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Gan De
(c. 400 B.C. - c. 340 B.C.)
Chinese astronomer who was one of the earliest to make observations and record them with dates and coordinates. He wrote Suixing Jing (Treatise on Jupiter), which though lost, was reference by later writers. Nothing is known of Gan De's life; the dates given are very approximate. However, it is known he was recording observations in summer 365 B.C. about Jupiter, and—it has been speculated—its satellite Ganymede (2000 years before Galileo).
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Science Quotes by Gan De (3 quotes)
Every 12 years Jupiter returns to the same position in the sky; every 370 days it disappears in the fire of the Sun in the evening to the west, 30 days later it reappears in the morning to the east...[Observation in 4th century B.C.]
— Gan De
In the lost book Suixing Jing (Treatise on Jupiter), quoted in the extensive compilation Kaiyuan Zhanjing, (The Kaiyuan Treatise on Astrology (compiled 718-726). Quotation as given in Norman K. Glendenning, Our Place in the Universe (2007), 126. Source cited in Helaine Selin, Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures (1997), 342.
In the year of chan yan..., Jupiter was in [the Zodiacal Division of] Zi, it rose in the morning and went under in the evening together with the Lunar Mansions Xunu, Xu and Wei. It was very large and bright. Apparently, there was a small reddish (chi) star appended (fu) to its side. This is called “an alliance” (tong meng).
— Gan De
As given in Chinese Astronomy and Astrophysics (1981), 5, 242.
Jupiter was very large and bright. Apparently, there was a small reddish star appended to its side. This is called “an alliance.”
[Observation in summer 365 B.C., speculated to be of Ganymede.]
[Observation in summer 365 B.C., speculated to be of Ganymede.]
— Gan De
In the lost book Suixing Jing (Treatise on Jupiter), quoted in the extensive compilation Kaiyuan Zhanjing, (The Kaiyuan Treatise on Astrology (compiled 718-726). As given Helaine Selin, Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures (1997), 342. It has been speculated that it was the moon Ganymede beside Jupiter, by Xi Zezong in 'The Discovery of Jupiter’s Satellite Made by Gan De 2000 years Before Galileo,' Chinese Physics (1982), 2, No. 3, 664–67.
In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion.
(1987) -- 
