How are solar and lunar eclipses formed? When will there be a solar eclipse?

Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Solar eclipse 1. Eclipse II. Solar eclipse 1. Its occurrence is related to the shadow of the moon and the earth. Under the irradiation of the sun, the earth and the moon are dragging long shadows away from the sun. The sun, the earth and the moon are all spheroids, and the sun is much bigger than the earth and the moon. Therefore, the main part of their shadow is a convergent cone with its top facing away from the sun, which is called umbra. In the umbra, all the solar disks are covered, so it is dark (strictly speaking, the umbra of the earth is not completely dark due to the refraction of the atmosphere). Because the sun is a spherical light source, there is a transition zone between light and shade around the umbra. This is a divergent cone much larger than the umbra, called penumbra. In this shadow area, you can get part of the sun's brilliance, so it is not completely dark. In penumbra, the extension line of the umbra cone is an emission cone coaxial with and opposite to the umbra, which is called pseudo-umbra. It is a special penumbra, the central part of the sun's disk is covered, and the edge part of the sun is still visible, so it is not completely dark. Different parts of penumbra and pseudo-umbra have different degrees of light and shade: the closer to umbra, the darker it is; The farther away from the umbra, the less sun gear is covered and the brighter it is. The length of umbra varies with the size of the projected object and its distance from the sun. The larger the radius of a celestial body, the longer its umbra. The radius of the moon is about 27% that of radius of the earth. If the distance between the moon and the sun is equal, the length of the moon's umbra is also 27% of the earth's umbra. The farther a celestial body is from the sun, the longer its umbra is. In a year, when the earth (and the moon) approaches the perihelion, the umbra becomes longer; Near the perihelion, the umbra is very short. Within a month, before and after the full moon, the umbra of the moon is longer; Around the new moon, the umbra of the moon is shorter. According to the radii of the sun, the earth and the moon, and the average distance between the sun and the moon, the average length of the earth's umbra is 1377 000km, which is about 3.5 times that of the moon's umbra. At the new moon, the average length of the umbra is 374 500 kilometers, which is slightly less than the average distance between the moon and the earth (384 400 kilometers). Therefore, when the shadow of the moon reaches the earth, it can be the top of the umbra or its pseudo-umbra. Together, the moon drags its own shadow around the earth. When it reaches the sun surface of the earth, its shadow sometimes sweeps across the ground. At this time, in the area swept by the moon shadow, people see that the sun is covered by the moon wheel, which is called a lunar eclipse. When the moon goes around the earth with its back to the sun, it happens to be hidden in the umbra of the earth. At this time, from the perspective of the earth, the full moon loses its luster in the sky, which is an eclipse. As you can imagine, when an eclipse occurs, what you see in the moon and sky is an eclipse; When there is a solar eclipse on the earth, a small shadow appears on the bright "place" in the night sky of the moon, which can be called "Lingdi". There are three kinds of solar eclipses: total solar eclipse, partial solar eclipse and annular solar eclipse, also called annular solar eclipse. Their difference depends on which part of the moon's shadow covers the ground. As we know, the diameter of the moon is much smaller than that of the earth. Therefore, the umbra of the moon can only cover a small part of the ground at any time. In this small area, it seems that all the solar disks are covered, which is called a total solar eclipse. If the umbra of the moon was not long enough at that time, it was not the umbra of the moon but its pseudo-umbra that touched the ground. Then, the sun seen in the pseudoumbra is covered by the moon wheel in the middle and the edge is still shining, which is the annular eclipse. It goes without saying that when the umbra or pseudoumbra of the moon falls to the ground, its penumbra will also arrive at the same time. Therefore, there is an annular penumbra around the total solar eclipse or annular solar eclipse area. From there, the sun seems to be partially covered by the moon wheel, and the CD is not complete. This is a partial solar eclipse. In this way, at the same time, total solar eclipse and partial solar eclipse occurred in different parts of the earth; In the same area, there must be a partial eclipse stage before and after the annular eclipse. Due to the rotation of the moon around the earth and the earth itself, the eclipse zone moves on the ground, forming an eclipse zone. The middle part of the eclipse belt is a total solar eclipse (or annular solar eclipse) belt, and the north and south sides are partial solar eclipse belts. In the process of moving, the distance between the tip of the lunar umbra and the ground changes. Because of this change, it sometimes happens that the beginning and end stages of the solar eclipse are annular eclipses, while the total solar eclipse occurs in the middle stage. Such an eclipse is called a total solar eclipse. Sometimes, due to the deviation of the lunar shadow cone, the solar eclipse belts on the ground are all partial eclipse belts. Such an eclipse will always be a partial eclipse. Eclipses can be divided into total solar eclipse and partial solar eclipse, and there is no annular solar eclipse. The difference between a total lunar eclipse and a partial lunar eclipse lies in whether the moon is completely or partially hidden in the umbra of the earth, rather than at different observation points on the earth. When the moon is completely hidden in the umbra of the earth, the whole moon wheel becomes dark, which is a total lunar eclipse. If the moon only partially enters the umbra of the earth, then the moon wheel is incomplete and it is a partial solar eclipse. Naturally, before and after the total lunar eclipse, there must be a partial lunar eclipse. Sometimes, because the moon is far away from the umbra axis of the earth, the whole eclipse process is always a partial eclipse. Whether it is a total solar eclipse or a partial solar eclipse, similar eclipses are seen all over the world (night hemisphere) at the same time. Unlike solar eclipses, lunar eclipses have nothing to do with the penumbra and artifacts of the earth. When the moon enters the penumbra of the earth, the "eclipse" will not happen, because part of the sun's brilliance can be obtained in the penumbra, and it still illuminates the whole surface of the moon, but the brightness becomes slightly darker, and the moon wheel is still indispensable. This phenomenon is called a penumbral eclipse, and the Observatory usually does not give advance notice. As for why there is no eclipse? The reason is obvious, because at the orbital distance of the moon, the cross section of the umbra is much larger than that of the moon wheel. Among the above food types, the most rare, spectacular and fascinating is the total solar eclipse. When the total solar eclipse comes, the sky is dark, just like the sudden arrival of night, birds return to their nests, chickens and dogs enter their nests, and animals all show panic. Nothing is more exciting than the dark day of the sun. The most famous total solar eclipse in history (May 28th, 585 BC, in Asia Minor Peninsula, now Turkey) dramatically ended the five-year war between two ethnic tribes and became an interesting episode in the history of war. The total solar eclipse is also of great scientific significance. This is an excellent opportunity to study the sun. As we know, the brightness of the chromosphere and corona is very weak, and they are completely submerged in the sun at ordinary times. Only when there is a total solar eclipse, the source of atmospheric scattered light is cut off, and the sky is dark, the chromosphere and corona are particularly clear. Astronomers can take this opportunity to capture their spectra (at this time there is no light source behind them to produce Fraunhofer lines); The study of chromosphere and corona is of great significance for exploring the physical state of the sun itself and between the sun and the earth. For example, helium, known as the "solar element", was discovered by astronomers in the chromosphere spectrum taken during the total solar eclipse in 1868, while chemists did not discover it from the analysis of yttrium uranium ore until 1895. At that time, some people praised celestial spectroscopy for running ahead of chemistry. Helium atom is a kind of atom that is difficult to "excite". It needs a high temperature to make it emit visible light. Its spectral line appears in the chromosphere spectrum, indicating that the temperature in the chromosphere of the sun is very high. Some astronomers also use this once-in-a-lifetime opportunity to search for planets in the water and recent comets near the sun. Therefore, whenever there is a total solar eclipse, astronomers always carry heavy instruments and travel long distances to the total solar eclipse area for observation and research in various disciplines. The whole process of total solar eclipse can be divided into three stages: partial eclipse-total solar eclipse-partial solar eclipse. These three stages are divided into four food phases: first loss, second food, raw light and last contact. From food to light is the whole food stage; The first loss to food, the second loss to the last contact, is the partial eclipse stage before and after the total solar eclipse. Both the moon and the sun move eastward on the celestial sphere. The former takes the sidereal moon as the cycle, and the speed is about1310' every day; The latter takes the sidereal year as the cycle and the speed is about 59 feet per day. Obviously, the moon moves much faster than the sun. It chases the sun and the umbra of the earth from west to east at a speed of about1310'-59' =121'every day. In other words, the process of solar eclipse is the process that the moon catches up with the sun eastward on the celestial sphere, thus covering the sun. Therefore, the process of solar eclipse always starts from the western edge of sun gear and ends at the eastern edge. Similarly, the process of an eclipse is that the moon passes the umbra of the earth eastward on the celestial sphere, thus being blocked. Therefore, eclipses always start at the eastern edge of the moon and end at the western edge. In the process of the moon catching up with the cross section of the shadow of the sun and the earth, the two circular surfaces will be circumscribed and inscribed twice, which are the four eclipse phases above. For the total solar eclipse, these four eclipses mean: the first loss-the eastern edge of the full moon is tangent to the western edge of the full moon, and the partial solar eclipse begins. Eclipse-the eastern edge of the moon wheel is inscribed with the eastern edge of the same wheel, and the total solar eclipse begins. Light-the western edge of the moon wheel is inscribed with the western edge of the same wheel, and the total solar eclipse is over. The last contact-the western edge of the full moon is tangent to the eastern edge of the full moon, and the partial eclipse ends. For the process of total lunar eclipse, the significance of these four stages are: initial loss-the eastern edge of the lunar wheel is tangent to the western edge of the umbra section at the same place, and the partial lunar eclipse begins. Eclipse-the western edge of the moon wheel is inscribed with the western edge of the umbra of the earth, and the total lunar eclipse begins. Illumination-the eastern edge of the moon wheel is inscribed with the eastern edge of the umbra section of the earth, and the total lunar eclipse ends. The last contact-the western edge of the moon wheel is tangent to the eastern edge of the umbra section, and the partial eclipse ends. An annular eclipse also has an eclipse on it. However, it has no total solar eclipse stage. Therefore, although there are two inscribed lines between the sun and the moon, there is no real food and light. It doesn't matter whether the partial eclipse of the sun and the partial eclipse of the moon are light or light. In the process of solar eclipse and lunar eclipse, the moment when the center of the moon wheel is closest to the center of sun gear or the umbra section of the earth is called an eclipse. The degree to which sun gear or the moon wheel is "eaten" under the condition of heavy food is called food score. The calculation of the food part is based on the apparent diameters of the sun and moon rings. For example, a lunar eclipse of 0. 5 means that 50% (not half) of the diameter of the sun and moon wheels is covered. The score of food with partial eclipse is > 0, ∠TEM'. The greater the latitude of yellow latitude, the farther away from the intersection of yellow and white, and the solar eclipse limit is greater than the lunar eclipse limit. The food season is a period when solar and lunar eclipses may occur, which is related to food restriction. Because the occurrence of solar and lunar eclipses must meet two conditions at the same time, not all new moons and eclipses can occur. Therefore, solar and lunar eclipses can only occur at certain times of the year. As we know, the conditions of solar eclipse and lunar eclipse are that the sun and the moon must be at the same yellow-white intersection (eclipse), or separated by two yellow-white intersections (eclipse) or close to two yellow-white intersections. Comparatively speaking, the moon passes through the intersection of yellow and white frequently (twice a month), 24.5 times a year; And the sun comes to the intersection once every six months. Therefore, whether there was a solar eclipse or a lunar eclipse at that time mainly depended on whether the sun was located at or near the intersection of yellow and white. The time when the sun exceeds the food limit is called food season. Generally speaking, there are two food seasons in a year, about half a year apart. The length of the food season mainly depends on the size of the food limit. The greater the food restriction, the longer the food season. According to the size of the food limit and the annual movement speed of the sun (average 59' per day), people can calculate the approximate number of days in the food season. For example, if the minimum food limit of partial solar eclipse is 15.9, then its food season will not be shorter than15.9× 2÷59 ′ = 32.2 days. This length has exceeded the moon. In other words, during this time, the moon will come to the intersection once. So, there must be two eclipses in a year. As it happens, there is an eclipse at the beginning and end of each season, so there are four eclipses a year. For another example, if the maximum eclipse limit of the partial eclipse is 1 1.9, then its season length will not exceed11.9× 2 ÷ 59 ′ = 24.2 days. This length is less than a full moon. In other words, during this time, the moon may not necessarily come to the intersection. Therefore, there is not even an eclipse in some years; If there is, it can only be once a season, which happens to be twice a year. Because the intersection of yellow and white recedes to the west by about 20 degrees every year, an intersection year (also called the food year) is only 346.2600 days, which is about 19 days shorter than the tropic year. So there may be two situations as follows: First, there are two complete food seasons and one incomplete food season in a year. If the first food season has just started at the beginning of the year, in addition to the third food season in the middle of the year, the third food season may be ushered in the middle of February1the same year. In this case, there may be five eclipses and two eclipses this year. In the second case, there is a complete food season (the middle of the year) and two incomplete food seasons (the beginning and the end of the year) in a year. In this case, there may be four eclipses and three eclipses. In the former case, for example, if the first food season starts on June 65438+ 10 1, it coincides with the new moon and a solar eclipse occurs. In the next 346 days (an eclipse year), under the most favorable circumstances, four eclipses and two eclipses may occur in the two eclipse seasons. The third eclipse season begins around 65438+February 12. Because the 12 moon is 354.36 days, which is about 8 days older than the eclipse, the 13 eclipse will not occur until about 65438+February 20, and there may be another eclipse. The remaining date is less than half a month, even if there is an eclipse, it will have to wait until the beginning of the following year 1 month. However, this situation is very rare. Globally, there are more eclipses than eclipses. But for a place, the number of eclipses is far more than the number of eclipses. This is because during the eclipse, the eclipse area is very wide (it can be seen everywhere in the night hemisphere), while during the eclipse, only a very narrow area can be seen on the earth. According to statistics, for a specific location, a total lunar eclipse can occur every three or four years on average; But the total solar eclipse takes hundreds of years on average to encounter. So many people in the world have never seen a total solar eclipse in their whole lives. On July 22nd, 2009, China will see a total solar eclipse. The solar eclipse is 230 kilometers wide and 3000 kilometers long, spanning southern Tibet and the Yangtze River basin. The total lunar eclipse lasts 5-6 minutes (the longest total solar eclipse lasts about 7 minutes), which coincides with the sunny and hot weather in midsummer in the south of the Yangtze River, and the observation conditions are excellent. This will be a once-in-a-lifetime opportunity. The conditions of periodic solar and lunar eclipses contain various periodic astronomical factors, so they have strict and complex periodicity. First of all, the solar eclipse will happen in the new moon, and the eclipse will happen in front of us. The first month of the lunar calendar is a period of phase change, and its length is 29.5306 days. Secondly, when an eclipse occurs, the sun must be at or near the intersection of yellow and white. It is a periodic phenomenon that the sun passes through the intersection of yellow and white, and its cycle is the intersection year (food year), which is 346.6200 days Thirdly, when an eclipse occurs, the moon will come to or near the yellow-white intersection at the same time, and the period of the moon passing through the same yellow-white intersection twice in a row is the intersection month, that is, 27.438+022 days. In addition, when the moon approaches perigee, it runs fast; When approaching apogee, the running speed is slow. This difference in distance and speed is also a periodic change, and its period is the latest month, that is, 27.5546 days. The above four periods are combined into a * * * same period, that is, their least common multiple, which is called Sharo period. Its length is 6585.32 days, equivalent to 223 new months, almost equivalent to 242 intersection months, roughly equivalent to 239 recent months and 19 food years. It is listed as follows: the first lunar month (29.5306)×223 = 6585.32, the intersection month (27.2 122)×242 = 6585.35, the perigee month (27.5546)×239 = 6585.55, and the eclipse year (346.6200). As a result, the solar eclipse series of the last cycle appeared again. In the Charlotte cycle, the time of solar eclipse and lunar eclipse is roughly equal, and the types of solar eclipse and lunar eclipse are also the same. At the same time, every solar eclipse and lunar eclipse will be repeated after a Charlotte cycle. For example, the annular solar eclipse on September 23rd, 1987 in/kloc-0 will reappear on October 3rd, 2005. However, because the Charlotte cycle is not an integer multiple of the solar day, two solar eclipses or lunar eclipses corresponding to each other will not occur at the same time in one day. Its mantissa, less than 1 day, is 0.32 days, that is, 1/3 days, which delays the corresponding two eclipses by about 8 hours, so it is about 120 degrees west longitude. For example,1the annular solar eclipse on September 23rd, 987 can be seen in Russia, China and the Pacific Ocean. The annular solar eclipse that will occur on June 3, 2005 10 can be seen in the Atlantic Ocean, Africa and the Indian Ocean. In addition, strictly speaking, the Charlotte period is not equal to an integer multiple of the intersection month, perigee month and solar eclipse year. So the corresponding solar eclipse or lunar eclipse is just similar, but not exactly the same. In short, the Sharo cycle does not include all the factors related to the same day and solar eclipse. Its simple regularity has no absolute significance, so it cannot replace the specific calculation of solar eclipse.