Forum on Science Learning and Teaching, Volume 6, Issue 2, Article
From geocentric to heliocentric model of the universe, and the alternative perspectives
Historical Models in the European and Chinese Contexts
Before the seventeenth century, astronomy had developed differently in China and in Europe. The similarities of these two lines of scientific development are that, first, both focused on the study of the heavens (the order of the heavens as a major preoccupation), and that, second, both dealt with the calendar, cosmography (sometimes along with the study of the movements of the planets), and what we call today "astrology." The intellects in the two early worlds paid great attention to the sky and believed the heavens to be organized in order. Regulating the calendar, drawing the sky map, and investigating omens are the same tasks they undertook.
However, the early Chinese and Greek astronomy have fundamental differences: first, Greek astronomy highlighted planetary motions; as the apparent irregularities threatened the very notion of celestial order itself, the Greeks sought to geometrize them and in doing so turn irregularities into regularities. In contrast, the Chinese were more confident in the inherent order of the heavens and more open minded about its possible messages for the earth. Chinese theories seem to have "imposed far less rigid patterns on the order they expected, and they would no doubt have been amazed at the Greek ambition to prove celestial regularities" (Lloyd, 1999).
Secondly, the early Chinese and Greeks developed very different models of the universe: the former primarily with a flat earth, round heaven, free heavenly bodies and infinite cosmos, and the latter with a round earth centred by layers of round heavens, bound heavenly bodies and finite cosmos/heavens. The motions of heavenly bodies were, for the Greeks, the consequence of the rotation of the concentric celestial spheres on a common axis, and, for the Chinese, generated by vapour with each having its own path around the earth (Chen, 1996). For the ancient Greek scientists, their aim was to provide a tempo-spatial model of the universe for explaining the apparent motions of the heavenly bodies - the sun, moon, planets and stars - as seen from the earth (Sun, 2000). In contrast, early Chinese cosmological theories did not give detailed descriptions of the movement of the heavenly bodies, as they are viewed as independent entities from one another, moving freely.
As perceiving virtually the same phenomena, why did the Chinese and the Greeks come up with fundamentally different world pictures? It may, as Needham (1959) commented, have something to do with the fact that the Chinese appeared to concentrate on the polar star (based on their keen observation to the sky) while the Greeks emphasised on the earth (or rather, where man is located) and, much later on, the sun. Furthermore, according to Lloyd (1999), despite the same subject matter of the both enquiries, the early Chinese and Greeks developed and presented very different theories and concepts, which are associated with the questions they chose to study and, consequently, the answers they chose to give to them.
In ancient China, three main theories of cosmology (Figure 2) can be distinguished. The most archaic Chinese cosmological model, Gai Tian (), consists of a flat earth and umbrella-like heavens, whereas its centuries-long opponent, Hun Tian ()model, was presented through the analogy of "egg" The flat earth was situated in the middle of the egg yolk and surrounded by water, while the heavens were like the egg shell. It should be noted that the heavens, no matter in which form, were always filled with Chi (;vapour) and accommodated the freely floating heavenly bodies, and therefore have nothing to do with the solid celestial shells as presented in Greek astronomy. For the Chinese, the heavens and the earth altogether form an observable and researchable world, beyond which is the infinite cosmos. The third model, Shuen Ye (), is said to be more a philosophical notion than a scientific theory. It did not discuss the forms of the earth and the heavens, but merely concentrated on the free moving objects in the sky and the empty and boundless space.
The Gai Tian Model (Hemispherical Dome)
The Hun Tian Model (Celestial Sphere)
The Shuen Ye Model (Infinity)
Figure 2 Three early Chinese models of the universe
It is worth noting that the shape of the earth had not been a problem for either of the early Chinese and Greeks before the seventeenth century when missionaries arrived in China. For the Chinese the earth had been always flat, whereas the Greeks had taken for granted the earth was spherical. This seemed to be, at least at the outset, associated with what they considered as "ideal" form. That is, for the Chinese, the word of flat or square -fan -is associated with the much valued virtue of being righteous and robust, and in contrast, the Greeks considered spherical to be the "perfect" form, as evident in Plato's text. Yet, more distinguishing is that the Greeks went further to seek evidence by conducting experiments, while the Chinese simply kept to premise the flat earth in their astronomy (Chu, 1999).
It is argued that the lack of emphasis on "reasoning" gave rise to the standstill of Chinese theories. Chinese science is fundamentally influenced by the Confucian model of cognition which tends to use personal experience to make rational inductions. As a result, Chinese scientific theories dwell on direct experience and technology. The Chinese scientists considered their tasks as "discovering" and "following" the natural rules, rather than "reasoning" because of the confines of human intellectual comprehension. As late as in the Qing () dynasty (1644-1911), the eminent scholar Ruan Yuan () still complained that Western astronomers successively changed their theories in explaining astronomical phenomena: "The laws are always changing ... I don't know where the real reason lies." He then concluded that "heavenly laws are so profound and subtle that they lie beyond human ability". Theories should therefore express certainties rather than search for reasons. Only in this way can theories "last forever without error". Consequently, the Chinese did not establish a structural view of nature that substantially requires "reasoning" as embraced in the Western science. In other words, the Chinese did not attempt to make systematic connections between natural principles that people had in mind; they "had sciences but no science, no single conception or word for the overarching sum of all of them"(Sivin, 1995)
Briefly, the main characteristics of the ancient Chinese models of the universe can be listed as follows:
- The phrase, "the heavens and the earth" was used to refer to their researchable universe, which is an observable space based in the earth; beyond the heavens there is unknown infinite cosmos. That is, for the Chinese, the universe was in fact infinite, but they confined their models to a space called "the heavens and the earth".
- The earth is flat.
- The heavens are round; the heavenly bodies are floating, unattached to the heavens, and moving freely.
- There is a lack of emphasis on reasoning and consequently the structural view of nature.
These features interestingly are distinguished from those of the Greek cosmological models:
- The universe is finite, where "the heavens and the earth" are located.
- The earth is round (spherical).
- The heavens are layers of solid spheres; the heavenly bodies are attached to the layers respectively.
- Efforts are made to search for reasons and to establish a structural view of nature.
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