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Zhang Heng

From Wikipedia, the free encyclopedia

Zhāng Héng
Zhāng Héng
This is a Chinese name; the family name is Zhang.

Zhang Heng (張衡, Pinyin: Zhāng Héng, Wade-Giles: Chang Heng) (78139 AD) was an astronomer, mathematician, inventor, artist, poet, statesman, and literary scholar of the Eastern Han Dynasty in ancient China. He had extensive knowledge of mechanics and gears, applying this knowledge to several of his known inventions. According to historian Joseph Needham, Zhang Heng was noted in his day for being able to "make three wheels rotate as if they were one (neng ling san lun tu chuan yeh)". He is best known for his invention of the world's first seismometer device, which discerned the cardinal direction of earthquakes from incredibly far distances. In the realm of early science, he is often compared by historians to his contemporaries in ancient Greece and ancient Rome.

Contents

[edit] Life

Born in what is now Nanyang, Henan, Zhang Heng was an accomplished writer at twelve. At sixteen, he left home to pursue his study in the capital cities. He spent at least ten years of his youth in literature studies and writing. He published several well recognized literary writings, and was admired for his straightforward style and natural poetic ability. In a poem criticizing the previous Western Han Dynasty, Zhang Heng once wrote:

Those who won this territory were strong; Those who depended on it endured. When a stream is long, its water is not easily exhausted. When roots are deep, they do not rot easily. Therefore, as extravagance and ostentation were given free reign, The odour became pungent and increasingly fulsome [1].

Zhang Heng began his studies in astronomy at the age of thirty, and began publishing his works in astronomy and mathematics. In 116, at the age of thirty-eight, Zhang became a government official for the court of Emperor An of Han. Zhang took on several positions since then (mostly high-level academic posts), becoming the chief astrologer for the Han court. In his humble Confucian sensibility, Zhang respectfully declined many promotions that were offered to him that would have greatly advanced his career. Zhang eventually accepted the promoted position of President of the Imperial Chancellory. However, the 3rd century Chinese philosopher and poet Fu Xuan once lamented in an essay of his over the fact that Zhang Heng was never placed in the Ministry of Works. Writing highly of Zhang and the 3rd century mechanical engineer Ma Jun, Fu Xuan wrote:

...neither of them was ever an official of the Ministry of Works, and their ingenuity did not benefit the world. When (authorities) employ personnel with no regard to special talent, and having heard of genius neglect even to test it - is this not hateful and disastrous? (Needham, 42)

[edit] Achievements

Before his work in astronomy, mathematics, and technological invention, Zhang was a famed and notable literary author of poetry. Xiao Tong (501-531) immortalized several of Zhang's works in his anthology of literature, Wen xuan. Rhapsodies (fu 賦) include "Western Metropolis Rhapsody" 西京賦 (WX 2.36), "Eastern Metropolis Rhapsody" 東京賦 (WX 3.51), "Southern Capital Rhapsody" 南都賦 (WX 4.68), "Rhapsody on Contemplating the Mystery" 思玄賦 (WX 15.213), and "Rhapsody on Returning to the Fields" 歸田賦 (WX 15.222). The latter fu is an especially interesting piece, being very short compared to his other, mainly long epedeictic fu, and possessing a lyrical quality and refinement beyond its time. A set of four short lyric poems shi 詩, entitled "Lyric Poems on Four Sorrows" 四愁詩, is also included with Zhang's preface (WX 29.414). This set constitutes some of the earliest heptasyllabic shi Chinese poetry written.

In terms of invention, Zhang Heng was a prolific and revolutionary inventor for his time. Zhang Heng invented the first odometer device in China, an achievement alongside earlier contemporaries Archimedes and Heron of Alexandria from the Hellenized West. An odometer is a device which mechanically or electronically measures the distance traveled by an operated vehicle (found standard in modern automobiles), and was a (mechanical) device used by the Roman and Han-Chinese empires in roughly the same time frame.

Replica of Zhang Heng's seismometer Houfeng Didong Yi
Replica of Zhang Heng's seismometer Houfeng Didong Yi

Zhang Heng is also the first known person in history to apply motive power (water wheel, hydraulics) to rotate the astronomical insturment of the armillary sphere (the Greek Eratosthenes invented the first armillary sphere in 255 BC, while the Chinese armillary sphere was invented in 52 BC by Geng Shou-chang and Luo-xia Hong). He described this invention in his Hun-i chu.

In 132, Zhang Heng presented to the Han court what many historians consider his most impressive invention. Zhang Heng invented the first seismometer, called Houfeng Didong Yi (lit. instrument for measuring the seasonal winds and the movements of the Earth), for determining the exact direction of tremors and earthquakes. According to the Book of Later Han, his copper-made urn-shaped device (with swinging pendulum inside) was able to detect the direction of an earthquake from hundreds of miles/kilometers away (which was essential for the Han government in sending quick aid and relief to regions devastated by this natural disaster). On June 13, 2005, Chinese seismologists announced that they had created a replica of the instrument [2].

In his publication of Ling Xian (靈憲, Mystical Laws, a summary of astronomical theories at the time), he approximated pi as 730/232 (or approx 3.1466). In one of his formulae for spherical volume calculation, he also used pi as the square root of 10 (or approx 3.162). Zhang Heng theorized that the universe was like an egg with the stars on the shell and the Earth as the yolk. This was similar to the Western geocentric model before the coming of Galileo Galilei. He catalogued 2500 stars alone and recognized over 100 constellations, more than the Greek Hipparchus (astronomer), who catalogued 800 stars. In 123, Zhang Heng corrected the Chinese calendar to harmonize with the seasons according to his astronomical observations.

[edit] Named in his honour

He also features as a Great Engineer in the PC game Civilization IV.

[edit] References

Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part II. Taipei: Caves Books, Ltd.

[edit] See Also

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aa - ab - af - ak - als - am - an - ang - ar - arc - as - ast - av - ay - az - ba - bar - bat_smg - bcl - be - be_x_old - bg - bh - bi - bm - bn - bo - bpy - br - bs - bug - bxr - ca - cbk_zam - cdo - ce - ceb - ch - cho - chr - chy - co - cr - crh - cs - csb - cu - cv - cy - da - de - diq - dsb - dv - dz - ee - el - eml - en - eo - es - et - eu - ext - fa - ff - fi - fiu_vro - fj - fo - fr - frp - fur - fy - ga - gan - gd - gl - glk - gn - got - gu - gv - ha - hak - haw - he - hi - hif - ho - hr - hsb - ht - hu - hy - hz - ia - id - ie - ig - ii - ik - ilo - io - is - it - iu - ja - jbo - jv - ka - kaa - kab - kg - ki - kj - kk - kl - km - kn - ko - kr - ks - ksh - ku - kv - kw - ky - la - lad - lb - lbe - lg - li - lij - lmo - ln - lo - lt - lv - map_bms - mdf - mg - mh - mi - mk - ml - mn - mo - mr - mt - mus - my - myv - mzn - na - nah - nap - nds - nds_nl - ne - new - ng - nl - nn - no - nov - nrm - nv - ny - oc - om - or - os - pa - pag - pam - pap - pdc - pi - pih - pl - pms - ps - pt - qu - quality - rm - rmy - rn - ro - roa_rup - roa_tara - ru - rw - sa - sah - sc - scn - sco - sd - se - sg - sh - si - simple - sk - sl - sm - sn - so - sr - srn - ss - st - stq - su - sv - sw - szl - ta - te - tet - tg - th - ti - tk - tl - tlh - tn - to - tpi - tr - ts - tt - tum - tw - ty - udm - ug - uk - ur - uz - ve - vec - vi - vls - vo - wa - war - wo - wuu - xal - xh - yi - yo - za - zea - zh - zh_classical - zh_min_nan - zh_yue - zu -

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aa - ab - af - ak - als - am - an - ang - ar - arc - as - ast - av - ay - az - ba - bar - bat_smg - bcl - be - be_x_old - bg - bh - bi - bm - bn - bo - bpy - br - bs - bug - bxr - ca - cbk_zam - cdo - ce - ceb - ch - cho - chr - chy - co - cr - crh - cs - csb - cu - cv - cy - da - de - diq - dsb - dv - dz - ee - el - eml - eo - es - et - eu - ext - fa - ff - fi - fiu_vro - fj - fo - fr - frp - fur - fy - ga - gan - gd - gl - glk - gn - got - gu - gv - ha - hak - haw - he - hi - hif - ho - hr - hsb - ht - hu - hy - hz - ia - id - ie - ig - ii - ik - ilo - io - is - it - iu - ja - jbo - jv - ka - kaa - kab - kg - ki - kj - kk - kl - km - kn - ko - kr - ks - ksh - ku - kv - kw - ky - la - lad - lb - lbe - lg - li - lij - lmo - ln - lo - lt - lv - map_bms - mdf - mg - mh - mi - mk - ml - mn - mo - mr - mt - mus - my - myv - mzn - na - nah - nap - nds - nds_nl - ne - new - ng - nl - nn - no - nov - nrm - nv - ny - oc - om - or - os - pa - pag - pam - pap - pdc - pi - pih - pl - pms - ps - pt - qu - quality - rm - rmy - rn - ro - roa_rup - roa_tara - ru - rw - sa - sah - sc - scn - sco - sd - se - sg - sh - si - simple - sk - sl - sm - sn - so - sr - srn - ss - st - stq - su - sv - sw - szl - ta - te - tet - tg - th - ti - tk - tl - tlh - tn - to - tpi - tr - ts - tt - tum - tw - ty - udm - ug - uk - ur - uz - ve - vec - vi - vls - vo - wa - war - wo - wuu - xal - xh - yi - yo - za - zea - zh - zh_classical - zh_min_nan - zh_yue - zu