■ Shu Xiu
Everyone thinks that China's ancient poems have a high level of literature and art, but some people say that some poems contain scientific truth. You may be a little surprised, right? Will this happen? In fact, science and art are interlinked. Scientists and artists are observing nature. Scientists discover and reveal nature through observation and experiments, while artists express nature in different ways, but they can also discover nature when observing nature. Some of China's ancient poems contain some scientific truths. The sun sets slowly near the western hills, and the Yellow River flows into the East China Sea. Take a step further. This is the Heron House by Wang Zhihuan, a poet in the Tang Dynasty. The poet climbed the stork tower and looked at the distant mountains in the west. The setting sun gradually sets along the mountain, rolling the Yellow River far away and heading for the sea. If you want to see the scenery farther away (thousands of miles away), you must stand higher and climb to a higher floor. It is generally believed that standing high and seeing far is because standing high can avoid obstacles. In fact, this understanding is incorrect. There are no obstacles on the earth, and people's vision will be limited to a certain range, because the earth is a sphere. That's why people look at sailing boats from afar at the seaside. The first thing they see is the mast of the ship, and then they can see the hull. The farther a person's line of sight is from the tangent point of the earth's sphere, the farther the horizon is and the farther he can see. The higher a person stands, the farther the line of sight is from the tangent point of the earth. Flying farther from the space station, you can see half the earth on the moon. "But you only need to go up a flight of stairs, you can broaden your horizons by 300 miles." It contains the concept that the earth is a sphere. Zhang Ji, another Tang Dynasty poet, described another natural phenomenon in a night-mooring near maple bridge. He wrote in his poem: Frosty night, Jiang Feng, fishing fire, worrying about sleep. In the lonely Hanshan Temple outside Suzhou, the bell that rang in the middle of the night reached the passenger ship. In his poems, Zhang Ji described the night view of the river. Crows crow at the setting of the moon, and first frost is unstoppable. Facing the maple trees on the shore and the fishing fires in the river, I am even more worried and sleepless. In the middle of the night, the bell of Hanshan Temple outside Gusu (Suzhou) reached the passenger ship. Pay attention to two phenomena: midnight bell and frost all over the sky. Why can people on passenger ships hear the bell clearly at night? In addition to being quiet and quiet at night, another important reason is that when sound waves enter from one medium to another or into areas with different densities of the same medium, the propagation path of sound waves will bend, which is called refraction. During the day, the ground temperature is relatively high, and the temperature decreases upward. Due to the difference of temperature distribution in the vertical direction, sound refraction will occur. The sound wave propagating along the horizontal direction travels faster near the ground than far away from the ground, and the sound propagation path bends upward, that is, the sound travels faster in warmer air than in cold air. So sound doesn't travel very far along the ground during the day. On frosty nights, the ground temperature is very low, while the air temperature far away from the ground is relatively high, so that the sound can be refracted downwards and spread far near the ground, and people on passenger ships can clearly hear the bells of Hanshan Temple. Liu Yuxi, a poet in the Tang Dynasty, carefully observed the time, place and method of gold panning, and wrote a poem entitled "Langtaosha Ci": Rizhao Chengzhou River is foggy, and gold diggers are all over the river. Behind the beautiful jewels is sand full of waves. The gold rush is in the morning. The sun shines on the water island "Chengzhou" in the middle of the river, and the dense fog hanging over the river slowly dissipates. The river is gradually clearing up. The location of the gold rush is in the river bend, where women are looking for gold. The poet observed carefully, so he described natural phenomena very accurately. The water content in the air along the river is high. When the temperature drops at night, the water in the air will be supersaturated and form fog beads. When the sun comes out, the temperature rises, the fog beads evaporate and the fog disappears. This is the natural landscape contained in the poem "The Fog of Chengzhou River in Rizhao". The women who seek gold gather in the river bend because the water outside the river bend is faster, which can better separate placer gold from the sand. So "the gold rush is full of rivers." "Forever" is a place where mountains bend and water bends. The process of gold panning is based on the famous Archimedes principle, that is, the buoyancy of an object in water is equal to the gravity of the water it displaces. According to legend, Archimedes was lost in thought when identifying the authenticity of a pure gold crown, and discovered this important rule when taking a bath. Sand and placer gold have a larger proportion than water and will not float on the water. Stir the river bottom sediment containing placer gold to make it float. The resultant force (gravity-buoyancy) of the same volume of sand in water is different from that of placer gold, which has a greater resultant force (because the ratio of placer gold is large) and a faster decline rate. In running water, sand and placer gold will settle in different places. So sand is separated from placer gold. Beauty jewelry and royal seals are made of sand stirred by waves. Wang Zhihuan's "Liangzhou Ci" describes a bleak scenery outside Yumenguan: the Yellow River is far above the white clouds, and the lonely city is Wan Ren Mountain. Why use the elegy of willow to complain about the delay of spring, old Yumenguan, a spring breeze is not blowing! Looking around, the rushing Yellow River seems to meet the white clouds on the horizon. The castle stands on a high mountain, which makes it even more lonely and small. The ground is the Yellow River and the sky is white clouds. Why did they meet in the poet's eyes? Is it the poet's illusion? No. When people look around, they will feel that they are in the center of a circle that you can see. The edge of this circle is the horizon. The horizon is inaccessible. When you walk towards it, it will retreat. When you step back, it comes to you again. Looking around, the horizon meets the sky, so the Yellow River in the distance seems to meet the white clouds on the horizon. How far is the horizon from us? It is related to the observer's height on the earth's surface and the radius of the earth. According to the calculation, a person of medium height can see no more than 4.8 kilometers on the flat ground. If you stand higher, your vision will be farther. The moon is 3476 kilometers in diameter, slightly larger than the earth's diameter 12756 kilometers. On the moon, the distance between the observer and the horizon is only 2.3 kilometers. The diameter of Jupiter is about 1 1 times that of the earth, and the distance between the observer and the horizon on Jupiter is 15 km. Li Bai was the most famous poet in the Tang Dynasty, and was called "Poet Fairy". His poem "Looking at Lushan Waterfall" is like a beautiful picture: the incense burner in Rizhao is full of purple smoke, and the waterfall hangs in front of Sichuan. On the high cliff, it seems to be thousands of feet high, which makes people think that the Milky Way has fallen from heaven to earth. The poet stood under the censer peak and looked at Lushan censer peak in the sun. Purple smoke wrapped around the peak, and the falling waterfall seemed to hang on the water in front of the mountain. The majestic waterfall rushing down is so spectacular that people can't help wondering whether the Milky Way fell from the ninth heaven. The mountain peak is surrounded by purple smoke, which seems difficult to see clearly. Is the poet blinded by it? Or did you make a far-fetched description? Neither, the poet made careful observation, and such a situation is possible under certain conditions. This is one of the many explanations of "purple smoke", which is supported by scientific principles. As we all know, sunlight can produce rainbows through small water droplets. Why does the sun appear purple when it shines on Lushan incense burner peak? It turns out that light will scatter when it passes through smoke particles. When the diameter of these smoke particles is smaller than the wavelength of light waves, the intensity of scattered light is inversely proportional to the fourth power of the wavelength of incident light. This relationship is called Rayleigh scattering law. Rayleigh was the winner of 1904 Nobel Prize in Physics. In order to explain the long-term puzzling problems such as "why the sky appears blue", he deduced the "Rayleigh scattering law". Visible light consists of red, orange, yellow, green, cyan, blue and purple. Perhaps the diameter of the water mist produced by Xianglufeng Waterfall on the day when Li Bai watched the Waterfall was similar to the wavelength of purple light, so purple light was the strongest scattered light. Li Bai noticed this phenomenon and wrote it into his own poems. "Rizhao incense burner produces purple smoke" is a true portrayal at that time. Poets in the Tang Dynasty can't have today's knowledge of physics, but they are very serious when writing poems. They carefully observe the phenomena in nature and write them accurately in poems. Today, when we see these poems, we can not only praise their artistic genius, but also realize how serious they are in exploring nature!