caption death_date death_place religion birth_place field birth_date known_for residence image article_title name
a in 1955 stamp of zhang heng issued by china post ad 139 78 luoyang , china daoism , chinese folk religion nanyang , china astronomy , ethnography , mechanical engineering , calendrical science , metaphysics , , poetry mathematics , seismology , hydraulics , geography ad 78 seismometer poetry , universe model , lunar eclipse and solar eclipse , theory hydraulic-powered armillary sphere , pi calculation , nanyang , luoyang zhang heng.jpg zhang heng
 zhang heng zh 張衡
zhang heng

zhang heng -lrb- chinese : t , s , p `` zhāng héng '' ; ad 78 -- 139 -rrb- , formerly romanized as chang hêng , was a han chinese polymath from nanyang who lived during the han dynasty .
educated in the capital cities of luoyang and chang ` an , he achieved success as an astronomer , mathematician , scientist , engineer , inventor , geographer , cartographer , artist , poet , statesman , and literary scholar .
zhang heng began his career as a minor civil servant in nanyang .
eventually , he became chief astronomer , prefect of the majors for official carriages , and then palace attendant at the imperial court .
his uncompromising stance on historical and calendrical issues led to his becoming a controversial figure , preventing him from rising to the status of grand historian .
his political rivalry with the palace eunuchs during the reign of emperor shun -lrb- r. 125 -- 144 -rrb- led to his decision to retire from the central court to serve as an administrator of hejian in hebei .
zhang returned home to nanyang for a short time , before being recalled to serve in the capital once more in 138 .
he died there a year later , in 139 .
zhang applied his extensive knowledge of mechanics and gears in several of his inventions .
he invented the world 's first water-powered armillary sphere to assist astronomical observation ; improved the inflow water clock by adding another tank ; and invented the world 's first seismometer , which discerned the cardinal direction of an earthquake away .
he improved previous chinese calculations for pi .
in addition to documenting about 2,500 stars in his extensive star catalog , zhang also posited theories about the moon and its relationship to the sun : specifically , he discussed the moon 's sphericity , its illumination by reflected sunlight on one side and the hidden nature of the other , and the nature of solar and lunar eclipses .
his `` fu '' -lrb- rhapsody -rrb- and `` shi '' poetry were renowned in his time and studied and analyzed by later chinese writers .
zhang received many posthumous honors for his scholarship and ingenuity ; some modern scholars have compared his work in astronomy to that of the greco-roman ptolemy -lrb- ad 86 -- 161 -rrb- .
