Compass, called Sina in ancient times, is mainly composed of magnetic needles installed on the shaft. Under the action of natural geomagnetic field, the magnetic needle can rotate freely and keep in the tangential direction of magnetic meridian. The north pole of the magnetic needle points to the north pole, so this property can be used to identify the direction.

The invention of compass should be the result of gradual improvement over a long period of time, and the forms in different periods should appear in different forms. In the Tang Dynasty, the activities of scholars of geomancy were quite active, and they began to emphasize the choice of direction, so it became a top priority to find a more convenient pointing device than a magnetic spoon. So the iron pointer and floating magnetic needle in the shape of iron guide fish or tadpole came into being.

Qiu Yanhan, a geomancer in Shaanxi Province who lived in the Kaiyuan period of the Tang Dynasty (7 13-74 1), was praised by later geomancers as the earliest founder of the three needles (straight needle, sewing needle and middle needle) in geomantic theory.

Second, papermaking.

Papermaking is one of the four great inventions in China. Paper is the crystallization of the long-term experience and wisdom of the ancient working people in China. This is an outstanding invention in the history of human civilization. China is the first country in the world to raise silkworms and weave silk. In ancient China, the working people spun silk from superior cocoons, and the remaining evil cocoons and diseased cocoons were made into silk floss by bleaching.

Since ancient times, the working people in China have known about sericulture and silk reeling. During the Qin and Han dynasties, the handicraft industry with cocoon as silk floss was very popular. This method of treating secondary cocoons is called flossing, and the basic points of operation include repeatedly beating and mashing silkworm clothing. This technology later developed into beating in paper making. In addition, in ancient China, lime water or plant ash water was often used to degum silk and hemp, which also gave the enlightenment of degumming plant fibers in papermaking. Paper was developed with the help of these technologies.

Third, gunpowder.

Gunpowder, as its name implies, can be caused by sparks, flames and other violently burning drugs. According to Fan Ziran, China had been used for folk livelihood in the Spring and Autumn Period, and Fan Ziran said that "saltpeter leads a long way". Gunpowder is one of the four great inventions in China. It is a substance that can burn quickly and regularly under the action of appropriate external energy, and at the same time produce a large number of high-temperature gases.

At the end of the Tang Dynasty, gunpowder had been used in the military. In the first year of God's Blessing (904), Yang Xingmi led an army to besiege and led Zheng (leading troops to fire, burning dragons and shamans, and leading strong men to the city first, but the quilt was urgent). The (Fei Huo) here refers to (artillery) and (rocket). (artillery) is to make the powder into a ring, ignite the messenger wire and throw it out with a trebuchet; A rocket is to tie a powder ball under an arrow, light a fuse and shoot it out with a bow. In the Song Dynasty, wars continued, which accelerated the development of gunpowder weapons.

Fourth, printing.

Printing is one of the four great inventions of working people in ancient China. Engraving printing was invented in the Tang Dynasty and was widely used in the middle and late Tang Dynasty. In Song Renzong, Bi Sheng invented movable type printing. Although movable type printing appeared in Song Dynasty, it was not widely used, while block printing was still widely used.

Printing in China has a long history and is widely spread. It is an important part of China culture; It germinated with the birth of China culture and evolved with the development of China culture. In terms of origin, it has experienced four historical periods: origin, ancient times, modern times and contemporary times, with a development course of more than 5,000 years.

In the early days, in order to record events and spread experience and knowledge, the people of China created early written symbols and sought the media to record these characters. Limited by the means of production at that time, people can only use natural objects to record words and symbols. For example, Chinese characters are carved on natural materials, such as rock walls, leaves, animal bones, stones and bark.

V. Seismograph

Seismograph is a masterpiece created by Zhang Heng, a scientist in the Eastern Han Dynasty. During the Eastern Han Dynasty when Zhang Heng lived, earthquakes were frequent. Zhang Heng has a lot of personal experience about earthquakes. In order to master the national earthquake dynamics, after years of research, he finally invented the Hou Feng seismograph in the first year of Yangjia (AD 132), which was also the first seismograph in the world.

During the Eastern Han Dynasty when Zhang Heng lived, earthquakes were frequent. According to the Records of Five Elements in the History of the Later Han Dynasty, there were 26 * * * earthquakes in the thirty years from the 4th year of Yonghe (AD 92) to the 4th year of Andi Yan Guang (AD 125). Earthquake areas sometimes reach dozens of counties, causing ground fissures and landslides, houses collapsing, rivers flooding and huge losses.

Zhang Heng has many personal experiences about earthquakes. In order to master the national earthquake dynamics, after years of research, he finally invented the world's first seismograph-Hou Feng seismograph in the first year of Yangjia (AD 132). At that time, an earthquake in the western region was successfully predicted by using this instrument, which attracted the attention of the whole country. This is earlier than the earthquake history recorded by instruments in western countries 1700 years.