Is the initial composition of the earth uniform?

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The earth is divided into an inner sphere and an outer sphere. The inner sphere is independent of each other and is the crust, mantle, and core. The outer spheres are intersecting and are the atmosphere, hydrosphere, and biosphere.

Therefore, the only thing that belongs to both the plate tectonic system and the atmospheric biological system is the crustal sphere. Plates belong to the earth's crust, and the surface soil of the earth's crust has air at the bottom of the atmosphere, and there are organisms in the crustal soil, so it is also related to the biosphere.

Rotation. Hundreds of years ago, many methods were proposed to prove the rotation of the earth, and the famous "Foucault pendulum" made us really see the rotation of the earth, but why does the earth rotate around its axis? Why does it revolve around the sun?

This is a question that has been of great interest to scientists for many years, and roughly speaking, rotation is a basic form of motion of the celestial bodies in the universe, but in order to truly answer this question, it is necessary to first understand how the sphere and the solar system are formed. The creation of the Earth's rotation and revolution is closely related to the formation of the solar system.

Modern astronomical theories suggest that the solar system was formed by the so-called primordial nebula, a very thin cloud of gas that contracted to the center under the influence of some kind of perturbation 5 billion years ago. After a long period of evolution, the density of the matter in the central part became higher and higher, and finally it reached the point where it could trigger a thermonuclear reaction, and it evolved into the sun. The residual gas around the sun gradually forms a rotating disk-like gas layer, which gradually gathers into solid particles, microplanets, and primordial planets in the gas layer through the processes of contraction, collision, capture, and accumulation, and finally forms independent solar system objects such as large planets and asteroids.

We know that to measure the speed of a straight-moving object, it can be expressed in terms of velocity, so what is the measurement of the rotation of the object? One way to do this is to use "angular momentum".For an object revolving around a fixed point, its angular momentum is equal to the mass multiplied by the velocity, multiplied by the distance of the object from the fixed point.

There is a very important law of conservation of angular momentum in physics, which is to say, a rotating body. If it is not acted upon by an external moment, its angular momentum does not change due to the change in the shape of the object. For example, a ballet dancer, when he suddenly folds his arms in the middle of rotation (the distance between the center of mass and the fixed point becomes smaller), his rotation speed increases, because only in this way can the angular momentum be maintained.

This law plays an important role in the generation of the Earth's rotation speed.

The primordial nebulae that formed the solar system originally had angular momentum, and after the formation of the solar and planetary systems, its angular momentum would not be lost, but it would inevitably be redistributed, and each star would get a certain amount of angular momentum from the primordial nebula in the long process of accumulating matter. Since angular momentum is conserved, the planets will also rotate faster and faster during contraction. The earth is no exception, the angular momentum it obtains is mainly distributed in the rotation of the earth around the sun, the mutual rotation of the earth-moon system and the rotation of the earth, which is the origin of the earth's rotation, but to really analyze the orbital motion and rotation motion of the earth and other major planets still requires scientists to do a lot of research work.

That is to say, in the formation of the Earth, motion, especially rotation, accompanied the formation of the Earth from beginning to end, rather than the beginning of its rotation or revolution for some reason after the formation of the Earth.

The formation of the primitive earth.

Before the formation of the earth, there were many asteroids in the universe revolving around the sun, and these planets collided with each other to form the primitive earth, when the earth was still a hot fireball, and as the collision gradually decreased, the earth began to cool slowly from the outside to the inside, producing a thin layer of hard shell - the earth's crust, at this time the earth was still in a hot state. A large amount of gas is ejected from the inside of the earth, which carries a large amount of water vapor, which forms a circle of atmosphere surrounded by the periphery of the earth, the position of the earth from the sun is not too close to the water vapor is evaporated by the sun, and the size of the earth itself has enough gravity to pull the atmosphere, so the earth will have a unique atmospheric environment, and the atmosphere begins to rain after the formation, and the original ocean is formed.

About 4.7 billion years ago, dust gathered in the universe to form the Earth and the other planets of the solar system in which it is located. At that time, the air did not contain oxygen, but contained a lot of carbon dioxide (carbon dioxide gas) and nitrogen.

Originally, the Earth was small, but it continued to increase in size due to the constant impact of small stars in the universe. And when it hits, the energy gathers, the temperature rises, and eventually melts into a liquid.

Soon, the number of star impacts decreased, and the temperature of the Earth's surface decreased, forming the Earth's crust. This is the surface of the earth today. However, magma in the Earth's interior is constantly erupting, forming a large number of volcanoes. The water vapor in the volcanic ash cools and condenses into water, which forms the ocean.

View from outer space: white, white clouds. Brown, brown continents and islands. Blue, blue ocean. Or, looking at the Earth from outer space, the Earth is a blue planet with 78% of its surface covered by oceans.

The blue color of the Earth as seen from space is due to the interaction between the sun's rays and the Earth's atmosphere.

When sunlight enters the celestial atmosphere, air molecules and particles such as dust, water droplets, and ice crystals in the atmosphere will scatter sunlight to the surrounding areas.

Once upon a time, Earth was a blue planet. The sea is the main part of the earth, and it is almost a world of water. It is conceivable that if you travel around the world on a giant ship, you will see not only the blue sea, but also the deep blue sea; If you're looking at the Earth from space aboard the Shenzhou-10 spacecraft, you'll want to reach out and hold it – because you'll see a huge, beautiful sapphire in front of you.

I don't know how many billions of years have passed, and the earth has become a beautiful colored ball, like a beautiful little girl, flowers and branches. Red, blue, green, purple ......These colors are all over the globe. There are also colors that I can't say and have never seen before.

Look, the flowers are blooming in spring, the green trees are in the shade in summer, the fresh fruits are fragrant in autumn, and the snow is white in winter, which is very beautiful! The lush forest, when the wind blows, ripples green, is very beautiful. The sea is still so blue and so beautiful.

But one day, the color of the earth changed.

There are fewer and fewer of those lush forests, replaced by the terrible yellow desert. Humans have cut down and destroyed the birds' homes for their own benefit. As everyone knows, what human beings really destroy is the only home for their own survival!

There are fewer and fewer green plains, less and less sea, and in their place are cities. The taller and taller buildings are being built, the earth is almost out of breath, more and more garbage, more and more car exhaust, and the earth has to hold its breath and breathe! Why is it always gray in some cities?

Where is the scene of the fish playing happily in the creek? The creek is no longer the same creek it used to be. The water that used to be clear and visible did not know where to go, the fish did not know where to hide, and the people who came to fetch water to wash clothes were gone.

What you see are discarded paper, white plastic bags, dead rabbits floating on the water.

The color of the earth has changed ......Alas, what is the reason?

Blue and green, and white.

From the outside to the inside: the atmosphere, hydrosphere, biosphere, lithosphere, asthenosphere, mantlesphere, outer nuclear liquid sphere, and solid inner core.

The geosphere is divided into two parts: the outer and inner spheres of the earth. The Earth's outer sphere can be further divided into four fundamental layers, namely the atmosphere, hydrosphere, biosphere, and lithosphere; The Earth's inner sphere can be further divided into three fundamental spheres, namely the mantle sphere, the outer nuclear liquid sphere, and the solid inner core. In addition, there is an asthenosphere between the Earth's outer and inner Earth's spheres.

In this way, the entire Earth consists of a total of eight spheres, in which the lithosphere, asthenosphere and inner sphere together constitute the so-called solid Earth. 】

The gravitational force exerted on an object is actually the resultant force of the gravitational pull of the earth on the object and the centrifugal force generated by the rotation of the object with the earth.

The gravitational force is not equal to the gravitational pull of the Earth's weight on the object. Due to the rotation of the earth itself, in addition to the poles, the objects in other places on the ground are moving in an approximate uniform circular motion around the earth's axis together with the earth, which requires a centripetal force directed perpendicularly to the earth's axis, and this centripetal force can only be provided by the earth's gravitational force on the object, and we can decompose the earth's gravitational force on the object into two components, one component f1, which points to the earth's axis, and the magnitude is equal to the centripetal force required for the object to move in an approximate uniform circular motion around the earth's axis; The other component, g, is the gravitational force on the object. where f1 = mrw 2 (w is the angular velocity of the earth's rotation, r

is the radius of rotation of the object), and the magnitude of f1 can be seen to be zero at the poles, increasing with decreasing latitude, and the maximum f1max in the equatorial region. Because the centripetal force of an object is very small, in general, it can be approximated.

The gravitational force of an object is equal to the gravitational force, i.e. the effect of the rotation of the earth can be omitted in general. where the gravitational component of gravity provides gravitational acceleration, and the centripetal component of gravity provides the direction of maintaining rotation with the Earth.

Cardiac acceleration. The magnitude of gravity can be measured with a dynamometer, and the magnitude of the pull or pressure of an object moving in a stationary or uniform linear motion on the dynamometer is equal to the magnitude of gravity.

The heavier the copy

The greater the gravitational pull of the earth, the more the object is subjected to, it is right. Bai gravity is (primarily) made by the gravitational pull of the earth.

Gravity is also affected by other DAO forces. For example, the hydrogen balloon floats upwards due to the action of air buoyancy, and the hydrogen balloon not only has no gravity, but also produces lift, which can be said to be the hydrogen balloon is not subject to the gravitational pull of the earth. So gravity is that the gravitational pull of the earth is not right for the object.

The gravitational force between two objects is directly proportional to their mass and inversely proportional to the square of the distance. i.e. f=gmm r 2, g is the gravitational constant, which is n*m 2 kg 2.

Huh: Good question.

The book is right.

1.On the one hand, the solution is to assume that the object does not rotate with the Earth, but is only subject to the Earth's gravitational pull on it2On the other hand, the concept of gravity, which you understand correctly, should contain the centripetal force that you said"Gravitation and gravity are equivalent"Guess it's a misunderstanding, and if you think about the basic concept, because there's no solution, I'm guessing that the misunderstanding has something to do with a given constant like g.

3.And then again, it's possible that the book uses an approximation, as upstairs says, but I don't think it's likely.

The centrifugal force generated by that rotation is not of the same order of magnitude as the gravitational force of the earth on the object, that is, it is more than 1000 kilometers apart, so it is negligible in general simple calculations

Gravity is generally considered to be gravitational, which is a hassle to save you. Except for the students of the physics department, it is estimated that the students of other departments do not need to calculate the centripetal force.