Winter solstice

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Image:Earth-lighting-winter-solstice EN.png

In astronomy, the winter solstice is the moment when the earth is at a point in its orbit where one hemisphere is most inclined away from the sun. This causes the sun to appear at its farthest below the celestial equator when viewed from earth. Solstice is a Latin borrowing and means "sun stand", referring to the appearance that the sun's noontime elevation change stops its progress, either northerly or southerly. The day of the winter solstice is the shortest day and the longest night of the year.

In the northern hemisphere, the winter solstice usually falls on December 21/December 22, which is the southern hemisphere's summer solstice. At this time, the sun appears over the Tropic of Capricorn, roughly 23.5 degrees South of the earth's equator. In the southern hemisphere, winter solstice falls on June 21/June 22, which is the northern hemisphere's summer solstice. At this time, the sun appears over the Tropic of Cancer.

Since the winter solstice, summer solstice, vernal equinox, and autumnal equinox were probably observed for the first time by people in the northern hemisphere, these naming conventions originally corresponded to the northern hemisphere's seasons. In most reckonings, the winter solstice is midwinter. In Ireland's calendar, the solstices and equinoxes all occur at about midpoint in each season. For example, winter begins on November 1, and ends on January 31.

In the Chinese calendar, the winter solstice is called dōng zhì (冬至, "winter's extreme") and is traditionally regarded as one of the year's most important Jiéqìs, comparable to Chinese New Year. Rather confusingly, the character 至 may also mean "arrival" in other contexts, but it is clear that the Chinese consider "winter's arrival" (立冬 lì dōng, literally "establishment of winter") to be a separate Jiéqì which falls on or around November 7 instead.

The winter solstice is the time when the Germanic festival of Yule was celebrated; it is celebrated today as a Neopagan Sabbat. Many cultures celebrate or celebrated a holiday near (within a few days) the winter solstice; examples of these include Yalda, Saturnalia, Christmas, Karachun, Hanukkah, Festivus, Kwanzaa, and HumanLight. In her fiction, Ursula K. Le Guin calls the solstice celebration "The Festival of Sunreturn". (See also List of winter festivals)

The solar term Dongzhi in Chinese astronomy

Dongzhi (冬至) is a solar term begins when Sun lies between the celestial longitude of 270° and 285°. It sometimes refers in particular to the day when Sun exactly at the celestial longitude of 270°. It usually begins around December 22, and ends around January 6.

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