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