The Earth and Physical Sciences of Shen Kua

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The Earth and Physical Sciences of Shen Kua

Overview

Shen Kua was a Chinese scientist, mathematician, and soldier in the eleventh century. He found success in many endeavors, but is perhaps best known for his work in the earth sciences, where he made many valuable contributions. Among these were the invention of the magnetic compass, remarkably accurate speculations about the origins of fossils, and essays covering many aspects of other geologic features. Much of his work was not known outside China, and would not be repeated anywhere else for over 700 years.

Background

Chinese civilization dates back thousands of years and is the source of the oldest recorded history on Earth. For much of human history, Chinese government, agriculture, science, and technology were equal or superior to that of the West. In many ways, whether a civilization makes scientific and technological advances depends on whether it has a central government, urban civilization, and productive agriculture, because in order to discover and invent, a society needs scientists and inventors. This requires agriculture that is sufficiently productive so a significant portion of the population is not tied to the land, a relatively efficient method of distributing food to the cities, and some way of encouraging and supporting scientists and inventors.

In China, the development of relatively efficient agriculture and a large population made it possible to form a coherent government centuries before this occurred in Europe, and Chinese society was relatively stable for long periods of time. Because of this, China not only developed the world's first real bureaucracy, but also some of the world's first scientists.

The T'ang dynasty, which had been marked by a stifling bureaucracy that discouraged innovation, began to collapse about 750. This process lasted over 200 years, and resulted in a China that was a hodgepodge of small kingdoms. In the middle of the tenth century, the Sung dynasty began to consolidate power and reestablished a central Chinese government. Also at this time, China's center of political power shifted from the northern cradle of Chinese civilization to the more prosperous, and more liberal, south. Shen Kua was born during this time of re-invigoration.

Like many urban Chinese at that time, Shen Kua was primarily educated at home by his mother. He entered the government as a civil servant and quickly proved himself by offering wise advice on many difficult issues. Among the problems he tackled successfully were draining swamps to reclaim land for agriculture, using silt dredged from rivers as fertile farming soil, and helping with military preparations. As he rose in the Chinese civil service, he also became interested in the sciences, including astronomy and mathematics. Unfortunately, he also became entangled in factional politics, and this led to his dismissal from government service.

Shen Kua spent the last years of his life at his estate, which he named "Brush Talks from the Dream Brook," writing a collection of documents that summarized much of what he had learned during his life. These essays covered an astonishing array of topics, many of them drawn from his personal experience and researches. Shen Kua wrote about earth sciences, astronomy, economics, government, mathematics, astronomy, and other areas. In all his essays, Shen Kua showed an impressive grasp of the principles of a wide variety of fields and made many suppositions that have since proved to be relatively accurate.

In particular, Shen Kua was first to suggest that fossils represented the remains of dead animals, and that the rocks in which they were found had originally been beneath water. He was also first to suggest that, by depositing silt for long periods of time, rivers and streams could form land and rocks that could gradually extend into the sea, causing the continent to become larger. And, noting bamboo fossils in an area that was dry and barren, he suggested that the climate must have changed at some time in the past because bamboo only grew in humid places. Shen Kua also was first to suggest that coal might be a better fuel than charcoal, given that China's forests were being cut down to burn for charcoal at a rapid rate. He also noticed that the soot from burning petroleum could be used to make ink, and some of the petroleum "mines" he initiated still produce petroleum for this purpose (and others). All these observations would not be rediscovered in Europe for 800 or 900 years. Perhaps Shen Kua's most important contribution was the observation that magnetized needles can be used to find direction.

In the area of astronomy, Shen Kua insisted on maintaining daily records of a variety of astronomical phenomena. From these observations, solar and lunar eclipses, planetary motions, sunspot activity, and even supernovae, were recorded faithfully long after his death. He also showed a gift for visualizing and describing the motions of astronomical bodies, and was first to attempt to describe these motions using trigonometry.

Impact

Although we now know that Shen Kua wrote reasonably accurate descriptions of a variety of geological processes, his works did not have a significant impact on eleventh-century China. In addition, by the time his works were first read by Europeans, most had been rediscovered by European scientists and were no longer "new." However, Shen Kua is generally recognized as one of the greatest Chinese scientists of all time.

In his geologic theorizing, he suggested that ancient climates, such as those that once supported bamboo groves in a now-barren desert, must have changed to explain the fossils he saw. He also suggested that, for marine fossils to be found far inland and at relatively high elevations, the sea must have retreated, or the rocks must have been lifted up out of the water. He further noted that, because of the amount of silt carried to sea by China's rivers, the land must be extending into the ocean a little at a time. All these observations are still held to be reasonable descriptions of physical processes that have taken place on Earth since its formation. Although he could not have known some of the mechanisms by which these processes took place, he had a remarkably keen understanding of the geological processes that had shaped the China he lived in.

Perhaps the most important contributions made by Shen Kua were the daily astronomical observations he insisted upon. These observations have been used recently to help understand long-term changes in solar activity. They constitute an almost unbroken record of sunspots stretching back nearly a millennium, and seem to be highly accurate and reliable. At least two supernovae have been very accurately dated using Chinese records of strange "new" stars that appeared in the heavens, and other Chinese observations have provided data that support theories and calculations regarding some orbital and rotational properties of Earth and the Moon.

Unlike European scientists many centuries later, Shen Kua did not explain his observations by referring to catastrophic events. Where European scientists insisted on a biblical interpretation of natural phenomena (e.g., suggesting that Noah's Flood explained sedimentary rocks and fossils), the Chinese seem to have had no such tradition. This does not mean that Chinese scientists were "better" than Europeans or vice versa, but it helps to demonstrate that science takes place within a culture and not in isolation. European scientists fit their theorizing into a biblical framework because the Bible was so profoundly important to European culture, and scientists were a part of that culture. In contrast, the Chinese creation story did not involve a huge flood (although many non-European creation stories did), and the Chinese religion emphasized worship of a larger number of gods and their ancestors. These religious and cultural differences, combined with a longer cultural history, helped to shape the way Shen Kua and his fellow scientists observed their world.

Shen Kua's scientific work provided some necessary information to the Chinese, even though much of it was either ignored or neglected for centuries. Today, he is remembered primarily for being a keen observer of nature and a brilliant thinker about the meaning of his observations. His works were part of the beginnings of a Chinese tradition in science that has a history longer than any other in the world. They also provide an excellent example of how scientists from separate cultures, in this case Chinese and European, can observe the same phenomena (for example, sedimentary rocks and fossils), yet come away with completely different explanations and theories because of their different cultural traditions.

P. ANDREW KARAM