How often is the total lunar eclipse and the total solar eclipse? (Xiamen)

1. The "season" of solar and lunar eclipses

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 about 12 degrees near the intersection of the ecliptic and the white dot, 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.

2. 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 and lunar eclipses can be up to 6 times, namely, 4 solar eclipses and 2 lunar eclipses. But in fact, sometimes the number of solar and lunar eclipses in a year can be 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 on the ecliptic (this interval is called "eclipse year") is shorter than a year (365.2422 days), only 346.62 days, which is 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.

3. 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.