(78 – 139 AD)

Zhang Heng (sometimes written as Chang Heng) was a polymath whose works spanned across arts and sciences. His contributions, which nourished successive generations of scholars, pertained to mathematics, astronomy, seismology, hydraulics, geography and cartography. Even the great Liu Hui was inspired by his works. Likewise, many ancient scholars (who were not scientifically inclined) benefitted from his poems and other artistic works. Zhang Heng was also among the first scientists to methodically describe solar and lunar eclipses, as well as to assert that moonlights do not originate from the moon: but are mere reflections of sunrays. He did improve several mathematical formulae, and derived better approximations for constants such as pi. His most notable engineering exploit involved the design and development of the first water-powered armillary sphere, with which he gained better cosmic insights. Another remarkable invention he made was the development of the first known seismoscope. This gadget was so sensitive as to accurately detect the cardinal direction of an earthquake occurring hundreds of kilometers away. The reinvention of odometer, as well as the famous Chinese south-pointing chariot, is attributed to him. Heng complimented his scientific exploits with significant contributions to literature and philosophy. He was highly influential in his lifetime; and remained so long after his death. His works inspired both Oriental and Western scholars. Named in his honor are: the Chang Heng lunar crater, the 1802 Zhang Heng asteroid, and the Zhanghengite (which is a golden-yellow mineral discovered in 1986: comprising mostly of copper, zinc, iron, aluminium and chromium).


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