China is among the earliest countries to develop astronomy, and boasts the fastest development. As one of the four advanced natural science subjects in ancient China, astronomy, with the innovative calendars and surprising inventions, played an important role in the world's history of astronomical development.

Like people of other cultures, the ancient Chinese paid close attention to the heavenly bodies and their movements, because the sun, moon, stars and their movements were the most eternal features that the ancient people could observe.

Since the ancient Chinese believed that the perceived movements of the stars were closely related to the destiny of the country and its rulers, for thousands of years they recorded their movements with great attention. From the 16th century BC to the end of the 19th century AD, almost every dynasty appointed officials charged with the sole task of observing and recording the changes in the heavens. Such observations and records have left a rich astronomical legacy.

A long time ago, people noticed that the sun and moon sometimes suddenly lost their brightness. People could not figure out the reason and feared that, once gone, the brightness would not return and would mean the end of the world. Precisely because of this, the ancient Chinese began to observe solar and lunar eclipses, recording the time and size of the coverage, and searching for the reasons for eclipses. The earliest solar eclipse record that can be verified appears in a bone inscription dating back to the Shang Dynasty(about 1600-1100 BC). Studies have proved that the solar eclipse recorded actually took place on May 26, 1217 BC, thus also proving that it was the first reliable record of an eclipse man ever made. Records of lunar eclipses, however, date back to an even earlier time. Bone and tortoise shell inscriptions recorded five lunar eclipses that took place during the 14th and 13th centuries BC.

While Western astronomers of the Renaissance period were still arguing in 1615 who was the first to discover sunspots, Chinese astronomers had already accumulated numerous records on sunspots. Now it is known that the earliest records of sunspots were made in 28 BC by Chinese astronomers during the reign of Emperor Cheng of theWestern Han Dynasty. From then until the late Ming Dynastyin the mid-17th century, Chinese history books recorded more than 100 sunspots. Furthermore, they also took note of other phenomena concerning the sun, such as solar prominences and coronas. The first record of a solar prominence has been found in a tortoise shell inscription, which describes "three suddenly bursting fires eating a chunk of the sun". According to statistics, sunspots occur in a cycle every 11.33 years on average, which is in conformity with ancient Chinese documents and once again testifies to the fact that records of sunspots made by ancient Chinese people are a very valuable astronomical legacy.

China also compiled a huge amount of records on meteoric showers. The Bamboo Annals records a meteoric shower in 2133 BC in today'sHenan Province. This is the first mention in the world of a meteoric shower.

Meteorites, both of iron and of stone, often fall to the earth, and this was noticed by the ancient Chinese. Song Yingxing, a scientist of the late Ming period, once said, "When stars fall to the earth, they become stones." Shen Kuo, a scientist of the Song Dynasty, observed three meteoric explosions one evening in 1064, and described in detail an incident of meteorites falling into the gardenof a farmer inJiangsu Provincein his book Dream Stream Essays.

During theSpring and Autumn Period, some 2,200 years ago, Chinese documents already had entries on what later came to be known as Halley's Comet. The record of the comet, which appeared in 613 BC, inSpring and Autumn Annalsis recognized as the earliest mention of Halley's Comet in the world.

The scientific and technological achievements of theWarring States Period(475-221 BC) are very impressive. The various feudal states all had their own court astronomers. The most famous among them -- Gan De of the State of Chu and Shi Shen of the State of Wei -- together wrote The Gan and Shi Book of the Stars, which accurately record the positions of 120 stars, constituting the world's earliest star chart. The lid of a lacquer chest of the Warring States Period unearthed inSuizhou,Hebei Province, has a list of the 28 constellations, China's earliest record of the entire list of the constellations.

Novas and supernovas are all variable stars created by nova outbursts. During an outburst, the brightness of a nova may increase during a matter of a few days by several thousand or even dozens of thousands of times. Then it will gradually dim, to eventually return to its original brightness after several or dozens of years. Outbursts of supernovas are on an even grander scale, increasing their brightness by up to hundreds of millions of times.

Many records in ancient China on happenings of the stars were the most accurate and complete in the world. In terms of data, they held the highest rate of application. It is entirely beyond the imagination of ancient astronomers that their records could serve modern scientific studies. In future along with further developments in science, these ancient records may well prove to be of even greater values.

The period from the 3rd to the 6th centuries was an important stage in the development of culture and science in China, as many outstanding scientists emerged.Zu Chongzhi(420-589) made outstanding contributions to mathematics, astronomy and machine building. In astronomy, the Daming Calendar he worked out was China's most advanced calendar of his era. After observations and studies, he concluded that a year lasted exactly 365.24281481 days which was only 46 seconds different from the modern estimate. In order to commemorate Zu's outstanding contributions to science, a mountain on the moon has been named after him.

Yi Xing (683-727), a monk of the Tang Dynasty, led a large-scale project to identify the locations of the major stars, and, based on the results, concluded that the length of a degree of the meridian line was 351.27 li by Tang measurement, which meant 123.7 km. This was the first measurement of the meridian ever done in the world.
Around the year 723, Yi Xing and his colleagues constructed an armillary sphere which could move in synchronization with the movements of the heavenly bodies at night. It was installed in anobservatoryestablished in Chang'an (Xi'an), the capital of the Tang Dynasty.

Astronomical studies made impressive headway during the Song Dynasty (960-1279). During this period, five large-scale observations of the sky were undertaken, resulting in star maps. The stone planisphere kept inSuzhoutoday was first drawn during the reign of Emperor Yuanfeng (1078-85) and then committed to stone in 1247 by Wang Zhiyuan of the Southern Song Dynasty. On the map are 1,434 stars, the ecliptic, the equator, the Milky Way and the twenty-eight constellations. The lower part of the planisphere is occupied by explanations totaling 209 characters, which constitute a concise introduction to the astronomical knowledge man had grasped by that time. This is China's earliest and most complete star map still extant.

Shen Kuo was a noted scientist of the Northern Song Dynasty. He left behind a great store of notes and research findings in the fields of geography, geology, astronomy and mathematics. His work Dream Stream Essays contains early discussions of thecompassand movable typeprinting. This book is of great value for the study of the history of science.

Guo Shoujing (1231-1316), a noted scientist of the Yuan Dynasty, made major improvements to the sundial. First he created a tower sundial, raising its height from the original 2.66 meters to 13.33 meters, which drastically increased its accuracy. Based on his research, the calendar was revised. His calendar had 365.2425 days in a year, which was only 26 seconds different from the time it takes the earth to go around the sun. His achievement was 300 years earlier than the finalization of the modern calendar.

Guo Shoujing made great contributions in the areas of astronomy, the calendar and water conservation. He made or improved 13 kinds of astronomical instruments. In 1296, he improved the armillary sphere into an astronomical observation apparatus, in which he discarded the ecliptic ring, and combined the azimuth, equatorial torquetum and sundial into one, which not only simplified the structure but also made the armillary sphere more accurate. It overcame the shortages of the armillary sphere in having too many rings, being difficult to operate and having limited measuring capacity. The equator device in Guo's new instrument was an important invention in astronomical apparatus making and very similar to that in modern astronomical telescopes. Occupying an important position in the world's history of astronomy, Guo's torquetum was 300 years earlier than a similar instrument produced by Danish astronomers.

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