The Great Scientist Shen Kuo and Brush Talks from Dream Brook

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Shen Kuo（1031-1095）was a scientist，polymath，general，diplomat，and financial officer，who was the inventor of compasses for navigation.His most famous book，Brush Talks from Dream Brook，written between 1086 and 1093，involves earth sciences，astronomy，mathematics，economics，government and other areas.It was 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 were drawn from his personal experience and researches.Shen Kuo made many suppositions that have since proved to be accurate.

In particular，Shen Kuo was the first to suggest that fossils represent the remains of dead animals，and that the rocks in which they were found had originally been beneath water.He was also the first to suggest that，by depositing silt for long periods of time，rivers and streams can 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 Kuo also was the 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.All these observations would not be rediscovered in Europe for 800 or 900 years.Perhaps Shen Kuo’s most important contribution was the observation that magnetized needles can be used to find direction.Although Si Nan一a ladle-like compass made of loadstone-was invented in the State of Zheng early in the Spring and Autumn or Warring States Period，Shen Kuo discovered that compasses do not point to true south but deviate slightly to the east.This was a decisive step to make them useful for navigation.It was not until the early 15th century that Europeans knew about the magnetic declination.

In the area of astronomy，Shen Kuo insisted on maintaining daily records of a variety of astronomical phenomena.From these observations，solar and lunar eclipses，planetary motions，sunspot activities，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 the first to attempt to describe these motions using trigonometry.