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Wikipedia notes that, while knowledge Earth is approximately spherical was obtained in ancient Greece, and became standard among educated people in Europe and the Middle East long before 1300 AD, China persisted in the flat-Earth model until a Jesuit influence in the 1600s, despite a 1267 gift of a Persian globe from Jamal ad-Din. China is also in usual in that its flat-Earth model was of a square rather than a circle, the latter common in other cultures.

My guess is that knowledge elsewhere of Earth's shape derived from Greek texts (and replication of the experiments they described), and that it wasn't so much that China was "the odd one out" as that there were very few independent realisations of the Earth's sphericity. However, feel free to correct me on this.

Why was Chinese astronomy so slow to adjust on this point? Why did Jamal ad-Din make so much less of an impression than the later Jesuits?

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  • $\begingroup$ First question: was there any Chinese astronomy separate from astrology back then? Besides, spherical earth (separate from heliocentrism) is determinable from Sun-shadows, but it takes one person with proper insight to run the experiments. $\endgroup$ – Carl Witthoft Dec 12 '17 at 19:43
  • $\begingroup$ I'm not sure what you're referring to as "China persisted in the flat-Earth model until...1600s". There's at least this: en.wikipedia.org/wiki/Armillary_sphere, and you can read related stuff in en.wikipedia.org/wiki/Chinese_astronomy. How would you conclude the nature of the beliefs held by "educated people" who were not experts? $\endgroup$ – Lee David Chung Lin Dec 12 '17 at 20:06
  • $\begingroup$ @LeeDavidChungLin The armillary sphere concerns celestial objects' arrangements around Earth, not whether Earth is itself spherical. I think a 1609 encyclopaedia claiming Earth to be flat is a good sign of what educated people thought back then, unless their authors in China were in the habit of humouring misconceptions limited to the inexpert. $\endgroup$ – J.G. Dec 12 '17 at 21:12
  • $\begingroup$ China had extensive contact with Indian and Islamic societies, who were aware of the Earth being a sphere, and Chinese astronomers were aware that lunar eclipses were due to the Earth's shadow, which again makes it likely the idea would have occurred to them. My guess as to why the traditional view held out despite this is due to the strong importance of Geomancy amongst the Chinese elite. This tied geography to traditional religious texts that pre-dated the idea of a spherical earth, and worked from a model of a flat, square world. $\endgroup$ – simplicio Dec 12 '17 at 23:18
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It is hard to say why history happened one way rather than another. But we can point at some differences between ancient Greece, Hellenistic Mediterranean or Renaissance Europe and ancient and medieval China that arguably contributed not only to the persistence of flat Earth, but to the cultural slow motion generally, see Is the Scientific Method uniquely Western? for a broader theme. The former were a motley of city-states or countries with high levels of diversity, mobility and cultural exchange, while China was a much more culturally uniform traditional society that favored isolationism. Traditional societies effect change differently than dynamic ones, their tools and procedures improve through accumulation of incremental glacial changes, generational trial and error, rather than through intentional innovation guided by scientific inquiry. Here is Stein's characterization of Babylonian mathematics, that applies as well to Chinese astronomy:

"...for the Babylonians, mathematics was not an enterprise, but a lore and a skill possessed by the priestly or scribal class, for use in essentially administrative functions, and passed on from generation to generation much as were the techniques of the craft guilds in the middle ages. Of course, the techniques had to have been discovered; and innovations might occur from time to time; but invention or discovery was no more the business of those trained in the lore, than it was the business of the medieval master of a craft."

In recent decades there has been some progress in evolutionary modeling of cultural development, see. e.g. Is human cultural evolution Darwinian? by Mesoudi et al. (2004), although the approach is still controversial. From this perspective traditional societies suppress random drift, and do not provide enough opportunities for cultural "mutations" (so-called "memes") to spread and gain a foothold even when they do arise. This is how endemic populations are maintained in stable isolated environments.

Flat square Earth surrounded by round heaven was the traditional belief integrated with other mythical beliefs, the language used to think about the heavens was mythical and poetic, not geometric or precise. Zhang Heng (78-139 AD) writes:

"The heavens are like a hen's egg and as round as a crossbow bullet; the earth is like the yolk of the egg, and lies in the centre... Heaven takes its body from the Yang, so it is round and in motion. Earth takes its body from the Yin, so it is flat and quiescent". [in case you thought that the "yoke" of Earth is spherical]

Was there a compelling reason to change this belief? It depends on one's view of "compelling". And we often forget how the same observations can be interpreted in many different ways, and reconciled with just about anything. Essentially the same measurements that Eratosthenes used to estimate the Earth's circumference Chinese astronomers who wrote Huainanzi in the 2nd century BC interpreted to calculate the height of the Sun above the earth. This is just geometric inversion. What about the shadow of the Earth on the Moon during the eclipses, which is one of Aristotle's main arguments for spherical Earth? Eclipses are rare events of little practical significance, and in a traditional society would not be valued as highly as in the cosmopolitan Hellenistic world. But for what it is worth some Chinese astronomers, like Li Ye in 13th century, Jamal-ad-Din's contemporary in Kublai Khan's time, did challenge the idea that the Earth was square, he thought it was still flat but round like the sky.

There was one earlier exception that confirms the rule. China underwent a remarkable period of cultural innovation during the Song dynasty (960–1279), sometimes compared to European Renaissance. The invention of gunpowder and widespread use of printing press and paper money in China date to this period. Shen Kuo (1031–1095), a polymath often compared to Leonardo, among other things invented nautical compass, measured the distance between the North star and the true north, improved designs of the armillary sphere, and, most importantly for us, wrote on solar and lunar eclipses explaining how phases indicated that the Sun and the Moon were spherical rather than flat like fans. The Sun and the Moon, yes, but not the Earth, see Did the ancient Chinese know the earth is a sphere? Close, but Song China did not develop systematic theoretical and empirical science just as Shen Kuo stopped short of spherical Earth.

As to why the Jesuits had more of an effect than Jamal ad-Din that is relatively easy to explain. Kublai Khan let him set up an Islamic Astronomical Bureau in Beijing, rival to the traditional Chinese bureau, and had his subordinates check calculations of the Chinese. This maintained the traditional bureaucracy but hardly inspired the spirit of scientific cooperation. And the surrounding traditional community would not have been affected much even if the Chinese bureau did change its mind. Jesuits, on the other hand, were preaching directly to the people.

A good source on historical interaction of China with Western science is Elman's On Their Own Terms: Science in China, 1550-1900.

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The idea of a "Chinese Flat Earth" is an ideological old one that comes back from time to time. The last version is https://www.academia.edu/22174185/AN_ANCIENT_CHINESE_FLAT_EARTH_COSMOLOGY . In about 2,000 BCE the Chinese astronomers had already discovered the cause of eclipses (shadow of the Earth/Moon), in the IV century BCE they had constructed their first (found) Armillary Sphere (http://viewofchina.com/ancient-chinese-cosmology/). But what most "scholars" forget to mention is that the Chinese had up to 8 schools of astronomy (variations of 3 basic ones). The two main schools were: the OLDEST one was called "the wise school" and adopted the spherical Sky model, "the unwise school" was nearer to the "flat Earth" model. Many astronomers at the time did not know how to make calculations (inherited positions from fathers, very influential in the court) and repeated old manuals. Maps were more schematics (graphs) than real maps (as we study them today) and most of the maps were square/rectangular with a "square" China and eventually some neighbor or People outside the limits of China. The most cited text for the Chinese Flat Earth is a mathematical manual (without figures) with instructions on how to calculate the dates (aiming the solstice) based on a gnomon and its shadow that takes the sky and the Earth as flat parallel planes ("as above, as bellow"), and based in this imprecise model extrapolates by similarity of triangles some calculations about the distance of the Sun, etc. The format of the Earth was not important for them (they already knew it because of the eclipses and did not care much). The calendrical calculations, the calculation of the eclipses and positions of the Sun/Moon (precise) in the sky (without a geometrical model) and the 5 planets (not so precise) was their focus. "Europeans" (because of the colonization ideology) usually have a hard time to accept that China had almost all what China needed inside China (center of the civilized world for them) and the rest was seen as barbarians after Chinese products. To leave China was a burden. In this site: https://www.theepochtimes.com/new-evidence-ancient-chinese-explorers-landed-in-america-excites-experts_1348894.html ) and in the famous "1421: The year China discovered the World" there are evidences of the Chinese presence (for trade and discovery and not "colonization"/exploitation) in Central America. Another practical point is map projections. If you need a "precise" Map/Chart a spherical Earth is important, if you are OK with a schematic/relative positions of places draw, them it is not even a problem to be discussed. If you use a geometrical model for astronomical calculations a spherical Earth is important, if you have an algebraic model, it is not. If you torture enough the historical data, your ideological interpretation will make them confess anything. Most People and ancient cultures did not care about most problems our contemporary westernized world care.

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  • $\begingroup$ Could you clarify whether this is meant as an answer to the question (they “did not care much”), or as an objection a.k.a. comment on it (they “already knew it because of the eclipses” since “about 2,000 BCE”) [source?]. $\endgroup$ – Francois Ziegler Aug 12 '18 at 10:55
  • $\begingroup$ @francois-ziegler : I believe that it's an answer and a good one. It explains how and why western concerns and points of view were irrelevant to points of view widely held in China, and expands on the point made by Conifold that Chinese astronomy, like Babylonian mathematics, was about traditional lore and skill to which invention and discovery (generically, and hence also inter alia, about the figure of the earth) were inessential if not irrelevant. $\endgroup$ – terry-s Aug 19 '18 at 20:26
  • $\begingroup$ @terry-s OK, then +1 as such. I just found it confusing to see this mixed with an apparent (and unsourced) claim that they actually knew sphericity all along. $\endgroup$ – Francois Ziegler Aug 22 '18 at 22:50

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