This is how our Earth looks like to
the far-away cosmic observer. This color it owes to its air and
water covers. There are a lot of sciences connected with the Earth, the names of which begin with “geo” ( in Greek- Earth)- geography, geology, geophysics, etc. Let us look at it for a while as a “celestial body”. After all, it is the third planet in the Solar system and when we pay attention to its sisters, we should not forget it.
The Earth rotates on an elliptical orbit around the Sun. The distance between them changes from 147 000 000 km ( in the beginning of January) to 152 000 000 km ( in the beginning of July) and is approximately 149 500 000 km. Its average speed is 29,76 km/sec and it makes its annual tour for 365 days, 6 hours, 9 minutes and 10 seconds. It makes a rotation around its axis for 23 hours, 56 minutes and 4 seconds. As you see, the period of the rotation around its axis and the day ( 24 hours) are not entirely the same.
Now, when we have finished our trip through the far-away cosmic worlds, it is time for us to “go back to Earth” and to recover our respect to the mother planet. This is why we will inform you that the mass of our Earth is equal to the “astronomical” number 5 970 000 000 000 000 000 000 tones. Looks solid, right? Its average diameter is 12 742 km, but the Earth is slightly flattened at the poles- its equatorial diameter is 14 km longer than its polar.
The volume of the Earth is 1 083 000 000 000 cubic km. Its average density is 5,52 times bigger than this of the water. We can boast that we live on the second most solid celestial body of the Solar System after the planet Mercury. The overall surface of the Earth is 510 100 000 quadrate km, of which 361 059 000 quadrate km are covered with water (71%) and only 149
How has the Earth been formed as a planet? When learning about the origin of the Solar System, we saw how from the initial cloud of cosmic dust and gases, along with the Sun, a lot of other smaller centers of accumulation were formed. The radioactive elements and the pressure warmed up their substance, the elements weighing more sank to the center and the lighter elements emerged on the surface and gradually began to harden up.
The Earth crust was initially, before around 3,5-4 billion years, was very thin and under the pressure of the gases and the vapors constantly cracked. But gradually it cooled down and began to fold. The first values and mountains were formed. While the Earth was calming down, the vapors of the atmosphere were liquefying and falling in great quantities onto the Earth as rain. They again evaporated because of the hot crust. This process continued for millions of years, till the surface of the Earth calmed down. Then, before around 3 million years, for the first time there were suitable conditions for the appearing of life on the Earth.
Let us see what is the structure of the Earth as a celestial body! Let us begin with the cosmic space and direct to its center!
At a first touch with the Blue planet we will get at around 50- 60 000 km from its hard surface. Somewhere there vends its outer ring ( as you see, not only Saturn, but also the Earth has a ring , even though it does not consist of meteoric pieces) of charged particulars ( mainly electrons).
We pass through it quickly ( as it is dangerous for all living beings) and we leave it at a height of 20 000 km to enter the inner ring, which is even more dangerous. It consists mainly of protons and spreads from 600 to 5 000 km above the Earth’s surface. But even at a height of 3 000 km we enter the upper layers of the atmosphere, the so called exosphere.
The ionosphere begins at the height of 900 km, after that the stratosphere ( at 80 km) and, in the end- the troposphere ( at a height of 15 km).
We are now at the bottom of the airy ocean, surrounding the Earth. Under us are the hydrosphere ( the water cover) and the lithosphere ( the core of the Earth). We bravely continue our way downwards, to the center of the Earth, through its rocky layers. The crust of the Earth is 30-75 km thick under the matrixes and 3-10 km under the oceans.
Under the lithosphere is situated the mantle of the Earth. It spreads to the depth of 2 900 km. Under it is the core of our planet. It has a diameter of 7 000 km.
In the very center is situated the subcore with a diameter of around 2 600 km.
In the core of the Earth the electron layers of the atoms are strongly deformed because of the high temperature ( some thousand degrees) and big pressures ( up to 3 500 000 atmospheres). The density of the subcore is 12-17 times bigger than this of the water.
This way, starting from the furthest galaxies, we came to the center of our planet.
