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Sun-Earth Day 2009: Total Solar Eclipse, China

Sun-Earth Day 2009: Total Solar Eclipse, China

Ancient Eclipses in China

By Dr. Sten Odenwald

Department of Physics
Catholic University

Introduction

Whenever we think of a country's contribution to astronomy, we first tend to consider its most ancient roots. With Chinese astronomy, those roots go back far longer than any other modern culture. Among the most ancient writings and 'oracle bones' uncovered through painstaking archeology, we see the legacy of the first sightings of eclipses, aurora, sunspots and the solar corona. In their striving to create the most accurate calendar systems, we encounter an early and precise knowledge of the movements of the sun, moon and planets.

Motivations

In ancient China, astronomical observations were performed, not out of abstract curiosity for the sky, but for the practical purpose of keeping track of the civil calendars based upon lunar and solar cycles. Any unusual phenomenon involving celestial bodies was noted for potential omens, either good or bad, that might befall the current Emperor. The superstitious kings of the Shang dynasty in China (1766 to 1123 BC) used astronomical divination as a guide to politics, economics, culture and even etiquette!

Within the ancient Chinese belief system, not all things celestial were of equal importance. Chinese astronomers spent a great deal of time cataloging the stars and their movements than in predicting the movements of planets. They quickly fell behind the Babylonians in the sophistication of their solar system studies. Because the Chinese sought a life of balance and regularity, planets were interlopers and a reminder of 'life out of balance', unlike the fixed stars. Not surprisingly, the worst event, and a cause for great concern, was the solar eclipse, which they thought was caused by a dragon eating the sun.

Archeologists have learned much about these ancient beliefs through the recovery of thousands of oracle bone inscriptions near cities such as Yinxu, which was the capital city of the Yin Dynasty (later-Shang Dynasty). Divination was a widespread practice in the Shang Dynasty that saw oracle bone inscription develop into a mature and comprehensive writing system - eventually to become the modern writing system.

To use oracle bones, the Emperor would ask the priest a question 'Will the river flood its banks next week?' The question was carved into a tortoise shell or other animal bone. A bronze pin would be heated and placed over the bone to create cracks. The cracks would then be 'read' to find the answer to the question. Archeologists know from the 100,000 oracle bones unearthed since the 1800's that these were often not passive questions. A great number of animals and humans were sacrificed to have communion with their Ancestors, and to influence whether the Emperor received a favorable reply.

Since then, and through hundreds of political and social changes, the Chinese have been credited with keeping the longest continuous watch of the sky since the advent of oracle bone inscriptions ca 2400 BC. Not only were oracles noted, which were divined from the shapes of cracks in tortoise shells, but commentaries on celestial phenomena were noted and remarked upon. Unfortunately, by modern standards, the vast majority of astronomical records before ca 720 BC are so brief that many scarcely mention the date of the event, let alone any details about what the eclipse may have looked like.

This all changed ca 720 BC in the state of Lu - the birthplace of Confucius. Over the course of 240 years, the circumstances for 37 solar eclipses were noted. These records are known to archeo-astronomers for the accuracy of their dates, although no mention is made of the time of day or any descriptive details.

Why is there so little literature that has survived from these ancient times? One possibility is that the founder of the Ch'in Dynasty ca 213 BC was known to have staged a "burning of the books" pogorum that swept the country but miraculously left the state of Lu alone. Since the time of the Han Dynasty, ca 206 BC through the fall of the Ch'ing (Manchu) Dynasty in 1911, extensive records continue to be uncovered that describe a vast array of celestial comings-and-goings.

Eclipse Observations

It is impossible to read ancient Chinese astronomical history without encountering the sad plight of court astrologers Hsi and Ho. To them is attributed the earliest mention of a total solar eclipse among all ancient records before 2000 B.C. Not even the civilization of Ancient Egypt, for which the sun was the chief deity, Ra, were total solar eclipses recorded on any extant monument, despite a civilization with a written record as far back as ca 3,500 BC.

Hsi and Ho were believed to have been two astrologers who served the Emperor Chung K'ang around 2134 B.C. On October 22 of that year, a total solar eclipse occurred and it was recorded in the ancient Chinese document Shu Ching, that 'the Sun and Moon did not meet harmoniously'. By some accounts, the two astrologers were negligent in their duties and did not foretell the event for the Emperor. They were summarily beheaded for their negligence of duty. Given that no one prior to 100 AD could reliably anticipate total eclipses, there must have been quite a few similar events played out over the silent millennia.

Some archeologists dispute that these may have been actual individuals by those names, but that the names may have been those of minor solar deities, making the story an allegory for a ritual that takes place when something goes wrong in the heavens, or that the people were real but that the names were their titles (e.g. 'Ho' the Second Brother). Even the date of the eclipse is merely an educated guess given that there were several eclipses visible around that time of the century from China. Nevertheless, it is a popular and oft-cited story even in modern times, and supports the view that total solar eclipses were noted in China for thousands of years before they were an understood phenomenon involving the moon's motion.

Although actual images of Chinese eclipse writings are not as yet easy to find in the literature, one example, dating from the Eastern Han Dynasty mentions the eclipses of 118 A.D. and 120 A.D. The later eclipse has the interesting story behind it that it foretold the death of the Empress Teng's death in 122 A.D.

"Jan 18, 120 AD: "Yuan-ch'I reign-period, 6th year, 12th month, day wu-wu, the first day of the month. The Sun was eclipsed. It was almost complete; on Earth it was like evening. It was 11 deg in Hsu-nu. The Female Ruler was upset by it; two years and three months later, Teng, the Empress Dowager, died." (Hou-han-shu, chp. 28):"

From the San-kuo to the Sui dynasty (220 - 617 AD), the major source of solar eclipse observations come from the astrological treatises and the Sung-shu.

Aug 10, 454 AD: "Hsiao-chien reign period, 1st year, 7th month, day ping-shen, the first day of the month. The Sun was eclipsed; it was total; all the constellations (i.e. lunar lodges) were brightly lit." (Sung-shu, chp.34)

In records from the T'ang dynasty (617-960 AD; dates include the Wu-tai period), eight solar eclipses are cited as being either total or very large. These were recorded in 756, 761, 879, and 888 AD (total solar eclipses) and 702, 729, 754, and 822 AD (partial eclipses).

The principle source of solar eclipse observations from the Sung, Kin, and Yuan dynasties (960-1368 AD) are the astrological treatises. Total eclipses are listed for the years 977, 1221, and 1275 AD. Annular, partial and unspecified eclipses are noted for 1022, 1054, 1135, 1214, 1292 and 1367 AD.

Jan 21 1292 AD: "Chih-yuan reign-period, 29th year, 1st month, day chia-wu. The Sun was eclipsed. A darkness invaded the Sun, which was not totally covered. It was like a golden ring. There were vapors like golden earrings on the left and right and a vapor like a halo completely surrounding it." (Yuan-shih, chp. 48)

During the Ming dynasty (1368-1644 AD), total solar eclipse observations are found in the histories of Ming provinces after 1500 AD. Prior to 1500 AD, eclipse records can be found in the Imperial Annals. These observations, however, are not of total solar eclipses.

Aug 20, 1514 AD: "At the hour of wu suddenly the Sun was eclipsed; it was total. Stars were seen and it was dark. Objects could not be discerned at arm's length. The domestic animals were alarmed and people were terrified. After one (double-)hour it became light." (local history of Tung-hsiang county, Chiang-his province)

Chinese Firsts

Although total solar eclipses were a cause for alarm and ill-omen, lunar eclipses were not feared by the people because they were so commonly seen. As a matter of fact the earliest recording of one was not until 1065 BC. Before this time, the event was only slightly mysterious. Lunar eclipse had weak astrological meaning in ancient China, so systematic records began from up to the 5th century. There were 545 records before 1500 AD in which 78 reported a total eclipse; 54 timed to the maximum or the contacts, 39 recorded maximum magnitude.

They were the first to spot Halley's Comet in 240 BC. As the "broom star" on the handle of Yin. But in the 613 BC Spring and Autumn Annals ( ?? Chunqiu) of Confucius, he noted that "In July, there was a comet that entered the Big Dipper." ("???,????????" qiu qiyu, you xing1bi r y bei3d ou).

The Mawangdui silk, a sketch book of cometary forms and the disasters associated with them, was compiled ca 300 B.C., but the knowledge it encompasses is believed to date as far back as 1500 B.C. Comets had been recorded, and drawn since the Shang Dynasty (1600 - 1046 BC).

The Chinese developed a system of 283 constellations, with identifies based upon natural objects rather than deities and historical figures as was the style of the Ancient Greeks. Constellations were called palaces, and the brightest star was the Emperor Star, with the fainter stars being the Princes. A constellation was called a "palace," with the major star being the emperor star and lesser stars being princes. The Fourth Century astronomer Shih-shen catalogued 809 stars among these constellations, but without any surviving sketches or sky maps, we an exact identification of these constellations is impossible from the earliest history of Chinese observations.

We know that they called the North Star, Bei Ji, and eventually created star maps like the one below. In the famous Dunhuang star map of 700 AD. This map is thought to date from the reign of Emperor Zhongzong of Tang (705-710 AD), founded in Dunhuang. The Dunhuang manuscript is the oldest surviving star map in the world. Ursa Major, Sagittarius and Capricornus are recognizable. The three colors (white, black and yellow) indicate the schools of astronomy of Shih Shen, Kan Te, and Wu Hsien. The whole set of star maps contained 1,300 stars.

They also noted sunspots as they would be infrequently observed when the sun was near the horizon and could be safely viewed through atmospheric absorption. No sketches of these sightings survives, although numerous written recordings have been found dating from ca 28 BC and later. The earliest mention may have been by an early astronomer Gan De (ca 500 BC). A sighting was also noted in the 165 BC encyclopedia The Ocean of Jade, of a figure identified as wang that appeared on the sun; a symbol like a cross with bars drawn across the top and bottom. By May 10, 28 BC, sunspots were noted in the official Imperial histories of China. Between 28 BC and 1638 AD, the historian Joseph Needham (1900-1995) identified 112 sightings in these records during the time before telescopic observations began in the West starting with Galileo in 1609.

Ancient Observatories

By 2300 BC, ancient Chinese astrologers already had sophisticated observatory buildings, and as early as 2650 BC, Li Shu was writing about astronomy. According to historical records, a total of 27 observatories were built in the Yuan Dynasty but only the one in Dengfeng is known to have survived. Gaocheng Observatory is the oldest facility of its kind in China. The observatory dates to the early portion of the Yuan Dynasty (1271-1368 AD).

Established in 1279 AD by the famous astronomer Guo Shoujing, it was designed originally for use in predicting the time of the solstice each year. Astronomers at the site were able to calculate the actual length of the year to 365.2425 days some 300 years before Europeans managed to develop the Gregorian calendar.

The scientific value of Total Eclipses.

Total solar eclipses happen at a specific geographic location and time. Thanks to detailed mathematical models that account for the detailed shape of the earth and moon, tidal effects, perturbations by the sun, and supported by precise measurements of the moons orbit to uncertainties less than a kilometer, we can predict modern eclipses to within the minute at any location on Earth in recent times. There are, however, long term effects that are hard to measure from modern data. The farther back we attempt to predict eclipses, the less accurate they become as computational errors grow, and modern data becomes less able to specify ancient lunar trajectories and times. Thanks to historical data on ancient eclipses that give their times and locations and dates, modern eclipse models can be used to confirm these ancient eclipses and improve the long-term accuracy of the orbital dynamics models.

Descriptive reports of historical solar studies also help astronomers take note of the changing appearance of the solar corona, sunspots and the solar activity cycle.

Modern total solar eclipses are also scientifically useful for allowing astronomers to study the solar corona with optical instruments far better than those on orbiting satellites. This allows astronomers to search for new phenomena such as interplanetary dust grains evaporating in the solar corona.

Future Total Eclipses Visible from China

During the next 90 years, there will be 7 more total solar eclipses visible from China.

  • July 22, 2009
  • March 20, 2034
  • Sept 2, 2035
  • April 30, 2060
  • August 24, 2063
  • April 21, 2088
  • October 4, 2089

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