A large number of hypotheses were put forth by different philosophers and scientists regarding the origin of the earth. One of the earlier and popular arguments was by German philosopher Immanuel Kant. Mathematician Laplace revised it in 1796. It is known as Nebular Hypothesis. According to this theory there was a hot and rotating gas cloud called Nebula in the space. From Nebula there was a gradual loss of heat due to its rotation which resulted in cooling of its outer surface. This gradual cooling caused contraction in size of Nebula, but its speed increased due to angular momentum. The outer layer was separated from the remaining part of Nebula. The centre of Nebula became ‘Sun’ and the planets were formed of the smaller units. The lighter material gases and the heavier dust particle gave the fact of inner and outer planets. In 1950, Otto Schmidt in Russia and Carl Weizasear in Germany somewhat revised the ‘nebular hypothesis’, though differing in details. They considered that the sun was surrounded by solar nebula containing mostly the hydrogen and helium along with what may be termed as dust. The friction and collision of particles led to formation of a disk-shaped cloud and the planets were formed through the process of accretion.