Yi Xing

Yi Xing (* 683, † 727), Chinese一行, Pinyin: Yi Xing, outdated romanization I Hsing, a Chinese astronomer, mathematician, engineer, and Buddhist monk of the Tang Dynasty was (618-907). His monk's name can mean both " whole journey " or " the Allfähige ". With worldly name he was called Zhang Sui (张 遂).

Technology

He built a water-powered armillary sphere and controlled by a balance whose parts are automatically rotated to a common drive in a variety of speeds. The fastest gear had moved daily at 2928 teeth, the slowest every five days by one tooth. His masterpiece was a further development of similar equipment that had been constructed AD in China since the 2nd century.

Measurements

Faced with the challenge to improve the calendar, in particular, but parallax, ie, to predict solar and lunar eclipses, he established a system of twenty observatories one, ten near the 114th meridian (indicated by today's Greenwich date), distributed from the 17th parallel in Jiaozhou in Vietnam until the 50th parallel on Lake Baikal. His reference to the measurements Calculated calendar movement comprised seven volumes.

In Gaocheng, the site of one of its observatories, a larger was built in the 11th century, in its successor in the 13th century under Kublai Khan, in turn, a new, the only one from the old China, which is still preserved today.

Discoveries

Yi Xing's value for the distance of degrees of latitude, and thus the earth's circumference was 11.4 % higher than the actual, 123.7 km instead of 111 km.

He realized that eclipses did not affect the entire globe, but had to occur at different times in different parts of the world.

He discovered the proper motion of the fixed stars, ie, the change of angles at which they are seen from Earth. So he came to the realization that they could not sit on a spherical shell, as previously assumed in China.

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