Translated by DeepSeek V4 Pro. Translations can be inaccurate, please refer to the original post for important stuff.
Jianlin SuJune 16, 2010#681
Happy Dragon Boat Festival
It is that time of the year again
for the festival... I won’t say much, but in short: be
happy! By the way, I hope Scientific Space
receives support from even more people!
The Astronomical Meaning of the “Dragon Boat
Festival”
In Chinese history, the “Dragon Boat Festival” (Duanwu Festival) is
also known as the “Duanwu (Five) Festival, Duanyang Festival, Zhongwu
Festival, Tianzhong Festival, and Tianchang Festival.” What do these
names mean?
Have you eaten Zongzi today?
In ancient Chinese, “Duan” has three meanings: “beginning, upright,
and extreme”; “Wu” and “Five” have the meanings of “middle, upright, and
extreme.” This means that “Duanwu” is, first and foremost, an
astronomical and ethno-mathematical concept. As we know, the earliest
Xia Calendar in China was a ten-month solar calendar, where a solar year
was calculated according to ten months. In the basic counting of “ten,”
five is the middle number, marking the return position of a solar year.
This is somewhat similar to the “stopping point, dead center” in
circular motion or the “inflection point” on a curve in modern physics.
Since the implementation of the “Taichu Calendar,” a lunisolar calendar
in the Western Han Dynasty, the two solar terms of Winter Solstice and
Summer Solstice have represented the positions of the sun on the Tropic
of Capricorn and the Tropic of Cancer, respectively. That is to say, in
a year, the Winter Solstice in the Xia Calendar (approximately December
21–22 in the Gregorian calendar) is the festival located at the extreme
position of the Tropic of Capricorn, while the Summer Solstice (June
21–22 in the Gregorian calendar) is the festival located at the extreme
position of the Tropic of Cancer.
The Winter Solstice is the day when people in the China region
experience the shortest daylight and the longest night of the year.
Every year after the Winter Solstice, the sun begins to move from south
to north relative to the Earth; thus, the daylight begins to lengthen
and the night begins to shorten based on the Winter Solstice. In
contrast, when the sun moves step by step to the position of the “Summer
Solstice” relative to the Earth, it is the day when people in the China
region experience the longest daylight and the shortest night. After the
Summer Solstice, the sun begins to move from north to south relative to
the Earth, so the daylight begins to shorten and the night begins to
lengthen under this reference frame of the Summer Solstice.
