B.1. Early Theories

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B.1. Early Theories-

Nebular Hypothesis	By German philosopher Immanuel Kant. Mathematician Laplace revised it in 1796. The hypothesis considered that the planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating. Later in 1900, Chamberlain and Moulton considered that a wandering star approached the sun. As the passing star moved away, the material separated from the solar surface continued to revolve around the sun and it slowly condensed into planets.
Binary Theories	The arguments considered of a companion to the sun to have been coexisting.
Revised Nebular Hypothesis	By Otto Schmidt in Russia and Carl Weizascar in Germany 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
The Moon	Only natural satellite of the earth.
Early Theory	In 1838, Sir George Darwin suggested that initially, the earth and the moon formed a single rapidly rotating body. The whole mass became a dumb-bell-shaped body and eventually it broke. It was also suggested that the material forming the moon was separated from what we have at present the depression occupied by the Pacific Ocean
Giant Impact’ “The Big Splat Theory-	A body of the size of one to three times that of mars collided into the earth sometime shortly after the earth was formed. It blasted a large part of the earth into space. This portion of blasted material then continued to orbit the earth and eventually formed into the present moon about 4.44 billion years ago.
Origin Of Life	The last phase in the evolution of the earth Modern scientists refer to the origin of life as a kind of chemical reaction, which first generated complex organic molecules and assembled them. This assemblage was such that they could duplicate themselves converting inanimate matter into living substance. The record of life that existed on this planet in different periods is found in rocks in the form of fossils. The microscopic structures closely related to the present form of blue algae have been found in geological formations much older than some 3,000 million years. It can be assumed that life began to evolve sometime 3,800 million years ago