Historical Developments in Chinese Calendar / Astronomy
2637BC Earliest recorded use of some form of calendar system was during Emporer Shih Hwang Ti's reign. During his 61st year reign he introduced the 1st cycle of the Zodiac (which we now referred to as the Sexagenary Cycle).
2000BC The Chinese divided the Equator into 24 segments, each 15° in longitude. The period taken by the Sun to traverse each segment is called a chi (approx. 15.23 days). Each chi is given a name, eg. Li chun is the time when the Sun's true longitude is between 315° and 330° meridian.
1500BC Chinese astronomical knowledge was inscribed onto Oracle bones. Records include sightings of novas, supernova and bright comets.
1300 BC The Chinese figured out the solar year was approximately 365.25 days and the synodic month to be about 29.53 days.
700BC->300BC Earliest known almanac - Xia Xiao Zheng, primarily a farmers calendar. Later versions contained more astronomical data, allowing the determination of the number of days in a month and number of months in a year.
370BC->270BC Earliest attempts to catalog various stars. The catalogue contained 1,464 stars. The position of the star was described by 3 parameters. The celestial sphere was divided into 28 unequal segments or xiu (lines joining Nth-Sth pole). Each xiu was named after a constellation that it contained (eg: Fang, Xin, Wei, etc). Angular measurements (du) was also used - there are 365¼ du's to a complete circle. A star's was specified as 101 du from the pole, 42 du from the beginning of Xin and how far from the edge of the xiu. This is analogous to current days use of longitude / latitude, azimuth / altitude or right ascension / declination to pinpoint a star.
350BC Shih Shen knew the Moon moved irregularly. By contrast, the Sun's irregularity was only discovered in 570AD. The Moon's irregular motions were only incorporated into the almanacs later in 200AD.
200BC Astronomical knowledge improved significantly and the data was quite precise.
90BC Earliest known detailed description in China of the motion of the planets.
29BC Chinese astronomers observed Sun spots by looking through slices of Jade.
20BC Chinese knew how eclipses were caused, though there were some disagreement.
8BC Predict eclipses using the 135-month period.
7BC Best known almanac - The Sun Tong contained relatively accurate data for the Sun, Moon and the planets.
✍: K H Leong
2021-09-07, 437👍, 0💬
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