A little knowledge of physics, about 200 words.

1. Little knowledge of the earth is about 200 words.

A little knowledge of the earth is about 200 words 1. The information about the earth is about 200 words.

The earth is the third planet in the solar system from the inside out, and the earth-like planet with the largest diameter, mass and density in the solar system.

The equatorial radius is 6378.2 kilometers, ranking fifth among the planets. The earth has an atmosphere and a magnetic field. 7 1% is a blue planet whose surface is covered with water and the rest is land.

The earth is the home of millions of creatures, including human beings, and the only celestial body in the known universe. The earth is 4.5 billion years old. There is a natural satellite-the moon, whose cycle of rotation around the earth is 27.32 days, while the cycle of rotation of the earth from west to east is nearly 24 hours, and the cycle of rotation around the sun is one year.

The earth is an irregular ellipsoid with slightly flat poles. 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. The earth has accumulated from the primitive solar nebula to the present.

At present, the best estimate of the age of the earth is 4.55 billion years. Generally speaking, the age of the earth refers to its astronomical age. The astronomical age of the earth refers to the time from the beginning of the earth to the present, which is closely related to the hypothesis of the origin of the earth.

2. Earth science knowledge essay 200 words grade three

science

Real science can benefit mankind, while pseudoscience will bring disaster to one side. We study science in order to promote human progress, so we should have a kind and harmonious heart, keep an indifferent and peaceful heart to face science, be kind to science and make good use of it. Finally, I hope everyone can love science, learn science and use science. As long as we study hard and never give up, we will get real science.

One by one, whimsy makes "impossible" a reality, which is the clever use of scientific knowledge by human beings. All scientists have made great discoveries since childhood, and the door of science is always open to children who love to explore. Students, you also strive to make the impossible possible and make our life more exciting!

Walking into science, there are many wonderful things in the scientific community. Observing meteorology, collecting specimens, scientific experiments, popular science activities, life discovery, etc. It's all an exploratory science. Human beings make progress because of science, and science innovates because of human beings. Human can't live without science, and science can't live without human.

3. Little knowledge of geography, less than 200 words.

The relationship between tourism and geography

People's travel is closely related to geography. As the saying goes, before going out to see the weather, going on a business trip or traveling, we should know the weather forecast released by CCTV, which depends on people's ability to recognize weather symbols, be familiar with weather systems such as cold front, warm front, high pressure, low pressure, cyclone, anticyclone and frontal cyclone, and reasonably choose travel time, transportation mode, tourist route and the number of things they carry with them, so as to achieve economic and minimum time, successfully complete the work and achieve enjoyment on the way. For example, when traveling, according to the regional characteristics, choose a reasonable mode of transportation: drifting in the mountains and valleys; In the boundless and endless sand sea, we should choose the "boat of the desert"-camel; Choose a fine horse on the grassland where the wind blows and the grass blows low and cattle are raised, and it is as smooth as flying; In Jiangnan water town, we choose boats to shuttle across the river.

4. Ask for about 200 words of scientific knowledge.

Meteorite is a stone body in which cosmic meteors outside the earth leave their original orbit or are scattered on the earth into pieces. It is a precious and rare physical specimen for human beings to directly understand the stars in the solar system, which is of great collection value.

According to the observation of Canadian scientists in 10, more than 20 tons of meteorites landed on the earth every year, about 20 thousand pieces. Because most meteorites fall in sparsely populated areas such as oceans, weeds, forests and mountains, only dozens of meteorites are found and collected every year, and the number is very small.

Meteorite, when not falling into the earth's atmosphere, is a kind of stone, iron or a mixture of stone and iron floating in outer space. If it falls into the atmosphere, it will become a meteorite that we usually see falling to the ground without being burned by the atmosphere. Simply put, the so-called meteorite is the debris left by a tiny asteroid "hitting the earth". China is the first country to find meteorites in the world. It was in the Neolithic Age, and then it was recorded in writing until the end of the 20th century. There are many names marked by "meteorite", such as "Meteor Mountain" and "Meteor Lake".

Meteorites are generally divided into three categories according to composition, namely iron meteorites, also known as meteorites. Generally, the content of iron and nickel is above 95, including 80-95 iron and 5-20 nickel.

The density is 8 to 8.5. Other components may include sulfides, diamonds, rare earth elements and silicates.

Iron meteorites account for about 3 of the total number of meteorites. The world No.3 iron meteorite was discovered in Qinghe, Xinjiang, China at the end of 19, with a size of 2.42* 1.85* 1.37 and a weight of about 30 tons.

This meteorite contains 88.67% iron and 9.27% nickel. It contains many kinds of minerals that are not found on the earth, such as pyrite, zeolite and other cosmic minerals.

Supernova Sometimes, looking up at the starry sky, you may be surprised to find that there is a bright star in a certain star area that you have never seen before! However, after only a few months or even days, it gradually disappeared. This "strange" star is called a nova or supernova.

In ancient times, it was also called "guest star", which means "visiting star". Novas and supernovae are a kind of variable stars.

When people saw them suddenly appear, they once thought they were just newborn stars, so they were named "new stars". In fact, they are not only newborn stars, on the contrary, they are dying old stars.

In fact, they are exploding red giants. We have mentioned more than once that when a star enters old age, its center will shrink inward, while its outer shell will expand outward, forming a red giant.

The red giant star is very unstable, and one day it will explode violently, throwing its shell out and revealing the white dwarf or neutron star hidden in the center. In the Big Bang, the star will lose most of its mass and release huge energy at the same time.

In this way, in just a few days, its luminosity may increase by hundreds of thousands of times. Such stars are called "new stars". If the explosion of a star is more violent, its luminosity can even be increased by more than100000 times. Such a star is called a supernova.

The intensity of supernova explosions is unbelievable. It is said that the energy it pours out in a few days is equivalent to the energy emitted by a young star in hundreds of millions of years, so that it looks as bright as the whole galaxy! The explosion of nova or supernova is an important part of celestial evolution.

It is the glorious funeral of old stars and the promoter of new stars. The explosion of supernovae may trigger the birth of countless stars in nearby nebulae.

On the other hand, the ashes of nova and supernova explosions are also important materials for the formation of other celestial bodies. For example, many material elements on our planet today come from stars that have long since disappeared.

The volume of the sun is 6.5438+0.3 million times that of the earth, and it is the central celestial body of the solar system. An ordinary star in the milky way galaxy.

The average distance from the earth 1.496 million kilometers, the diameter 1.390 million kilometers, and the average density 1.409g/cm? 3. The mass is 1.989 * 10 33g, the surface temperature is 5770 Kelvin, and the center temperature is 15 million Kelvin. From inside to outside, there are the nuclear reaction area of the sun, the troposphere of the sun and the atmosphere of the sun.

Thermonuclear reactions continue in its central region, and the energy generated is emitted into space by radiation. One of the 2.2 billion energies radiates to the earth and becomes the main source of light and heat on the earth.

The sun is an ordinary star, and it has spent about half of its main sequence career on the Herro diagram. It is a hot gas (strictly speaking, plasma) ball with a mass of 1989 100 billion tons (about 330,000 times the mass of the earth) and a diameter of1392,000 kilometers (about 109 times the diameter of the earth).

Its average density is 1.4 times that of water, but this average density implies a wide density range, from the ultra-high density core to the thin outer layer. As a stellar sun, its overall appearance is luminosity of 38.3 billion watts and absolute magnitude of 4.8. It is a yellow G2 dwarf with an effective temperature of 5800 Kelvin.

The average distance between the sun and the earth around it is 149597870km(499.005 light seconds or 1 astronomical unit). By mass, it is composed of 7 1% hydrogen, 26% helium and a small amount of heavy elements.

The angular diameter of the circular surface of the sun in the sky is 32 minutes, which is very close to the angular diameter of the moon as seen from the earth. What a wonderful coincidence (the diameter of the sun is about 400 times that of the moon, and the distance from us is just 400 times that of the earth and the moon), which makes the eclipse look particularly spectacular. Because the sun is much closer to us than other stars, its apparent magnitude reaches -26.8, making it the brightest celestial body on earth.

The sun rotates once every 25.4 days (average period; The equator rotates faster than high latitudes) and revolves around the center of the Milky Way every 200 million years. The sun is slightly flattened due to its rotation, which is 0.00 1% different from the perfect sphere, which is equivalent to a difference of 6km between the equatorial radius and the polar radius (the earth is 2 1km, the moon is 9km, Jupiter is 9000km, and Saturn is 5500km).

Although the difference is small, it is important to measure this flatness, because any slightly larger flatness (even 0.005%) will change the influence of solar gravity on Mercury's orbit, making the test of general relativity based on Mercury's perihelion precession unreliable. You think it's too long. You can cut a little from the middle.

5. Information about the earth, about 100 to 200 words.

Earth is one of the eight planets in the solar system (Pluto was listed as a dwarf planet in 2006 because its orbit is different from the other eight planets), 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. As a planet, the earth originated from the primitive solar nebula 4.6 billion years ago. The earth will interact with other celestial bodies in outer space, including the sun and the moon. The earth is the home of millions of creatures, including human beings, and the only celestial body in the universe where life is known. The equatorial radius of the earth is 6378. 137㎞, the polar radius is 6356.752㎞, the average radius is about 637 1㎞, and the equatorial circumference is about 40076㎞. On the earth, it is 71. The earth is the only planet found so far where human beings live.

The earth is the source of our life, and there are many elements in the crust, among which oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium account for 98.04%, while more than 80 other elements only account for 1.96%!

6. Important and important knowledge about the earth only needs 200 words, and it is fast and fast.

400 million years ago, the sky was round, including human beings. This period is called sidereal year, and there is a thick mantle on the earth. English: The moon 300 million years ago caused tidal phenomena on the earth, which is the center of the universe. At present, the earth is the only celestial body in the known universe where life exists.

The earth's surface was divided into several hard parts until the increasing brightness of the sun wiped out the biosphere on the earth. Together with the earth's magnetic field, the ozone layer blocks harmful rays from the universe and stabilizes the inclination of the earth's axis, its geological history and orbit. Through diplomacy, they move on the surface of the earth in geological years, but they do not exist on the surface of all other planets. The only natural satellite on the earth, including God's creation of human beings.

Westerners usually call the earth Gaia, which means "Mother of the Earth". On the 26 th solar day [9], the earth's axis is tilted by 23, and the rest are divided into continents and islands. Liquid water is necessary for all known life. Humans living on the earth often call the earth the world, and life was born within 654.38 billion years. Since then, the rotation speed of the earth has slowed down. The earth is expected to continue to have life and protect life on land after10.50 billion years. About 38 to 465,438 billion years ago, it was born in 45 years. Now the earth is born at 45, with a liquid outer core and a solid iron inner core, so that creatures that need oxygen are born at 0.4 (inclined 23 perpendicular to the orbital plane.

The earth will interact with other celestial bodies in outer space, [10] and thus produce seasonal changes on the planet surface with a period of 1 sidereal year. Humans on the earth are divided into about 200 independent countries and tours. Human civilization has had many views on this planet, and the asteroid impact in the later period of the big bombing greatly changed the surface environment.

The earth is home to millions of creatures. According to the physical characteristics of the earth, the time for the earth to go around the sun is rotation. [7] [8] The interior of the earth is still very active, and the earth-like planets with the largest mass and density, trade and war are interrelated, so that life on the earth can continue periodically. About 7 1% of the earth's surface is ocean, which is equal to 365.26 times. , is also the diameter of the solar system.

The mineral and biological resources of the earth maintain the global population (0.4) and also make the ozone layer form. The biosphere of the earth has changed the atmosphere and other environments, including the sun and the moon, or the plate: the earth) is the third planet in the solar system from the inside out.

7. Important knowledge about the earth only needs 200 words, which is fast and fast.

Earth (English: Earth) is the third planet in the solar system from the inside out, and it is also the earth-like planet with the largest diameter, mass and density in the solar system.

Humans living on the earth often call the earth the world. The earth is home to millions of creatures, including humans.

At present, the earth is the only celestial body in the known universe where life exists. The earth was born 4.54 billion years ago, and life was born within 65.438+0 billion years.

Since then, the earth's biosphere has changed the atmosphere and other environments, enabling the birth of organisms that need oxygen and the formation of the ozone layer. Together with the earth's magnetic field, the ozone layer blocks harmful rays from the universe and protects life on land.

The physical characteristics, geological history and orbit of the earth enable life on the earth to continue periodically. The earth is expected to continue to have life in/kloc-0.5 billion years until the increasing brightness of the sun destroys the biosphere on the earth.

The earth's surface is divided into several hard parts, or plates, which move on the earth's surface in geological cycles. About 7 1% of the earth's surface is ocean, and the rest is divided into continents and islands.

Liquid water is necessary for all known life, but it does not exist on the surface of all other planets. [7][8] The interior of the earth is still very active, with a thick mantle, a liquid outer core and a solid iron core.

The earth will interact with other celestial bodies in outer space, including the sun and the moon. At present, the time required for the earth to orbit the sun is 366.26 times that of its rotation, which is called a sidereal year, which is equal to 365.26 solar days [9]. The inclination of the earth's axis is 23.4 (23.4 from the vertical of the orbital plane), [10], thus producing seasonal changes on the planet's surface with a period of 1 sidereal year.

The earth's only natural satellite was born on the moon 4.53 billion years ago, which caused tidal phenomena on the earth, stabilized the inclination of the earth's axis and slowed down the earth's rotation. About 38 to 465,438+billion years ago, the asteroid impact in the later stage of the big bombing greatly changed the surface environment.

The mineral and biological resources of the earth maintain the global population. Humans on the earth are divided into about 200 independent countries, which are connected with each other through diplomacy, tourism, trade and war.

There have been many views on this planet in human civilization, including that God created human beings, the sky is round and the earth is the center of the universe. Westerners usually call the earth Gaia, which means "Mother of the Earth".

8. A little knowledge of geography is about 100 words.

Small knowledge of geography

1. Phenomenon directly caused by solar activity (aurora)

2.9. 1 1 The incident happened at about 9: 00 a.m. in new york, USA. At this time, the time in Beijing (East Eighth District) is (9. 1 1 Sunday night 10 o'clock). P.S. The time in the East is earlier than that in the West.

3. Guilin landscape is (formed by external forces), and (Mount Fuji, Mount Tai, the Great Rift Valley in East Africa) is internal forces.

4. There are often typhoons in the Pacific Ocean in summer and autumn, and the precipitation types in summer and autumn in eastern China are mostly frontal rain.

5. (Ocean current) affects ocean transportation. 6. (Squirrel, black bear) is a typical animal in temperate deciduous broad-leaved forest belt.

7. The characteristics of confined groundwater are (good water quality, not easy to be polluted)

8. At present, the five major energy consumption in the world are: (oil, coal, natural gas, water and nuclear energy).

9. The three major varieties of grain production in the world are: (wheat, rice and corn).

10. The four largest grain-producing countries in the world (China, USA, Indian and Russian).

1 1. The basic celestial body is (nebula, star) 12. The main air pollutant that forms acid rain is (sulfur dioxide).

13. The grasslands in China are mostly distributed in (plateaus and mountains in non-monsoon areas).

14. It is the difference between land and sea that forms the non-zonal difference of geographical environment.

15. The largest landlocked country in the world is (Kazakhstan).

16. The Danube is the largest river in Europe.

17. World Trade Organization (China, Hongkong, Macau and Taiwan Province provinces are members of this organization).

18. Provinces (Jiangsu, Anhui, Henan, Shaanxi, Gansu, Xinjiang) that the Eurasian Continental Bridge from Lianyungang passes through in China 19. The main distribution areas of coal in China (Shanxi, Inner Mongolia, Shaanxi and Guizhou).

20. Provinces that do not border with neighboring countries are (Guizhou, Qinghai, Ningxia).

The largest plateau: the Brazilian plateau

The narrowest mountain range: the Andes

The river with the largest flow: Amazon River

The longest river: Nile

The largest freshwater lake: Lake Superior.

The highest peak: Mount Everest.

The smallest country: Vatican

The most densely populated country: Monaco

The country with the largest gold production: South Africa

Minimum temperature: -89 degrees at the East Pole Station.

The highest railway: Qinghai-Tibet Railway

The largest sea: Coral Sea (over 4.79 million square kilometers), followed by * * * Sea and South China Sea.

The smallest sea: Malahi, followed by the Azov Sea and Bohai Sea.

The highest salinity ocean: the Red Sea, which is also the youngest ocean.

The lowest salinity sea: Baltic Sea

The only sea without a coastline: the sargasso sea.

The Ocean with the Most Islands: Aegean Sea

The most famous tidal bore: Qiantang River Tide

The largest ocean: the Pacific Ocean, which is also the deepest, has the highest water temperature and the most manganese nodules.

The smallest ocean: the busiest ocean in the Arctic Ocean: the Atlantic Ocean (why? )

The largest ocean current: west wind drift, which is also the largest cold current.

The largest warm current: the Mexican warm current

The largest archipelago: Malay archipelago

The highest island: New Guinea, which is also the largest island belonging to both countries.

The only island belonging to the Three Kingdoms: kalimantan island.

The longest strait: mozambique channel.

The deepest strait: Drake Strait, which is also the widest strait.

The most tortuous strait: strait of magellan

The channel that ships pass the most: the English Channel.

The busiest channel for oil transportation: the Strait of Hormuz.

The largest bays: Bay of Bengal, Gulf of Mexico and Gulf of Guinea.

Asia is the largest continent in the world;

Asia has the longest coastline in the world;

Asia is the most populous continent in the world;

Mount Everest is the highest mountain in the world;

The Qinghai-Tibet Plateau is known as the "roof of the world" and is the highest plateau in the world.

* * * Peninsula is the largest peninsula in the world;

The Caspian Sea is the largest lake in the world;

The Dead Sea is the lowest depression in the world.

Malacca Strait is the longest strait in the world.

Indonesian sunda islands is the place where volcanoes are most concentrated in the world;

China produces the most rice in the world;

The Han Qing subsea tunnel is the longest subsea tunnel in the world.

Laos ranks first in the world in benzoin production;

Myanmar teak production ranks first in the world;

Thailand's potassium salt reserves rank first in the world;

Thailand's rubber exports rank first in the world;

Malaysia's tin reserves rank first in the world; Bangladesh's jute production ranks first in the world;

India's mica exports rank first in the world;

Saudi Arabia's oil reserves rank first in the world;

Kazakhstan's tungsten reserves rank first in the world;

Ganges delta is the largest delta in the world;

Malay Archipelago is the largest archipelago in the world;

The Yarlung Zangbo Grand Canyon is the largest canyon in the world.

Mariana Trench is the deepest part of the ocean.

9. 200 words of information about the earth

The above is copied from me, and I used it to answer other questions! ! ! ! ! Overview of the Earth The Earth is one of the eight planets in the solar system. It has been 4.6 billion years since its birth.

According to the order from near to far from the sun, it is the third star, after Mercury and Venus. It ranks fifth in size among the eight planets. In English, the earth is the only name that doesn't come from Greek and Roman mythology.

The word Earth in English comes from Old English and Germanic. Of course, there are many other languages.

In Roman mythology, the goddess of the earth is called Tellus-fertile land (Greek: Gaia, mother of the earth). Earth data age: 4.4 ~ 4.6 billion years.

Period of revolution: About 365.2422 days. Length of tropic year: 366.2422 days. Orbit of revolution: pear-shaped

Early July is perihelion, and early June of 1 is perihelion. Rotation period: sidereal day is 23 hours, 56 minutes and 06 seconds.

The solar day is 24 hours. Direction of rotation: from west to east.

Satellite (nature)-1 (moon) The main components of the atmosphere-nitrogen (78%), oxygen (2 1%) and carbon dioxide (0.037%), water vapor (0.03%), rare gas (0.933%) and the main component of the earth's crust-oxygen.

Equatorial radius = 6378. 140km polar radius = 6356.755km average radius = 637 1.004km equatorial circumference = 40075. 13km volume = 10832 billion cubic kilometers. Mass = 5.9742 * 10 2 1 ton.

Average density = 5.5 18g/cm 3 Earth surface area =5. 1 1 100 million square kilometers. Ocean area = 36174.53 million square kilometers.

(accounting for 70.8% of the total surface area) Land area = 65,438+49 million square kilometers (accounting for 29.2% of the total surface area) Latitude 1 Length =1.133-0.559 cos 2 φ km (at latitude φ). 3cosφ-0.094cos3φ km The speed of sound in the atmosphere (0 degree) V South magnetic pole: 66 S 66 S, 140 E The acceleration of gravity on the earth's surface (φ = 45): g = 9.806 1 m/s? The earth surface detachment velocity = 1 1.2km/s aberration constant (J2000) k = 20.49552 "equatorial angle (j2000) ε = 23 26' 21."448 total precession of the yellow diameter (j2000).

Its northern end always points to the vicinity of Polaris, and the direction of the earth's rotation is from west to east; Seen from above the North Pole, it rotates counterclockwise. The earth rotates once, which is about 23 hours and 56 minutes. This time is called sidereal day. However, on earth, we feel that a day is 24 hours, because the reference we choose is the sun.

Because the earth's rotation and revolution are carried out at the same time, this four-minute gap is the result of the superposition of the earth's rotation and revolution. Astronomy calls the 24 hours we feel 1 day solar day.

The rotation of the earth produces the alternation of day and night. The alternation of day and night makes the surface temperature of the earth neither too high nor too low, which is suitable for human survival.

Schematic diagram of the earth's revolution The average angular velocity of the earth's rotation is 15 degrees per hour. On the equator, the linear speed of rotation is 465 meters per second.

All kinds of celestial bodies in the sky are reflections of the earth's rotation. People first measured time by the rotation of the earth.

Studies show that every hundred years, the earth's rotation speed will slow down by nearly 2 milliseconds, which is mainly caused by tidal friction, which also makes the moon move away from the earth at a speed of 3~4 cm per year. In addition to the long-term slowdown of the earth's rotation speed, there are irregular changes from time to time, and the real reason for this change is still unclear.

The movement of the earth around the sun is called revolution. Seen from above the North Pole, it rotates counterclockwise around the sun.

The route of the earth's revolution is called orbit. It is an elliptical orbit close to a perfect circle.

The sun is located in one of the two focal points of the ellipse. Every year, 6543810.3, the earth moves to the nearest position to the sun, which is called perihelion. On July 4, the earth moved to the farthest position from the sun, which is called apohelion.

The direction of the revolution of the earth is also from west to east. The length of the orbit is 940 million kilometers, and the time required for one revolution is one year, about 365.25 days. The average angular velocity of the earth's revolution is about 1 degree per day, and the average linear velocity is about 30 kilometers per second.

The perihelion has a faster revolution speed, while the apohelion has a slower revolution speed. The plane on which the earth rotates is called the equatorial plane, and the plane on which the earth revolves is called the ecliptic plane.

The angle of intersection between the two planes is called the ecliptic angle, and the earth axis is perpendicular to the equatorial plane, and the angle of intersection with the ecliptic plane is 66 34', or the angle of intersection between the equatorial plane and the ecliptic plane is 23 26', indicating that the earth revolves around the sun obliquely. Earth seismic wave We can know the interior of the earth by drilling, but now the most advanced drilling can only penetrate 14 km. If we compare the earth to an egg, even the skin of the egg has not penetrated. Later, scientists finally knew the key to open the door to the center of the earth-seismic waves. At the beginning of the 20th century, Yugoslav seismologist Mohorovicic suddenly realized that seismic waves are "ultrasonic detectors" for us to explore the interior of the earth! Seismic wave is the seismic wave emitted during an earthquake. It has two kinds: shear wave and longitudinal wave. Shear waves can only pass through solid materials, while longitudinal waves can freely pass through any kind of materials, such as solids, liquids and gases.

When the density of passing matter is high, the propagation speed of seismic wave is fast, and when the density of passing matter is low, the propagation speed is slow. Mohorovicic found that the propagation speed of seismic waves suddenly accelerated at 33 kilometers underground, which indicated that the density of materials here was very high and the composition of materials was different from that of the earth's surface.

This depth inside the earth is called "Moho". 19 14 years, American seismologist Gutenberg found that at 2900 kilometers underground, the velocity of longitudinal waves suddenly slowed down and the shear waves disappeared. This shows that the density of matter here has become smaller, and there is no solid matter. The center of the earth is here, leaving only liquid and gas.

This depth is called "Gutenberg surface". The mystery of the center of the earth has finally been clarified: from the outside to the inside, the earth is divided into three layers by Moho surface and Gutenberg surface, namely crust, mantle and mantle.