Gan De

Gan De was a 4th century BC Chinese astronomer and astrologer . Chr.

Gan De came from Shu , Qi or Lu , the sources do not agree. According to Shiji, it comes from Qi.

He is one of the earliest Chinese astronomers known by name. The writings Suixing jing (a treatise on Jupiter, then called Suixing, star of the year ) and Tianwen xinzhan (astrological predictions) come from him. Excerpts or quotations are collected in Kaiyuan Zhanjing (Kaiyuan treatise on astrology, between 718 and 726 AD). Like his contemporary Shi Shen , he also wrote a star catalog with coordinates, which later became part of a joint catalog by himself and Shi Shen ( Gan Shi xin jing ). The coordinates given there, however, correspond to a later period (around 70 BC).

He gave precise information about Jupiter in its twelve-year period and stated that in 365 BC. To have observed a companion of Jupiter (which could only be the brightest Jupiter moon Ganymede ), which is possible under ideal conditions, although it is mostly outshone by the shine of Jupiter (Ganymede is only 5.9 arc minutes away from Jupiter and Jupiter 760 - times brighter). The companion appeared reddish to him, which, strictly speaking, cannot be observed with its low brightness. He knew the concept of the synodic period of the planets and determined it for Mercury to be 136 days (today 115.9), Venus as 587.25 days (today 583.9) and Jupiter as 400 days (today 398.9).

literature

Li Di: Gan De , in Thomas Hockey (Ed.): Biographical Encyclopaedia of Astronomers . Springer 2005, p. 404
Xi Zezong: The Discovery of Jupiter's Satellite Made by Gan De 2,000 Years Before Galileo, In: Chinese Physics Volume 2, 1982, pp. 664–667 (and Acta Astrophysica Sinica Volume 1, 1981, p. 87)
Huang Yi-Long: Gan De , in: Helaine Selin (Ed.), Encyclopaedia of the history of science, technology, and medicine in non-western cultures Springer, 1997, p. 957

Web links

John J. O'Connor, Edmund F. Robertson : Gan De. In: MacTutor History of Mathematics archive .

Individual evidence

↑ ^a ^b ^c Li Di: Gan De in Thomas Hockey (Ed.), Biographical Encyclopaedia of Astronomers . Springer 2005, p. 404.
↑ ^a ^b Huang Yi-Long: Gan De , in: Helaine Selin (Ed.), Encyclopaedia of the history of science, technology, and medicine in non-western cultures. Springer, 1997, p. 957.
↑ A reprint of Kaiyuan Zhanjing, ed. Qutan Xida, appeared in 1985 in the Taiwan Commercial Press, Taipei

personal data
SURNAME	Gan De
BRIEF DESCRIPTION	chinese astronomer
DATE OF BIRTH	4th century BC Chr.
DATE OF DEATH	4th century BC Chr.

[li-1] Li Di: Gan De in Thomas Hockey (Ed.), Biographical Encyclopaedia of Astronomers . Springer 2005, p. 404.

[yi-2] Huang Yi-Long: Gan De , in: Helaine Selin (Ed.), Encyclopaedia of the history of science, technology, and medicine in non-western cultures. Springer, 1997, p. 957.

[3] A reprint of Kaiyuan Zhanjing, ed. Qutan Xida, appeared in 1985 in the Taiwan Commercial Press, Taipei