Science brings back Zhang Heng’s seismometer to life

Zhang Heng’s seismometer invented in A.D. 132 was the first seismoscope in the world but was lost by the end of the Dong Han dynasty（about A.D.190—220）. To demonstrate this great scientific invention, since 1875 about 13 reconstructed models have been proposed throughout the world; however, all of them were conceptual and did not function as a seismoscope. Among these models, the exhibition model reconstructed by Wang Zhenduo in 1951 was the most popular. Unfortunately, this model contained a fundamental mistake and other faults, and so aroused serious criticism from academic circles. In 2002 the China Earthquake Administration and Bureau of Cultural Relics organized experts to carry out a new study of the scientific reconstruction of Zhang Heng’s seismometer. The present study reports some new findings and corrects existing misunderstandings. It has been verified that there is more than one historical record related to the seismometer, it successfully detected an earthquake on 13 December 134, and its principle of operation was based on a suspended pendulum. Zhang’s invention played an important role in enlightening scientific thinking at the beginning of modern seismology. The new model has now been completed and possesses the following features: its inner structure consists of five parts, the external shape is similar to the warming wine jars of the Han dynasty, and it has toad-shaped feet. In addition to being consistent with historical records and Han culture characteristics, the new model functions well as a robust seismoscope. The phenomenon corresponding to the Longxi earthquake may be reproduced, which indicates a leap from a conceptual model to a reconstruction of the scientific instrument. An overview of the relevant research is presented.