The natural phenomena related to eclipses are introduced in detail.

As the moon moves a long distance from west to east in the starry sky every day, its shape is constantly changing, which is the phase change of the moon, called the moon phase. "People have joys and sorrows, and the moon has a full moon." The full moon and the full moon here refer to the "phase change of the moon": different images of the moon illuminated by sunlight seen on the earth.

Because the moon itself does not give off light, half of the sphere facing the sun is bright and the other half is dark under the sunlight. Because the position of the moon relative to the earth and the sun has changed, the side irradiated by the sun sometimes faces the earth and sometimes faces away from it; Sometimes the part of the moon facing the earth is larger, and sometimes it is smaller, so there are different moon phases.

Whenever the moon moves between the sun and the earth, and the hemisphere illuminated by the sun faces away from the earth, people can't see the moon on the earth. This day is called "new moon", also called "new moon", which is the first day of the lunar calendar.

After the new moon, the moon moves in the direction of the earth's rotation, and the bright area gradually turns to the earth. On the earth, you can see the moon with a slender silver hook appearing in the western sky, with its arch facing the sunset. This month is called "moth eyebrow month", which is the third and fourth day of the lunar calendar.

Then, the moon is away from the sun day by day in the sky. On the eighth day of the seventh lunar month, half the bright area faces the earth, and people can see half the moon (the convex surface faces west). This month is called "the first quarter moon".

When the moon moves in the opposite direction to the earth, that is, on 15, 16 and 17 of the lunar calendar, the bright areas of the moon are all facing the earth, and we can see a full moon, which is called "full moon" or "full moon".

After the full moon, the west side of the bright area began to lose money. On the 22nd and 23rd of the lunar calendar, you can see another half moon (the convex surface faces east), which is called "the last quarter moon". During this period, the moon is getting closer and closer to the sun and can only rise in the east at midnight.

After another four or five days, the moon turned into a moth-eyebrow-shaped moon bud, with its bow back facing the rising sun. This month is called "the waning moon".

When the moon moves between the sun and the earth again, it returns to the "new moon" state.

This is how the moon phase changes. If we use the period of the moon's phase change (that is, the whole process of the moon's phase change) to calculate, from the new moon to the next new moon, or from the full moon to the next full moon, it is a "shuowangyue" with an interval of about 29.53 days. The length of a month in the China lunar calendar is determined according to "Shuowangyue".

solar eclipse

Eclipse means that the moon revolves around the earth and moves between the sun and the earth. If the sun, the moon and the earth are just in a straight line, the moon blocks the sunlight that hits the earth, and the shadow behind the moon just falls on the earth. At this time, the eclipse happened. People in the shadow of the moon on the earth began to see the sun gradually weakening, and the sun was covered by a circular shadow. When the sky is dark and completely covered, the brightest stars and planets can be seen in the sky. After a few minutes, the sun gradually emerged from the shadow edge of the moon and began to shine and make the last contact. Because the moon is smaller than the earth, only people in the shadow of the moon can see the solar eclipse. Total lunar eclipse occurs when the moon blocks all the sun, partial solar eclipse occurs when the moon blocks part of the sun, and annular solar eclipse occurs when the moon blocks the central part of the sun. The duration of the total solar eclipse shall not exceed 7 minutes 3 1 sec. The longest time of annular eclipse is 12 minutes and 24 seconds. China has the oldest solar eclipse record in the world, and there have been exact solar eclipse records for over 0/000 years BC.

scientific explanation

A solar eclipse is a typical example of light traveling in a straight line in a celestial body. When the moon moves between the sun and the earth, it is not always like this. When a lunar eclipse occurs, two conditions need to be met. First of all, the solar eclipse always happens on the first day of the lunar calendar. Not all eclipses will happen on the first day of the lunar calendar, because the orbit of the moon (ecliptic) and the orbit of the sun (ecliptic) are not on the same plane. There is an included angle of 59 between the ecliptic plane and the ecliptic plane. On the first day, if both the sun and the moon move near the intersection of the ecliptic and the ecliptic, and the sun and the intersection form a certain angle (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 is near or far, the shadow formed by the sun being blocked by the moon can be divided into umbra, pseudo-umbra (formed when the moon is far away from the earth) and penumbra on the earth. The observer can see the total solar eclipse in the umbra; Annular eclipse can be seen in the range of pseudoumbra; Only a partial solar eclipse can be seen in the penumbra.

When the total solar eclipse occurs, it can be divided into five eclipse images according to the positional relationship between the round surface of the moon and the round surface of the sun: 1. Initial loss. The moon moves faster than the apparent speed 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 "cuts in" with the eastern edge of the sun is called an eclipse, which is the beginning of the total solar eclipse, when the moon covers the whole sun; 3. Eat a lot. It is the deepest eclipse moment of the sun, and the center of the moon moves to the center closest to 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 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 the last contact. Since then, the moon has completely "left" the sun, and the eclipse is over.

There are many mountains on the surface of the moon, and the edge of the moon is irregular. At the moment of the lunar eclipse or the arrival of light, when the valley on the edge of the moon fails to completely cover the sun, 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. Sometimes a lot of particularly bright lights or spots are formed, like a string of pearls embedded around the sun. This phenomenon is called Bell 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 the solar eclipse can be seen on the earth is also limited, because the moon is relatively small and its umbra is relatively small and short, so the umbra will not sweep the earth for a long time. Because the average length of the umbra of the moon (373,293 kilometers) is shorter than the average distance between the moon and the earth (384,400 kilometers), there are more annular eclipses on the whole earth than total solar eclipses.

title

Description: How did a part of the sun disappear? This is the part of the sun hidden behind the moon. This is the first partial solar eclipse in 2005 and the last total solar eclipse observed before March 2006. During a solar 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 solar eclipse can be observed spanned South America and North America in the south. The scene in the above picture was taken by a hand-held digital camera last Friday. After a day's rain in Mount Holly, North Carolina, USA, some eaten suns temporarily penetrated the dark clouds. After taking a series of images, this best photo of the solar eclipse was combined with another photo that was not very good but had a plane.

frequency

The following are the global solar eclipses in the 20th century (190 1- 1999):

Partial eclipse 78

Annular eclipse 73

Total solar eclipse 7 1

Mixed food 6

A total of 228 people

Knowledge of watching solar eclipse

During this period, the sun will not emit any special rays. Observations of solar eclipses are often misinterpreted. The sun will not predict the occurrence of solar eclipse on the earth, nor will it emit other rays, so it is harmless to stay outdoors during the solar eclipse. But should we stare at 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 cornea. People stare or squint at the sun out of curiosity. Of course, the partial solar eclipse is still very dazzling. If you watch the sun for a long time, your cornea will be damaged unconsciously. 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. No matter whether the eclipse occurs or not, don't look directly at the sun with your eyes; Don't use so-called "sunglasses"; Don't use "sunglasses", not even a few folded ones; Don't look at the image of the sun in the mirror or on the water;

Looking at the sun with a welding mirror14; Watch it with a specially coated Myra mirror, which can be obtained from the famous planetarium or science museum; Build an aperture projector.

The story of solar eclipse

For ancient people, the solar eclipse was very terrible. If you can understand the influence of the sun on grain planting and daily life, you will be concerned about why the sun suddenly disappeared in the sky. In ancient China, people thought that the solar eclipse was caused by a dragon devouring the sun. Other civilizations also think this is an ominous sign, and there are many "solutions": playing drums, shooting arrows at the sky, taking things or offering sacrifices to people. 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 reason. At that time, Emperor 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 the astronomical phenomena regularly. At that time, comets and meteors could not be predicted, 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.

appendix

Knowledge about the sun

solar prominence

Prominence is a kind of solar activity phenomenon that protrudes beyond the edge of the sun's surface. When prominence appears, colored balls in the atmosphere resemble burning grasslands, and rose-red tongue-shaped gas rises like fire, with different 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, they are shaped like earrings attached to the edge of the sun, hence the name "prominence". Prominences rise about tens of thousands of kilometers. Large prominences can be hundreds of thousands of kilometers higher than the surface of the sun, with a general length of about 200,000 kilometers, and individual prominences can reach 1.5 million kilometers. Prominences are much darker 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 strange phenomenon of solar activity. Its temperature ranges from 5,000 to 8,000. Most prominences rise to a certain height and then slowly land on the surface of the sun. However, some prominences float in the lower layer of the corona, and the temperature is as high as 2 million K, which is as strange as a piece of unmelted ice in a hot steelmaking furnace. In addition, the density of prominence is 654,330 higher than that of corona.

solar 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 most active year of solar activity, the corona is close to a circle; In quiet years, 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 (CME) 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 can affect the earth more than it. When there is a strong explosion and coronal mass ejection on the sun, the powerful plasma flow carried by the solar wind may reach the polar regions of the earth. At this time, the aurora appears at the poles of the earth. The forms of aurora are ever-changing. Aurora has also been found on some planets with magnetic fields in the solar system. Flares occurring in the corona are called X-ray flares, and their 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.

Rilang

An ejection phenomenon of solar photospheric matter. It usually occurs over sunspots and has strong reproducibility. When a broken wave falls behind along the rising path, it will trigger a new broken wave to take off, and so on, but the scale and height are getting smaller and smaller every time until it disappears. Surfing at the edge of the sun looks like a bright hill with a sharp peak at the top. The height of the rise is different. Small surfing is only a few hundred kilometers, big surfing can reach 5000 kilometers, and the maximum surfing can reach 1 ~ 20000 kilometers. The maximum speed of the projectile can reach 100 ~ 200 kilometers per second, which is more than 100 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 each bundle of fibers is very small apart, which shines and moves together as a whole.

Solar activity forecast

The change of the state of 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, X-ray flares directly cause ionospheric disturbances on the earth, thus affecting short-wave communication on 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 at high latitudes. According to statistics, strong 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 early warning. As a systematic scientific research object, the space environment of the sun and the earth began in 1957 when humans entered space. The 1950s and 1970s were the exploration stages, and people gradually realized the importance of space environment. On the basis of a lot of exploration, a static model describing the environment is established and some important spatial activities are predicted. After 1980s, driven by demand, the research on the space environment of the sun and the earth developed rapidly. Since 1979, the international conference on solar-terrestrial prediction has been held as scheduled every four years, and its scale has been expanding. In order to unite and coordinate the work of major countries, a joint forecasting center was established. Headquartered in the United States, there are 10 regional alarm centers distributed all over the world. Our Beijing alarm center is one of them. After entering the 1990s, scientists vividly called it "space weather".

Solar activity cycle

The average period is 22 years, and it includes two sunspot cycles of 1 1 year. 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 prominence, flare and frequency fluctuation of magnetic effect, and magnetic effect includes aurora and enhancement of radio interference to the earth. The basic sunspot cycle (sometimes called solar activity cycle) of1year was announced by Schwabe in 1843. Some people try to link the solar activity cycle with the changes of other phenomena, such as the slight change of the diameter of the sun, the change of tree rings, and even the fluctuation of the stock market.