Chapter 82 81 Zhang Heng and the Seismograph

During the reign of Emperor Zhang of the Han Dynasty, the politics of the Eastern Han Dynasty was relatively stable.After the death of Emperor Zhang of the Han Dynasty, the Hanhe Emperor who succeeded to the throne was only ten years old. The Queen Mother Dou came to power and let his elder brother Dou Xian control the power of the court. The Eastern Han Dynasty began to decline. During this period, a famous scientist Zhang Heng came out. Zhang Heng is from Nanyang.At the age of seventeen, he left his hometown and went to Chang'an and Luoyang successively to study hard in Taixue. At that time, Luoyang and Chang'an were very prosperous cities, and the princes and nobles in the cities lived a life of luxury and lust.Zhang Heng is not used to these things.He wrote two literary works "Xijing Fu" and "Tokyo Fu" (Xijing is Chang'an, Tokyo is Luoyang), satirizing this phenomenon.It is said that he spent a total of ten years writing these two works after careful consideration and repeated revisions, which shows that his spirit of research is very serious.

But Zhang Heng's specialty is not literature, he is particularly interested in mathematics and astronomy.The imperial court heard that Zhang Heng was a learned man, and summoned him to be an official in Beijing, first as a doctor in the palace, and later as Taishiling, and asked him to be in charge of observing astronomy.This work fits well with his research interests. After his observation and research, he concluded that the earth is round, and the moon reflects light only through the sun.He also believed that the sky is like an egg shell, covering the outside of the earth; the earth is like the yolk of an egg, in the middle of the sky.Although this kind of theory is not completely accurate, but more than 1,800 years ago, the ability to express this kind of scientific insight cannot but make later astronomers admire.

Not only that, Zhang Heng also used copper to make an instrument for measuring astronomy called "armillary sphere".Astronomical phenomena such as the sun, moon and stars are engraved on it.He managed to use water power to turn this instrument.It is said that which stars rise from the east and which stars set to the west can be seen clearly on the armillary sphere. During that period, earthquakes occurred frequently.Sometimes once a year, sometimes twice a year.A major earthquake affected dozens of counties. City walls and houses collapsed, and many people and animals were killed or injured.

At that time, the feudal emperors and ordinary people regarded the earthquake as an unlucky sign, and some even took the opportunity to spread superstition and deceive the people. However, Zhang Heng did not believe in God or evil. He carefully inspected and tested the recorded earthquake phenomena, and invented an instrument for earthquake prediction called "seismograph". The seismograph is made of bronze, shaped a bit like a wine jar, engraved with eight dragons around it, and the heads of the dragons stretch out in eight directions.Each dragon's mouth contained a small copper ball: under the dragon's head, squatted a copper toad, aiming at the dragon's mouth and opening its mouth.When an earthquake occurs in which direction, the mouth of the dragon facing that direction will automatically open and spit out the copper ball.The copper ball fell into the toad's mouth and made a loud noise, which sounded an earthquake alarm.

One day in February 138 A.D., Zhang Heng's seismograph was facing the west of the dragon's mouth, which suddenly opened and spit out a copper ball.According to Zhang Heng's plan, this is the report of an earthquake in the west. However, there was no sign of an earthquake in Luoyang that day, and no one heard of an earthquake nearby.Therefore, everyone talked a lot, saying that Zhang Heng's seismograph was a deceptive thing, and some even said that he deliberately spread rumors to cause trouble. A few days later, someone rode a fast horse to report to the court that a major earthquake had occurred in Jincheng and Longxi, more than a thousand miles away from Luoyang, and even the mountains collapsed.Everyone is convinced.

But at that time, eunuchs or relatives were all in power in the imperial court. Talented people like Zhang Heng were not only not reused, but were suppressed and excluded.When Zhang Heng was a servant, because he was close to the emperor, the eunuchs were afraid that Zhang Heng would expose their faults in front of the emperor, so they spoke bad things about Zhang Heng in front of the emperor.He was transferred out of the capital and went to Hejian to be the country's prime minister. Zhang Heng died of illness when he was sixty-one years old.He left brilliant achievements in the history of science in our country.