56 Facts About Zhang Heng

Zhang Heng, formerly romanized as Chang Heng, was a Chinese polymathic scientist and statesman who lived during the Han dynasty.

Zhang Heng began his career as a minor civil servant in Nanyang.

Zhang Heng applied his extensive knowledge of mechanics and gears in several of his inventions.

Zhang Heng 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.

When he was ten, Zhang Heng's father died, leaving him in the care of his mother and grandmother.

An accomplished writer in his youth, Zhang Heng left home in the year 95 to pursue his studies in the capitals of Chang'an and Luoyang.

At age 23, Zhang Heng returned home with the title "Officer of Merit in Nanyang", serving as the master of documents under the administration of Governor Bao De.

Zhang Heng spent much of his time composing rhapsodies on the capital cities.

When Bao De was recalled to the capital in 111 to serve as a minister of finance, Zhang Heng continued his literary work at home in Xi'e.

Zhang Heng began his studies in astronomy at the age of 30 and began publishing his works on astronomy and mathematics.

Zhang Heng was promoted to Chief Astronomer for the court, serving his first term from 115 to 120 under Emperor An and his second under the succeeding emperor from 126 to 132.

Under Emperor An, Zhang Heng served as Prefect of the Majors for Official Carriages under the Ministry of Guards, in charge of receiving memorials to the throne as well as nominees for official appointments.

Zhang Heng considered the teachings to be of questionable stature and believed they could introduce errors.

In 132, Zhang Heng introduced an intricate seismoscope to the court, which he claimed could detect the precise cardinal direction of a distant earthquake.

In Zhang Heng's memorial discussing the reasons behind these natural disasters, he criticized the new recruitment system of Zuo Xiong which fixed the age of eligible candidates for the title "Filial and Incorrupt" at age forty.

Zhang Heng pointed to specific examples of past court intrigues involving eunuchs, and convinced Shun that he should assume greater authority and limit their influence.

The eunuchs attempted to slander Zhang Heng, who responded with a fu rhapsody called "Fu on Pondering the Mystery", which vents his frustration.

Rafe de Crespigny states that Zhang Heng's rhapsody used imagery similar to Qu Yuan's poem "Li Sao" and focused on whether or not good men should flee the corrupted world or remain virtuous within it.

Zhang Heng read many of the great works of history in his day and claimed he had found ten instances where the Records of the Grand Historian by Sima Qian and the Book of Han by Ban Gu differed from other ancient texts that were available to him.

Zhang Heng's account was preserved and recorded in the 5th-century text of the Book of Later Han by Fan Ye.

Zhang Heng compiled a commentary on the Taixuan by the Daoist author Yang Xiong.

Zhang Heng's work was similar to Ban's, although the latter fully praised the contemporaneous Eastern Han regime while Zhang Heng provided a warning that it could suffer the same fate as the Western Han if it too declined into a state of decadence and moral depravity.

Zhang Heng gives me a sword to my delight; A jade I give her as requite.

Somewhat similar to the description of Sima Xiangru, Zhang Heng described the Western Han emperors and their entourage enjoying boat outings, water plays, fishing, and displays of archery targeting birds and other animals with stringed arrows from the tops of tall towers along Chang'an's Kunming Lake.

The focus of Zhang Heng's writing on specific places and their terrain, society, people, and their customs could be seen as early attempts of ethnographic categorization.

Zhang Heng used it as a means to criticize himself for failing to obtain high office, but coming to the conclusion that the true gentleman displays virtue instead of greed for power.

Declercq states that these two groups would have been "anxious to know whether this famous scholar could be lured over to their side", but Zhang Heng flatly rejected such an alignment by declaring in this politically charged piece of literature that his gentlemanly quest for virtue trumped any desire of his for power.

Zhang Heng wrote about the various love affairs of emperors dissatisfied with the imperial harem, going out into the city incognito to seek out prostitutes and sing-song girls.

Besides criticizing the Western Han emperors for lavish decadence, Zhang Heng pointed out that their behavior and ceremonies did not properly conform with the Chinese cyclical beliefs in yin and yang.

In formula, with D as diameter and V as volume, D:V = 16:9 or V=D; Zhang Heng realized that the value for diameter in this formula was inaccurate, noting the discrepancy as the value taken for the ratio.

From this formula, Zhang Heng calculated pi as the square root of 10.

Zhang Heng calculated pi as = 3.1466 in his book Ling Xian.

Zhang Heng supported the "radiating influence" theory to explain solar and lunar eclipses, a theory which was opposed by Wang Chong.

Zhang Heng viewed these astronomical phenomena in supernatural terms as well.

Zhang Heng suggested that the Earth could be round like the heavens, a spherical Earth theory fully accepted by mathematician Li Ye but not by mainstream Chinese science until European influence in the 17th century.

Zhang Heng was the first to address this problem, indicated in his writings from 117, by adding an extra compensating tank between the reservoir and the inflow vessel.

Zhang Heng mounted two statuettes of a Chinese immortal and a heavenly guard on the top of the inflow clepsydra, the two of which would guide the indicator rod with their left hand and point out the graduations with their right.

Zhang Heng mentioned a "jade dragon's neck", which in later times meant a siphon.

Zhang Heng wrote of the floats and indicator-rods of the inflow clepsydra as follows:.

Zhang Heng provided a valuable description of his water-powered armillary sphere in the treatise of 125, stating:.

Zhang Heng's water-powered armillary sphere had profound effects on Chinese astronomy and mechanical engineering in later generations.

Water-powered armillary spheres in the tradition of Zhang Heng's were used in the eras of the Three Kingdoms and Jin dynasty, yet the design for it was temporarily out of use between 317 and 418, due to invasions of northern Xiongnu nomads.

In 132, Zhang Heng presented to the Han court what many historians consider to be his most impressive invention, the first seismoscope.

The Book of Later Han records that, on one occasion, Zhang Heng's device was triggered, though no observer had felt any seismic disturbance; several days later a messenger arrived from the west and reported that an earthquake had occurred in Longxi, the same direction that Zhang Heng's device had indicated, and thus the court was forced to admit the efficacy of the device.

Zhang Heng's device had eight mobile arms connected with cranks having catch mechanisms at the periphery.

Zhang Heng's device included a vertical pin passing through a slot in the crank, a catch device, a pivot on a projection, a sling suspending the pendulum, an attachment for the sling, and a horizontal bar supporting the pendulum.

Hong-sen Yan states that modern replicas of Zhang Heng's device have failed to reach the level of accuracy and sensitivity described in Chinese historical records.

Zhang Heng argued that transverse shock would have rendered Wang's immobilization mechanism ineffective, as it would not have prevented further motion that could knock other balls out of their position.

Barbieri-Low speculates that Zhang Heng only designed his seismoscope, but did not actually craft the device himself.

Zhang Heng asserts that this would most likely have been the job of artisans commissioned by Zhang.

Rafe de Crespigny asserts that it was Zhang Heng who established the rectangular grid system in Chinese cartography.

Su Song directly named Zhang Heng's water-powered armillary sphere as the inspiration for his 11th-century clock tower.

However, some scholars point out that Zhang Heng's writing lacks concrete scientific theories.

Zhang Heng's poetry was widely read during his life and after his death.

The philosopher and poet Fu Xuan of the Wei and Jin dynasties once lamented in an essay over the fact that Zhang Heng was never placed in the Ministry of Works.

Zhang Heng's inventions were comparable even to those of the Author of Change.