#节气科普.3 If we want to understand "Lichun" from multiple angles, we may as well leave the earth for a while, for example, suppose we stand outside the earth from a third perspective to observe "Lichun"...
At this time, because our foothold is not on the earth, it is easy for us to see more clearly that the earth is "rotating" on the one hand, and running around the sun ☀ on the other hand.
Crucially, we can see more clearly that the Earth is not polarized in space, but that there is an oblique angle of the Earth's axis of rotation; the Equatorial Plane of the Earth, the Axis of The Earth's Rotation, which as a whole presents an angle with the plane of the Earth's orbit around the Sun.
At this time, if we open one eye, close the other eye, and look at the relationship between the earth and the sun ☀, we will find that because the earth is constantly rotating at an oblique angle, the direct point of the sun's ☀ rays on the earth is also changing.
If we continue to squint one eye, like a target, and look closely, we will find that the best direct point of sunlight on the blue planet of The Earth is between about 23.5° and 23.6° at the north and south latitudes. That is to say, if we take the Earth's equator as the central line, the direct point of the sun is actually only in the middle zone of 23.5 degrees north and south of the Earth, "scanning"!
Therefore, scientists call the dimensional line of about 23.5° to 23.6° north and south of the earth as the Tropic of Cancer!
The direct point of the sun moves in between, and the time of year (365 days) moves back and forth!
If we want to know how far the sun's direct rays move every day, we only need to use the knowledge of secondary school geography to calculate it! The reference value for the big is 23.5° ×4=94° moving 94°/365≈0.2575° per day on average
If we still feel that the calculation is a bit complicated, then we may as well find a space-time "reference point" of the sun ☀, for example, the "vernal equinox" day, which is the best reference, because the direct point of the sun ☀ on the vernal equinox day will be exactly at the equator!
We are lichun today, another 15 days is rain, another 15 days of stinging, another 15 days of spring equinox...
At this time, we might as well go back to Earth, bask in the spring sun above us, close our eyes, and think about the way the sun ☀ is coming back from the Tropic of Cancer to the northern hemisphere (the direct point) ... Well! In another 44 days, The Sun ☀ Mother will be back at the equator!
Getting closer and closer to us!
At this time, because we have returned the perspective and foothold of observation to the Earth, we will observe that the direct point of the sun ☀ is moving back and forth between the Tropic of Cancer, "scanning", like the light scanning of a photocopier.
It's easy to observe some regularities, such as:
1. In the area of the Tropic of Cancer of the Earth, the maximum value of the sun's ☀ direct point once a year is the summer solstice day in the hemisphere, and the minimum value is the winter solstice day in the hemisphere;
2. The vast area between the Tropic of Cancer is the maximum of the direct solar point twice a year - it has two direct solar rays, a minimum value - the winter solstice day in the hemisphere;
3. In the equatorial region, the maximum value of the direct sun point is twice, and the minimum value is also twice;
4. Outside the Tropic of Cancer, the maximum of the direct solar spot once a year - the summer solstice day in the hemisphere, the minimum value once a year - the winter solstice day in the hemisphere.
In other words, the direct point of the sun and the temperature change on the earth are different!
Only in this way, the Tropic of Cancer in the northern hemisphere of the earth, like an invisible line, separates the temperate and tropical zones of the northern hemisphere from north to south; it also connects North Africa, the Arabian Peninsula, India, China, the Pacific, the Central and Atlantic countries and regions from east to west.
In the case of China in the northern hemisphere, Taiwan, Guangdong, Guangxi and Yunnan are the provinces of China on the Tropic of Cancer.
A line of latitude with multidisciplinary astronomical climatic characteristics, passing through the above four provinces and regions. Hualien and Chiayi in Taiwan, Shantou, Conghua and Fengkai in Guangdong, Wuming and Wuzhou in Guangxi have established Tropic of Cancer markers, and the Tropic of Cancer also crosses 5 prefectures and 16 counties in Yunnan...
Because the direct points of the sun ☀ between the Tropic of Cancer bring different amounts of light and heat, it is generally said that the vast area between the Tropic of Cancer is generally referred to geographically as tropical.
However, we should note here that climatology is not entirely divided in this way, because climatology also takes into account not only the direct point of the sun, but also the impact of ground currents, monsoons, mountains, etc. on the climate.
Climatologically, the tropics usually refer to areas where the average temperature of the coldest month is above 18 °C (16 degrees Celsius), and the average temperature of the hottest month is above 22 °C.
Therefore, although Guangzhou, Hong Kong, Macau, etc. are also south of the Tropic of Cancer, they may still be classified as "subtropical" in climatology.
Speaking of which, it is not difficult to find that the climate outcome of a region usually depends on two factors - the time and the location. We can't simply and mechanically look up at the sun ☀ in the sky, or look down at the "feng shui" on the ground and immediately judge how!
In the study of Traditional Chinese medicine, we have the heavenly "five luck and six qi" law can be referenced, but also combined with the specific climate environment on the ground and the impact of social culture on people, but also specifically combined with the individual's physique to multi-angle ginseng, not simply pinch the finger of a thing!
——Laoxia Institute of Natural Life2022.2.4
