There is only one earth lesson plan.

Teacher: I heard that you are all very clever. I want to ask you a question. Try to be open-minded when answering: where are we now?

Student: In the school auditorium.

Teacher: (shaking his head) Not open-minded.

Health: In XX.

Health: In China.

Health: On Earth.

Yes, we are in Shenzhen, China and Earth. Please all stand up and stamp your feet: what is under our feet?

Health: the earth.

Teacher: (Blackboard: Earth) We call it Earth together.

Health; (Qi) The earth-

Teacher: Did the Earth hear that? Why doesn't it respond? Let's call again: Hello, Earth! If the earth hears it, she will applaud warmly. Let's go

Born (together, affectionately) to Earth-Hello-

(Behind the students, the teachers applauded warmly. )

Teacher: The earth has heard our call. Ok, let's start the class now.

[first category]

Teacher: Students, today the teacher will take you on a space trip in the shenzhou spaceship designed and manufactured by China. Please close your eyes. Our spaceship is about to launch. Ok, the spaceship has risen into space. Please open your eyes and look at the beautiful scenery in space.

Play the video of the planets in space, and the earth will gradually become clear and finally freeze.

Teacher: Students, this blue planet is our earth. Do you like it? Please praise our earth in one sentence.

Health: Earth, you are so beautiful!

Health: Earth, you are so great! I like you!

Teacher: Please scan the first paragraph of the text quickly and see how the earth is praised in the text.

Health: "The earth, the mother of human beings and the cradle of life, is so beautiful, spectacular and amiable."

Teacher: Please read this sentence with emotion.

Health: (read aloud with emotion)

Teacher: Why is the earth called "the mother of mankind" and "the cradle of life"? Please read the text by yourself with questions.

Student: (Read the text by yourself and get a preliminary understanding of the content. The teacher asked the students to read through the text.

Teacher: Now let some students read to you. Who will read it first?

Student: (Raise your hand in succession)

Teacher: So many students are willing to study. Ok, I'll ask the monitor to recommend one.

(The monitor recommended student A)

Teacher: (to the monitor) Can you tell me why you recommended her?

Monitor: She has a high level of reading, great courage and a very loud voice.

Teacher: Please read paragraphs 1 and 2, and read out the characteristics that the monitor praised you.

(Student A reads the text)

Teacher: Indeed, as the monitor said, the reading level is high. Who will read it next? Now please recommend one (to student A).

(student a recommends student b)

Teacher: (to student A) Why do you recommend him?

Student A: He reads fluently and is very emotional.

Teacher: (To student B) Please read paragraphs 3 and 4, and read out the characteristics of fluency and emotion.

(student b reads the text)

Teacher: Very emotional. Ok, who will read it next? Does anyone volunteer? (Students raise their hands to student C one after another) Please read paragraphs 5, 6 and 7. Let's talk about the characteristics of your reading first.

Health: Although I am not as good as them in reading, I have made great progress. I have feelings, too.

(Students read the text and act it well. )

Teacher: Applause. Who reads the last two paragraphs? (Many students raise their hands) Ok, read together.

(The whole class reads the text together)

Teacher: Next, I will check the students' understanding of the words. Look at the screen.

Understand the dotted words first, then explain the words:

Compared with the vast universe, the earth is small.

Health: misty, very small. Small is small.

Teacher: Explain the following words in the same way.

Life, roaming, boats dry up.

Teacher: Please talk to each other.

(Students tell each other the meaning of words)

Teacher: Please think carefully: Are there any rules to understand these words?

Health: These words have similar meanings. When we explain these words, we can use the meaning of one of them to explain.

Teacher: Look at the next word.

Explain words with examples:

natural resource

Teacher: Please read the text quickly. What are "natural resources"?

Health: mineral resources, water resources, forest resources, biological resources and atmospheric resources.

Teacher: Now these natural resources are divided into two categories. Do you know why?

Mineral resources (non-renewable)

Water resources, forest resources,

Biological resources and atmospheric resources (renewable)

Health: The former is a non-renewable natural resource, while the latter is a renewable natural resource.

Teacher: Look at the following set of words.

Read and understand the words:

... no ... but ... even ...

Teacher: Please find out the relevant sentences and read the meanings of these words in the sentences. After the students practice, the teacher asks a student to read aloud, which is not very good.

Teacher: "Millions of years, even hundreds of millions of years …" How to distinguish between "millions of years" and "hundreds of millions of years"?

(Students read again to understand better)

Teacher: There are several groups of related words in the text. Please find out the relevant sentences and read them by yourself according to the above method.

(Students read related sentences)

Teacher: This is the end of word understanding. This text is an exposition of scientific knowledge. Please read the text quickly and think: What scientific knowledge does the text tell us about the earth?

Health: This text tells us that the earth is beautiful, but it is also very small. The resources on the earth are limited.

Teacher: Do you have anything to add?

Health: The article also tells us that when the earth's resources are exhausted, we can't move to other planets.

Teacher: Let's look at the topic. Why do we use "there is only one earth" as the topic? Please complete the following sentence: Because "there is only one earth", so …

Health: Because there is only one earth, we should protect it.

Teacher: Please read the last paragraph of the text and recite it as soon as possible.

(Students read and recite)

Teacher: Please recite the last paragraph together.

(After students recite collectively, class is over)

[second category]

Teacher: We recite the last paragraph of the text together.

(The whole class recited the last paragraph collectively)

Teacher: By studying this text, we have a deeper understanding of the earth. Protecting the earth and cherishing life are our common beliefs. However, not everyone thinks so. Look at two online news first.

Bush abandons Tokyo agreement

In March last year, President Bush announced that the United States had withdrawn from the Tokyo Protocol. Bush said that once this agreement is implemented, millions of jobs will be lost in the United States and the American economy will be affected. The Tokyo Protocol requires more than 40 major industrial countries in the world to reduce their greenhouse gas emissions to the level of 1990 within 10. The United States is the largest industrialized country in the world, which emits a large amount of industrial waste gas such as carbon dioxide into the atmosphere every day.

Bush will not attend the "Save the Earth" meeting.

In September this year, world leaders held a "Save the Earth" meeting in South Africa to discuss the future of mankind and the fate of the Earth. US President George W. Bush refused to attend the meeting, which aroused unanimous doubts from the delegates. A representative said: "The whole world demands that substantial measures be taken to save the earth and eliminate poverty. As the richest man and the only superpower in the world, it is really the worst president in the world not to attend the meeting. "

Teacher: What do you think after reading these two messages? Are you in this mood? (Students raise their hands) Before you speak, please make an expression. Let me know how you really feel through this expression.

(Students make various expressions)

Teacher: Some look very angry; Have a plenty of a thinking look; Some are very excited; Others seem particularly confused ... now please say what you think.

Health: Bush, you are a terrible president!

Health: Bush, you are too selfish.

Health: The President of the United States should step down immediately.

Health: Bush, how can you be the president of a big country?

Teacher: Mr. Lu Xun once said: abuse and intimidation are by no means fighting. We need to find a way to get Bush to change his attitude and get attention. If Bush is in front of us, I want to ask my classmates to convince him. Please write a persuasion draft first. Please read the text carefully, find reasons to convince Bush in the text, and apply the relevant knowledge learned from extracurricular books. Pay attention to persuasion methods, persuasion skills and persuasion attitude.

(Students write persuasion draft, and teachers tour to guide)

Teacher: (imitating Bush's tone) I am the current president of the United States, and my belief is that American interests are above everything else. I heard that some children in China have opinions on my environmental protection policy, and I want to hear their opinions. But I'm busy, so I have to hurry.

Health 1: President Bush, you shouldn't …

Bush: Who are you? Why are you talking to me like that?

Health 1: Hello, President Bush. I am a pupil in China. I know from the internet that you don't want to attend the "Save the Earth Conference", and I'm disappointed. Mr. Bush, we only have one earth, which is the home of people all over the world. We should all take more care of our earth. The mineral resources on the earth are very limited and non-renewable. Although air resources and water resources can be regenerated, they cannot be destroyed at will. At present, more than 60% of the earth is short of water, the air pollution is quite serious, acid rain often falls, and the atmospheric hole over Antarctica is getting bigger and bigger. These are the consequences of industrial pollution. The United States is the largest industrialized country in the world, which emits the most exhaust gas into the atmosphere every day. Therefore, you must change your attitude and pay attention to protecting the earth. We strongly urge you to sign the Tokyo Protocol.

Bush: I know everything you said. But I don't think it's that serious. Our technology in America is so advanced that there is no problem that cannot be solved. Besides, we can go to other planets. All right, bye.

Health 2: Bush, don't go!

Bush: Who are you? What are you doing?

Health 2: I am the embodiment of justice, and I will sue you!

Bush: Accuse me? With what?

Health 2: Listen! Your country, the United States, is the country that emits the most exhaust gas, conducts the most nuclear tests and consumes the most oil ... As the president of a big country, you should have a sense of responsibility! You can't just focus on your own interests. If the earth is destroyed, you Americans have nowhere to run. Because scientists have proved that there is no second planet suitable for human habitation within at least 40 trillion kilometers centered on the earth. At that time, your presidency will be lost, so you must seriously consider it!

Bush: Ah, what a wonderful little girl from China. Although my attitude is very strict, what I said has some truth. It seems that I have to think about it. Listen to other children's opinions again.

S3: (doing dolphin swimming) Hello, Mr. Bush. Nice to meet you.

Bush: Who are you? How did this happen?

Health 3: I am a dolphin, the spirit of the ocean, and I ask you for help on behalf of all the animals in the ocean. The sea water pollution is so serious that we can hardly survive. In the past, we lived freely in the ocean. But then a lot of sewage flowed into the ocean, our home was seriously damaged, and our companions in the ocean suffered heavy casualties ... (Tears streaming down their faces)

Bush: I sympathize. What do you want me to do？

Health 3: I hope you will take action to save the earth and the animals and plants in our ocean.

Bush: OK, I will seriously consider your opinion.

…………

Teacher: Students, your performance just now was so wonderful that even the conceited American President Mr. Bush was moved by you. Because you have good reason and sincere attitude. This also shows that you understand the text thoroughly. I suggest you write a letter to Bush in the name of your class, hoping to really change his attitude. Class is over. The earth is one of the eight planets in the solar system, with the international name "Gaia", ranking third in the order from near to far from the sun. It has a natural satellite-the moon, forming a celestial system-the earth-moon system.

First, the description of teaching materials

This lesson introduces the knowledge about the earth from the perspective of human existence, expounds the truth that there is only one earth for human existence, and explains the significance of protecting the earth's ecological environment.

The text begins with what astronauts see when they look at the earth from a distance in space, and leads to an introduction to the earth. Then, from the small size of the earth in the universe, the narrow range of human activities, the limited natural resources owned by the earth, uncontrolled exploitation or random destruction, it is explained that the earth is facing the threat of resource depletion; Then it is proved by the research results of scientists that when the earth's resources are exhausted, there will be no second planet for human habitation; Finally, it is concluded that there is only one choice for human beings, and that is to carefully protect the earth and its ecological circle.

Second, teaching suggestions

1. The key point of teaching this course is to guide students to understand that there is only one earth in the process of independent reading. Let the students read through the text first, at least twice, so that they can have a general understanding of the text. Then, we can put forward "from what aspects does the text explain that there is only one earth", guide students to read the text carefully, and organize students to exchange and discuss on the basis of reading the text carefully. Through communication and discussion, students can understand the truth that there is only one earth from the following aspects.

(1) From the position of the earth in the whole universe, the earth is very small. The radius of the earth is only over 6,300 kilometers, and it is like a ship in the whole universe. A number, a metaphor, illustrates the insignificance of the earth in the universe.

(2) The scope of human activities is very small. The area of the earth's surface is 5? 1 100 million square kilometers, and the land inhabited by human beings "only accounts for" one fifth of it.

(3) The earth's resources are limited, suffering from uncontrolled exploitation and random destruction. The formation of mineral resources takes "millions or even hundreds of millions of years", and if it is exploited without control, it may be in danger of "exhaustion". Renewable resources, such as water resources, forest resources, biological resources and atmospheric resources, can not be "regenerated" because of people's "random destruction" and "abuse of chemicals", but also create "ecological disasters" and threaten human survival.

(4) There is no second planet for human habitation. In this paper, scientists' research results are cited to show that there is no second planet suitable for human habitation "at least within 40 trillion kilometers centered on the earth". As for the idea of establishing an immigration base on Mars or the moon, even if it is "realized", it is impossible for many people to live.

2. The astronaut's exclamation "Our earth is so lovely and fragile at the same time" quoted in the article is a difficult point for students to understand. To guide students to understand this, we can first find out this sentence and read it, and say under what circumstances it was said. Then we can grasp the key words "lovely", "broken" and "at the same time" in this sentence and contact the whole class to talk about where the earth is lovely, where it is easy to be broken and why it should be emphasized. To understand the "loveliness" of the earth, we can think from the sights and natural resources seen by "looking at the earth from afar". To understand the fragility of the earth, we can think from the aspects of "unrestrained", "wanton destruction" and "wanton abuse". Emphasizing "simultaneity" means emphasizing the duality of the earth: both lovely and fragile. The purpose of emphasizing "simultaneity" is to remind people that if resources are destroyed at will, the lovely earth may be broken. If the ecological environment of the earth is carefully protected, the lovely earth will be even more lovely.

3. This class pays great attention to the accuracy of words and the rigor of writing in expression. In teaching, students should be guided to experience in reading and enhance their sense of language. "thinking? The purpose of the third question "exercise" is to arouse students' thinking about the words used in such sentences. When guiding students to do this problem, we can ask them to read the sentence after removing the added words, and then read the original sentence again to compare the differences in expression of the words that don't need to be added. Then, ask students to find similar sentences from the text and analyze and compare them in the same way; Finally, guide students to experience the expressive effect of these sentences in reading the text.

The range of human activities on the earth is very small, but human beings can develop new areas of activities, such as the ocean. The natural resources on the earth are limited, but human beings can develop and utilize new energy sources, such as nuclear energy. Therefore, when emphasizing "there is only one earth", we can also guide students to realize this significance and let them realize that while protecting the earth, we should also vigorously develop new fields and new energy sources.

This lesson is an explanatory article. To guide students to read such works, we should not only inject our own feelings like reading narrative, but also pay attention to the rigor of writing and show the logical power of such works. For example, "yes, scientists have put forward many ideas, for example, to establish an immigration base on Mars or the moon. But even if these ideas can be realized, how many people can live? " When reading this passage, the word "but" is preceded by a level. You can read the word "imagination" more in a plain tone to emphasize that it is just an idea. We should emphasize "but" to draw people's attention to the content after "but". We can emphasize "even if", which makes people feel that it is still unknown whether this idea can be realized. We should emphasize "how many people" slightly, so as to make people realize that even if an immigration base is established on Mars or the moon, only a few people can live there.

6. Explanation of words: roaming: roaming; Travel. Brilliant: this is the pearl and jade that dazzles people. Here, the stars are bright and dazzling

Universe: the infinite space including the earth and all other celestial bodies. Geology: composition and structure of the earth's crust.

Gift: It used to refer to the reward given by the emperor, but now it generally refers to charity out of pity. Generosity: Be generous.

Exhausted: exhausted. Witness: I saw it with my own eyes. Abuse: excessive use, excesses.

Three. References:

1. Several figures of ecological environment in China?

Serious soil erosion. According to the satellite remote sensing calculation of 1992, the area of soil erosion in China is 179? 40,000 square kilometers, accounting for 18 of the land area? 7%。

Desertification is developing rapidly. Desertification land has reached 654.38 0.49 million square kilometers, accounting for 654.38 0.5% of the national territory. 5%。

Water pollution has increased significantly. 42% of urban water sources are polluted.

2. The ranking of China's main resources per capita in the world 144 countries.

The land area is 1 10.

The cultivated land area is 126.

After that, the grassland area was the 76th.

The back forest area is 107.

3. Forest resources crisis. As a terrestrial ecosystem, forest is the most important part of ecological environment. It not only provides wood and various forest by-products, but also has the functions of water conservation, soil and water conservation, wind and sand fixation, climate regulation, agricultural and animal husbandry production, biological species preservation and ecological balance maintenance. China is a Shaolin country, and its per capita forest area and forest volume rank behind 107 in the world. The serious problem is that the forest resources in China are declining in quantity and quality. Compared with 198 1976, the national forestland area decreased by 3.09 million hectares. According to the survey, the forest area of 23 provinces, autonomous regions and municipalities in China has decreased, and the main reasons for the decrease are deforestation and deforestation. Xishuangbanna is a relatively complete tropical rain forest area in China, where many tropical and subtropical plants and rare animals grow. Due to improper reclamation, the average annual deforestation was 220,000 mu, and the forest coverage rate in 0949 was 65,438+69,000. 4% dropped to 26% of 1980.

4. Groundwater pollution in Beijing. Beijing is short of water resources, and groundwater resources are in danger of being seriously polluted. Pollution sources mainly come from people themselves and nature. From a natural point of view, every northwest wind will bring a lot of sand and dust to Beijing. After falling to the ground, it will be carried through the surface by the rain and pollute the groundwater. Human pollution of groundwater is more serious than the consequences caused by nature. At present, almost all industrial and domestic water in Beijing is discharged into rivers without strict treatment. The polluted river water permeates the riverbed and coastal surface, causing groundwater pollution. Man-made pollution also comes from over-exploitation of groundwater. Over-exploitation leads to a significant drop in the groundwater level, which makes all kinds of harmful substances contained in groundwater highly concentrated. In order to solve the problem of water shortage in Beijing, the South-to-North Water Transfer Project should be implemented. However, if we do not pay attention to solving groundwater pollution, even if more than one billion cubic meters of South Water is transferred to Beijing every year, it may not cover groundwater pollution. More importantly, Beijing's water consumption will far exceed today's, and Beijing's water resources situation will be more severe.

5. The reduction of cultivated land area. China has a large population and a small population. From 1978 to 1994, the cultivated land decreased by 68.8 million mu and the population increased by 2? 300 million. Per capita arable land from 1? 55 mu reduced to 1? 19 mu. In Guangdong, Fujian, Zhejiang and other provinces, the per capita arable land has dropped to less than 0? 6 acres, so that people call cultivated land "life-saving field". However, in recent years, burial has become a common practice, not only burying the dead, but also building graves for the dead ancestors, and even building empty graves for the living, resulting in the waste of fertile land. This is a very serious problem.

The earth is the third farthest planet from the sun, and its distance from the sun is about 150000000 kilometers. It takes 365.256 days for the earth to go around the sun and 23.9345 hours for its rotation. Its diameter is 12756 km, which is only larger than Venus 100 km. In our earth's atmosphere, 78% is nitrogen, 265435.

The earth was formed 4.6 billion years ago, about 654.38+600 million years ago. The earth only had 9 hours every day and night, much faster than now, about 800 days a year. By 600 million years ago, day and night were extended to 20 hours, and a year was shortened to 440 days. The reason may be mainly due to the tidal gravity of the moon. It is generally believed that the formation of the earth originated from the solar nebula. In the past 46 million years, the earth has evolved from a uniform sphere to the present "circular" structure. The average thickness of crust is17km, and the thickness of mantle is about 3473km. The mantle temperature is1000 ~ 3,000 degrees Celsius, and the core thickness is about 3,473 kilometers, accounting for 16.3% of the earth's volume. This substance is in a liquid state, and the core temperature is as high as 6000 degrees Celsius. The earth is one of the eight planets in the solar system, with the international name "Gaia", ranking third in the order from near to far from the sun. It has a natural satellite-the moon, forming a celestial system-the earth-moon system.

The earth rotates from west to east and revolves around the sun at the same time. The combination of the earth's rotation and revolution has produced the alternation of day and night and seasonal changes on the earth (the speed of the earth's rotation and revolution is uneven). At the same time, due to the gravity of the sun, the moon and nearby planets, as well as the influence of many factors such as the earth's atmosphere, oceans and materials inside the earth, the direction of the earth's rotation axis will change in space and the earth itself. The inertial centrifugal force produced by the earth's rotation makes the spherical earth gradually expand from the poles to the equator, becoming a slightly flat ellipsoid of revolution at present, and the polar radius is about 2 1 km shorter than the equatorial radius.

Apollo spacecraft saw on the moon that the earth was composed of a series of concentric layers. The earth has a core (core), mantle (mantle) and crust (crust) structure. There are hydrosphere, atmosphere and magnetosphere outside the earth, forming a beautiful coat around the solid earth.

As a planet, the earth was born in the primitive solar nebula 5.6 billion years ago.

Basic parameters of the earth:

Equatorial radius: ae = 6378 136.49.

Polar radius: ap = 6356755.00 meters.

Average radius: a = 637 100 1.00 m.

Equatorial gravity acceleration: ge = 9.780327 m/s 2.

Average rotational angular velocity: ω e = 7.29115×10-5 radians/second.

Flatness: f = 0.0033528 19.

Mass: m ⊕ = 5.9742×1024kg

Geocentric gravitational constant: ge = 3.986004418×1014m3/S2.

Average density: ρ e = 5.5 1.5g/cm3.

Mass ratio of the sun to the earth: S/E = 332946.0.

The mass ratio of the sun to the earth-moon system: s/(m+e)= 328900.5.

Revolution time: T = 365.2422 days.

Average distance from the sun: a =1.49597870×101m.

Revolution speed: v =11.19 km/s.

Surface temperature: t =-30 ~+45.

Ground atmospheric pressure: p = 10 13.250 mbar.

Surface gravity acceleration (equator) 978.0 cm/s 2

Surface gravity acceleration (polar) 983.2 cm/s 2

The rotation period is 23: 56: 4 (when the sun is flat).

The half-length diameter of the orbit is 149597870 km.

The eccentricity of the orbit is 0.0 167.

Period of revolution 1 sidereal year

The intersection of yellow and red is 23 degrees and 27 minutes.

The structure of the earth's sphere

The ocean area of the earth is 36 1745300 square kilometers.

The crust is 80.465 kilometers thick.

The depth of the mantle is 2808.229 km.

The core radius is 3482.525 kilometers.

The surface area is 5 10067866 km2.

It was not until recently that people clearly knew the structure of the earth. The whole earth is not an isotropic body, but has an obvious circular structure. The composition, density and temperature of each layer of the earth are different. In astronomy, studying the internal structure of the earth is of great significance for understanding the movement, origin and evolution of the earth, exploring the structure of other planets, and even the origin and evolution of the whole solar system.

The sphere of the earth is divided into two parts: the outer ring and the inner ring. The outer circle of the earth can be further divided into four basic circles, namely, atmosphere, hydrosphere, biosphere and lithosphere; The inner circle of the earth can be further divided into three basic circles, namely mantle circle, outer nuclear liquid circle and solid inner circle. In addition, there is a asthenosphere between the outer and inner circles of the earth, which is the transition layer between the outer and inner circles of the earth and is located at an average depth of about 150 km below the ground. In this way, the whole earth contains eight spheres, in which the lithosphere, asthenosphere and the inner circle of the earth together constitute the so-called solid earth. The atmosphere, hydrosphere, biosphere and lithosphere surface in the outer circle of the earth are generally studied by direct observation and measurement. At present, the research on the inner circle of the earth mainly adopts geophysics methods such as seismology, gravity and high-precision modern space geodetic observation inversion. The distribution of spheres on the earth has a remarkable feature, that is, the interior of the solid earth and the altitude above the surface are basically parallel up and down, while near the surface of the earth, spheres are interspersed or even overlapped with each other, among which the biosphere is the most obvious, followed by the hydrosphere.

atmosphere

The atmosphere is the outermost gas layer in the outer circle of the earth, surrounding the ocean and land. There is no exact upper limit of the atmosphere, and there are still thin gases and elementary particles at the height of 2000 ~ 16000 km. There is also a small amount of air in the ground, soil and some rocks, which can also be considered as a part of the atmosphere. The main components of the earth's atmosphere are nitrogen, oxygen, argon, carbon dioxide and trace gases less than 0.04%. The total mass of gases in the earth's atmosphere is about 5.136×1021g, which is equivalent to 0.86 millionth of the total mass of the earth. Due to gravity, almost all gases are concentrated in the height range of 100 km above the ground, and 75% of the atmosphere is concentrated in the troposphere range from the ground to 10 km. According to the distribution characteristics of the atmosphere, it can be divided into stratosphere, mesosphere and thermosphere above troposphere.

steam

The hydrosphere includes oceans, rivers, lakes, swamps, glaciers and groundwater. This is a continuous but irregular circle. Overlooking the earth from a height of tens of thousands of kilometers, we can see the white clouds formed by water vapor in the earth's atmosphere and the blue ocean covering most areas of the earth, making the earth a "blue planet". The total mass of the earth's hydrosphere is1.66×1.024g, which is about 1/3600 of the total mass of the earth, and the mass of marine water is about 35 times that of terrestrial water (including rivers, lakes, surface rock pores and soil). If the whole earth had no ups and downs of solid parts, the whole world would be covered by a water layer as deep as 2600 meters. The atmosphere and hydrosphere combine to form the fluid system on the surface.

The earth is one of the eight planets in the solar system, with the international name "Gaia", ranking third in the order from near to far from the sun. It has a natural satellite-the moon, forming a celestial system-the earth-moon system.

The earth rotates from west to east and revolves around the sun at the same time. The combination of the earth's rotation and revolution has produced the alternation of day and night and seasonal changes on the earth (the speed of the earth's rotation and revolution is uneven). At the same time, due to the gravity of the sun, the moon and nearby planets, as well as the influence of many factors such as the earth's atmosphere, ocean and materials inside the earth, the direction of the earth's rotation axis will change in space and the earth itself. The inertial centrifugal force produced by the earth's rotation makes the spherical earth gradually expand from the poles to the equator, becoming a slightly flat ellipsoid of revolution at present, and the polar radius is about 2 1 km shorter than the equatorial radius.

Apollo spacecraft saw on the moon that the earth was composed of a series of concentric layers. The earth has a core (core), mantle (mantle) and crust (crust) structure. There are hydrosphere, atmosphere and magnetosphere outside the earth, forming a beautiful coat around the solid earth.

As a planet, the earth was born in the primitive solar nebula 5.6 billion years ago.

Basic parameters of the earth:

Equatorial radius: ae = 6378 136.49.

Polar radius: ap = 6356755.00 meters.

Average radius: a = 637 100 1.00 m.

Equatorial gravity acceleration: ge = 9.780327 m/s 2.

Average rotational angular velocity: ω e = 7.29115×10-5 radians/second.

Flatness: f = 0.0033528 19.

Mass: m ⊕ = 5.9742×1024kg

Geocentric gravitational constant: ge = 3.986004418×1014m3/S2.

Average density: ρ e = 5.5 1.5g/cm3.

Mass ratio of the sun to the earth: S/E = 332946.0.

The mass ratio of the sun to the earth-moon system: s/(m+e)= 328900.5.

Revolution time: T = 365.2422 days.

Average distance from the sun: a =1.49597870×101m.

Revolution speed: v =11.19 km/s.

Surface temperature: t =-30 ~+45.

Ground atmospheric pressure: p = 10 13.250 mbar.

Surface gravity acceleration (equator) 978.0 cm/s 2

Surface gravity acceleration (polar) 983.2 cm/s 2

The rotation period is 23: 56: 4 (when the sun is flat).

The half-length diameter of the orbit is 149597870 km.

The eccentricity of the orbit is 0.0 167.

Period of revolution 1 sidereal year

The intersection of yellow and red is 23 degrees and 27 minutes.

The structure of the earth's sphere

The ocean area of the earth is 36 1745300 square kilometers.

The crust is 80.465 kilometers thick.

The depth of the mantle is 2808.229 km.

The core radius is 3482.525 kilometers.

The surface area is 5 10067866 km2.

It was not until recently that people clearly knew the structure of the earth. The whole earth is not an isotropic body, but has an obvious circular structure. The composition, density and temperature of each layer of the earth are different. In astronomy, the study of the internal structure of the earth is of great significance for understanding the movement, origin and evolution of the earth and exploring other problems.