowing of crops and the monitoring of winter reserves of food.
Many cultural mythologies and traditions are derived from this.
Observations
Although the instant of the solstice can be calculated, direct observation of the solstice by amateurs is impossible because the sun moves too slowly or appears to stand still (the meaning of "solstice"). However, by use of astronomical data tracking, the precise timing of its occurrence is now public knowledge.