Question

What are the three theories on how Earth was formed?

Answer 1

Hint: This question is still there in the minds of the scientists that how Earth was formed. Although there are three major theories that explain how the formation of Earth happened: “The core accretion theory”, “The disk instability theory” and “The pebble accretion theory”.

Complete step by step answer:
The core accretion theory:
According to this theory our solar system was a giant cloud of dust and gas which was termed as solar nebula. As this giant cloud started rotating about its axis, due to the force of gravity it broke up into parts. The sun became the center of the nebula and the planets formed from its fragments which were bound together by gravitational forces. The other elements of the solar system such as the asteroids, comets, the planets that are farther away from the sun, comets, etc. were formed from just clouds of gas because the solar winds could not take away the lighter elements from them. On the other hand, our planet Earth was affected by the solar wind due to which its lighter elements were taken away and only heavy elements like rocks were left which came up together due to gravitational force from the Earth.

The disk instability theory:
This theory tells that the protoplanetary disc which is a rotating disk made up of dust and gas, broke up into small fragments due to its gravitational instability due to their massive structure. These fragments were just clouds of gas which finally evolved into planets.

Pebble accretion theory:
This theory states that the planets were made from small pebble-like particles which came together to form bigger units. This theory explains the formation of the four planets: Mercury, Venus, Earth and Mars.

Note: The solar system is considered to form 4.54 billion years ago. There are many theories that explain the formation of Earth and other planets. Some even say that all the planets are a part of the sun and are formed when some fragments of the sun fall off from it.