Traditional Culture Encyclopedia - Weather forecast - Eclipse, what is it?
Eclipse, what is it?
Scientific explanation
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Eclipses are typical examples of light propagating in a straight line in celestial bodies. When the moon moves between the sun and the earth, it doesn't happen every time. There are two conditions to meet when an eclipse happens. First, solar eclipses always occur on the first day of the lunar calendar. Not all solar eclipses will occur on the first day, because the orbit of the moon (the ecliptic) and the orbit of the sun (the ecliptic) are not on the same plane. There is an included angle of 5 9' between the ecliptic plane and the ecliptic plane. If both the sun and the moon move near the intersection of the ecliptic and the ecliptic on the first day, and the sun is at a certain angle from the intersection (eclipse limit), an eclipse will occur, which is the second condition to be met.
Because the orbits of the moon and the earth are not perfect circles, and the distance between the sun and the moon and the earth is near and far, the shadow formed by the sun's shading by the moon can be divided into umbra, pseudoumbra (formed when the moon is far away from the earth) and penumbra on the earth. The observer can see the total solar eclipse within the umbra; Annular eclipse can be seen in the range of pseudoumbra; Only partial solar eclipse can be seen in the penumbra.
When the total solar eclipse occurs, it can be divided into five kinds of eclipse images according to the position relationship between the round surface of the moon and the round surface of the sun: 1. The moon moves faster than the apparent motion of the sun. The moon caught up with the sun during the eclipse. When the eastern edge of the moon just "touches" the western edge of the sun, it is called the first loss, which is the first "circumscribed" and the beginning of the solar eclipse. 2. Eat well. About an hour after the initial loss, the moment when the eastern edge of the moon and the eastern edge of the sun "cut in" is called eclipse, which is the beginning of the total solar eclipse, when the moon covers the whole sun; 3. Eat a lot. It is the moment when the sun is the deepest eclipse, and the center of the moon moves to the nearest center of the sun; 4. light. The moment when the western edge of the moon and the western edge of the sun "cut in" is called light, which is the end of the total solar eclipse; It usually takes only two or three minutes from eating to lighting, and the longest time is no more than seven and a half minutes; 5. last contact. About an hour after the birth of light, when the western edge of the moon "touches" the eastern edge of the sun, it is called last contact. From then on, the moon completely "leaves" the sun, and the eclipse ends.
There are many high mountains on the surface of the moon, and the edge of the moon is irregular. When the valley on the edge of the moon fails to completely cover the sun at the moment when the eclipse or light comes, the uncovered part forms a luminous area, like a crystal diamond; The reddish aperture around constitutes the "ring" of the diamond ring, which looks like a diamond ring inlaid with bright gems on the whole. Sometimes a lot of particularly bright light or light spots are formed, as if a string of pearls were embedded around the sun, which is called Belle Pearl (Belle is a French astronomer).
whether it is a partial solar eclipse, a total solar eclipse or an annular solar eclipse, the time is very short. The area where solar eclipse can be seen on the earth is also very limited, because the moon is relatively small and its umbra is relatively small and short, so the umbra does not sweep across the earth for a long time. Because the average length of the umbra of the moon (373,293 kilometers) is less than the average distance between the moon and the earth (384,4 kilometers), the number of annular eclipses occurs more than the total solar eclipse on the whole earth.
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Why did a part of the sun disappear? This is the part of the sun that was hiding behind the moon. This is the first partial solar eclipse in 25 and the last total solar eclipse that can be observed before March 26. During the eclipse, the sun, the moon and the earth are in a straight line. This total solar eclipse first appeared in the South Pacific, and the area where partial eclipse can be observed spanned South America and North America to the south. The scene of the above image was taken by a hand-held digital camera last Friday. After a rainy day in Holly Mountain, North Carolina, USA, some of the eaten sun temporarily penetrated through the dark clouds. After taking a series of images, this best photo of the solar eclipse is combined with another photo that is not so good but has a plane.
frequency of occurrence
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The following are the times of solar eclipses worldwide in the 2th century (191-1999):
partial solar eclipse 78
annular solar eclipse 73
total solar eclipse 71
mixed food 6
a total of 228
people who watched the solar eclipse. The observation of solar eclipse is often misinterpreted. The sun will not predict the occurrence of solar eclipse on the earth and will not emit other rays, so it is harmless to stay outdoors during the eclipse. But should we stare or glance at the partial eclipse? Although the sunlight during the eclipse is much weaker than usual, if you look straight, it will still hurt your eyes and damage your cornea. People stare or squint at the sun out of curiosity. Of course, the partial eclipse is still dazzling. If you look at the sun for a long time, your cornea will be damaged before you know it. During the eclipse, the eyes were damaged not because of the abnormality of the sun, but because people were curious and didn't pay attention to protective measures. Don't look directly at the sun with your eyes, whether an eclipse occurs or not; Don't use so-called "sunglasses"; Don't use "sunglasses", not even a few stacked ones; Don't look at the image of the sun in the mirror or on the water;
Look at the sun with No.14 welding mirror; Watch it with a specially coated Myra mirror, which can be obtained from the famous planetarium or science museum; Construct a hole projector.
The story of the solar eclipse
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For the ancient people, the solar eclipse was very terrible. If you can understand the influence of the sun on grain cultivation and daily life, you will be concerned about why the sun in the sky suddenly disappeared. In ancient China, it was thought that the solar eclipse was caused by a dragon swallowing the sun. Other civilizations also thought it was an ominous sign, and there were many "solutions": playing drums, shooting arrows at the sky, taking things or offering sacrifices to people, etc. It is said that there was a fatal solar eclipse report error. This means that two astronomers in China in the 2nd century BC did not report the solar eclipse for some reasons. At that time, the emperor of China thought he was the son of heaven, and attached great importance to astronomical phenomena. He thought it was a hint from heaven, so he invited a group of astronomers to observe astronomical phenomena regularly. Comets and meteors could not be predicted at that time, but eclipses could be predicted. The two astronomers didn't tell the emperor about the solar eclipse, and the emperor was furious and beheaded them. Astronomers then were much more dangerous than they are now.
knowledge about the sun
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prominence
prominence is a kind of solar activity phenomenon that protrudes outside the edge of the solar surface. When a prominence appears, the color ball in the atmosphere resembles a burning grassland, and the rose-red tongue-shaped gas rises like a fire, with various shapes, some like clouds, some like arch bridges, some like fountains, some like clumps of grass, and some are as beautiful as festive fireworks. On the whole, their shapes are just like earrings attached to the edge of the sun, hence the name "prominence". The rising height of prominence is about tens of thousands of kilometers, and the large prominence can be hundreds of thousands of kilometers higher than the solar surface, generally about 2 thousand kilometers long, and individual prominence can reach 1.5 million kilometers. Prominences are much dimmer than the photosphere, so they can't be observed with the naked eye at ordinary times, and can only be seen directly during a total solar eclipse. Prominence is a very peculiar phenomenon of solar activity. Its temperature ranges from 5, to 8, K. Most of the prominences rise to a certain height, and then slowly land on the solar surface. However, some prominences float in the lower layer of the corona with a temperature as high as 2 million K, that is, they don't attach or disintegrate, just as strange as a piece of unmelted ice in a blazing steel-making furnace. Moreover, the density of prominences is 1 times higher than that of the corona.
corona
the outermost atmosphere of the sun is called the corona. The corona extends several times to dozens of times the diameter of the sun. In the year of maximum solar activity, the corona is close to a circle; In a quiet year, it is oval.
b] There are large irregular dark areas in the corona, which are called coronal holes. Coronal hole is an area with low gas density in the corona. There are three kinds of coronal holes: polar coronal holes, isolated coronal holes and extended coronal holes. Solar energy loses material in the form of solar wind-material particle flow. Coronal hole is an important source of high-speed solar wind. Coronal mass ejection is a very macroscopic and huge material and magnetic field structure that occurs in the corona. It is a sudden explosion phenomenon of large-scale dense plasma. Nothing affects the earth more than it. When there are strong explosions and coronal mass ejections on the sun, the powerful plasma stream carried by the solar wind may reach the polar regions of the earth. At this time, aurora appears at the poles of the earth. The form of aurora is ever-changing. Aurora is also found on some planets with magnetic fields in the solar system. The flare that occurs in the corona is called X-ray flare, and its wavelength is only 1 ~ 8 angstroms or less. It directly causes the disturbance of the earth's ionosphere, thus affecting the earth's short-wave communication.
solar wave
a kind of ejection phenomenon of solar photosphere material. It usually happens over sunspots, and it has a strong ability to reappear. When a surf falls behind along the rising path, it will trigger a new surf to take off, and so on, but its scale and height are smaller and smaller every time until it disappears. Surfing at the edge of the sun appears as a small bright hill with a sharp spike at the top. The rising heights are different, ranging from a few hundred kilometers for small surfing to 5, kilometers for large surfing, with the largest reaching 1-2, kilometers. The maximum speed of the projectile can reach 1 ~ 2 kilometers per second, which is more than 1 times faster than the fastest reconnaissance plane. When they reach the highest point, they begin to descend under the influence of the sun's gravity until they return to the surface of the sun. From the high-resolution observation data, it is found that surfing is composed of a very small bundle of fibers, and the distance between each fiber is very small, which shines together and moves together as a whole.
solar activity forecast
the change of the state of the space environment between the sun and the earth is becoming more and more important to the modern cutting-edge technology on which modern life and production depend. As mentioned earlier, the X-ray flare directly causes the ionosphere disturbance of the Earth, thus affecting the short-wave communication of the Earth. Solar proton events will endanger the sensors and control equipment of astronauts and spacecraft, and also pose a radiation threat to passengers and crew flying in high latitudes. According to statistics, intense solar activity is related to earthquakes, volcanic eruptions, droughts and floods, heart and nervous system diseases and traffic accidents. Therefore, solar activity and solar-terrestrial physical prediction are very important. Solar activity forecasting is divided into long-term, medium-term and short-term forecasting and warning. As a systematic scientific research object, the solar-terrestrial space environment began in 1957 when humans entered space. The 195s and 197s were the exploration stage, and people gradually realized the importance of space environment. On the basis of a large number of explorations, a static model describing the environment is established, and some important space activities are predicted. After the 198s, driven by the demand, the research on the space environment between the sun and the earth has developed rapidly. Since 1979, every four years, the international conference on solar-terrestrial prediction has been held as scheduled, and its scale has been expanded one after another. In order to unite and coordinate the work of major countries, a joint forecasting center was established. Headquartered in the United States, there are 1 regional alarm centers distributed around the world. Our Beijing regional alarm center is one of them. After entering the 199s, scientists vividly called it "space weather".
Solar activity cycle
This cycle is 22 years on average, and it includes two 11-year sunspot cycles. In each cycle, the polarity of sunspots is opposite, and the changes of other solar phenomena have two highs and two lows like sunspots. These solar phenomena include the frequency fluctuation of prominence, flare and magnetic effect, and the magnetic effect includes aurora and the enhancement of radio interference on the earth. The 11-year basic cycle of sunspots (sometimes called solar activity cycle) was announced by Schwabe in 1843. Some people try to link the solar activity cycle with the changes of other phenomena, such as the small changes in the diameter of the sun. Even the change of tree rings is related to the solar cycle.
The earliest record of solar eclipse
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On May 26th, 1217 BC, people living in Anyang, Henan Province, China were engaged in all kinds of normal activities, but an amazing thing happened. People look up at the sky, and suddenly there is a gap in the radiant sun, and the light color is dim. However, after missing a large part, it began to recover. This is the earliest record of solar eclipse in human history. It is carved on a piece of Oracle Bone Inscriptions.
The observation of solar eclipse in ancient China kept the continuity of records. For example, in the annals of Spring and Autumn Annals, there were 37 eclipses in 244 years from 77 BC to 476 BC. The records of solar eclipses from the 3rd century A.D. continued into modern times, lasting for 16,7 years.
The longest solar eclipse
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The longest solar eclipse (the moon is between the sun and the earth) lasts for 7 minutes and 31 seconds. The solar eclipse that occurred in western Philadelphia in 1955 and lasted for 7 minutes and 8 seconds was the longest in recent years. It is predicted that there will be a solar eclipse lasting 7 minutes and 29 seconds in the mid-Atlantic in 2186. In 1995, a mother and a child were photographed during an eclipse in Bangkok, Thailand, which was a total eclipse in some parts of the country. The longest duration of the lunar eclipse (the shadow of the moon moving into the earth) is 1 hour and 47 minutes. On July 16, 2, people saw this scene on the west coast of North America.
Because the orbits of the moon and the earth are not perfect circles, and the distance between the sun and the moon and the earth is near and far, the shadow formed by the sun's shading by the moon can be divided into umbra, pseudoumbra (formed when the moon is far away from the earth) and penumbra on the earth. The observer can see the total solar eclipse within the umbra; Annular eclipse can be seen in the range of pseudoumbra; Only partial solar eclipse can be seen in the penumbra.
Ten-year solar eclipse schedule
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The best observation point of year, month and day type
28 2 7 circumpolar Antarctica, Pacific Ocean
28 8 1 All Canada, Arctic Ocean, Russian Federation and China
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