Origin of the Earth

Origin of the earth is directly related to the origin of the solar system, as the earth is one of the members of the solar system. Many hypotheses have been proposed to explain the formation of the solar system. All these theories can be grouped into the following two general classes.

1. Formation of the solar system quickly and violently: Old planetesimal hypotheses, Nebular hypotheses, new planetesimal hypotheses and tidal hypotheses are some examples of it.
2. Formation of the solar system slowly and moderately: A dust cloud aggregation hypothesis is an example of it.

Some hypotheses about the origin of the earth

Old planetesimal hypothesis:

This hypothesis state that very large amount of matter was thrown out of the sun due to the collision of the sun and another star. Those hot matters cooled and the other planets along with the earth were formed and the remaining mass was the sun.

Nebular hypothesis:

According to Nebular hypothesis, the sun and the planets were formed from a large whirling cloud of hot gases and dust. As the surface of the cloud cooled by the radiation, a ring of the matter was formed at the equatorial region of it. The ring was escaped out from the surface of the main mass and the first planet was formed. The process was repeated again and again till the entire solar system was formed and the remaining mass became the sun.

New planetesimal hypothesis:

This hypothesis is slightly different from the old planetesimal hypotheses suggested by Buffon. According to this hypothesis, the two stars did not collide but came very close to one another, and due to the gravity of the star, great bulges rose by the sun and the materials remained as large spiral arms and when they cooled, they broke away from the sun and the broken materials combined together to produce the planets and the remaining gaseous matter became the sun.

Tidal hypothesis:

According to this hypothesis, a passing star had exerted a tidal pull on the sun but the effect was to cause a long filament of gases to be drawn from the sun. The outer part of the filament escaped into space, the inner part came back into the sun and the middle part formed a series of round structures of different sizes, which were the planets.

Dust cloud hypothesis:

This hypothesis proposed that the sun and the planets were formed from a large cloud of gases and dust. The light of the star pushed the atoms of the gases and dust to form huge particles which were attracted to each other by the pull of gravity. A huge ball of materials formed the sun and the part of the cloud of dust and gases stayed around the sun and slowly rotated. The huge whirlpools originated in this rotating clouds formed planets. In this way, the earth was originated in its cold stage.

Reason behind evolution of living beings on earth

Evolution of earth started before 4.5 billion years ago. When the evolution of earth started there was no suitable atmosphere for living beings. Various changes on the earth have made the atmosphere of the earth suitable for the evolution of living beings. Some reason behind evolution of living beings on earth are:

1. Availability of necessary substances for living beings like, air, water etc.
2. Availability of abundant water.
3. Favourable temperature for living beings.