Causes of solar and lunar eclipses

Causes of solar and lunar eclipses

Both the earth and the moon do not emit light. When the sun shines on a non luminous and opaque object, there is a shadow behind it. On the side of the earth and the moon behind the sun, there is also a long shadow. From the picture, we can see that the shadow is composed of two parts: the darkest part of the shadow is called the umbra, The sun can not be seen in the moon's penumbra; the slightly dim shadow around the penumbra is called penumbra, and only a part of the sun can be seen in the moon's penumbra
The earth revolves around the sun, the moon revolves around the earth, and with the earth revolves around the sun. Therefore, in a circle of the moon around the earth (29 days and a half), when the moon goes between the sun and the earth, if the sun, the moon and the earth are in or close to a straight line, it will cover the sun and cause a solar eclipse
Similarly, when the moon goes to the side of the earth facing away from the sun, if the sun, the earth and the moon are in or close to a straight line, that is, when the moon enters the earth's umbra, an eclipse occurs
There are three kinds of solar eclipses: partial solar eclipse, annular solar eclipse and total solar eclipse. The part of the moon that covers the sun is called partial solar eclipse, The occurrence of these three kinds of eclipses is related to the position of the sun, the moon and the earth, and also depends on the distance between the moon and the earth
The moon is much smaller than the sun. Its diameter is about one fourth of the diameter of the sun, and the distance between the moon and the earth is also about one fourth of the distance between the sun and the earth. Therefore, from the earth's point of view, the round surfaces of the moon and the sun are almost the same size, so they can be covered up to produce an eclipse
The sun, moon and earth during the total solar eclipse on August 11, 1999
The earth's orbit and the moon's orbit are ellipses. The distance between the sun and the earth, or between the moon and the earth, is not fixed. Sometimes it is far, sometimes it is near. Therefore, the length of the umbra of the moon is different. The longest umbra of the moon is 379660 km, and the shortest umbra is 367000 km. The shortest umbra of the moon is 356700 km, The farthest distance is 406700 km. If the umbra of the moon is larger than the distance between the earth and the moon at some time, the total solar eclipse can be seen in the area swept by the umbra of the moon. If the umbra of the moon is smaller than the distance between the earth and the moon, the tip of the umbra of the moon cannot reach the surface of the earth, Then, the annular eclipse can be seen in the area swept by the small shadow cone (called pseudoumbra) extended from the shadow tip. Partial eclipses can be seen in the area swept by the lunar penumbra. The closer to the total eclipse area in the partial eclipse area, the greater the degree of partial eclipse. Where the lunar penumbra and penumbra have not swept, there is no eclipse at all
Whether it is a partial solar eclipse, a total solar eclipse or an annular solar eclipse, the time is very short. The longest time to see a total solar eclipse at the same place is not more than seven minutes and forty-five seconds. The area to see a solar eclipse on the earth is also very limited. This is because the moon is relatively small, and its umbra is relatively small and short. Therefore, the umbra does not sweep over a wide range on the earth for a long time, Because the average length of the lunar umbra (373293 km) is less than the average distance between the moon and the earth (384400 km), the number of annular eclipses is more than that of total eclipses（

Do you know the types of solar eclipse and lunar eclipse!
In one sentence, because it's a form

Solar eclipse - total solar eclipse, partial solar eclipse, annular solar eclipse
Eclipse - total eclipse, partial eclipse, penumbra eclipse

My reading experience and harvest
About 600 words

French thinker Montesquieu said: "like reading, is equal to the lonely sunlight in life into a moment of great enjoyment." Shakespeare said: "books are the nutrition of the world, life without books, like no sunshine; wisdom without books, like birds without wings." open your books, let you go into the books, or have a dream, In reading, we improve; in reading, we are happy; in reading, we gain
Always like to read a meaningful essay, aromatic; natural; rich; long
Always like to read an interesting story book, magic; fresh; beautiful; moving
I always like to sit on the bench in the library and enjoy the fragrance of books. It's like walking into the garden of Eden of God. You boldly pick the fruit of wisdom, so you know everything
Originally, I didn't like reading. I always thought books were boring and plain. Therefore, I never touched those books, so I was always criticized by the Chinese teacher in the composition class. In my distress, I thought: can reading really help me enrich my composition? So, I absorbed the nutrition of books bit by bit, and harvested the fruits of books bit by bit, I copied all of them in my reading notes. Gradually, I found that reading was fun and fun. So I absorbed and harvested them one by one. Finally, my composition became a model for students to write in the composition class, and soon after, I published an article. This made me more confident and really understood the benefits of reading. From then on, I jumped into the sea of books
Every Sunday, I must go to the bookstore, even if it is snowy and rainy. Every night, I must read an article, no matter how long it is, no matter what time it is. Sometimes, in my dream, I am holding my favorite book, sometimes, birthday gift is also a book. In a word, when I see a book, I will be refreshed. That feeling is like meeting water in the desert
I always like to go to Cong Cong's sister's house. Her study is the longest place for me and her. As soon as I enter her study, I habitually take out a book from the bookshelf, spread it on my legs, find a place to sit down at will, and then go to the book. Maybe because of the book bar, we have become intimate friends. We often talk about our reading experience and the little things we have gained in the book together, We should read books that are helpful to us. If we read some filthy things, we will be irresponsible to our life. We can't harvest anything that is beneficial to us. We should know that many towering trees are destroyed by our own insects. Therefore, we should read some positive books and our books. Only by reading these books can we harvest sunshine
As the saying goes, people have three treasures of spirit, poetry and calligraphy. In order to acquire knowledge, we need to read; in order to improve self-cultivation, we need to read; in order to change our destiny, we need to read. Growth can not be without books, success can not be without books. Love reading! "Books are medicine, reading can cure stupidity."
Reading is the wing of life flying. Books are our wings. With them, we can soar to the sky, fly to success, and fly higher and farther. Books are our keys. With them, we can open the door to happiness
I read, I harvest. Harvest knowledge, harvest strength, harvest wisdom
I read, I harvest. Harvest happiness, harvest courage, harvest success
Read, harvest, taste and forge ahead! Let's bathe in books and enjoy them. Books are gold, precious and incomparable; books are sunshine, infinite energy. Hold books!
Books are the ladder of human progress. For those who are eager for spiritual prosperity, reading is a very happy thing. They can abandon sleep and forget food. Books teach me too much and move me too much. In reading, I harvest; in reading, I grow up. I love reading, I love harvest
I learn by reading