There are 1 popular science tips. Let's learn about the following: 1. Why do people yawn? When we feel tired, a lot of carbon dioxide has been produced in our body. When there is too much carbon dioxide, we must increase oxygen to balance our body's needs. Why do people turn white when they get old? There is a substance called melanin in our hair. Why do you growl when you are hungry, and growl when you are hungry? This is because the food you have eaten before is almost digested, and although the stomach is empty, the gastric juice in the stomach will continue to secrete. 5. Why can't native birds fly because their feathers are too soft and their wings are too small to fly at all? 6. Why can't the food go bad easily? When people make canned food, they pump all the air out of the can. Then seal it, even if the food inside is stained with a little bacteria in the absence of air. Seventh, why do babies cry all the time when they are born, and they cry all the time when they are born, because they are breathing the first mouthful of air and making a sound similar to crying. Eighth, why do lizards' tails keep bouncing when they are broken and backward? When lizards are attacked, their tails will even cause paragraphs due to severe muscle contraction. Based on the broken tail, there are still some nerves alive, which will bounce constantly to distract the enemy's attention, so as to escape. 9. Why can't we turn off the lights and watch TV? The screen and images of TV are relatively small, and our vision should be highly concentrated and expanded in the dark. We are particularly sensitive to the strong reaction of the light on the TV screen, which will stimulate our eyes and reduce our vision by ten. Who are the top ten marshals of China, Zhu De, Peng Dehuai, He Long, Chen Yi, Liu Bocheng, Luo Ronghuan, Xu Xiangqian, Nie Rongzhen, 1 Ye Jianying, that's all for sharing today. I hope I can help you.