why is the sky blue?
we see the sky is often blue, especially after a heavy rain, the sky is blue like limpid, refreshing, Yue Yue fei. Why is the sky blue?
the atmosphere itself is colorless. The blue sky is a picture of atmospheric molecules, ice crystals, water droplets and sunlight.
the sun enters the atmosphere, such as red light, long wavelength, transmission capacity, through the air toward the ground; and the wave length of the light purple, blue, blue, ice, water droplets hit the atmosphere molecules, etc., it is prone to the phenomenon of scattering. The scattered purple, blue and green light filled the sky, and the sky was blue.
the inventor of paper
Cai Lun is one of the greatest inventors in ancient China, the inventor of papermaking. Before the invention of paper, people of all countries have to find ways to use the ancient, stone, bricks, leaves, bark, wax, copper, lead, linen and skins, leather and so on, recorded text.
in China’s Shang Dynasty, it was the words carved into the shells and stroke of cattle, sheep and pig animal scapula; then, people used to a specification of wood (also known as Jane) and bamboo (also called slips) to write articles; later, also used to silk silks for the paper book written procedures. In the Eastern Han Dynasty, with the development of economy and culture, bamboo, silk, more can’t adapt to the need of writing. In order to create an ideal material for writing, Cai Lun in the previous paper on the basis of using waste silk floss, using bark, hemp head, rags, scrap nets as raw materials, successfully created a portable, economical paper, summed up a set of perfect papermaking method, the papermaking technology has been accepted leap progress. Ad 105, Cai Lun will be caused by the paper dedicated to the court, praised by the emperor. From then on, people use this paper, and in the country known as "Cai Houzhi Tsai Lunzao paper".
121 ad, the Eastern Han Dynasty imperial court internal politics involve Cai Lun, the emperor ordered him to surrender. Cai Lun is ashamed of trial, namely bath body, put on the most beautiful clothes, and then commit suicide.
ad eighth Century, our country has been widely used in paper, after which a few centuries, China will be exported to various parts of the paper in Asia, and Yan Bao paper secret. In 751, the Tang Dynasty and the conflict in the Arabia Empire, the Arabs captured several Chinese paper craftsmen. It wasn’t long before the paper industry began to rise in Samarkand and baghdad. So, in Arabia papermaking technology will gradually spread around the world, there are widely used in paper, then through Arabia to the North American and European countries. According to historical records, in the invention of papermaking Cai Lun after more than 1000 years before the establishment of the first European paper factory. Although the modern paper industry has been developed, but its basic principles are still the same as the Cai Lun paper. The seven or eight is the papermaking raw material has been replaced by the pulp, but made advanced printing paper, cigarette paper, paper and stencil, but still used rags, Cai Lun bark, hemp head, waste.