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       Ancient oracle bones once believed to foretell dayto-day events in China have been used by Jet Propulsion Laboratory researchers and their colleagues to help determine how much the Earth's rotation is slowing down.

       Based on inscriptions on the oracle bones, the researchers have fixed the exact date and path of a solar eclipse which was seen in China in the year 1302 B.C.

       That in turn led them to conclude that the length of each day was 47/1,000ths of a second shorter in 1302 B.C. than it is now.

       Their findings are reported in a talk delivered today (June 12) by JPL astronomer Dr. Kevin D. Pang at the 174th meeting of the American Astronomical Society in Ann Arbor, Michigan.

       Working with Pang were East Asian language professor Hung-hsiang Chou of the University of California at Los Angeles, physicist Dr. Kevin Yau of Durham University in England, astronomer John A. Bangert of the U.S. Naval Observatory and mathematician Dharam V. Ahluwalia of JPL.

       The oracle bones studied by the researchers are actually pieces of tortoise shell used by seers during China's Shang Dynasty in the 14th century B.C.

       The bones' existence was unknown to historians until 1899, when a Chinese scholar became ill and sent his servant to an apothecary for medicines. One of the ingredients -- sold by the apothecary as "dragon's bone" -- proved to be bone chips with words inscribed on them in ancient Chinese.

       Over the following years, the bones' source was traced to the city of Anyang, about 450 kilometers (300 miles) southwest of Beijing. Anyang was the capital of the Shang Dynasty in ancient China.

       Some 25,000 oracle bones were excavated in Anyang during the 1920s and 1930s, and were taken to the Chinese Academy of Science in Taiwan when Chinese Nationalists moved there in 1949. About 135,000 more pieces are in private collections or have been excavated since the founding of the People's Republic of China.

       The oracle bone studied by Pang and his colleagues is part of the collection now in Taiwan.

       The bone's inscription -- dated the 51st day of the cycle then in progress in the calendar system used in China continuously from time immemorial -- states that "Diviner Ko asks if the following day would be sunny or not."

       The bone is useful to astronomical researchers because it records not only the diviner's question but also the eventual outcome of the next day's weather. On the reverse side the inscription continues, "... 52nd day, fog until next dawn. Three flames ate the Sun, and big stars were seen."

       Pang and his colleagues interpreted that statement
as a description of a total eclipse of the Sun. The "three flames" would be coronal streamers licking out from the Sun's surface, visible only during total eclipses. In addition, the masking of the Sun by the Moon would allow Earth observers to see stars during daytime.

       The researchers faced a problem, however, because historical records were not complete enough to tell precisely what year -- according to the modern calendar -- the oracle bones dated from.

       Using computers to calculate dates and paths of total solar eclipses visible in Shang China, the research team came up with two eclipses that might be the one referred to by the oracle bone. One of the eclipses was on June 5, 1302 B.C., the other on March 4, 1250 B.C.      

       The researchers then turned to records of eclipses of the Moon in Shang Dynasty China to decide which of the two dates was right.

       The seers who reported the lunar eclipses were known to work for King Wu Ding, who was also the patron of the seer who recorded the solar eclipse on the oracle bone. The lunar eclipses were known to span the years 1322 to 1278 B.C. That would cover the period of the solar eclipse of 1302 B.C., but not the solar eclipse of 1250 B.C.

       The final step in their quest was to use a computer model of the Earth's rotation to see how fast the Earth must have been spinning for such an eclipse to be seen from Anyang, China, on the given day. If the Earth's rotation were faster or slower, the eclipse path would be moved to the
east or west of Shang China, and the total eclipse would not have been seen there.

       According to Pang, the value they came up with -- a day 47/1,000ths of a second shorter in the 14th century B.C. -- is consistent with other studies of ancient eclipses from historical records.

       Last year Pang and several colleagues studied three eclipses reported in Chinese historical writings in 532 A.D., 899 B.C. and 1876 B.C. Their current study of the oracle bones, however, is the first time Pang's team has worked with an eclipse record from an archaeological artifact as opposed to ones in collected writings.

       The research is not only useful in determining how fast the Earth's rotation has been gradually slowing down, Pang said, but also helps historians by establishing an exact date in the reign of King Wu Ding. Dates in Chinese history before the 9th century B.C. tend to be uncertain.

       The research was supported by the U.S. Naval Observatory and Dudley Observatory of Schenectady, New York. Earth rotation and length-of-day information was provided by NASA's Office of Space Science and Applications. 6-12-89 FOD # 1245      

Note to Editors: Photo art is available to illustrate this story. Please contact the JPL Public Information Office at telephone (818) 354-5011.

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G:June 12, 1989

This map shows the path of a total solar eclipse on June 5, 1302 B.C., as determined by JPL researchers and colleagues. The eclipse was described in early Chinese characters inscribed on an oracle bone excavated from the city of Anyang. The bone includes a description of a total solar eclipse, which means that the path of eclipse totality must have fallen over the city of Anyang. That in turn allowed the researchers to calculate that the length of each day was 47/1,000ths of a second shorter in 1302 B.C. than now.


6/12/89 FOD