Author Topic: Origin of Earth - Theories and Hypothesis  (Read 6485 times)

engineer

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Origin of Earth - Theories and Hypothesis
« on: February 11, 2010, 10:28:34 AM »
There are various scientific theories of origin and evolution of the earth

1.Nebular Hypothesis
2.Planetesimal Hypothesis
3.Gaseous Tidal Hypothesis
4.Binary Star Hypothesis
5.Gas Dust Cloud Hypothesis
 

Nabular Hypothesis
1.German philosopher, Kant and French mathematician, Laplace
2.Earth, planets and sun originated from Nebula.
3.Nebula was large cloud of gas and dust. It rotates slowly.
4.Gradually it cooled and contracted and its speed increased.
5.A gaseous ring was separated from nebula
6.Later the ring cooled and took form of a planet
7.On repetition of the process all other planets came into being
8.The central region, nebula became sun.
Objections:
■Sun should have the greatest angular momentum because of its mass and situated in the center, however, it has only two percent of momentum of the solar system
■How the hot gaseous material condensed in to rings
 

Planetesimal Hypothesis
1.Chamberlin and Moulton proposed the theory in 1904
2.The sun existed before the formation of planets
3.A star came close to the sun.
4.Because of the gravitation pull of the star, small gaseous bodies were separated from the sun
5.These bodies on cooing became small planet's
6.During rotation the small planets collided and form planets
Objections:
■The angular momentum could not be produced by the passing star.
■The theory failed to explain how the planetesimals had become one planet
 

Gaseous Tidal Theory
1.Jeans and Jeffrey proposed the theory in 1925
2.Large star came near the sun. Due to gravitational pull a gaseous tide was raised on the surface of the sun.
3.As the star came nearer, the tide increased in size.
4.Gaseous tide detached when star move away.
5.The shape of the tide was like spindle.
6.It broke into pieces-forming nine planets of the solar system

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Origin of Earth - Theories and Hypothesis
« on: February 11, 2010, 10:28:34 AM »

anthonygree

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Re: Origin of Earth - Theories and Hypothesis
« Reply #1 on: July 02, 2010, 02:27:09 PM »
The age of the Earth was once, and still is, a matter great debate. In 1650 Archbishop Ussher used the Bible to calculate that the Earth was created in 4004BC. Later on in the mid-nineteenth century Charles Darwin believed that the Earth must be extremely old because he recognised that natural selection and evolution required vast amounts of time.
 
THE EARLY ATMOSPHERE
The present composition of the atmosphere is:    21%    OXYGEN
   78%    NITROGEN
   0.04%    CARBON DIOXIDE
   ~0.9%    ARGON

The atmosphere wasn't like this when the Earth was created over 4 billion years ago.