"What did you say?"

When Chen Long returned to the Jueshi Continent with Zixia, Qingxia, Qinglian and Miaoshan, Li Maozhen and the others brought him good news for the first time.

"Your Majesty, our people have found the Milky Way Earth." Li Maozhen smiled and repeated what she had just said again.

"Have you found Earth, so can I really go home? Mom and Dad, brother, and sister! ”

Chen Long was excited and muttered.

For going home, Chen Long's heart is greater than everything, even if he travels through different worlds, it is not as important as going home.

"Alright, let's go!"

Subsequently, Chen Long put away the Emperor Chen Heavenly Palace, sat on Kaisha's Great Sword spaceship, and first passed through the teleportation array of the Ten Thousand Worlds Sect and left the Jueshi Continent.

"Jue Shi Continent, goodbye!"

I took one last look at the Jueshi Continent.

Jueshi Continent, this familiar and unfamiliar place for Chen Long, has nostalgia and reluctance.

Chen Long recalled the scenes of the past.

"Let's go!"

In the end, he still left the Jueshi Continent!

After several teleportations, Chen Long and the others came to the Milky Way, which was like a vast galaxy in the starry sky, and the waves were spectacular!

Fly aboard Kesha's Great Sword spaceship and head towards the Earth of your dreams.

The spacecraft soon entered the Earth-confines solar system and flew towards the Earth little by little.

The closer he got to the earth, the more nervous Chen Long's heart became.

Far away, the people on the spaceship saw the Earth, the blue planet.

For this blue planet, such as Chen Long, Keisha, Liang Bing, Rose, Cream, and Reina, they are all very familiar.

Although Keisha and the other women are from the Earth of the Super Seminary World, the shape of the Earth is the same.

Looking at the starry sky, the blue planet, Chen Long remembered an introduction to the earth that he saw on the Internet when he was on the earth.

In 1543, Copernicus first fully proposed the concept of the rotation and revolution of the earth in his book "On the Motion of the Heavenly Bodies". Since then, a large number of observations and experiments have proved that the earth rotates from west to east. In 1851, the French physicist Foucault successfully conducted a famous experiment (Foucault pendulum test) in Paris, proving the rotation of the earth. The rotation period of the earth is about 23 hours, 56 minutes and 4 seconds, the orbit of the earth is elliptical, the semi-major diameter of the orbit is 149597870 kilometers, the eccentricity of the orbit is 0.0167, the orbit period is one sidereal year, the average speed of the revolution is 29.79 kilometers per second, and the angle between the ecliptic and the equator (the angle of the yellow equator) is 23 °27′. The combination of the Earth's rotation and its orbital motion produces the alternation of day and night, the change of seasons and the distinction of the five zones (tropical, north-south temperate and north-south cold zone) on the earth. The rate at which the earth turns white is uneven, with long-term variations, seasonal variations, and irregular variations. At the same time, due to the gravitational effects of the sun, moon and planets, as well as the various effects of the atmosphere, oceans and internal materials of the earth, the direction of the earth's axis of rotation in space and the earth's body will change, that is, precession and nutation, pole shift and yellow-red angle changes.

Shape and size

The concept that the earth is spherical can be traced back to the fifth and sixth centuries BC. At that time, the Greek philosophers of the Pythagoreans only came up with the idea that the sphere is the most beautiful. Aristotle scientifically demonstrated for the first time that the earth is a sphere based on the fact that the shadow of the moon is a circle at the time of the lunar eclipse. As early as the Warring States Period, the philosopher Hui Shi had put forward the idea that the earth was spherical.

In the third century BC, the ancient Greek geographer Eratosthenes succeeded in measuring the length of the meridian between Aswan and Alexandria using triangulation. During the Tang Dynasty in China, under the guidance of his entourage, a survey team led by Nangong Shuo carried out the earliest arc measurement in the plain area north and south of the Yellow River in Henan Province, and calculated the difference in the height of the North Pole horizon by one degree, which is equivalent to a difference of about 351 li and 80 steps between the north and south (the length unit of the Tang Dynasty is 5 feet = 1 step, 300 steps = 1 li), so that the radius of the earth can be calculated. This work predates similar work by the Arabs by about 100 years. In modern times, in addition to the use of geodetic methods; Gravity measurements can also be used to determine the equilibrium shape of the Earth. After the artificial earth satellite was launched, the geodynamic geodesy method has been greatly developed. In 1976, in the astronomical constant system of the International Astronomical Union, the radius of the earth's equator was α 6378140 meters, and the earth's flattening factor of 1/f was 298.257. The earth is not a positive sphere, but an oblate sphere, or in other words, more like a pear-shaped rotating body. The observation results of artificial earth satellites show that the earth's equator is also an ellipse, according to which the earth can be considered to be a triaxial ellipsoid. The inertial centrifugal force of the Earth's rotation causes the spherical Earth to gradually expand from the poles to the equator, becoming the current slightly flattened spheroid shape, and the polar radius is about 21 km shorter than the equatorial radius. The uneven distribution of materials in the earth's interior further causes the irregularity of the shape of the earth's surface. In geodesy, the so-called shape of the earth refers to the shape of the geoid on which the gravitational position is the same everywhere, which is an isotopic plane. The gravitational effect of the sun and the moon on the earth causes tidal phenomena in the oceans and atmosphere on the earth, and also causes the solid earth (to some extent, an elastic body) to undergo elastic deformation, which is the so-called "solid tide".

Mass and acceleration due to gravity

The mass of the Earth is 5.976×l0^27 grams, which is determined according to the law of gravitation. The determination of the mass of the Earth provides a basis for determining the mass of other celestial bodies. From the mass of the earth, it can be concluded that the average density of the earth is 5.52 g/cm3.Any particle on the earth is affected by the gravitational force and inertial centrifugal force of the earth, and the resultant force of the two is gravity.The gravitational force decreases with increasing altitude and also changes with latitude.The acceleration of gravity at the equator is 978.g(cm/s2), The two poles are 983.2 G. There are also gravity anomalies in some places, which reflect the unevenness of the distribution of materials in the earth's interior. Gravity anomalies are related to geological structures and mineral deposits. The Earth's gravitational constant is 9.8N/kg, which is 6 times that of the Moon.

structure

The Earth can be seen as consisting of a series of concentric layers. In the interior of the earth, there are core, mantle, and crust structures. Outside the Earth, there is a hydrosphere, an atmosphere, and a magnetosphere, forming a coat around the solid Earth. The magnetosphere and atmosphere block direct ground bombardment from space by ultraviolet rays, X-rays, energetic particles, and numerous meteors.

More than seven-tenths of the earth's surface is covered by blue oceans, and lakes and rivers occupy only a small part of the earth's surface waters. The liquid water layer on the Earth's surface, called the hydrosphere, has been formed for at least 3 billion years. The surface of the earth is composed of various rocks and soils, the ground is rugged, and the low-lying parts are flooded into oceans and lakes; The land above the water has plains and mountains. The total vertical undulation of the earth's solid surface is about 20 kilometers, and it is the summit of Mount Everest (according to the Chinese mountaineering team, The difference in elevation between Mount Everest is 8844.43 meters above sea level and the deepest ocean depth (about 11 kilometers in the Mariana Trench), which is more than half the average thickness of the continental crust.The ocean floor is as uneven and not calm as the land.The age of the rocks on the ocean floor is much younger than that of the land.Most of the rocks on the land are less than two billion years old.Sedimentary rocks can be found everywhere on the land, indicating that these places may have been oceans in ancient times.Although there are a small number of craters on the surface, it is difficult to find a similar one to the moon, There are as many craters as Mars and Mercury, which is the result of the continuous weathering, erosion and disintegration of the Earth's surface by external forces (water and atmosphere) and internal forces (earthquakes and volcanoes).

For a long time, it has been believed that the tectonic movement of the earth's crust is mainly manifested in the uplift and subsidence of the ground, which is mainly vertical movement, and horizontal movement is secondary. In the past ten years, more and more scientists believe that the upper part of the earth not only has vertical motion, but also has greater horizontal motion, and the relative positions of the oceans and continents are also changing in geological time. In 1912, Wegener proposed the continental drift hypothesis. However, for a long time, many scientists rejected the continental drift hypothesis, because it was hard to believe that there was such a force to tear apart the original continental block, causing each fragment to drift to its present position. In the early sixties, Hess and Dietz proposed the hypothesis of ocean floor expansion, arguing that global tectonics is a direct result of the continuous expansion of the ocean floor. It is precisely because of the development of the oceanic floor expansion hypothesis and the theory of plate movement that the theory of continental drift has been re-emphasized.

The uppermost layer of the earth is about a few tens of kilometers thick is a very strong lithosphere, and a layer hundreds of kilometers thick below it is the asthenosphere, which is less intense, and the material in this layer is plasticized under long-term stress. The lithosphere floats on the asthenosphere. When the energy (primordial heat and emitted heat) is released in the Earth's interior, the uneven distribution of temperature and density in the earth causes the convective movement of mantle materials. Mantle convective materials move in both directions along the fissures of the mid-ocean ridges in the ocean floor, and new ocean floors are constantly formed. In addition, the old ocean floors continue to expand outward, and when they approach the continental margin, they are inserted under the continental crust under the downward drag force of mantle convection, causing a series of tectonic movements in the lithosphere. This convection can cause the entire ocean floor to renew every 300 million years. The lithosphere is fragmented by some active tectonic belts and divided into several discontinuous units called continental plates. Lebichon divides the global lithosphere into six plates: the Eurasian plate, the American plate, the African plate, the Pacific plate, the Australian plate, and the Antarctic plate. The expansion of the seafloor causes the movement of continental plates. The intercrushing of tectonic plates has created huge mountain systems, which are the case with mountain systems from the Alps through Turkey and the Caucasus to the Himalayas; In some places, the rocks of two plates sink at the same time, creating an abyss on the ocean floor, and in addition, the movement of the plates also causes volcanoes and earthquakes. The theory of plate motion is still evolving, and there are many controversial issues.

Origin and evolution

The systematic scientific study of the origin and evolution of the earth began in the middle of the eighteenth century, and many theories have been proposed to this day. The prevailing belief is that the Earth, as a planet, originated from the primordial solar nebula 4.6 billion years ago. Like other planets, it has undergone some common physical evolution processes, such as accretion and collision. At the beginning of the formation of the earth's fetus, the temperature was low and there was no hierarchical structure, but the temperature of the earth gradually increased due to the bombardment of meteorite materials, the heat caused by radioactive decay and the gravitational contraction of the primitive earth. With the increase of temperature, the internal materials of the earth are becoming more and more plastic, and there is a phenomenon of local melting. At this time, under the action of gravity, the differentiation of matter begins, the heavier material outside the earth gradually sinks, the lighter material inside the earth gradually rises, and some heavy elements (such as liquid iron) sink to the center of the earth, forming a denser core (the observation of seismic waves shows that the outer core of the earth is liquid).

In the early stages of the Earth's evolution, the primitive atmosphere escaped completely. With the recombination and differentiation of matter, various gases that were originally in the earth's interior rose to the surface through volcanic eruptions and other actions to become the second generation of atmosphere, and later, due to the photosynthesis of green plants, it further developed into the modern atmosphere. On the other hand, the temperature of the Earth's interior increases, causing the crystalline water inside to vaporize. As the surface temperature gradually decreases, gaseous water condenses and rainfalls to the ground to form a hydrosphere. About 30 to 4 billion years ago, single-celled life began to appear on the earth, and then gradually evolved into a variety of organisms, until advanced organisms such as humans constituted a biosphere.

Earth data

Orbital long radius (astronomical distance unit) 1.000

Orbital long radius (million km) 149.6

Sidereal period of revolution (days) 365.26

The conjunctional period of the revolution (days)-

Orbital eccentricity 0.0167

Orbital inclination (degrees) 0.0

Ascending node ecliptic longitude (degrees) 0.0

Perihelion ecliptic longitude (degree) 102.3

Average orbital speed (km) 29.79

Equatorial radius (km) 6371

Earth's circumference (km) 40030

Flat ratio 0.0034

Mass (mass of the earth = 1) 1.000

Density (g/cm³) 5.52

Equatorial gravity (Earth = 1) 1.00

Escape velocity (km/s) 11.2

Rotation period (days) 0.9973

Yellow-red angle (degrees) 23.44

Albedo 0.30

Maximum Brightness-

Satellite (confirmed) 1

plate

In 1968, Le Pichon divided the global earth's crust into six major plates; Pacific Plate, Eurasian Plate, African Plate, American Plate, Indian Plate (including Australia) and Antarctic Plate. With the exception of the Pacific plate, which is almost entirely oceanic, the remaining five plates include both continents and oceans.

29% of the Earth is land and 71% is ocean. The global land mass can be divided into seven continents: Asia, Africa, Europe, Oceania, South America, North America, and Antarctica.

The world's oceans can be divided into four oceans; Pacific, Atlantic, Indian and Arctic Oceans!

The Earth is getting closer and closer, and finally, the spaceship stops on the surface of the Earth.

At this moment, Chen Long's heart was very excited, and because of this, the spaceship stayed on the outer surface of the earth, and he didn't think about what would happen if the earth's satellite photographed them......

……

"Brother......

"Brother, brother...... Woohoo......"

"Son......

"Dragon...... My dragon......"

……

What's going on? In the blur, Chen Long heard the voices of his parents, his younger siblings, and they were crying heartbreakingly.

"What's wrong with me? Why is it obscure? Am I not coming home with my wives? Back to Earth? ”

……

Is all this ...... It's just that...... A...... Dream!

"The End of the Book"!

(PS: Thank you very much for the great companionship of this sentence, this is the end of the book, thank you again.) There were a thousand words of thanks, but in the end, there was only one word of thanks left! ）

The Heavens Hongyan Group has ended, thank you all for accompanying you all the way, thank you very much! In the end, some other articles may be updated, so if you don't like it, you don't need to read it.

(End of chapter)