Zhang Heng and the Seismometer

by | Jul 1, 2010 08:00 PM ET

Marshall Brain

Behold, the seismometer. But where did it come from? Meet Zhang Heng, born in 78 A.D. in China. Centuries before the European renaissance, Zhang had all the makings of a renaissance man. He was a statesman, an artist, a scholar, and most importantly an inventor. During his time at the Imperial Court, Zhang perfected several inventions such as a water powered armillary sphere and a water tank. However, history has paid homage to one of his inventions above all the others. The seismometer. The seismometer is a device that measures the motion of the ground, picking up vibrations made by eruptions, earthquakes, and although this didn't happen in Zhang's time, nuclear explosions. In 132 A.D., Zhang invented a device that uses a series of eight bronze balls and a pendulum to indicate the direction of a seismic disturbance. When an earthquake occurred, the ball closest to the earthquake's origin point would drop into a base of a bronze vessel. At the time, Chinese scholars were not aware of tectonic plates, and many believed that seismic disruptions came from global imbalances in Yin and Yang. Zhang concluded they were caused by moving air. Regardless of his accuracy in guessing the cause of earthquakes, Zhang successfully built a system to monitor seismic disturbances, and the basic principals he discovered are still used by seismologists today.

So, how genius is this inventor? On the American Dream scale, he gets a five. Zhang rose from the ranks of educated but not particularly wealthy families to establish himself as one of the chief intellectual forces in the Imperial Court. On the benefit to humanity scale, he gets a five. Geologists, seismologists, and other earth scientists continually tweak the basic principles of these machines, and over time, they may be able to use these machines to predict earthquakes, which could save countless lives. On the ripple effect scale, he gets a five. Although the seismometer was invented over a thousand years ago, the principals Zhang discovered are still in use today. Any way you look at it, the Zhang seismometer is definitely Stuff of Genius.

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