【Traditions English】Summer Solstice 夏至

The summer solstice , also known as estival solstice or midsummer , occurs when one of the Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere (Northern and Southern). For that hemisphere, the summer solstice is when the Sun reaches its highest position in the sky and is the day with the longest period of daylight. Within the Arctic circle (for the northern hemisphere) or Antarctic circle (for the southern hemisphere), there is continuous daylight around the summer solstice. On the summer solstice, Earth's maximum axial tilt toward the Sun is 23.44°. [3] Likewise, the Sun's declination from the celestial equator is 23.44°. The summer solstice occurs during summer. [4] This is the June solstice in the Northern Hemisphere and the December solstice in the Southern Hemisphere . Depending on the shift of the calendar, the summer solstice occurs sometime between June 20 and June 22 in the Northern Hemisphere [5] [6] and between December 20 and December 23 in the Southern Hemisphere. [7] The same dates in the opposite hemisphere are referred to as the winter solstice . Since prehistory, the summer solstice has been seen as a significant time of year in many cultures, and has been marked by festivals and rituals. Traditionally, in many temperate regions (especially Europe), the summer solstice is seen as the middle of summer and referred to as "midsummer". Today, however, in some countries and calendars it is seen as the beginning of summer. 夏至 ，是 二十四節氣 之一。每年6月21日前後（20日～22日）， 太陽 到達 黃經 90°時開始。是最早被確定的一個 節氣 。西元前7世紀，古人用 土圭 量日影，夏至這一天日影最短，因此把這一天稱作「夏至」。 《 月令七十二候集解 》：「五月中……夏，假也，至，極也，萬物於此皆假大而至極也。」 《漢學堂經解》（ ISBN 9787806940235 ）所集崔靈恩《三禮義宗》：「夏至為中者，至有三義：一以明陽氣之至極，二以明陰氣之始至，三以明日行之北至。故謂之至。」
夏至日太陽直射點 夏至日太陽幾乎直射 北回歸線 ， 北半球 白晝最長， 北極圈 及其以北的地區太陽整日不落，形成面積最大的 極晝 區。此日過後，陽光直射位置向南移動，北半球白晝逐漸減短，日出、日落的方位也開始往南移動，直至冬至為止。在北回歸線及其以北地區，正午 太陽高度 亦日漸降低，日影逐漸被拉長。但由於太陽輻射到地面的能量仍比地面向空中發散的多，所以在短時間內氣溫繼續升高。 「至」也有極點的意思。在傳統的 陰陽 理論中，夏至是陽氣生發到極點，開始收藏的節氣。 《 易經 》 姤卦 ，為五月卦，一陰起於下（ 夏至一陰生，冬至一陽生 ），孚夏至之時令。陽氣雖盛已經失勢，陰長陽消之象。 與 冬至 相同的是，夏至在中國古代也是重要的 傳統節日 （ 節氣 ），只是現代活動相對比較少