I have to talk about watching the sky at night.

Zhuge Liang's observation of the night sky is scientific and reasonable, knowing that there is a grass boat to borrow arrows and that there is a wind to worship the east wind. But seeing the astronomical phenomena, I knew that Cao Cao was not worthy of death, and sent Guan Yu to Huarong Road, knowing that Pang Shiyuan would rest when he saw the stars, which was a bit like the traditional astronomy and geography in China. Five lines of gossip and Taoism belong to simple science, and science and superstition are mixed together. From a scientific point of view, Kong Ming should be able to predict the weather, which is unlikely to be accidental, because Zhuge Liang is sure that there will be an east wind that night. According to what he learned in Longzhong, Zhuge Liang judged the Eight Diagrams and the Twelve Qi Festival through his erudition, and combined his personal judgment with the climate along Jiangdong and the Yangtze River. It is inferred that there will be an easterly wind in 1 1 month. Because in winter, if the weather changes regularly, it will rain after a warm period of time, and then the northwest wind will hang up, and then the weather will be fine and cold, and then it will gradually warm up, and then it will probably blow northwest wind. Zhuge Liang guessed this rule. Zhuge Liang ordered Guan Gong to capture Cao Cao in Huarong Road. As a result, Guan Gong released Cao Cao. Even Liu Bei saw it and asked Zhuge Liang, why did you send Guan Gong to see Cao Cao when you knew that Guan Gong was old? Zhuge Liang made it clear that Cao Cao's life should not be decided by watching the celestial phenomena at night, so he sent Guan Yu to send a letter for mercy and let Cao Cao go. Liu Bei can do nothing. Now we all know that astronomical phenomena have nothing to do with people. This is Zhuge Liang lying to Liu Bei. Why did Zhuge Liang cheat Liu Bei? Why did you let Cao Cao go? According to the situation at that time, only three pillars were relatively stable. If Cao Cao was arrested and killed at that time, Liu Bei's inheritance was unstable at that time, and Sun Quan sent troops to Xuchang, it would be a great event, and Liu Bei had no land and no city, which would be won by Sun Quan soon. So let Cao Cao go, and Liu Bei still has a way out. If he is killed, it will be difficult for him to protect himself. According to the novel, Liu Bei only had Jiangxia County at that time, and it was a tiny place. How can he compete with a strong enemy! And Cao Cao's 830 thousand army was destroyed, and its strength was greatly damaged. It can hardly go any further south. At that time, Zhuge Liang wanted to divide the world into three parts, and Wu Dong (Lu Su also proposed to divide the world into three parts in history) also wanted to gain a foothold. Therefore, in order to realize the ideal of "restoring the Han Dynasty", Liu Bei had to stand on his own feet. If Cao Cao was killed, the northern Cao Wei Group would be leaderless, and Sun Quan was in high spirits at that time, so as long as Sun Quan went north to attack Cao Wei, it would be a piece of cake, and then two-thirds of Liu Bei's world would be wasted and his life would be in jeopardy. Therefore, Zhuge Liang arranged this for Liu Bei's future consideration. If Guan Yu was not guarding Huarong Road and Zhang Fei and Zhao Yun were guarding it, Cao Cao would die. After Cao Cao's death, there will be chaos in the north, and the north will return to the situation of hegemony. At this time, it is indeed possible for Sun Quan to attack the Central Plains northward. If Sun Quan invades the Central Plains and occupies Xudu, then Sun Quan will choose whether to establish or abolish the Han Constitution. I think Sun Quan is most likely to choose the former. If Emperor Xian of Han Dynasty is abolished, he will become another Dong Zhuo, or even a public enemy of other forces. Besides, if Sun Quan marched into the Central Plains, wouldn't he be afraid of other forces uniting against him? Aren't you afraid that Liu Bei of Jiangxia stabbed him in the back? Therefore, Sun Quan's Northern Expedition is unlikely.