Origin of the earth(Solar System) The Nebular Hypothesis assumed that during past there existed a large, hot, gaseous nebula rotating in space. Gradual cooling led to contraction and increase in speed of revolution about its axis. Therefore it bulge out due to greater and progressively increasing centrifugal force prevailing in that region and ultimately a gaseous ring separated out of globe and continue to revolve round the nebula and similarly ten rings were formed out of which give rise to planet and other were broken into smaller fragments. The hypothesis was rejected as it failed to satisfy the angular momentum conversation. If this hypotheses is assumed to be correct then Sun might have given rise other planets as being part of nebula due to it’s high speed. The next theory of recognisable importance Chamber and Moulton who were of the opinion that the planets were formed as a result of mutual interaction between the Sun and the another star of suitable size. This theory was named Planetesimal Hypothesis. The theory states due to approach of larger star, tidal distortion were raised upon the surface of the Sun and these in conjunction with the eruptive force prevalent in the Sun knows as Solar Prominences. Many gaseous bolts were shot in the space due to distortion. The planets which have their orbit intersection must collide and coalescence to give rise to other planets.
However the theory got rejected as their were authors suggesting that collision could have let to the melting of planets.
Jeans and Jeffreys theory knows as the Gaseous Tidal hypothesis. This theory accepts the fact of biparental origin of Solar system however disruptive forces theory was totally rejected. It was supposed there must be a larger star moving in space due its nearer approach tidal pull was raised on the surface of the Sun . At a stage when the star began to recede the tidal pull was detached from the body of the Sun in the shape of spindle bulging near center and tapering at the both ends. Thus ejected in space was naturally extremely unstable and immediately broken into down into smaller fragments leading to evolution of ten planets and one which broke down giving rise to planetoids. This hypothesis was widely accepted owing to it’s simplicity and capable of explaining the placements of planets and features relating to the distribution of mass and density in them .
Later the Gaseous tidal hypothesis was rejected astronomers like Otto Schmidt and c von Weitzsacker considered the planets have been formed from matter diffused in space . according to theory that sun was surrounded by revolving disc shaped cloud made up of gas dust and planets were formed.