1. Papermaking: In the first year of Yuan Xing in the Eastern Han Dynasty (A.D. 105), Cai Lun used bark, broken fishing nets, rags and hemp heads as raw materials on the basis of summarizing the previous experience in making silk-woven crystals.
Plant fiber paper suitable for writing was made, and the papermaking technology was improved, making paper a widely used writing material. It is called "Cai Hou Paper". Have a unified understanding of the concept of paper. What kind of article is called a "paper"?
Second, the compass, the compass is a simple instrument used to identify the direction. Originally known as Sina. The main component is a magnetic needle that can rotate freely on the shaft. The magnetic needle can be kept in the tangential direction of magnetic meridian under the action of geomagnetic field.
The north pole of the magnetic needle points to the geographical south pole, which can be used to identify the direction. It is often used in navigation, geodesy, tourism and military affairs.
3. Gunpowder A black or brown explosive, made of potassium nitrate, charcoal and sulfur by mechanical mixing, was first made into powder, and then generally made into particles of different sizes for different purposes. Smokeless powder was used as the only military propellant until it was adopted.
Iv. Printing, Printing It is reported that Bi Sheng invented clay movable type printing in the Northern Song Dynasty, which is regarded as the earliest movable type printing technology in the world. However, the movable type printing in the four great inventions is not the predecessor of modern printing, and according to Needham, the movable type printing in the Northern Song Dynasty has many disadvantages.