How did the solar eclipse form? The so-called "eclipse" refers to the astronomical scene in which one celestial body is completely or partially blocked by another celestial body or its shadow. There are three kinds of eclipses: total solar eclipse, partial solar eclipse and annular solar eclipse. The principle of solar eclipse is that some parts of the earth are covered by the shadow of the moon. The solar eclipse must occur in the new moon, the first day of the lunar calendar. This is because only on that day will the moon appear on the line between the sun and the earth, so that the moon can block the sun and form an eclipse. Similarly, the eclipse must appear on the lookout day, which is the fifteenth day of the lunar calendar. You may ask, why is there no solar eclipse on the first day of every month, and why is there no eclipse on the fifteenth day of every month? This is because in addition to the above conditions, there are other factors that affect the appearance of the solar eclipse. We call the earth's orbit around the sun ecliptic and the moon's orbit around the earth white. The ecliptic plane and the ecliptic plane are not the same, and there is an average angle of 5 09' between them, which changes at any time. A solar eclipse will only occur when the moon moves to the ascending intersection of the ecliptic and the ecliptic and approaches the descending intersection. There are three kinds of solar eclipses: partial eclipse, annular eclipse and total solar eclipse. The part of the moon that covers the sun is called a partial solar eclipse. The moon only covers the central part of the sun, and a circle of the sun's surface is exposed around the sun, which is called annular eclipse like a halo. A total solar eclipse is when the sun is completely obscured. The occurrence of these three different solar eclipses is related to the changes of the positions of the sun, the moon and the earth, and also depends on the changes of the distance between the moon and the earth. The moon is much smaller than the sun, its diameter is about a quarter of the diameter of the sun, and the distance between the moon and the earth is almost a quarter of that between the sun and the earth, so from the perspective of the earth, the circular surfaces of the moon and the sun are almost the same size, so it can cover up and cause an eclipse. The orbit of the earth and the orbit of the moon are both ellipses. The distance between the sun and the earth and the distance between the moon and the earth are not fixed, sometimes far and sometimes near, so the length of the umbra of the moon is different. The longest umbra of the moon is 379,660 kilometers and the shortest is 367,000 kilometers, while the distance between the earth and the moon is 356,700 kilometers and the farthest is 406,700 kilometers. If the umbra of the moon is larger than the distance between the earth and the moon at a certain moment, the total solar eclipse can be seen in the area swept by the umbra of the moon on the earth. If the lunar umbra is less than the distance between the earth and the moon, and the tip of the lunar umbra cannot reach the earth's surface, then the annular eclipse can be seen in the area swept by the small shadow cone (called pseudo-umbra) extending from the shadow tip. A partial solar eclipse can be seen in the area swept by the penumbra of the moon. The closer to the total food area, the greater the degree of partial eclipse. Where the umbra and penumbra of the moon are not swept, there is no solar eclipse at all. The following are the global solar eclipses in this century (190 1- 1999): the number of solar eclipses: partial eclipse for 78 days, total eclipse for 73 days, mixed eclipse for 7 1, and total eclipse for 6 days. The process of solar eclipse can be divided into five stages, but only total solar eclipse has the whole process, while partial solar eclipse and annular solar eclipse have no light. Initial loss: At the moment when the sun and the moon are circumscribed for the first time, the west of the photosphere of the sun just cuts into the east of the moon. Eclipse: the moment when the sun and the moon cut in for the first time and the photosphere of the sun has just been completely covered by the moon. Eclipse: The moment when the distance between the center of the moon and the center of the sun is the smallest. Cold light: the moment when the sun and the moon are inscribed for the second time, and the sun ball just appears from the west of the moon. Last contact: the sun and the moon are circumscribed for the second time, and the photosphere of the sun has just completely left behind the moon. The first loss, food, light and last contact are also called the first, second, third and fourth contact respectively. The law and cycle of solar eclipse Because the earth revolves around the sun and the moon revolves around the earth and the movement of the yellow and white intersection points is regular, a roughly similar solar eclipse and lunar eclipse will occur at regular intervals. As early as ancient times, Babylonians discovered that the cycles of solar and lunar eclipses were 233 moons, namely 18 1 and 1/3 days, namely the Sharo cycle. How to observe the solar eclipse? Watch the eclipse, don't look directly at the sun with your eyes. Decades ago, dozens of people in Germany were blind because they watched the eclipse directly with their eyes! Why does eating breakfast directly with your eyes hurt your eyes and even make people blind? It turns out that sunlight and invisible infrared rays contain a lot of heat energy, which will be generated after being absorbed by objects. Everyone has this experience. Look directly at the sun with your eyes, even for a short moment, your eyes will be greatly stimulated. After a long time, the eyes become black and it is difficult to recover. This is because you have a lens in your eye, which can act as a condenser. Looking at the sun, the heat energy of the sun gathers on the retina of the fundus, which will make you feel dazzling; If after a period of time, the retina will be burned and blind. When there is a solar eclipse, most of the time it is a partial solar eclipse, and the moon only blocks part of the sun, and the rest is the same as usual, so looking straight with your eyes for a long time will also burn your eyes. Usually you can put a piece of blackened glass in front of your eyes (you can also blacken the glass on fireworks). The thickness of the ink layer should be uniform, so that the eyes can see the sun turn bronze through it, which looks neither dazzling nor clear. Sometimes I pour water with ink into people's pots and watch the sun reflect in the water. Others take full exposure negatives and look at them together. People who watch through binoculars must add a filter in front of the camera, and the principle is to weaken the sunlight, so as not to burn their eyes. But don't put your eyes close to the telescope and look at the sun directly, or you will burn your eyes. When not observing, don't point the telescope or camera at the sun, and cover the lens, so as to avoid the lens absorbing too much heat and causing it to burst. The principle of lunar eclipse. On the fifteenth and sixteenth days of the lunar calendar, the moon runs in the opposite direction to the sun. At this time, if the centers of the earth and the moon are roughly on the same straight line, the moon will enter the umbra of the earth and produce a total lunar eclipse. If only a part of the moon enters the umbra of the earth, a partial lunar eclipse will occur. When the moon enters the penumbra of the earth, it should be a penumbral eclipse, but it is not called an eclipse because the brightness drops very little, so there are only two kinds of eclipses: total eclipse and partial eclipse. Eclipses always occur in sight (full moon), but not every time, which is the same as not every new moon has an eclipse. Under normal circumstances, the moon either passes above the Earth's umbra or leaves under the Earth's umbra, and rarely or partially passes through the Earth's umbra, so an eclipse will not occur under normal circumstances. Eclipses occur up to three times a year, and sometimes they never happen at all. The process of an eclipse can be divided into five stages: initial loss, eclipse, eclipse, luminescence and last contact. First loss: The moon has just touched the umbra of the earth, marking the beginning of the eclipse. Eclipse: The western edge of the moon is inscribed with the western edge of the Earth's umbra, and the moon just enters the Earth's umbra. Eclipse: The center of the moon is closest to the center of the Earth's umbra. Luminescence: the eastern edge of the moon is inscribed with the eastern edge of the umbra of the earth, and the total solar eclipse phase ends at this time. Final contact: the western edge of the moon is tangent to the eastern edge of the umbra of the earth. At this time, the whole eclipse was over. The degree of eclipse is called "eclipse", which is equal to the ratio of the farthest distance from the edge of the moon wheel to the umbra of the earth and the meridian of the moon when the eclipse is serious. In ancient times, people did not understand the scientific truth of solar eclipse, and the fear of solar eclipse was no less than that of solar eclipse. It is said in foreign countries that Columbus sailed to Jamaica in South America at the beginning of the16th century, and there was a conflict with the local aborigines. Columbus and his sailors were trapped in a corner, without food and water. The situation is very critical. Knowing that there would be a total lunar eclipse that night, Columbus, who knew something about astronomy, shouted to the natives, "No food, no moonlight!" " In the evening, Columbus's words came true, and there was no moonlight. When the natives saw this scene, they were afraid, so they quickly made peace with Columbus. The solar eclipse in Mesopotamia in 2283 BC was the earliest in the world, followed by that in China in 1 136 BC. Eclipses have been promoting the development of human understanding. As early as 188 1 years ago, Zhang Heng, an astronomer in Han Dynasty in China, made clear the principle of lunar eclipse. In the 4th century BC, Aristotle saw that the shadow of the earth was round from the solar eclipse, but inferred that the earth was spherical. Alistair, an ancient Greek astronomer in the 3rd century BC, and Hipparchus in the 2nd century BC both proposed to measure the relative size of the Sun-Earth-Moon system through solar eclipse. Iba Valley also proposed to observe the lunar eclipse in two distant places at the same time to measure the geographical longitude. In the 2nd century AD, Ptolemy used the ancient lunar eclipse records to study the movement of the moon, and this method has continued to this day. Before the appearance of rockets and artificial earth satellites, scientists have been exploring the atmospheric structure of the earth by observing eclipses.