Chapter - 2
Origin and Evolution of Earth ️
Earth :-
The earth, which is considered to be the abode of human beings, is the abode of all living and non-living components along with human beings.
️ How did the Earth originate?
This question has always been a matter of contemplation for scientists. This chapter presents a brief description of the formation process of not only the earth but the universe and all its celestial bodies. Knowing this chapter through questions will be a new experience.
️ Development stage of the earth :-
In the beginning our earth was rocky hot and deserted . Its atmosphere was also very rare , which was composed of hydrogen and helium gases . In the course of time, some such events happened, due to which the earth became beautiful and favorable conditions for water and life developed on it.
Life on earth evolved about 460 million years ago from today. The structure of the Earth is layered , in which the composition of each layer from the outer boundary of the atmosphere to the center of the Earth is different from each other . Later on, the lithosphere and the atmosphere were created. The origin of life on Earth occurred in the last phase of its formation .
️ Development of atmosphere on earth :-
There are three stages of the development of the atmosphere on Earth .
In the first stage , hydrogen and helium were removed from the earth due to the solar wind.
In the second stage , during the cooling and differentiation of the earth, many gases and water vapor came out from inside the earth, in which water vapor, nitrogen, carbon-di-oxide, methane and ammonia came out in large quantities, but free oxygen was very less.
In the third stage , there were continuous volcanic eruptions on the earth, due to which vapors and gases were increasing. This water vapor condensed and converted into rain, due to which oceans were formed on the earth and life developed in them. After the evolution of life, the process of synthesis intensified and there was an excess of oxygen in the earth's atmosphere.
The initial concepts related to the origin of the earth :-
The main ancient concepts related to the origin of the earth were as follows:-
Nebula Hypothesis:- Immanuel Kant was the father of this hypothesis . According to them, the planets originated from the rotating clouds of gas and other substances.
Laplace improved this hypothesis by saying that due to the increasing angular momentum of the rotating nebula , the nebula became compressed and its outer part came out in the form of rings which later turned into planets.
According to Chamberlain and Molton , another star passed near the Sun at a fast speed. Due to whose gravitational force a cigar-shaped piece was separated from the surface of the Sun, later the planets were formed from that piece.
️ Division of Earth's geo-scientific chronology :-
The geo-scientific time sequence of the earth is divided into major, medium and minor stages, which are as follows:-
- Ian ( Eons )
- Mahakalpa ( Era )
- Period
- Epoch
Ian is the largest and epoch is the shortest period. From the origin of the earth till now the geological history of the earth has been divided into four ian. The current Ian is called Phanerozoic Ian .
This Ian is divided into three Mahakalpas .
- Purajivi Mahakalpa
- mid life cycle
- Navjivi Mahakalpa
The above mentioned great kalpas have been divided into kalpas and kalpas and shorter periods into yugas.
❇️ Nebula: -
Nebula or nebula refers to a rotating cloud of gas and dust and other substances .
️ Asteroids :-
There is a band of millions of small bodies between the outer planets and the terrestrial planets in the solar system, they are called asteroids.
According to scientists, how old is the earth?
4.6 billion years.
Big Bang Theory: -
The 'Big Bang Theory' is the universally accepted theory of the origin of the universe . According to the Big Bang theory, the expansion of the universe took place in the following states
According to the Big Bang theory, the three stages of the development of the universe :-
All the matter of which the universe is made today was situated in the form of a single atom whose volume was very small and the density was very high .
Due to the accumulation of excessive energy in the atom, it exploded and the universe expanded within a second of the explosion .
During the 3 million years before the Big Bang , the temperature dropped to 4500° Kelvin and atomic material was formed.
️ Formation of planets :-
Three stages of the formation of planets have been considered by scientists :-
The planets are formed from stars . The core was initially formed as a result of the force of gravity, around which a swirling saucer of gas and dust developed.
In the second stage, due to the condensation of the gaseous cloud, the matter around the core developed into small spherical bodies. Which were called planets.
Later , due to the increasing gravity, these planets got attached to each other and took the form of big bodies. This is considered to be the third and final stage of planet formation.
️ Difference between terrestrial planets and outer planets :-
The terrestrial planets were close to the parent star, so the gases could not condense there because of the high temperature, while the Jovian planets were far away, so the gases got condensed there.
The gas and dust particles of the terrestrial planets were blown away by the influence of the solar wind, but the solar wind could not remove the gases of the Jovian planets.
The terrestrial planets were small and had less gravitational force, so the gases did not stop on them due to the effect of solar winds. While the Jovian planets were heavy and being far away, they were protected from the effects of solar winds. So the gases stayed on them.
Origin of Moon :-
The origin of the Moon is the result of a major collision called ' The Big Splat '. This event happened about 4,44 billion years ago.
The Big Splat Theory related to the origin of the Moon :-
Under this theory, it is believed that shortly after the formation of the Earth, a body three times the size of Mars collided with the Earth . Due to this collision, a part of the Earth was broken and scattered in space . This substance started circling the earth in the form of moon. This event happened 4.44 billion years ago.
Contribution of differentiation process in the development of lithosphere :-
The process of separation of substances of lighter and heavier densities is called differentiation. During the formation of the Earth, due to the extreme heat, the substances of the Earth became liquid state, as a result of which a mixture of light and heavy density was prepared. Due to the difference in density, the heavy material moved to the center of the earth and the lighter matter came towards the surface or upper part of the earth. Over time, these substances cooled and developed into solid form in the form of crust.
The same side of the Moon is always visible when viewed from Earth. Why ?
When we see the moon from the earth, then only one part or one form is visible because the rotation period of the moon and the period of revolution are the same, so we are able to see only one side of the moon.
️ Lightyear :-
A light year is not a measure of time but a measure of distance . The speed of light is about 3 lakh kms. per second . The distance that light travels in a year will be one light year. It is 9.461 x 10 km. Is equal to . The average distance of the Earth and the Sun is 14 crore 95 lakh 98 thousand kilometers . In terms of light years, this distance is only 8.311 minutes .
Some important facts about the moon :-
- The diameter of the moon is 3475 km.
- The average distance of the Moon from Earth is -3,84,000 km.
- The surface temperature of the moon - 127 ° C during the day. and -163 ° C at night.
- The rotation and revolution period of the moon is -27¹/₂ days.
- The mass of the Moon is 1/81 of the mass of the Earth.
- The gravitational force of the Moon is 1/6th of the gravitational force of the Earth.
- It is believed that the Moon was formed from the same material that was scattered from the Pacific region as a result of the 'The Splat' event, which now sits in the form of the Pacific Ocean Trench.
