Very rare! There will be only 7 times in the 21st century, and the "total annular solar eclipse" will shock the audience

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According to media reports, a special solar eclipse will take place on April 20 - a total annular solar eclipse. According to experts, if a total solar eclipse is visible in one part of the country and an annular solar eclipse is visible in another part of the country, it is called a total annular solar eclipse, also known as a "hybrid eclipse" or "compound eclipse", which is very rare.

A very small partial solar eclipse can be seen in a few areas of my country, such as Hainan, Guangdong, Fujian, and Taiwan. The eclipse magnitude is the ratio of the obscured part of the solar disk to the diameter of the sun. The larger the eclipse magnitude, the greater the degree of obscuration of the solar disk.

What are total solar eclipse, partial solar eclipse and annular solar eclipse?

A solar eclipse is when the moon moves between the sun and the earth. If the three are in a straight line, the moon will block the light from the sun to the earth, and the dark shadow behind the moon will fall on the earth. This is when a solar eclipse occurs. In folklore, this phenomenon is called "the dog eclipsing the sun".

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Because the actual volume of the Sun is much larger than that of the Moon, a total solar eclipse can usually only be seen in a very small area on Earth because the Moon's umbra is just a small dot relative to the Sun.

During an annular solar eclipse, when the moon is at its apogee, the moon's umbra cone cannot reach the earth; what reaches the earth is the pseudo-umbra cone extended from the umbra cone. At this time, the apparent diameter of the moon is slightly smaller than that of the sun. Therefore, the photosphere at the edge of the sun is still visible, forming a bright ring surrounding the moon's shadow.

The reason for a partial solar eclipse is that the observer falls in the penumbra of the moon. The observer will see that part of the sun is covered by the shadow of the moon, but the other part continues to shine.

Whether it is a partial solar eclipse, a total solar eclipse or annular solar eclipse, the duration is very short. The area on Earth where a solar eclipse can be seen is also very limited. This is because the moon is relatively small, and its umbra is also relatively small and short, so the umbra does not sweep across a wide area on Earth and does not last long. Since the average length of the moon's umbra (373,293 kilometers) is less than the average distance between the moon and the earth (384,400 kilometers), as far as the entire Earth is concerned, annular solar eclipses occur more often than total solar eclipses.

There are five types of total solar eclipse phenomena

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1. First eclipse. The apparent motion of the moon is faster than that of the sun. During a solar eclipse, the moon catches up with the sun. When the eastern edge of the moon just "touches" the western edge of the sun, it is called the first eclipse. It is the first "external tangent" and the beginning of the solar eclipse.

2. The beginning of the solar eclipse. About one hour after the first contact, the moment when the eastern edge of the moon and the eastern edge of the sun are "intersecting" is called the beginning of the solar eclipse. For a total solar eclipse, the moon covers the entire sun at this time, while for an annular solar eclipse, the sun begins to form a ring. During a solar eclipse, the positional relationship between the moon's shadow and the sun's disk when they are intersected for the first time also refers to the moment when this positional relationship occurs.

The eclipse occurs after the first contact. From the first contact, the moon continues to move eastward, the part of the sun's disk covered by the moon gradually increases, and the intensity and heat of the sunlight decrease significantly. When the eastern edge of the moon's disk is tangent to the eastern edge of the sun's disk, it is called the end of the eclipse. The direction of the sky is opposite to the east-west direction on the map.

3. Maximum eclipse. This is when the sun is most deeply eclipsed, and the center of the moon moves to the closest distance to the center of the sun; during a partial solar eclipse, when the sun is most covered by the moon, the positional relationship between the two; during a total solar eclipse and annular solar eclipse, when the sun is completely covered by the moon and the distance between the two centers is the closest, the positional relationship between the two. It also refers to the moment when the above positional relationship occurs.

4. Beginning of the eclipse. The moment when the western edge of the moon and the western edge of the sun are "inner" is called the beginning of the eclipse, which marks the end of the total solar eclipse. It usually takes only two to three minutes from the beginning of the eclipse to the beginning of the eclipse, and no longer than seven and a half minutes.

For a solar eclipse, after the eclipse is greatest, the moon continues to move eastward relative to the sun.

5. Re-eclipse. About one hour after the sunrise, when the western edge of the moon touches the eastern edge of the sun, it is called the re-eclipse. From this time on, the moon is completely "separated" from the sun, and the solar eclipse ends.

Both a total solar eclipse and annular solar eclipse have the above five processes, while a partial solar eclipse has only three processes: first contact, maximum eclipse, and last contact, but no end of eclipse or beginning of light.

The earliest record of a solar eclipse in human history was in China

On May 26, 1217 BC, people living in Anyang, Henan Province, my country, were carrying out various normal activities, but an amazing thing happened. People looked up at the sky and saw that the sun, which had been shining brightly before, suddenly had a gap and its light color dimmed. However, after a large part was missing, it began to recover. This is the earliest record of a solar eclipse in human history. It was engraved on a tortoise shell in oracle bone script.

Total solar eclipse confirms Einstein's theory of general relativity

Significance and Value The main reason why a total solar eclipse is valued is that it has great astronomical observation value, because the moon will dim the originally dazzling sun and reveal the originally difficult-to-observe corona. Many important astronomical and physical discoveries in the history of science were made using the opportunity of a total solar eclipse, and only through this opportunity.

The most famous example is a total solar eclipse in 1919, which confirmed the correctness of Einstein's general theory of relativity. In 1915, Einstein published the general theory of relativity, which seemed extremely difficult to understand and incredible at the time. This theory predicted that light would bend in a huge gravitational field. The strongest gravitational field that humans can touch is the sun, but the sun itself emits very strong light, and it is impossible to see whether the faint starlight in the distance bends when passing near the sun. But if a total solar eclipse occurs and the sunlight is blocked, it is possible to measure whether the light turns and how much it turns. The opportunity appeared in 1919, but the total solar eclipse belt was in the South Atlantic, which was very far away and difficult. British astronomer Eddington set out with an observation team full of enthusiasm and curiosity. The observation results were very consistent with the results calculated by Einstein in advance, and since then, the theory of relativity has been recognized by the world.

Do not observe a total solar eclipse directly

Medical experts point out that "solar retinitis" is almost impossible to treat, in which the macula of the retina is burned by the ultraviolet and infrared rays of the sun for a long time. The macula of the retina is the most sensitive part of the retina, which focuses light and makes the image clear. Once burned, the macula of the retina will never recover. You may not feel the burn, but a reaction will appear after a few hours, and in severe cases, blindness will occur.

When watching a total solar eclipse, the first thing to note is: never look directly at the sun with your naked eyes or any optical equipment (such as a telescope, etc.)! This is not just a suggestion, but a very serious warning.

How to avoid some accidents? Here are some methods to introduce to you.

1. Quick and easy observation method

In fact, the recommended method is to just use two pieces of white paper. One piece of white cardboard is used as the screen, and the other cardboard is poked with a pinhole. Lift the pinhole cardboard and keep it as far away from the screen cardboard as possible. The farther the two cards are from each other, the larger the image will be.

Of course, there is an even simpler way. You only need your own hands to help. Raise your hands with your fingers perpendicular to each other and cross and overlap. Then your hands form a net with many small holes, which can be used as simple imaging holes.

(ii) Buy observation glasses or lenses

Protective glasses require a pair of special glasses. There are special glasses for sun observation protection on the market, and the price is about 5 yuan.

(III) Observation of ink droplets

Take a basin of water (or a small cup), drop a relatively large amount of black ink into the water, and you can observe the solar eclipse in the water. (Plane mirror imaging).