Diary of total solar eclipse on July 22, 2009, about 700 words.

The so-called "eclipse" refers to the astronomical scene in which one celestial body is completely or partially blocked by another celestial body or its shadow. There are three kinds of eclipses: total solar eclipse, partial solar eclipse and annular solar eclipse. The principle of solar eclipse is that a part of the earth is covered by the shadow of the moon. The solar eclipse must occur in the new moon, the first day of the lunar calendar. This is because only on that day will the moon appear on the line between the sun and the earth, so that the moon can block the sun and form an eclipse. Similarly, the eclipse must appear on the lookout day, which is the fifteenth day of the lunar calendar.

There are three kinds of solar eclipses: partial eclipse, annular eclipse and total solar eclipse. The part of the moon that covers the sun is called a partial solar eclipse. The moon only covers the central part of the sun, and a circle of the sun's surface is exposed around the sun, which is called annular eclipse like a halo. A total solar eclipse is when the sun is completely obscured. The occurrence of these three different solar eclipses is related to the changes of the positions of the sun, the moon and the earth, and also depends on the changes of the distance between the moon and the earth.

The moon is much smaller than the sun, its diameter is about 400% of the diameter of the sun, and the distance from the moon to the earth is almost 400% of the distance from the sun to the earth. So from the earth's point of view, the orbits of the moon and the sun's sphere and the moon's orbit are all ellipses. Neither the distance from the sun to the earth nor the distance from the moon to the earth is fixed, but sometimes it is far and sometimes it is close, so the umbra length of the moon is different. The longest umbra of the moon is 379,660 kilometers, and the shortest is 367,000 kilometers. The nearest distance between the earth and the moon is 356,700 kilometers, and the farthest distance is 406,700 kilometers. If the umbra of the moon is larger than the distance between the earth and the moon at a certain moment, the total solar eclipse can be seen in the area swept by the umbra of the moon on the earth. If the lunar umbra is less than the distance between the earth and the moon, and the tip of the lunar umbra cannot reach the earth's surface, then the annular eclipse can be seen in the area swept by the small shadow cone (called pseudo-umbra) extending from the shadow tip. A partial solar eclipse can be seen in the area swept by the penumbra of the moon. The closer to the total food area, the greater the degree of partial eclipse. Where the umbra and penumbra of the moon are not swept, there is no solar eclipse at all. The circular surface is almost equal in size, so it can cover up and cause an eclipse.

The orbit of the earth and the orbit of the moon are both ellipses. The distance between the sun and the earth and the distance between the moon and the earth are not fixed, sometimes far and sometimes near, so the length of the umbra of the moon is different. The longest umbra of the moon is 379,660 kilometers and the shortest is 367,000 kilometers, while the distance between the earth and the moon is 356,700 kilometers and the farthest is 406,700 kilometers. If the umbra of the moon is larger than the distance between the earth and the moon at a certain moment, the total solar eclipse can be seen in the area swept by the umbra of the moon on the earth. If the lunar umbra is less than the distance between the earth and the moon, and the tip of the lunar umbra cannot reach the earth's surface, then the annular eclipse can be seen in the area swept by the small shadow cone (called pseudo-umbra) extending from the shadow tip. A partial solar eclipse can be seen in the area swept by the penumbra of the moon. The closer to the total food area, the greater the degree of partial eclipse. Where the umbra and penumbra of the moon are not swept, there is no solar eclipse at all.