你知道這些冬至科普小知識嗎

What is the winter solstice, and why do we have it?

什麼是冬至？爲什麼有冬至這個節氣？

"Earth's axis is tilted 23.5 degrees relative to its orbit, and on December 21, Earth will be at the point in its orbit when the North Pole is tilted at its maximum away from the sun," Schneider told CBS News. "The effect of this in the Arctic is completely in darkness as Earth spins that day."

施奈德說：“地軸相對於自轉軌道的傾角爲23.5度。12月21日，地球的北極距離太陽最遠。這會導致當天北極圈地區完全見不到太陽。”

For those of us in the Northern Hemisphere, it's the day with the shortest amount of daylight — less than 12 hours — and our longest night of the year. However, that's not the case for everyone. While it's winter for those of us in the Northern Hemisphere, people in the Southern Hemisphere experience it as their summer solstice with the longest stretch of daylight.

對北半球的人們來說，冬至這一天白晝最短，不到12小時，夜晚最長。但並不是對所有人都這樣。北半球經歷寒冬時，南半球在這一天迎來白晝最長的夏至日。

When does the winter solstice occur?

冬至在哪天？

The Earth's North Pole will be tilted farthest from the sun at 11:27 am ET on Thursday, Dec. 21, 2017, according to the National Weather Service.

根據美國國家氣象局的數據，今年的冬至發生在美國東部時間2017年12月21日上午11點27分（北京時間2017年12月22日零點27分），此時北極距離太陽最遠。

Why isn't the winter solstice on the same day each year?

爲什麼每年的冬至都不是同一天？

The date of the winter solstice varies from year to year for people in different time zones. It typically occurs around Dec. 21 or 22, though on rare occasions it can be as early as Dec. 20 or as late as Dec. 23, according to the Weather Channel.

根據天氣頻道的數據，對不同時區的人們來說，冬至的日期每年會有變化。多數年份的冬至日都在12月21日或者22日，偶爾提早到20日，或者錯後到23日。

That's because our calendars aren't a precise match to the solar year.

這是因爲日曆與陽曆並非完全吻合。

Schneider writes: "Earth takes about 365 1/4 days to orbit the Sun. Next year, the moment of the solstice will be about 6 hours later at 5:23 pm ET. In 2019, it will be at 11:19 pm ET, so for people living in Puerto Rico and other time zones to the east, the date of the solstice will be on the 22nd."

施奈德寫道：“地球圍繞太陽公轉週期爲365又1/4天。明年的冬至比今年大約遲6個小時（美國東部時間下午5點23分），後年又推後到美國東部時間晚上11點19分。所以對於居住在波多黎各及以東時區的人們來說，冬至日期是22日。”

Is the winter solstice the coldest day of the year?

冬至日是全年最冷的一天嗎？

The winter solstice is not normally the coldest day of the year. There is actually a lag between the shortest day of the year and the coldest average temperatures, the National Weather Service reports.

美國國家氣象局報告說，冬至日通常不是全年最冷的一天。白晝最短的一天與平均氣溫最低的一天之間其實有延遲。

"The coldest time usually comes a month or two later because even though the amount of solar heating is beginning to increase, it isn't yet enough to reverse the cooling," Schneider says. "This effect, called 'the lag of the seasons,' is similar to how when you turn down the heat while you're cooking — the pot won't immediately reach its coolest temperature."

施奈德說：“全年最冷的時候通常比冬至日晚一兩個月，因爲儘管日照開始變長，但仍不足以改變寒冷的趨勢。這稱爲‘季節延遲’，就像你做飯時關火以後，鍋的溫度不會馬上降低。”

Will shadows on the day of the solstice be longer?

冬至日這天影子會變長嗎？

Noontime shadows on Thursday will be longest for those of us in the Northern Hemisphere because the sun doesn't rise as high in the sky. The closer you are to the Arctic, the longer the shadows (and the shorter your day) will be.

對北半球的人們來說，冬至這天中午時影子最長，因爲太陽的高度最低。越靠近北極圈，影子越長，白晝時間越短。

Why doesn't the earliest sunset come on the shortest day?

爲什麼白晝最短的當天日落並非最早？

The winter solstice may be the shortest day of the year, but that doesn't mean you'll have an early sunset. The exact date of the earliest sunset depends on your latitude, so it's not the same for everyone.

冬至日是全年白晝最短的一天，但並不意味着日落最早。日落最早在哪天取決於你所在的緯度，對每個地方的人來說都不同。

Ancient Chinese people divided 81 days after winter solstice(regarded as coldest time of the year) into 9 parts. Many used "double-nine" diagrams to count the days to spring, either by recording the weather or writing one stroke of a character on a daily basis.

中國古人將冬至日後的81天分爲九個“數九天”，視爲全年最冷的一段時間。民間有貼九九消寒圖的習俗，用於計數春天來臨之前的日子，有些是通過記錄天氣，有些則是通過每日寫一筆來計算數九天。

China has developed an unique festive food culture throughout the years. Eating dumplings is a common folk custom for many Chinese on the day of winter solstice, especially those living in the north.

冬至經過數千年的發展，形成了獨特的節令飲食文化，吃餃子則是多數中國人冬至的習俗。在北方尤其突顯。

When midwinter comes, vital movement begins to decline and calm down. In this period, eating an appropriate amount of nuts, such as peanuts, walnuts, chestnuts, hazelnuts and almonds, is good for one's body.

冬至來臨後，人們開始減少活動。這段時間食用適量堅果對身體非常有益，比如花生、核桃、栗子、榛子和杏仁。

People in Suzhou, Jiangsu province, are accustomed to eating wontons in midwinter. According to legend, during the midwinter feast 2,500 years ago, the King of Wu was disgusted with all kinds of costly foods and wanted to eat something different. Then, the beauty Xishi came into the kitchen to make "wontons" to honor the king's wish. He ate a lot and liked the food very much. To commemorate Xishi, the people of Suzhou made wontons the official food to celebrate the festival.

江蘇蘇州的人們習慣在冬至吃餛飩。根據歷史傳說，在2500年前的冬至時節，吳國國王厭倦了所有的昂貴美食，想吃些特別的口味。爲迎合吳王的心願，美女西施去廚房做了一碗餛飩。吳王很喜歡，吃了一大碗。爲了紀念西施，蘇州人會在冬至做餛飩慶祝節日。

In places such as Shanghai, people eat tangyuan, a kind of stuffed small dumpling ball made of glutinous rice flour to celebrate Winter Solstice.

在上海等地，人們吃湯圓慶祝冬至。湯圓是圓形的糯米粉團，中間塞滿餡料。

In Yinchuan, Ningxia Hui autonomous region, people call midwinter the "Ghost Festival". On that day, it is customary for people there to drink mutton and vermicelli soup and eat the dumplings in the soup. They give the midwinter soup a strange name: "brain" and share it with their neighbors.

在寧夏銀川，大家稱冬至爲“鬼節”。這天的習俗是吃羊肉粉湯餃子，此外他們還給這道美味起了個古怪的名字“頭腦”。粉湯餃子做好後還要給鄰居端上一碗。

During the Winter Solstice, Hangzhou residents traditionally eat rice cakes. In the past, before the approach of the winter solstice, every household would make the cakes to worship their ancestors or use as gifts for relatives and friends.

杭州居民有冬至吃年糕的傳統。過去每家每戶都會在冬至到來前製作年糕來供奉先人或者饋贈親友。

In some regions south of the Yangtze River, the whole family gets together to have a meal made of red-bean and glutinous rice to drive away ghosts and other evil things.

在我國長江流域以南的一些地區，在冬至之夜有全家歡聚一堂共吃紅豆糯米飯來驅避疫鬼的習俗。

Taiwan residents keep the custom of offering nine-layer cakes to their ancestors. People with the same surname or family clan gather at their ancestral temples to worship their ancestors in order of their ages. After the sacrificial ceremony, there is always a grand banquet.

臺灣地區還保存着冬至用九層糕祭祖的傳統。同姓或同家族的人們在祠堂前相聚，按輩分祭祖。祭祖儀式後還會舉辦盛宴。