Gan De

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Gan De (Chinese: 甘德; Wade-Giles: Kan Te, fl. 4th century BC) was a Chinese astronomer/astrologer born in the State of Qi [1] also known as the Lord Gan (Gan Gong). Along with Shi Shen, he is the first in history to compile a star catalogue, followed by the Greek Hipparchus who was the first in the Western tradition to create a star catalogue.

Contents

[edit] Observations

Gan De made some of the first detailed observations of Jupiter in recorded history. He described the planet as "very large and bright".[2] Gan De is reported to have seen one of the moons of Jupiter (either Ganymede or Callisto) with his naked eye in 364 BC,[3] long before Galileo Galilei's celebrated discovery of the same in 1610 (all four of the brightest moons are technically visible to the unaided eye, but in practice are normally hidden by the glare of Jupiter). By occluding Jupiter itself behind a high tree limb perpendicular to the satellites' orbital plane to prevent the planet's glare from obscuring them, one or more of the Galilean moons might be spotted in favorable conditions. Shi and Gan together made fairly accurate observations of the five major planets.[4]

[edit] Planetary periodic comparisons

Planet Period Predictions by Gan and Shi Modern day calculation
Jupiter sidereal period 12 years[4] 11.862615 years[5]
Venus synodic period 587.25 days[4] 583.92 days
Mercury synodic period 136 days[4] 115.88 days[6]

[edit] Celestial comparisons

Shi Shen and Gan De divided the celestial sphere into 3651⁄4°, as a tropical year has 3651⁄4 days. At the time, most ancient astronomers adopted the Babylon division where the celestial sphere is divided by 360°.[4]

[edit] Books

As the earliest attempt to document the sky during the Warring States Period, Gan De's work possesses high scientific value.[4] He wrote two books, the Treatise on Jupiter and the 8-volumes Treatise on Astronomical Astrology [7], both of which have been lost. Gan De also wrote the Astronomic star observation (天文星占, Tianwen xingzhan).[8]

It can be seen on the quotations under Shiji (volume 27) and Hanshu (volume 26), but was preserved mostly in the Treatise on Astrology of the Kaiyuan Era.[9]

In 1973, a similar catalogue by him and Shi Shen was uncovered in Mawangdui and was arranged under the name of Divination of Five Planets, it records the motion of Jupiter, Saturn, Venus and other planets in their orbits between 246 BC and 177 BC.

[edit] See also

[edit] Notes

  1. ^ Shiji 27 stated that he was from the State of Qi, however according to a commentary added by Xu Guang in the 4th century BCE state that he was from the State of Lu, further citation from another work dated to the 5th century by Ruan Xiaoxu given an account that he was from the State of Chu.
  2. ^ Hockey, Thomas A. [1999] (1999). Galileo's Planet: Observing Jupiter Before Photography. CRC Press. ISBN 0750304480
  3. ^ Xi Zezong, "The Discovery of Jupiter's Satellite Made by Gan De 2000 years Before Galileo," Chinese Physics 2 (3) (1982): 664-67.
  4. ^ a b c d e f Deng, Yinke. [2005] (2005). Chinese Ancient Inventions. ISBN 7508508378
  5. ^ (1992) in K. P. Seidelmann: Explanatory Supplement to the Astronomical Almanac. Mill Valley, California: University Science Books. Retrieved on 2007-08-08.  — p.706 (Table 15.8) and p.316 (Table 5.8.1)
  6. ^ NSSDC "Mercury Fact Sheet"
  7. ^ also known as the Gan's Treatise on Stars.
  8. ^ Peng, Yoke Ho (2000). Li, Qi and Shu: An Introduction to Science and Civilization in China. Courier Dover Publications. ISBN 0486414450
  9. ^ Another 2 volumes preserved texts were attributed to him and Shi Shen and were incorporated to the Daoist Canon during the Song Dynasty, more commonly known as the Treatise on Stars of Gan and Shi. However, the book is generally not considered to be the more reliable than the Treatise on Astrology of the Kaiyuan Era, due to the anachronistic of name of places, etc. in the texts.

[edit] References

  • Du Shiran et al (1992). Biographies of Ancient Chinese Scientists Series One: Gan De. Beijing: Kexue Chubanshe, 25-27. ISBN 7-03-002926-7. 
  • Ma Linghong (2002). Discoveries and Studies on the Bamboo and Silk Texts. Shanghai: Shanghai Shudian Chubanshe, 56-58. ISBN 7-80622-944-2. 
  • Gu Jianqing et al (1991). Great Lexicon on Chinese Arts of Necromancy. Guangzhou: Zhongshan University Press, 648. ISBN 7-306-00313-5. 
  • X. Zezong, The Discovery of Jupiter's Satellite Made by Gan De 2000 years Before Galileo, Chinese Physics 2 (3) (1982): 664-667.
  • Sky and Telescope, February , 1981.