What is the length of day and night in the northern hemisphere at the vernal equinox? What is an extreme day like?

Minute, also known as "Japan-China" and "Day-Night Minute" in ancient times, falls on March 20th or 2 1 every year, and the sun reaches the longitude of the Yellow River. According to the "Twenty-four solar terms": "In mid-February, it is divided into half, which is half of ninety days, so it is called minutes." Another article, Spring and Autumn Stories, Yin and Yang in and out, said: "At the vernal equinox, Yin and Yang are also half-phase, so day and night are cold and summer." Therefore, the significance of the vernal equinox, first, refers to the equal division of day and night, each of which is 12 hours; Second, in ancient times, it was spring from beginning of spring to long summer, and the vernal equinox happened to be in the three months of spring, and spring was equally divided.

In ancient China, the vernal equinox was divided into three periods: "One is to wait for the arrival of the Yuan bird; Second, wait for Lei Nai to make a sound; Third, wait for electricity. " In other words, after the vernal equinox, swallows will fly from the south, and when it rains, the sky will thunder and lightning.

March 20th or 2 1 is the vernal equinox among the 24 solar terms, and the vernal equinox solar term begins when the sun moves to 0 degrees (vernal equinox). A day is half of spring, so it is called vernal equinox. On the vernal equinox, the sun shines directly at the equator, and day and night are almost equal. Then the direct sunlight position gradually moved northward, and the days were long and the nights were short.

During the spring equinox and solar terms, the East Asian trough is obviously weakened, and the trough ridge activity in the westerly belt is obviously enhanced. From Mongolia to the northeast, there are often low-pressure activities and cyclone development. Low-pressure movement causes cold air to go south, and it is windy and windy in the north. When the long wave trough moves eastward, there will be continuous rainy and cold weather due to the intersection of cold and warm air masses.

During the vernal equinox, the daily average temperature in all parts of the country rose steadily to above 0℃, except in the mountainous areas and areas north of 45 north latitude all the year round. The severe cold has passed, and the temperature rises rapidly, especially in North China and Huanghuai Plain. The daily average temperature rises to above 10℃ almost at the same time as the rainy areas along the Yangtze River and the south of the Yangtze River, and it enters a beautiful spring. On the vast land, the willows are green on the shore, the grass is growing in Fei Ying, the wheat is jointing, the rape is fragrant, the peach blossom is red, Li Bai is welcoming the spring, and the yellow is yellow. South China is a scene of late spring. According to the climate law, the precipitation in Jiangnan increased rapidly at this time, and it entered the period of "peach blossom flooding" in spring; In the northeast, north and northwest regions where "spring rain is as expensive as oil", precipitation is still very little, so resisting the threat of spring drought is the main problem of agricultural production.

"Wheat rises at the vernal equinox, and every moment is worth 1000 yuan." In the northern areas with little rain in spring, we should pay close attention to spring irrigation, water saving and jointing fertilization, and pay attention to preventing late frost and freezing injury. South China still needs to continue to do a good job in drainage and flood prevention. Early rice seedling raising in Jiangnan and Jianghuai areas has started, and the weather changes frequently in early spring. Attention should be paid to soaking seeds to accelerate germination when cold air comes, and sowing in sunny days when cold air ends. The experience of the masses says, "A cold tail warms the head, so there is no need to worry about seedlings." According to the weather conditions, strive for 3-5 sunny days after sowing to ensure that all seedlings are sown at one time. Spring tea has begun to sprout, so it is necessary to apply quick-acting fertilizer to control pests and diseases in time and strive for high yield and high quality tea.

"February is the vernal equinox, and planting trees and fertilizing farmland is deep." The vernal equinox is also a good opportunity to plant trees. In ancient poems, there is a saying that "Niu Jiao girls started planting trees in the middle of the night, and it was the vernal equinox in the Ming Dynasty". In the hot busy farming season, we should continue to use our hands to green the mountains and rivers of the motherland and beautify our environment.

The vernal equinox is one of the solar terms reflecting the changes of the four seasons. In ancient China, beginning of spring, Changxia, beginning of autumn and beginning of winter were used to indicate the beginning of the four seasons. The vernal equinox, summer solstice, autumn equinox and winter solstice are in the middle of each season. On the vernal equinox, the sun shines directly on the equator, and the time between day and night is equal all over the earth. Therefore, the ancient vernal equinox and autumnal equinox are also called "equinox", and there is a folk proverb that "vernal equinox and autumnal equinox are equally divided day and night".

After the vernal equinox, the overwintering crops in most parts of southern China entered the spring growth stage. In central China, there is an agricultural proverb, "Wheat starts at the vernal equinox, and every moment is worth a thousand dollars". The temperature in most parts of the south continues to rise, but generally it doesn't rain as fast as the vernal equinox. In late March, the average temperature in northern South China is mostly 13℃ to 15℃, and in southern South China it is mostly 15℃ to 16℃. Most of the plateau has been melted by snow, and the ten-day average temperature is about 5℃ to 10℃. Most areas in South China, such as river valleys, have the highest temperature, with an average of 18℃ to 20℃. In the south, except for the marginal mountainous areas, the average daily temperature rose steadily to above 12℃ in 1978, which is beneficial to planting crops such as rice and corn, and is also very suitable for afforestation. However, before and after the vernal equinox, there is often a strong cold air intrusion in South China, and the temperature drops obviously, and the lowest can be as low as 5℃. Sometimes a small stream of cold air comes one after another, forming a low temperature and rainy weather that lasts for several days, which is not good for agricultural production. According to this feature, we should make full use of the weather forecast, grasp the cold tail and warm head, and sow in time.

On the vernal equinox, the sun shines directly at the equator, and day and night are almost equal. The difference is that it is spring in the northern hemisphere and autumn in the southern hemisphere. Then the direct sunlight position gradually moved northward, the solar radiation in the northern hemisphere gradually increased, and the weather became warmer day by day. At the same time, the days get longer and the nights get shorter. The spring equinox solar terms are affected by the intersection of cold and warm air masses, and the rain will also increase. No, this spring equinox, there is no sun in our province, but the clouds are getting thicker and thicker, and the rain is pouring down.

As the saying goes, "The spring equinox begins with wheat, and the fat and water should follow". A spring rain was warm. After the spring rain, I was busy plowing. The busy farming season in spring is about to begin, and spring management, spring ploughing and spring planting are about to enter a busy stage. After the vernal equinox, overwintering crops enter the growth period, so field management should be strengthened. As the temperature rises rapidly and the water demand is relatively large, farmers should strengthen water storage and moisture conservation.

Chunfen health

March 2 1 day is the vernal equinox among the 24 solar terms. "The vernal equinox, Yin and Yang. So it's hot and cold day and night. " A word "fen" tells the boundary between day and night, cold and heat. At this time, the longitude of the sun is 0 degrees and the position of the sun is above the equator. According to the lunar calendar, "it refers to the vernal equinox, which is about Sunday. The northern and southern hemispheres are equally divided day and night, which is also half of spring, so it is called the vernal equinox."

The vernal equinox is the midpoint of 90 days in spring, and the northern and southern hemispheres are equal in day and night. From this day on, the direct position of the sun gradually moved northward, and the length of day and night in the northern and southern hemispheres also changed. The northern hemisphere has long days and short nights, but the southern hemisphere is just the opposite. As soon as the spring equinox arrives, the rainfall increases obviously, and the national average ground temperature has stabilized at 10 degrees, which is the spring temperature defined by climatology. After the spring equinox and solar terms, the climate is mild, with plenty of rain and sunny days. Winter crops in most parts of China enter the spring growth stage, which is also the sowing time of early rice. Agricultural proverbs in different places have different opinions on the vernal equinox: there is a saying in Shandong that "the vernal equinox plants trees, the sun shines, and nothing happens"; Hubei has a "rainy spring equinox, everyone is busy, planting melons and beans before transplanting"; There is a saying in Guangdong that "the vernal equinox comes first, and rice competes for money".

Ouyang Xiu once had a wonderful description of the vernal equinox: "At half past the vernal equinox in Nanyuan, the wind and the smell of Ma Si are like peas and willows, and butterflies are flying." Whether in the north or the south, the vernal equinox and solar terms are good times for spring, and orchids are in full bloom in Taiwan Province Province, China.

Because the vernal equinox and solar terms divide day and night equally, people should pay attention to maintaining the balance of yin and yang in health care. Stalin said: "Relatively static objects and the possibility of temporary balance are the fundamental conditions for material differentiation and therefore life". In order to obtain the "basic conditions of life" of this "temporary balance state", maintaining the balance of yin and yang in the human body has become an important rule of health preservation. This rule is very important in spirit, diet, daily life, self-care and medication. How to use the law of yin-yang balance in health care, coordinate various functions of the body, achieve a balanced state inside and outside the body, and keep the organic whole of the human body relatively calm and balanced is the foundation of health care.

Su Wenzhi's Theory of Truth: "Carefully examine the position of Yin and Yang and adjust it to balance the period". That is to say, the human body should coordinate the physiological movements of viscera, qi and blood and essence with the external movements of brain, physical strength and exercise, and maintain the balance between supply and demand. Avoid inappropriate exercise and destroy the balance of the internal and external environment of the human body, accelerate the damage of some organs and the imbalance of physiological functions, and then cause diseases and shorten people's life. Modern medical research has proved that the imbalance of human life metabolism will lead to the imbalance of some elements in the body, that is, the accumulation of some elements is excessive and the content of some elements is insufficient, which will lead to premature aging and diseases. Some non-communicable diseases are related to the imbalance of human elements. For example, cardiovascular diseases and cancer, which are the most harmful to human health in the world, are closely related to the imbalance of material exchange in the body, and the reasons are all due to the imbalance of yin and yang. According to the research of balanced health care theory and the different physiological characteristics of different age groups, adjusting the corresponding diet structure, supplementing essential trace elements and maintaining the balance of various elements in the body will be beneficial to our human health.

Su Wengu's Confucius Theory: "Regulating Yin and Yang, supplementing if it is insufficient, and purging if it is excessive". Traditional diet and traditional Chinese medicine treatment can be summarized as tonifying deficiency and purging excess. Such as benefiting qi and nourishing blood, nourishing yin and strengthening yang, filling essence, promoting fluid production and tonifying deficiency; Relieving exterior syndrome, clearing away heat, promoting diuresis, purging, dispelling cold, expelling wind and drying dampness can be regarded as diarrhea. The practice of TCM health preservation proves that no matter tonic or diarrhea, we must insist on adjusting yin and yang and carry out scientific diet and health care, so as to effectively prevent and treat many non-communicable diseases.

The period from beginning of spring solar term to Tomb-Sweeping Day gas is the budding period of plant growth, and the human blood is also in a vigorous period, and the hormone level is also at a relative peak. At this time, the common non-communicable diseases that are prone to occur are hypertension, menstrual disorders, hemorrhoids, allergic diseases and so on. In this solar term, we should choose a diet that can keep the body function coordinated and balanced according to our actual situation, and avoid eating misunderstandings such as being too hot, too cold, too high and too healthy. For example, when cooking cold foods such as fish, shrimp and crab, in principle, it must be accompanied by onion, ginger, wine and vinegar, so as to avoid this dish being cold and cold, damaging the spleen and stomach and causing abdominal discomfort after eating. For another example, in the consumption of aphrodisiac dishes such as leek, garlic and papaya, eggs are often accompanied by nourishing yin in order to achieve the goal of complementary yin and yang. Maintain a relaxed, cheerful and optimistic mental state. In daily life, we should insist on proper exercise, regular sleep, quantitative meals and purposeful nursed back to health in order to achieve the best health care effect.

Anecdote of vernal equinox

Every spring equinox, tens of millions of people all over the world are doing "vertical egg" experiments. How this toy, called "China Custom", became a "world game" is still difficult to verify. However, the game is simple and interesting: choose a smooth and symmetrical fresh egg that has just been born for four or five days, gently stand it up and put it on the table. Although there are many losers, there are also many winners. The vernal equinox has become the best time for vertical egg games, so there is a saying that when the vernal equinox arrives, the eggs will be beautiful. The eggs that stand up are very beautiful.

Why do eggs stand easily at the vernal equinox? Although there are many sayings, there are many scientific reasons. First of all, the vernal equinox is a day with the same length of day and night in the northern and southern hemispheres. The inclination of the earth's axis is 66.5 degrees, which is in a relatively balanced state with the earth's orbital plane around the sun, which is beneficial to vertical eggs. Secondly, the vernal equinox is in the middle of spring, which is lukewarm, colorful, comfortable, quick-thinking, agile and easy to succeed in laying eggs. More importantly, the surface of the egg is uneven and there are many protruding "hills". The height of "mountain" is about 0.03mm, and the distance between peaks is 0.5-0.8mm. According to the principle that three points form a triangle and a plane is determined, as long as three "mountains" and the triangle formed by these three "mountains" are found and the center of gravity of the egg passes through this triangle, the egg can stand upright. In addition, it is best to choose eggs 4 ~ 5 days after birth, because at this time, the yolk of the egg is slack, the yolk sinks, and the center of gravity of the egg drops, which is conducive to the erection of the egg.

Vertical egg not only has many scientific principles, but also contains many rich and profound philosophical thoughts. Columbus, a famous Italian navigator, crossed the vast Atlantic Ocean and discovered the new American continent. Some people think that his discovery is "purely accidental". At a celebration meeting, Columbus suggested that the ladies and gentlemen attending the party try to stand the eggs on the table, but none of them succeeded. Columbus said, now watch me perform. He knocked down the egg, the shell broke and the egg stood up. Then he said, I found this. This is really easy, but why don't you?

The well-balanced and smooth curve of an egg is the reason why it is difficult to stand up, and it is also its charm. Leonardo da vinci, a famous European Renaissance painter, spent more than two years forgetting to eat and sleep, and practiced drawing egg curves every day, which laid a solid foundation for his later success in shaping the mysterious smile of Mona Lisa. In China, people call face shape "face shape" and take egg shape as the standard of face beauty, which fully shows the superb aesthetic appreciation level of our people and the aesthetic attributes of egg shape. However, for a long time, people have been unable to find the mathematical expression of the egg-shaped curve, and even mathematicians can only approximate the egg-shaped curve with rulers and compasses. No wonder artists who have painted thousands of egg circles also say that no two are exactly the same. Until modern times, mathematicians found the following mathematical equation of egg curve: x2/a2+y2/(ky+b) 2, where | k | < 1, which finally solved the problem of drawing egg curve for generations. Today, egg-shaped cars, airships, bridges, tunnels, gymnasiums, concert halls and other buildings can be seen all over the world, which perfectly combine science and culture, science and art, science and aesthetics.

Astronomical phenomena

In terms of time period, it refers to the position where the sun is located between 0 degrees and 15 degrees, from March 20th to April 5th. But in fact, it usually refers to the day when the sun is really at 0 degrees of the yellow meridian: March 20 or March 2 1.

Phenomena on the earth

At the vernal equinox, the direct point of the sun is on the equator, and then the direct point of the sun continues to move northward, so the vernal equinox is also called the ascending equinox.

At the vernal equinox, theoretically, the world is as long as day and night (see the dawn). After the vernal equinox, the days in the northern hemisphere are getting longer and shorter, and the nights in the southern hemisphere are getting shorter and shorter.

At the vernal equinox, there are no extreme days and nights in the world. After the vernal equinox, it began to be extremely daytime near the North Pole, and its scope gradually expanded. Near the Antarctic, the extreme day ends and the extreme night begins, and the scope gradually expands.

The sunshine at the vernal equinox, when the time of day and night is the same.

phenology,bioclimatology

The mysterious bird arrived: Ye Yan, the mysterious bird, coaxed, "The vernal equinox comes and the autumn equinox goes."

Thunder is sound: yin and yang are thin, which is thunder. At this time, the four yang are gradually flourishing, and there is still yin, so it is thin for sound; Yes, the rhyme club said, "It is difficult to exhale like gas." Shu Zhu said: "hair, still out."

Electricity: electricity, sunshine also; The four yang are flourishing, and the gas is exhausted and the light is born. Therefore, "Li Jie" said: "All voices are positive; It's just yang. " "Yi" said: "Thunder and lightning are combined into one chapter. "The Biography of the Ram also said," Electricity, Lei Guang. "Yes, Xu said," Thunder is the sun and electricity is the yin. "Not really. It is obvious that there is electricity without thunder in midsummer.