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Shen Kuo, 1031-1095 AD, China's Greatest Astronomer?


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Hello everybody. :)

 

During the Chinese Song Dynasty (960-1279 AD), the polymath scientist Shen Kuo (1031-1095 AD) could be viewed as China's greatest astronomer in terms of sheer amount of discovery and innovation. Although there are and were notable Chinese astronomers in modern times, none of them are pioneers in their field like Shen was in his. As his wikipedia article states:

 

Being the head official for the Bureau of Astronomy, Shen Kuo was an avid scholar of medieval astronomy, and improved the designs of several astronomical instruments. Shen is credited with making improved designs of the gnomon, armillary sphere, and clepsydra clock.[60] For the clepsydra he designed a new overflow-tank type, and argued for a more efficient higher-order interpolation instead of linear interpolation in calibrating the measure of time.[60] Improving the 5th century model of the astronomical sighting tube, Shen Kuo widened its diameter so that the new calibration could observe the polestar indefinitely.[60] This came about due to the position of the polestar shifting in position since the time of Zu Geng in the 5th century, hence Shen Kuo diligently observed the course of the polestar for three months, plotting the data of its course and coming to the conclusion that it had shifted slightly over three degrees.[60] Apparently this astronomical finding had an impact upon the intellectual community in China at the time. Even Shen's political rival and contemporary astronomer Su Song featured Shen's corrected position of the polestar (halfway between Tian shu, at -350 degrees, and the current Polaris) in the fourth star map of his celestial atlas.[61] Along with his colleague Wei Pu in the Bureau of Astronomy, Shen Kuo plotted out exact coordinates of planetary and lunar movements by recording their astronomical observations three times a night for a continuum of five years.[6] Although star maps were created then and in previous times, an extensively long and time-consuming method of astronomical observation on the scale of Shen Kuo and Wei Pu's project was not proposed in Europe until the time of the astronomer Tycho Brahe (1546–1601 AD).[6]

 

The astronomical phenomena of the solar eclipse and lunar eclipse had been known in China since at least the time of the astronomers Gan De (甘德; fl. 4th century BC) and Shi Shen (石申; fl. 4th century BC).[62] The philosopher Wang Chong (王充; 27–97 AD) and astronomer Zhang Heng (張衡; 78–139 AD) both wrote of 'radiation influence' theories for solar and lunar eclipse, as Zhang Heng correctly hypothesized that the brightness of the moon was merely light reflected from the sun.[63] Shen Kuo also wrote of solar and lunar eclipses, yet expanded upon this to explain why the celestial bodies were spherical, going against the flat earth theory for celestial bodies.[64] When Zhao Wen, the Director of the Astronomical Observatory, asked Shen Kuo if the shapes of the sun and moon were round like balls or flat like fans, Shen Kuo explained that celestial bodies were spherical because of knowledge of waxing and waning of the moon.[64] Much like what Zhang Heng had said, Shen Kuo likened the moon to a ball of silver, which does not produce light, but simply reflects light if provided from another source (the sun).[64] He explained that when the sun's light is slanting, the moon appears full.[64] He then explained if one were to cover any sort of sphere with white powder, and then viewed from the side it would appear to be a crescent, hence he reasoned that celestial bodies were spherical.[64] He also wrote that, although the sun and moon were in conjunction and opposition with each other once a day, this did not mean the sun would be eclipsed every time their paths met, because of the obliquity by a small degree of their orbital paths.[64]

 

Shen Kuo is also known for his cosmological hypotheses in explaining the variations of planetary motions, including retrogradation.[65] His colleague Wei Pu realized that the old calculation technique for the mean sun was inaccurate compared to the apparent sun, since the latter was ahead of it in the accelerated phase of motion, and behind it in the retarded phase.[66] Shen's hypotheses were similar to the concept of the epicycle in the Greco-Roman tradition,[65] only Shen compared the side-section of orbital paths of planets and variations of planetary speeds to points in the shape of a willow leaf.[67] Shen's work and theory of planetary motion can also be compared to the Persian astronomer Nasir al-Din al-Tusi (1201–1274 AD), who wrote the Zij-i Ilkhani.

 

The Song Dynasty astronomers of Shen's day still retained the lunar theory and coordinates of the earlier Yi Xing, which after 350 years had devolved into a state of considerable error.[6] To fix this, Shen and Wei kept similar astronomical records for the moon and sun as they did the planets, plotting its course down three times a night for five successive years.[6] Wei and Shen's work was deeply opposed by the officials and astronomers at court, who were offended by their insistence that the coordinates of the renowned Yi Xing were inaccurate.[68] They also gathered together to slander Wei Pu since he was born a commoner, yet his expertise exceeded theirs.[69] When Wei and Shen made a public demonstration using the gnomon to prove the doubtful wrong, the other ministers reluctantly agreed to correct the lunar error and the solar error as well.[68][70] Although correcting the lunar and solar errors was a success, the other ministers and officials eventually dismissed Wei and Shen's recorded course plotting of planetary motions.[18] Therefore, only the worst and most obvious planetary errors were corrected, while minor modifications to earlier estimates were still largely inaccurate.[69]

 

http://en.wikipedia.org/wiki/Shen_Kuo

 

Shen also discovered the concept of True North relative to a navigator's position while using a compass, as opposed to magnetic declination towards the magnetic north pole.

 

But Shen Kuo was more than just an astronomer. As his wiki article states, he was a "mathematician, astronomer, meteorologist, geologist, zoologist, botanist, pharmacologist, agronomist, ethnographer, encyclopedist, poet, general, diplomat, hydraulic engineer, inventor, academy chancellor, finance minister, and governmental state inspector." He was the first in literary history to describe the magnetic needle compass, the first in China to outline the use of a drydock, dismissed the old Chinese belief in three throat valves (instead just two, esophagus and trachea), was the first in China to write of the invention of movable type printing (by Bi Sheng, died 1051), described and experimented with camera obscura just decades after Ibn al-Haytham (died 1039) was the first to do so, and even formulated a hypothesis for geomorphology (land formation). The latter was based off of his observations of inland marine fossils found in the sides of mountain cliff sides thousands of miles away from the ocean, soil erosion, uplift, and his extensive knowledge of the deposition of silt. Shen Kuo also devised a theory of gradual climate change of different regions on earth, due to many observations, one including the finding of petrified bamboo found underground in Yan'an, Shaanxi, which is a dry desertous region that does not support the habitat for the growth of bamboos.

 

If there was anyone who would have rivaled him it was his brilliant contemporary Su Song (1020-1101 AD), who constructed an astronomical clocktower featuring an escapement mechanism and the world's oldest known use of an endless power-transmitting chain drive (used to operate the rotating armillary sphere crowning the top of the building). In 1092 AD Su Song published a treatise on his astronomical clock tower, which included a celestial atlas of five different star maps. His wiki article states:

 

Su Song also created a celestial atlas as well (in five separate maps), which had the hour circles between the xiu (lunar mansions) forming the astronomical meridians, with stars marked in quasi-orthomorphic cylindrical projection on each side of the equator, and thus was in accordance to their north polar distances.[16] Not until the work of Gerard Mercator in 1569 was a celestial map of this projection created in the Western world.[16] Furthermore, Su Song must have taken advantage of the astronomical findings of his political rival and contemporary astronomer Shen Kuo (1031-1095).[17] This is so because Su Song's fourth star map places the position of the pole star halfway between Tian shu (-350 degrees) and the current Polaris; this was the more accurate calculation (by 3 degrees) that Shen Kuo had made when he observed the pole star over a period of three months with his width-improved sighting tube.[17] The greatest significance of these star maps by Su Song, however, is that they represent the oldest existent star maps in printed form.[18]

 

http://en.wikipedia.org/wiki/Su_Song

 

Su Song also wrote a pharmaceutical treatise in 1070 with related subjects of botany, zoology, mineralogy, and metallurgy, much like Shen Kuo's writing in his Dream Pool Essays of 1088.

 

What does everyone else think?

Eric

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  • 3 years later...

I'm guessing by the silence on the issue that no one really gives a hoot about Shen Kuo. That's sad, the man was a pure genius.

 

I am still a little flabbergasted by the historical impact of it all,

but thanks for the info.

 

Wonder if he did anything with psychology?

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Eric - there were many great philosophers and scientists, so much so that a study of their history would preclude a study of the science that they were the progenitors of. I wouldn't recognize Galileo, Maxwell, or Gell-Mann - and I only know Newton and Darwin cos they are/were on our currency. In my opinion it's what they say rather than who said it first and when.

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