Traditional Culture Encyclopedia - Photography major - On a summer vacation in July and August in the 1990s, who saw the miracle in the sky in one night?

On a summer vacation in July and August in the 1990s, who saw the miracle in the sky in one night?

It was an eclipse.

On the fifteenth and sixteenth days of the lunar calendar, the moon runs in the opposite direction to the sun. At this time, if the centers of the earth and the moon are roughly on the same straight line, the moon will enter the umbra of the earth and produce a total lunar eclipse. If only a part of the moon enters the umbra of the earth, a partial lunar eclipse will occur. When the moon enters the penumbra of the earth, it should be a penumbral eclipse, but it is not called an eclipse because the brightness drops very little, so there are only two kinds of eclipses: total eclipse and partial eclipse. Eclipses always occur in sight (full moon), but not every time, which is the same as not every new moon has an eclipse.

lunar eclipse

lunar eclipse

The phenomenon that the moon is completely or partially covered by the shadow of the earth. A solar eclipse usually occurs on the 15th or 16th day of each month in the summer calendar, when the earth moves between the sun and the moon, but not every ecliptic can happen. Because there is an intersection between the ecliptic and the ecliptic, only on a moonlit night can the moon take photos of the solar eclipse continuously, and the earth's shadow can be seen near the intersection of the ecliptic and the ecliptic, so observers on the earth can observe the solar eclipse. Generally speaking, the number of eclipses occurs twice a year. The diameter of the sun is much larger than that of the earth, and the shadow of the earth can be divided into umbra and penumbra. The diameter of the earth is about four times that of the moon. In lunar orbit, the umbra diameter of the earth is still 2.5 times that of the moon. When a part of the moon is always covered by the umbra of the earth, a partial lunar eclipse will occur. When the moon completely enters the umbra of the earth, you can see the total lunar eclipse. If the moon enters the penumbra, the sunlight will also be blocked. This phenomenon is called penumbral eclipse in astronomy. However, because the sunlight in the penumbra is still very strong, the penumbra eclipse is not easy to distinguish with the naked eye in most cases. However, penumbral eclipses often occur. According to the observation data, the percentage of penumbral eclipse, partial eclipse and total eclipse in each century is about 36.60% and 34.46%.

■ solar eclipse

Total lunar eclipse is a special astronomical phenomenon, which means that when the moon moves to the shadow part of the earth, the area between the moon and the earth will be blocked by the earth because of sunlight, and now the moon is gone.

That is to say, at this time, the sun, the earth and the moon are just (or almost) in a straight line, so the light from the sun to the moon will be blocked by the earth.

As far as the earth is concerned, when an eclipse occurs, the directions of the sun and the moon will be different by 180 degrees, so the eclipse must occur in Wangwang (that is, around the lunar calendar 15). It should be noted that the orbits of the sun and the moon in the sky (called the ecliptic and the ecliptic) are not on the same plane, but have an intersection angle of about 5 degrees, so only when the sun and the moon are located near the intersection of the ecliptic and the ecliptic can they be connected in a straight line to produce an eclipse.

■ What kinds of eclipses are there?

Total lunar eclipse: when the whole moon enters the umbra of the earth.

Eclipse: When only a part of the moon enters the umbra of the earth.

Penumbral eclipse: at this time, the moon only passes through the penumbra of the earth, which leads to a slight decrease in the brightness of the moon surface, so it is difficult to be found.

■ Seven steps of total lunar eclipse

After the total lunar eclipse, the penumbra begins to eclipse: the moon just touches the penumbra, which is invisible to the naked eye at this time.

Initial loss: the moon slowly enters the shadow from the eastern edge, and the shadow of the moon and the earth is circumscribed for the first time.

Eclipse: The umbra of the moon entering the earth is engraved with the earth for the first time.

What to eat: the moment when the center of the full moon is closest to the center of the Earth's umbra.

Cold light: the moon moves in the umbra of the earth and is inscribed with the umbra of the earth for the second time.

Last contact: the moon gradually leaves the umbra of the earth and is circumscribed for the second time.

End of the penumbra eclipse: The moon leaves the penumbra, and the whole eclipse process officially ends.

■ Do you know?

Because the umbra of the earth is much larger than that of the moon, it also means that in the event of a total lunar eclipse, the moon will completely enter the umbra of the earth, so there will be no eclipse.

Eclipses occur up to three times a year, sometimes not once a year.

■ Eclipses and scientific research

The earliest lunar eclipse was recorded in Mesopotamia in 2283. When China was in the Han Dynasty, Zhang Heng had discovered the principle of solar eclipse. Aristotle in the 4th century inferred that the earth was round according to the circle of the earth's shadow seen during the solar eclipse. Aristak, an ancient Greek astronomer in the 3rd century, and Alistair in the 2nd century both proposed to measure the size of the sun, the earth and the moon by solar eclipse.

The principle of lunar eclipse. On the fifteenth and sixteenth days of the lunar calendar, the moon runs in the opposite direction to the sun. At this time, if the centers of the earth and the moon are roughly on the same straight line, the moon will enter the umbra of the earth and produce a total lunar eclipse. If only a part of the moon enters the umbra of the earth, a partial lunar eclipse will occur. When the moon enters the penumbra of the earth, it should be a penumbral eclipse, but it is not called an eclipse because the brightness drops very little, so there are only two kinds of eclipses: total eclipse and partial eclipse.

Eclipses always occur in sight (full moon), but not every time, which is the same as not every new moon has an eclipse. Under normal circumstances, the moon either passes above the Earth's umbra or leaves under the Earth's umbra, and rarely or partially passes through the Earth's umbra, so an eclipse will not occur under normal circumstances. Eclipses occur up to three times a year, and sometimes they never happen at all.

Lunar eclipse formation map

The process of lunar eclipse

The process of an eclipse can be divided into five stages: first loss, eating, eating, giving birth to light and last contact.

First loss: The moon has just touched the umbra of the earth, marking the beginning of the eclipse.

Eclipse: The western edge of the moon is inscribed with the western edge of the Earth's umbra, and the moon just enters the Earth's umbra.

Eclipse: The center of the moon is closest to the center of the Earth's umbra.

Luminescence: the eastern edge of the moon is inscribed with the eastern edge of the umbra of the earth, and the total solar eclipse phase ends at this time.

Final contact: the western edge of the moon is tangent to the eastern edge of the umbra of the earth. At this time, the whole eclipse was over.

The degree of eclipse is called "eclipse", which is equal to the ratio of the farthest distance from the edge of the moon wheel to the umbra of the earth and the meridian of the moon when the eclipse is serious.

In ancient times, people did not understand the scientific truth of solar eclipse, and the fear of solar eclipse was no less than that of solar eclipse. It is said in foreign countries that Columbus sailed to Jamaica in South America at the beginning of the16th century, and there was a conflict with the local aborigines. Columbus and his sailors were trapped in a corner, without food and water. The situation is very critical. Knowing that there would be a total lunar eclipse that night, Columbus, who knew something about astronomy, shouted to the natives, "No food, no moonlight!" " In the evening, Columbus's words came true, and there was no moonlight. When the natives saw this scene, they were afraid, so they quickly made peace with Columbus.

The solar eclipse in Mesopotamia in 2283 BC was the earliest in the world, followed by that in China in 1 136 BC. Eclipses have been promoting the development of human understanding. As early as 188 1 years ago, Zhang Heng, an astronomer in Han Dynasty in China, made clear the principle of lunar eclipse. In the 4th century BC, Aristotle saw that the shadow of the earth was round from the solar eclipse, but inferred that the earth was spherical. Alistair, an ancient Greek astronomer in the 3rd century BC, and Hipparchus in the 2nd century BC both proposed to measure the relative size of the Sun-Earth-Moon system through solar eclipse. Iba Valley also proposed to observe the lunar eclipse in two distant places at the same time to measure the geographical longitude. In the 2nd century AD, Ptolemy used the ancient lunar eclipse records to study the movement of the moon, and this method has continued to this day. Before the appearance of rockets and artificial earth satellites, scientists have been exploring the atmospheric structure of the earth by observing eclipses.