Editing Zhang Heng (section)

===Science and technology===
[[Image:Astrology della Robbia OPA Florence.jpg|thumb|right|200px|A [[Florence|Florentine]] marble carving of [[Ptolemy]] (86–161), who created an Earth-centered universe theory that the scholars [[Jin Guantao]], Fan Hongye, and Liu Qingfeng compare with Zhang Heng's theory published in 125<ref name="jin fan liu 1996 170"/>]]

Zhang Heng's mechanical inventions influenced later Chinese inventors such as Yi Xing, Zhang Sixun, Su Song, and Guo Shoujing. Su Song directly named Zhang's water-powered armillary sphere as the inspiration for his 11th-century [[clock tower]].<ref name="needham 1986 volume 4 part 2 466">Needham (1986), Volume 4, Part 2, 466.</ref> The cosmic model of nine points of Heaven corresponding with nine regions of earth conceived in the work of the scholar-official [[Chen Hongmou]] (1696–1771) followed in the tradition of Zhang's book ''Spiritual Constitution of the Universe''.<ref name="rowe 2001 88">Rowe (2001), 88.</ref> The seismologist John Milne, who created the modern seismograph in 1876 alongside Thomas Gray and [[James Alfred Ewing|James A. Ewing]] at the [[Imperial College of Engineering]] in [[Tokyo]], commented in 1886 on Zhang Heng's contributions to [[seismology]].<ref name="needham 1986 volume 3 626">Needham (1986), Volume 3, 626.</ref><ref name="yan 2007 124">Yan (2007), 124.</ref> The historian Joseph Needham emphasized his contributions to pre-modern Chinese technology, stating that Zhang was noted even in his day for being able to "make three wheels rotate as if they were one."<ref name="needham 1986 volume 4 85">Needham (1986), Volume 4, Part 2, 85–86.</ref> More than one scholar has described Zhang as a [[polymath]].<ref name="yan 2007 127"/><ref name="krebs 2003 31">Krebs (2003), 31.</ref><ref name="mair 2001 251"/><ref name="dillon 1998 378">Dillon (1998), 378.</ref> However, some scholars also point out that Zhang's writing lacks concrete scientific theories.<ref name="jin fan liu 1996 170">Jin, Fan, and Liu (1996), 170.</ref> Comparing Zhang with his contemporary, Ptolemy (83–161) of [[History of Roman Egypt|Roman Egypt]], [[Jin Guantao]], Fan Hongye, and Liu Qingfeng state:

::Based on the theories of his predecessors, Zhang Heng systematically developed the celestial sphere theory. An armillary constructed on the basis of his hypotheses bears a remarkable similarity to Ptolemy's earth-centered theory. However, Zhang Heng did not definitely propose a theoretical model like Ptolemy's earth-centered one. It is astonishing that the celestial model Zhang Heng constructed was almost a physical model of Ptolemy's earth-centered theory. Only a single step separates the celestial globe from the earth-centered theory, but Chinese astronomers never took that step.

::Here we can see how important the exemplary function of the primitive scientific structure is. In order to use the Euclidean system of geometry as a model for the development of astronomical theory, Ptolemy first had to select hypotheses which could serve as axioms. He naturally regarded circular motion as fundamental and then used the circular motion of deferents and epicycles in his earth-centered theory. Although Zhang Heng understood that the sun, moon and planets move in circles, he lacked a model for a logically structured theory and so could not establish a corresponding astronomical theory. Chinese astronomy was most interested in extracting the algebraic features of planetary motion (that is, the length of the cyclic periods) to establish astronomical theories. Thus astronomy was reduced to arithmetic operations, extracting common multiples and divisors from the observed cyclic motions of the heavenly bodies.<ref name="jin fan liu 1996 170"/>