Dear teachers and classmates, hello,

In the long river of history, the 5,000-year history books of the Chinese nation have written the endless pursuit of beauty and happiness, showing the indelible pursuit of democracy and prosperity. The long history and splendid civilization have never been interrupted. We know that the Chinese nation has four great inventions. What do they mean?

The four great inventions refer to the four great inventions in ancient China that had great influence on the world. Namely papermaking, compass, gunpowder and movable type printing. This statement was first put forward by Joseph Needham, a British sinologist, and was later inherited by many historians in China. It is generally believed that these four great inventions greatly promoted the development of politics, economy and culture in ancient China. These inventions spread to the west through various channels and had a great influence on the history of world civilization.

Let's talk about papermaking first. Papermaking is one of the four great inventions in China and an outstanding invention in the history of human civilization. China is the first country in the world to raise silkworms and weave silk. The working people of the Han nationality spun silk from the first-class cocoons, and the rest of the evil cocoons and sick cocoons were bleached to make silk floss. After floating, some residual flocs will be left on the mat. When the flossing frequency is high, the residual flossing on the pad will accumulate into fiber sheets, which can be peeled off after drying and can be used for writing. This kind of floc is called "He Qi" or "square floc" in ancient books because of its small number of by-products. This shows that the origin of papermaking of Han nationality in China is related to silk floss.

Let's talk about Cai Lun who improved papermaking! In the first year of Yuan Xing in the Eastern Han Dynasty (105), Cai Lun improved papermaking.

He made paper from bark, hemp head, cloth, fishing net and other raw materials through crushing, ramming, papermaking and baking, which is the origin of modern paper. This kind of paper is easy to find, cheap and has improved its quality, so it is gradually widely used. In order to commemorate Cai Lun's achievements, later generations called this kind of paper "Cai Hou Paper"

After papermaking, let's talk about gunpowder. Gunpowder was invented by Han people in China during the Sui and Tang Dynasties, and it has been more than 1000 years. The study of gunpowder began with the ancient Taoist alchemy. The ancients refined Dan medicine to live forever. The purpose and motive of alchemy are ridiculous, but its experimental method still has some merits, which eventually led to the invention of gunpowder.