Solar eclipse is a very rare phenomenon. Among the four kinds of solar eclipses, total solar eclipse is rare, because people in this area can observe the solar eclipse only when the umbra of the moon is projected on the earth's surface. Total solar eclipse is a magnificent natural landscape, so it often attracts many tourists to watch it overseas. For example, the total solar eclipse in Europe in 1999 attracted many tourists, and some travel agencies also launched itineraries specially designed for these tourists.
In ancient times, human beings lacked astronomical knowledge, and thought that the solar eclipse was caused by dogs eating the sky, or symbolized the arrival of disaster and held a ceremony during the solar eclipse. But in modern society, the significance of solar eclipse has been gradually abandoned by people.
The last total solar eclipse in China took place on July 22nd, 2009, and the next one will take place in the north of China on September 2nd, 2035, with a duration of 1 minute and 29 seconds.
The next total solar eclipse will appear near Easter Island in Chile on July 10, June 1 1 day and 20 12.
The seasons of solar and lunar eclipses. 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) form an angle of 5.9, there is not always an eclipse, but when the eclipse occurs, the sun and the moon must be 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.
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 29.53 days of the new moon. 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.
Not all solar eclipses can be called total solar eclipses, among which total solar eclipses are most easily mistaken for total solar eclipses:
Partial eclipse of the sun: China's history books say that "there will be food every day, and there will be endless life". The reason for the 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. The sun and the moon only partially overlap, and the food intake is measured according to the apparent distance between their centers (the maximum diameter of the moon covering the sun). Usually, partial solar eclipse is accompanied by other solar eclipses, such as total solar eclipse. But some eclipses can only be partial eclipses (no other eclipses), because the moon is too far away from the earth, and only the penumbra touches the surface of the earth.
Annular eclipse: when the moon is at apogee, the umbra cone of the moon 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 on the edge of the sun is still visible at this time, forming a bright ring around the shadow of the moon. (Outside the solar eclipse belt, the solar eclipse seen is a partial eclipse)
Total lunar eclipse: A total lunar eclipse will only occur when the earth's surface is very close to the top of the lunar umbra, or when the distance between the moon and the earth's surface is very close to the length of the lunar umbra. Because the earth is a sphere, when the umbra cone touches the earth, it is a total solar eclipse (usually in the middle of the eclipse zone). Because the umbra cone can't touch the earth at both ends of the food belt, only the pseudoumbra can reach below the earth, and it sees an annular eclipse. Therefore, when the total solar eclipse occurs, with the relative movement of the earth and the moon, there will be an annular eclipse → total solar eclipse → annular solar eclipse. The occurrence of total lunar eclipse is rare, and the latest one was on April 8, 2005.
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 narrow area on the earth, and only people in this area can see the solar eclipse. 1961The eclipse that occurred on the night of March 2nd 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. The solar eclipse in 2009 is once in 500 years and can be seen in Shanghai, Hangzhou and other places.
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.
The process of total solar eclipse can be divided into the following five periods: initial loss, eclipse, eclipse, luminescence and last contact.
The main reason why total solar eclipse is paid attention to is its great astronomical observation value.
Solar eclipse, especially total solar eclipse: it is an excellent opportunity for people to know the sun. The sun we usually see is only its photosphere, and two important levels of the solar atmosphere outside the photosphere-chromosphere and corona-are submerged in the bright brilliance of the photosphere. Chromosphere is the middle layer in the solar atmosphere, about 2000 kilometers thick above the photosphere; Outside the sun, it is surrounded by extremely high temperature (millions of degrees Celsius) but very thin plasma, and the range of plasma is several times larger than the sun itself. This is called the corona. The brightness of the corona is only one millionth of that of the sun itself. Usually, it is completely hidden in the blue sky caused by scattered light from the earth's atmosphere. During the total solar eclipse, the moon blocked the spherical surface of the sun, and red balls and silver corona appeared one after another on the dark sky background. Scientists can observe the chromosphere and corona at this specific time and under specific conditions, and take photos and spectrograms of the chromosphere and corona, so as to study the physical state and chemical composition of the sun. For example, when French astronomer Janssen observed the total solar eclipse on August 1868, he photographed the spectrum of solar bait and discovered a new element "helium", which was discovered on the earth by British chemist Remus more than 20 years later.
A solar eclipse can provide a good opportunity to study the relationship between the sun and the earth. The sun is closely related to the earth. When there is strong activity on the sun, its far ultraviolet rays, X-rays and particle radiation will be enhanced, which will disturb the earth's magnetic field and ionosphere and produce a series of geophysical effects such as magnetic storm, aurora disturbance and short-wave communication interruption. During the total solar eclipse, various geophysical phenomena changed because the moon gradually covered various radiation sources on the surface of the sun. Therefore, it is of practical significance to observe and study various geophysical effects during the total solar eclipse, which has become one of the important contents in the observation and research of the total solar eclipse.
Observing and studying the total solar eclipse is also helpful to study many topics related to astronomy and physics. Taking advantage of the total solar eclipse, we can look for planets in the orbits of the nearest stars and mercury. We can measure the bending of starlight when it passes near the sun, thus testing the general theory of relativity and studying the nature of gravity.
In addition, the solar eclipse is also of certain significance to the study of meteorological changes and biological reactions during the solar eclipse.
Many important astronomical and physical discoveries in the history of science were made by the opportunity of total solar eclipse, and only through this opportunity can they be made. The most famous example is a total solar eclipse in 19 19, which confirmed the correctness of Einstein's general theory of relativity. Einstein published the general theory of relativity in 19 15, which was extremely difficult to understand and incredible at that time. This theory predicts that light will turn in a huge gravitational field. The strongest gravitational field that humans can contact is the sun, but the sun itself emits strong light, and it is impossible to see whether the faint starlight in the distance turns when passing near the sun. However, if a total solar eclipse occurs and the sunlight is blocked, it can be measured whether the light has turned. The opportunity appears in 19 19, but the total lunar eclipse is in the South Atlantic, which is far away and difficult. British astronomer Eddington set out with an enthusiastic and curious observation team. The observation results are very consistent with Einstein's pre-calculation results, and the theory of relativity has been recognized by the world since then.
"God-given opportunity, don't miss the' secret'." On July 22nd, domestic astronomers lamented China's excellent "secret" of observing the 500-year total solar eclipse. This is the most spectacular total solar eclipse in this century. It is rare that the solar eclipse has a wide area, a long time and a large population. However, when you pay attention to the best observation points, observation equipment and other news, do you also know the most basic knowledge of total solar eclipse?
In ancient and feudal society, whenever there was a natural phenomenon of total solar eclipse, ignorant people would beat gongs and drums to drive away the "monsters" that devoured the sun until the end of the eclipse.