V Chinese Mathematics
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V Chinese Mathematics The ancient record of civilization in China began in the more northern Yellow River Valley where the Yangshao culture existed from about 5,000 to 2700 B.C.E. These people lived in the middle and lower parts of the river valley. They cultivated rice and millet, kept pigs, wove baskets and made pottery without a wheel. Their pottery was dyed red with black geometric designs painted on it, and also pictures of fish and human faces. Archeologists have found pottery from these people with the symbols for 1, 2, 5, and 7 painted on the dishes. The next culture, one which evolved from the Yangshao, was the Longshan culture, which thrived from 3,000 to 2,000 B.C.E., approximately. This culture domesticated the water buffalo, sheep and cattle. They made black pottery on a wheel. The pottery was not painted but decorated with grooved or raised rings. From about 2100 to 1600 B.C.E. the Xia (or Hsia) dynasty controlled the Yellow River Valley. Recent discoveries have unearthed a large city with a wall and a moat for defensive purposes surrounding the city. This city has been dated to the early Xia dynasty. It is in Henan Province in today’s China. From about 1500 to 1000 B.C.E the Shang dynasty controlled the area with a capital city at Anyang, also in current day Henan province, just north of the southern bend in the Yellow River. They also used the walled and moated city of the Xia, mentioned above. By 1300 B.C.E. the Shang scribes had invented a brush for writing on bamboo strips, and had a decimal system of writing numerals. We have records of their kings through oracle bones, bones with inscribed writing that were used to foretell the future. Their writing was pictographic and had pictures of the objects referred to in the writing as the symbols used to write. After the Shang dynasty we come to the period of classical Chinese culture, that of the Zhou (or Chou) dynasty. The early Zhou is usually dated from 1027 to 771 B.C.E. with the later Zhou extending from 770 to 256 B.C.E. During the later Zhou dynasty the territory controlled extended to include the more southern Yangtze River Valley. Also during this period the two social strata which formed the basis of Chinese society until 1911 were formed. These are the peasant farmer class and the scholarly scribes in more administrative positions. The Zhou nobility studied a curriculum of ritual, music, archery, horsemanship, calligraphy and mathematics. They had a sexagesimal calendar but a decimal arithmetic for daily life. During the 700’s B.C.E. the first construction on the Great Wall of China began, and iron was introduced into China. The period from 551 to 233 B.C.E. is known as the Hundred Schools Period of Chinese history. The great philosopher Lao Tsu seems to have predated Confucius in this period. His dates are a matter of speculation. A school of philosophy emerged from his teachings. He tried to reform the government. His philosophy was one of non-striving and non-interference, and came to be known as Taoism. He believed that his central principle could not be expressed in words, so his writings are contradictory and difficult to absorb. His ideas lead most people to a more passive role towards reform. He taught that the Tao is The Way, how the universe actually works, and trying to oppose it is fruitless activity. There were elements of mysticism in his world view. From about 550 to 470 B.C.E. the philosopher Kung Fu Tsu (Confucius) expounded a moral code that included respect for the past, for elders, loyalty, universal education and responsible government that would bring a decent life to all of its citizens. He stayed away from speculations on the nature of existence and the shape of the universe. His writings espouse a more activist way of dealing with life. A very old book, The Book of Diverse Crafts (Kao Gong Ji in Chinese), was written by 476 B.C.E. with later additions in the Warring States Period. The book includes the state of Chinese thinking on engineering, administration, astronomy, physics and mathematics at that time. In the area of mathematics it contains material on fractions, with tenths singled out as the commonest fractions in use, the geometry of measurement for use in surveying and building, standard metrological units and angle measurements of 90o, 45o and 22.5o. The third great philosopher of China is Master Mo, who lived about 470 to 390 B.C.E. He was a master engineer and an expert on fortifications. So he was sought out by rulers to help them become dominant rulers. He had a pacifist philosophy and did not ! think one should blindly follow the principles of the past, as they were innovative in their own day. He urged people to lead lives of self-restraint, avoiding both material and spiritual excesses. He evaluated actions based on their utility to promote the good for people. He argued for a universal benevolence and love for all people, whereas Confucius argued for deeper love for ones’ own parents and superiors. During the Warring States Period, from 403 to 221 B.C.E. the Chinese used a system of counting rods to calculate. This used bamboo, wood or ivory rods shaped like the numerals and arranged in columns by place value, with the larger powers of 10 going to the left. This has a natural place value arrangement, and has no need for a zero, as one merely left that column empty. It carried on the earlier base 10 arithmetic. Another old book is “The Records and Rites of the Zhou Dynasty (Liji in Chinese). In this book we find the curriculum for the Zhou nobility mentioned above as well as mention of the two main classes of administrative officials, the Sihuai who were statistical arithmeticians and the Chouren who were astronomers in charge of the calendar. In the second section we find mathematical problems included to support the development of mathematical innovation. The Book of Master Mo (The Mozi in Chinese) contains the beginnings of theoretical geometry in China. At the start are definitions of point, circle, line, surface and solid figures. In this book is the principle that “A stick, though half of it be broken off each day, will never be exhausted.” This suggests some interest in the idea of a limit 1 1 1 1 to us, and in the infinite series + + + """ + + """ = 1. 2 4 8 2n After the Zhou Dynasty the Qin (221 to 206 B.C.E.) rose to power in China. This Dynasty was a severe and ruthless government, which destroyed the old nobility and instituted large scale public works. With their military they were the first to unify all of China, but they did not! last long. They standardized the characters used in writing as well as Chinese metrology. They considered scholars dangerous to their power, and burned all books that were not for engineering or agriculture. The Imperial Library was destroyed in 206 B.C.E. The famous terra cotta army, a collection of 8,099 larger than life ceramic soldiers was buried with the first Qin emperor in an ornate mausoleum. This is near the Qin capitol city of Xi’an, on the Yellow river near the current city of Xianyang in Shaanxi province. The Han Dynasty avoided the excesses of the Qin, and lasted from 206 B.C.E. to 220 A.D. The Han reunited China, and extended it to cover most of central Asia. They reassembled old books from fragments and reopened schools. By the first century A.D. they were trading with Persia, Alexandrian Egypt and the Roman Empire. The famous Silk Road was thriving. Papermaking was invented in China by 100 A.D. It was in Egypt by 900 A.D. and in Spain by 1150 A.D. There are two venerable texts on Chinese mathematics which date from this Han Dynasty. They are the Zhoubi Suanjing (The Zhou Shadow Guage manual) and the Jiuzhang Suanshu ( The Nine Chapters on the Mathematical Art.) The Zhoubi Suanjing was primarily a book about astronomy which included plenty of mathematics. It was probably written between 100 B.C.E. and 100 A.D. There were two competing theories of astronomy at that time in China. Gai Tian theory held that the earth is an inverted basin bounded by four seas with a heaven that is a concentric hemisphere overhead. HunTian theory held that a rotating sphere contains the heavenly lights and is centered around the earth. The text records the measurements of the moon’s movements, those of the sun, and uses the Gougu Theorem (Pythagorean Theorem ) to calculate distances. Here Gu refers to the length of a vertical stick in the ground, while Gou refers to the shadow cast by the stick. The theory of similar triangles is part of the mathematics used in this book. A picture like the following for 3, 4, 5 triangles appears to justify the Gougu Theorem. It is claimed that this is just a numerical check, but 9 + 16 = 25 is an easier check. It seems that this picture, which generalizes, can be thought of as a proof. 4 3 5 5 5 5 3 4 The Zhoubi Suanjing, probably written around 100 A.D. but based on much earlier material, gives rules for calculating with decimal fractions and approximates square roots, without explicitly recording how to do this.