Lu Lun, a famous poet of the Tang Dynasty, wrote in his "Song under the Sai": "The geese are flying high in the dark moon, and Shan Yu is escaping at night. If I want to chase the Qingqi away, the heavy snow will cover my bow and knife." Two doubts:
When the mathematician Hua Luogeng read this poem, he raised a question: "When there is heavy snow in the north, the geese return south early. How can you see the geese flying high in the dark moon and sky." ——The level of the original poster As tall as Hua Luogeng. . Admire
In fact, the wild geese return south around the ninth month of the lunar calendar, and "Hu Tian flies in the snow in the eighth month." It seems that flying geese and heavy snow are not inconsistent. Furthermore, knowing that wild geese fly high, the sense organs do not necessarily have to be eyes. Why not ears? When you hear the cry of wild geese, don’t you know that there are geese flying high above?
First, it is still possible to see wild geese when it snows in the north.
The desert in northern my country is located on a plateau and is a high-latitude area. There is a possibility of being invaded by cold currents in advance and causing snowfall before winter begins. There are poems to prove it: Cen Shen's "Song of White Snow Sends Magistrate Wu Back to the Capital" "The north wind blows the white grass on the ground, and the snow is flying in August", Gao Shi's "Farewell to Dongda" "Thousands of miles of yellow clouds, white sun, north wind "The wild geese are blowing and the snow is falling." Both Cen and Gao were the two most famous frontier fortress poets in the Tang Dynasty. They both lived in the frontier fortress for at least ten years. During Gao's ten years, Cen entered the military camp five times and went out of the fortress twice. When they were in their prime, they both went to the frontier to join the army. Therefore, their poems are true portrayals of frontier life and actual conditions. Therefore, it is possible for snow to fall in August in Hu areas, not to mention the "northern wind blowing wild geese and snow".
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Secondly, there is still a problem with this poem. Wild geese are night blind. Can they fly at night?
From a zoological perspective, geese are night-blind birds, similar to chickens and ducks. That is to say, geese, like other poultry, also have "chicken eyes" and lose all vision in the dark. You can no longer see at night. If you are frightened when the moon is dark, will you fly high? I don't know. . But is it possible that they never found a habitat and kept flying. . .
Both geese and swans need to find a wide body of water to settle down before dark. If they cannot find it before dark, they will fly non-stop until dawn due to night blindness. Therefore, the prerequisite for wild geese not to fly at night is that there is a wide body of water to settle down. So in the situation where Beisei is almost a desert, can the poor wild geese find a rare oasis to stay every day? If they cannot be found, they must keep flying at night, so it is normal for geese to fly at night. Of course, you can't see wild geese in the dark night, but "the passing geese leave a sound" and you can tell by the sound alone.
The above discussion is about the migration time and night blindness habits of wild geese, but literary works should always be considered from a literary perspective: the wild geese that can still be seen in winter should be lonely geese and injured wild geese. The word "qixing" in the first sentence is a metaphor for Shanyu who lost the battle and fled alone. I think this explanation is very reliable. . .
After all, it is a literary work, and Mr. Lu should be allowed to use his imagination~~~~