How to calculate the time, process and principle of total solar eclipse

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The "season" of solar and lunar eclipses

Principle:

The eclipse must happen in the new moon, which is the first day of the lunar calendar. At this time, the moon is located between the earth and the sun, but because the orbit of the sun (ecliptic) and the orbit of the moon (ecliptic) are at an angle of 5 9', there is not always an eclipse on the first day, but when the eclipse occurs, both the sun and the moon must occur near the "yellow-white intersection" (rising intersection or falling intersection).

The occurrence of the solar eclipse must be that the new moon and the full moon appear in a certain boundary where the yellow and white intersect, and this boundary is called "food limit". The calculation shows that for the solar eclipse, if the new moon is within about 18 degrees near the intersection of the ecliptic and the ecliptic, the solar eclipse may occur; If the new moon is within about 16 degrees near the intersection of the ecliptic and the white road, there must be a solar eclipse.

For an eclipse, if the full moon is within 12 degrees near the intersection of the ecliptic and the ecliptic, an eclipse may occur; If the full moon is within about 10 degrees near the intersection of the ecliptic and the ecliptic, there must be an eclipse.

Because there are two intersections between the ecliptic and the ecliptic, and the distance between the two intersections is 180 degrees, there may be two eclipses a year, both of which are called "food seasons" and are separated by half a year.

The sun moves eastward about 1 degree on the ecliptic every day. Because the eclipse limit is about 18 degrees, it takes about 36 days for the sun to travel from 18 degrees west of the intersection of the ecliptic and the ecliptic to 18 degrees east of the intersection of the ecliptic, which means that each eclipse season is 36 days. For an eclipse, its food limit is about 12 degrees, so the monthly food season is only 24 days.

How many times a year?

An eclipse season is 36 days, which is longer than the average length of the new moon of 29.53 days. Therefore, in an eclipse season, there is bound to be an eclipse, or there may be two eclipses. There are two solar eclipse seasons in a year, so there are at least two solar eclipses in a year, and maybe four solar eclipses (if each solar eclipse season includes two solar eclipses).

An eclipse season is 24 days, which is shorter than the average days of a new moon (29.53 days). So there may or may not be a full moon in an eclipse season, which means there may or may not be an eclipse in this eclipse season. There are also two eclipse seasons in a year; "So in a year, there may be two eclipses, and even one eclipse will not happen.

In a year, the number of solar eclipses and lunar eclipses can reach up to 6 times, namely 4 eclipses and 2 eclipses. But in fact, sometimes the number of solar and lunar eclipses in a year can reach as many as seven times, that is, five eclipses and two eclipses, or four eclipses and three eclipses. For example, there were five solar eclipses and two lunar eclipses in 1935, and the same was true in the following 2 160 years; There were 4 solar eclipses and 3 lunar eclipses in 19 17 and 1982. So, why are there as many as seven eclipses in a year?

This is because under the gravity of the sun, the intersection of the ecliptic and the ecliptic will constantly move from east to west along the ecliptic, about 20 degrees a year, which is opposite to the direction in which the sun runs along the ecliptic. Therefore, the time interval when the sun passes through the same intersection twice in succession on the ecliptic (this interval is called "eclipse year") is shorter than that of a year (365.2422 days), only 346.62 days, about 652 days less. In this way, there will be two situations: one is that there are two complete food seasons and one incomplete food season in 365.2422 days a year. For example, the first food season starts from the beginning of 65438+ 10, and then after 346.62 days a year, the third food season will start from the middle of February of the same year. In this case, five solar eclipses and two lunar eclipses may occur. On the other hand, there are two incomplete food seasons (one at the beginning of the year and one at the end of the year) and a complete food season in 365.2422 days of the year. In this case, four solar eclipses and three lunar eclipses may occur.

To sum up, we can summarize the possible times of solar eclipses between China and Japan in a year as follows:

There are at least two eclipses a year, and they are all eclipses.

There may not be an eclipse in a year (for example,1980);

There can be at most seven eclipses a year: five eclipses, two eclipses (such as 1935), or four eclipses, three eclipses (such as 19 17, 1982).

Generally speaking, the most common situation is that there are four eclipses a year: two eclipses and two eclipses.

The above situation is only for the whole earth. As for a certain place on the earth, the chances of seeing an eclipse of the sun and the moon in a year are much smaller.

In addition, from the above figures, the number of solar eclipses in a year is more than that of lunar eclipses, but in fact people often see more solar eclipses than lunar eclipses. This is because when the solar eclipse occurs, people on the half of the earth with their backs to the sun can see it; When the solar eclipse occurs, the shadow cone of the moon only sweeps through a very narrow area on the earth, and only people in this area can see the solar eclipse, especially when the total solar eclipse occurs, the scope of the total solar eclipse belt is even smaller, with a width of only two or three hundred kilometers, so only a few people can see it. It takes an average of 200 to 300 years for a place to see a total solar eclipse. So it is not surprising that many people have never seen a total solar eclipse in their lives. For example, the lunar eclipse on the evening of March 2nd, 196 1, can be seen in China, Asia and Europe. The total solar eclipse occurred on1September 22nd, 968. In China, only parts of Xinjiang can see the total solar eclipse, while Beijing can only see the partial solar eclipse, while Shanghai can't see anything.

Global solar eclipses in the 20th century (190 1- 1999).

Number of species

Partial eclipse 78

Annular eclipse 73

Total solar eclipse 7 1

Mixed food 6

A total of 228 people

Periodicity of solar and lunar eclipses

Because the revolution of the earth around the sun and the revolution of the moon around the earth have certain laws, the occurrence of solar and lunar eclipses also has its periodicity.

As early as ancient times, the Babylonians found out according to their own long-term statistics that there were 223 moon cycles in the occurrence of solar and lunar eclipses. This cycle of 223 moons is called "Charlotte cycle", and "Charlotte" means repetition.

223 lunar months equals 6585.3 days (223×29.530588), namely 18 and 1 1.3 days. If there are five leap years in this period, it is 18 and 10.3 days. During this period, the relative position of the intersection of the sun, the moon and the yellow and white is constantly changing, but after a Sharo cycle, the intersection of the sun, the moon and the yellow and white almost returned to the original relative position, so there will be similar solar and lunar eclipses, but the position of the eclipse will change, so I won't elaborate here.

It was also found in the Han Dynasty that solar and lunar eclipses had a period of 135 moons. 135 moons equals 3986.6 days, which is about equal to 1 1 day less, that is to say 1 1 day less, there will be an eclipse. This cycle was recorded in the "Three Calendars" of the Han Dynasty, so it is also called "Three Calendars Cycle".

In addition, people also found that there are other solar and lunar eclipse cycles. For example, the Newcomb cycle with 358 moons (less than 29 days), the Milton cycle with 235 moons (19 years) and so on, but these cycles are very rough. We can only roughly calculate the date of the eclipse, but we can't determine the exact time, size and the area to be eaten. The exact time of solar eclipse and the situation of solar eclipse need to be strictly calculated, which belongs to the research scope of "food theory" in almanac astronomy. The Purple Mountain Observatory in China is responsible for forecasting solar and lunar eclipses.

Basic knowledge of total solar eclipse

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The process of total solar eclipse can include the following five periods: initial loss, eclipse, eclipse, luminescence and last contact.

The first solar eclipse always starts from the western edge of the sun's circular surface, because the moon revolves around the earth from west to east. When the eastern edge of the moon just touches the round surface of the sun (that is, when the eastern edge of the moon is tangent to the western edge of the moon), it is called the initial loss. The first loss is the moment when the eclipse begins.

The eclipse begins with the initial loss, that is, the partial eclipse stage. The moon continues to move eastward, the part of the sun's circular surface covered by the moon gradually increases, and the intensity and heat of sunlight are obviously reduced. When the eastern edge of the moon surface is inscribed with the eastern edge of the sun surface, it is called eclipse. At this time, the entire circular surface of the sun is covered, so the solar eclipse is the moment when the total solar eclipse begins.

Occurrence law of solar eclipse

Eclipses occur up to five times a year. If it appears five times, it must be a partial solar eclipse. There are at least two eclipses on the earth every year. Only partial solar eclipse can be seen in the polar regions. Total solar eclipse occurs every 1 year and a half. Every eclipse starts at a certain point at sunrise and then ends at sunset along the eclipse belt. About half a circle around the earth from the starting point to the end point.

saros

The same solar eclipse (total solar eclipse, annular solar eclipse and partial solar eclipse) will occur once every 1 1 day or 6585.32 days (Charro cycle), but the observable areas are different, and the types of solar eclipses are not necessarily the same only when the eclipse time is the same. Because the length of the Charlotte cycle is 6585.32 days, it is not an integer, so if there is another solar eclipse in the same place on the earth (not necessarily the same type of solar eclipse), you have to wait for three Charlotte cycles. The next solar eclipse will occur in one-third of the Charlotte cycle after each solar eclipse, and reappear in the same area after three Charlotte cycles of about 54 years and 33 days. At present, there are 12 different big Sharo cycles, one of which occurred in 1937, 1955, 19 1 and in 2009 (China Yangtze River valley, Wuhan and Hangzhou), which lasted for about 7.5 minutes.

Eclipse band and moon shadow

The moving speed of the eclipse belt (the shadow of the moon) in the equatorial region is about 65,438+0,65,438+000 miles per hour, and it reaches 5,000 miles per hour at the poles. The widest total solar eclipse zone is 167 miles. In the area where the total solar eclipse passes, the range of partial solar eclipse can be seen as high as 3000 miles. The total solar eclipse belt generally passes through the ocean or barren places.

Eclipse principle

The total solar eclipse occurs because the sun is close to the intersection of the lunar orbit and the earth orbit, and the moon is at the nearest point to this point. An annular eclipse occurs because the sun is close to the intersection of the moon's orbit and the earth's orbit, and the moon is farthest from this point. The eclipse begins with the initial loss, that is, the partial eclipse stage. The moon continues to move eastward, the part of the sun's circular surface covered by the moon gradually increases, and the intensity and heat of sunlight are obviously reduced. When the eastern edge of the moon surface is inscribed with the eastern edge of the sun surface, it is called eclipse. At this time, the entire circular surface of the sun is covered, so the solar eclipse is the moment when the total solar eclipse begins.

The total solar eclipse happened because of a magical symmetry. The diameter of the sun is 400 times that of the moon, and its distance from the earth is exactly 400 times that of the moon. Therefore, when the moon is completely between the earth and the sun, for those who are completely in the shadow of the moon, the surface of the sun is completely blocked. The sun turned black, leaving only a golden halo, and the sky turned indigo. Birds will get lost or fly back to their nests, while bats and other nocturnal animals may come out bleary-eyed.

Effects and phenomena of solar eclipse

During the total solar eclipse, the light passes through the cracks in the leaves and casts the shadow of the new moon. When a total solar eclipse occurs, animals often get ready to sleep or behave abnormally. When a total solar eclipse occurs, the local temperature usually drops by at least 20 degrees. When 99% of the sun's surface is covered, you can see the phenomenon of twilight in the morning. During the total solar eclipse, a narrow band of light will appear around the horizon, because the observer is not directly standing in the shadow of the moon, and there is a certain distance between the earth and the moon. Before the modern atomic clock appeared, astronomers studied the ancient solar eclipse records and found that the period of the earth's rotation slowed down by 0.05438+0 seconds every century.

Eclipse process

The process of total solar eclipse can include the following five periods: initial loss, eclipse, eclipse, luminescence and last contact.

First contact (of an eclipse)

Because the moon orbits the earth from west to east, the solar eclipse always starts from the western edge of the sun's circular surface. When the eastern edge of the moon just touches the round surface of the sun (that is, when the eastern edge of the moon is tangent to the western edge of the moon), it is called the initial loss. The first loss is the moment when the eclipse begins.

The second contact of total solar eclipse

Judging from the initial loss, it is a partial eclipse stage. The moon continues to move eastward, the part of the sun's circular surface covered by the moon gradually increases, and the intensity and heat of sunlight are obviously reduced. When the eastern edge of the moon surface is inscribed with the eastern edge of the sun surface, it is called eclipse. At this time, the entire circular surface of the sun is covered, so the solar eclipse is the moment when the total solar eclipse begins.

Mid eclipse

After the eclipse, the moon continued to move eastward. When the center of the moon was closest to the center of the sun, it was an eclipse.

third contact

For partial solar eclipse, the solar eclipse is the moment when the sun is covered by the moon the most. The moment when the moon continues to move eastward and the western edge of the moon meets the western edge of the sun is called luminescence, which is the moment when the total solar eclipse ends. Before the birth of light, the phenomenon of diamond rings and beads will reappear on the western edge of the sun, but will soon disappear. Then, a dazzling light shines on the west of the sun. Chromosphere, prominence and corona, which can be seen during the total solar eclipse, disappeared in the sun, the stars disappeared and the sun lit up again.

Final contact

After the light is generated, the surface of the moon continues to be far away from the surface of the sun, and the part of the sun that is blocked gradually decreases. The moment when the western edge of the moon surface is tangent to the eastern edge of the sun surface is called the last contact. At this time, the sun showed a disc shape again, and the whole process of total solar eclipse came to an end.

Bainite/diamond ring

When the sun is about to be completely blocked by the moon, a diamond-like arc light will suddenly appear on the eastern edge of the sun, just like the striking shining light on the diamond ring. This is the diamond ring, and at the same time, a string of luminous highlights will be formed in an instant, hanging high in the dark sky like a string of dazzling pearls. This phenomenon is called pearl food, which was first described by British astronomer Billy, so it is also called Bailey beads. This is because there are many rugged peaks on the surface of the moon. When the sun shines on the edge of the moon, it forms a "pearl-like bead" phenomenon. Belle pearls appear for a short time, usually only one or two seconds, and then the sun is completely blocked, resulting in a total solar eclipse.

magnitude of eclipse

Used to indicate the degree of solar eclipse. For solar eclipse, solar eclipse does not refer to the area covered by the circular surface of the sun, but refers to the ratio of the covered part of the diameter of the sun to the diameter of the sun. Take the diameter of the sun as 1, and if the solar eclipse is 0.5, it means that the diameter of the sun is covered by half; If the solar eclipse is 1, it means that the entire round surface of the sun is covered, and that is a total solar eclipse. Obviously, the larger the part, the greater the degree to which the sun is covered. The food fraction of partial solar eclipse is less than 1.0, and that of total solar eclipse is less than 1.0.

Food belt

Because the shadow cone of the moon is thin and long, when it falls on the earth's surface, it occupies a very small area, no more than one tenth of the total area of the earth, and the maximum diameter is only more than 260 kilometers. When the moon revolves around the earth, the shadow cone sweeps a relatively long area from west to east on the ground, and a solar eclipse can be seen in the area swept by the shadow of the moon. So this belt is called "Eclipse Belt". If there is a total solar eclipse in the belt, it is called a total solar eclipse belt; If there is an annular eclipse in the belt, it is called an annular eclipse belt. It can be seen that the range of partial solar eclipse is very wide, not like a strip, but a large area.

The total solar eclipse belt is a narrow path with a width of only two or three hundred kilometers and a length of several thousand to 10000 kilometers (sometimes the width of the total solar eclipse belt is only a few kilometers). Only in the area swept by the total solar eclipse belt can we see the occurrence of total solar eclipse or annular solar eclipse. On both sides of the total solar eclipse belt is a relatively wide penumbra swept area, where you can see the partial solar eclipse. The closer to the total eclipse zone, the greater the degree of partial eclipse; The farther away from the belt, the smaller the degree of partial eclipse; You can't see the eclipse beyond the penumbra.

Because the moon moves from west to east, its shadow also moves in the same direction, so the time to watch the solar eclipse varies from place to place. When the western area on the ground is already in the shadow area, people in this area have already seen the solar eclipse, but people in the eastern area can't see the solar eclipse at the same time, and they can't see the solar eclipse until the moon shadow moves eastward. Therefore, westerners always see eclipses before orientals.

Eclipses occur every year, but because the total eclipse belt is a narrow strip, it is estimated that every 200 ~ 300 years, a certain area or city will have the opportunity to be swept by the total eclipse belt. Therefore, for people living in a city, they may have never seen a total solar eclipse in their lives.

Eclipse duration

The duration of the eclipse is related to the speed of the lunar cone moving on the ground and the direction of the earth's rotation. For the total solar eclipse, the apparent diameter of the moon is only slightly larger than that of the sun, and the shadow of the moon moves quickly on the ground, so the total solar eclipse time is very short. The total solar eclipse time seen somewhere in the total solar eclipse belt is usually only two or three minutes, not more than seven minutes at most. If the total solar eclipse belt passes through the equator, the total solar eclipse can last for 7 minutes and 40 seconds, which is the best time to observe the total solar eclipse.

When an annular eclipse occurs, the moon is always near the apogee, and at this time the speed of the moon is slow, so the annular eclipse lasts for a long time. If the annular eclipse occurs near the equator, the time for observing the annular eclipse near the equator can be as long as 12 minutes and 42 seconds.

On a global scale, if you count the time when the penumbra of the moon begins to cover the sun, the whole process from the initial loss of contact to the last contact can be as long as three and a half hours.

During a partial solar eclipse, because the range of the moon shadow is larger than its umbra, the length of the eclipse depends on the size of the eclipse, and the larger the eclipse, the longer it takes.

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Total solar eclipse in East China at 9: 35 am on July 22, 2009.

The total solar eclipse on July 22, 2009 was the longest lasting one in the past century, reaching 6 minutes.

The longest total solar eclipse of the following year.

A total solar eclipse will occur in China in 2009. Among them, the total solar eclipse on July 22, 2009 was the longest lasting one in the past hundred years, reaching 6 minutes. This total solar eclipse can be seen in Shanghai, Hefei, Suzhou, Hangzhou and other Yangtze River basins, and Tongling is the best observation point. If the weather is fine, we can feel the feeling of suddenly turning black. Some documents point out that if there is a total solar eclipse, if the weather is fine, even the stars in the sky will be observed during the total solar eclipse!

Because the total solar eclipse swept through the densely populated Yangtze River Delta urban agglomeration in China, it attracted much attention.

August 2008 1

The eclipse is divided into 1.039, and the longest duration of the total eclipse is 2 minutes and 27 seconds. It can be seen in northeastern North America, Europe and parts of Asia, including northern Canada, Greenland, Novosibirsk, Mongolia, Xinjiang Uygur Autonomous Region, Gansu Province, Ningxia Hui Autonomous Region, Shaanxi Province, Shanxi Province and Henan Province in China.

In China, considering the sun height, geography, traffic and other comprehensive factors, Jinchang, Gansu Province is a better observation site. The Moon's umbra center will only pass 1 2km north of Jinchang Center, and the total solar eclipse time will be about1min for 45 seconds.