ORIGIN OF EARTH

The earth was probably originated 4600 million years ago. The earth is approximately one third of the age of universe.The sun and its planets were formed together from a spherical cloud of gases and dust particles by the process of condensation. As a cloud began to accelerate its rotation, gravity and inertia flattened into a photo planetary disk oriented perpendicularly to its axis of rotation. most of the mass began to concentrate on middle and began to heat up but small perturbations due to collisions. The angular momentum of other large debris created. Than the nuclear fusion of hydrogen and helium began, after the contraction large star i.e sun was formed. Rest of the larger fragments collides with each other to form larger planets including earth.

The earth was very hot that everything in at probably existed in gaseous state. The temperature of the earth was 5000-6000 degree centigrades for many years. Gradually, the earth began to cool down which took millions of years. The gases was condensed into a molten core and different elements got stratified according to their denisity. The oldest rock was found before 4 billions years ago i.e Galium (Ga). Heavy metals like Nickel, Iron formed solid core of earth and lighter metals come towards the surface of earth. Lighter elements such as Hydrogen, Helium, carbon, oxygen and nitrogen constituted into the early atmosphere. The earth had a reducing atmosphere i.e the free oxygen was not found in volcanic gases because the reduced substances immediately combined with oxygen to form oxides due to lack of free oxygen in the atmosphere and absence of ozone layer. The large amount of water on earth can never be formed by volcano alone. It was assumed the water formed from comets that contained ice, however most of the water on earth was probably derived from photo planets i.e comparable with today small icy moon of the outer planets. As the earth cooled rain was formed which gave rise to oceans. The new atmosphere probably contained ammonia, water vapour, carbon dioxide, nitrogen and small amount of other gases. due to which lif became possible on earth.