The origin of the Solar System

The origin of the Solar system is an important issue.

Without proper imagination regarding this issue,

internal structures and processes of the Earth can not

be easily inferred.  Within ancient ages, ideas on the

origin of the Earth and Solar System were only based

on religious beliefs.  For example, in ancient Greece,

Homer assumed that the Earth was similar to a disc

surrounded by ocean, and Greece had been the center of

this complex.  Meanwhile, this disc was on various

columns located on the God of seas’ shoulders.

Oriental people specially the followers of Brahma

religion assumed that the mentioned columns were on

the back of four huge elephants.

Different theories about the origin of the Earth are

divided into two main groups as follows; 1.

Spontaneous or binary theories and 2. Evolutionary or

individual theories.

 

1.Spontaneous theories: In accordance with this group

of theories, the Earth and other planets were produced

by mutual effect of the Sun and a heavenly body.

Therefore, they are called binary theories.  Here they

are mentioned briefly from historical point of view. 

 

1.1 Buffon theory: In 1745, Buffon who was a French

scientist presented his theory regarding formation of

the Earth and other planets.  He said that they might

be produced by pieces from the Sun collided with a

comet.  According to the knowledge that we have about

the comets this theory is cancelled.  At that time,

church convicted Buffon regarding the Bible legend

denial on creation issue.  Hence, Buffon had to put

aside his ideas.

 

1.2 Chamberlin-Moulton theory: These two American

scientists presented their theory between 1901 to

1905.  Based on this theory, by passing a star near

the Sun, an outward tail from the Sun tends toward

this star by gravitational force.  Its high

temperature caused various explosions under pressure,

and heavier parts of these pieces separated and

produced primary nucleus of planets. 

 

1.3 Jeffrey-Janis theory: This theory presented within

1918 and 1919.  In accordance with this theory, the

Sun had bigger volume when planets were formed.

Passing a star from close parts of the Sun separated a

thin and long piece of it.  As this massive piece was

unstable, it divided into pieces.  When these parts

moved near the Sun, some parts of planet separated

from them and produced satellites.

 

1.4 Russell theory: Russell is an American astronomer.

 In 1935, he said that the Sun could be binary star

and second star was smaller than the Sun.  The small

star and main star collided with each other and

planets of solar system were produced.

 

2. Evolutionary theories: these theories believe in

gradual formation of planets as follows (older

theories come first);

 

2.1 Kant theory: This theory presented in 1755.  Today

Sun was at the center of a complex made of gas, dust

and fine solid particles called “Nebula”.

Nebula rotated around the Sun by gravitational force.

After cooling process of early conglomerate, different

centers appeared.  Around each of these centers, some

parts of main nebula rotated.  Then, planets and their

satellites appeared.

 

2.2  Laplace theory: In 1796, P.S.M. Laplace published

a book under the name of “Explanation of the

World System” (Exposition du systeme du monde;

in French) and preseneted theories regarding the

origin of planets. 

In accordance with this theory, planets were formed

from a dilute material surrounding the protosun.  The

dimensions of this complex are bigger than the present

solar system.  The mentioned dilute material was cool

and condensed.  Its rotation speed was increased by

condensation speed and after a while affected outer

parts of the conglomerate by centrifugal force.  This

force gradually became more than the Sun’s

gravitational force.  Then some belts similar to the

Saturn’s belt appeared.  Next, splits occurred

in these belts and gradually planets produced. 

 

2.3  Ligonde theory: Within late 19th century,

Ligonde expressed the “meteorite

hypothesis” on solar system.  He believed that

the condensation of materials was the result of two

factors; 1. Non-elastic collision of particles and 2.

Viscosity among particles.  As a result of these two

forces, materials were condensed in a rotating disc

producing planets later on. 

 

2.4  Kuiper theory:  Within 1949, G.P.Kuiper commenced

his research on the solar system’s origin.  He

believed that the planets were not the result of a

permanent growth of smaller particles.  In fact, they

were formed as bigger planets than their current

conditions, at first.  Then, they lost some energy and

converted into the current conditions of planets.

Kuiper believed that the primary big mass was the

result of turbulent conditions in the primary cloudy

material.  This material and the Sun were formed,

simultaneously.  The Sun was the product of primary

cloudy material producing protoplanets later.  Kuiper

believed that the protoplanets were formed when the

Sun was not shining and radiating.

 

2.5 Yuri theory: In 1951, Yuri, the American

scientist, expressed his theory, which was slightly

different from others.  It was based on astronomical

data.  He believed that the Earth is the result of

accumulation and condensation of solid particles.  The

surface of these particles producing the Earth and

planets were warm from early stages of formation.

 

2.6 Alfven theory: Alfven, the Swedish physicist,

expressed his theory between 1942 and 1954.  He

believed that the Sun located in a hot and ionized

mass and had a powerful magnetic field surrounded by

available gases having electrical conductivity

characteristic.  Alfven described that four gaseous

masses were formed as follows;

1.Helium mass, 2.Hydrogen mass, 3. Carbon mass and

4.Iron-silicon mass.  In each of these masses,

impurities from other masses were available.  Planets

were formed by these four masses, later. 

 

2.7 Hoyle theory: In 1955, Hoyle, the British

scientist, presented this theory.   He believed that

the formation of planets was dependent to the

Sun’s formation.  In fact, they were all formed

by a gaseous cloud bearing a rotating strong magnetic

field.  This cloud was condensed and formed by

gravitational force available among its particles.

When its rotation speed increases, it gradually

changed into a flat ellipse.  It indicated by

calculations when equatorial diameter of mass reaches

the current location of Mercury’s orbit, the

central part of mass contracted, and finally the Sun

was formed.       

In accordance with this theory, the composition of

gaseous disc was slightly different from current

composition of the Sun and interstellar materials.

Basically, it includes hydrogen, helium and slight

amount of heavy minerals.  At first, only heavy

elements located in the back part of the disc, then

they continued to develop and accumulate.  Terrestrial

planets are mainly from iron, silicon and magnesium.

  

2.8 Schmidt theory: This theory was first presented by

Schmidt in 1943.  After his death, in 1956, it

presented by his colleagues with slight changes.

According to Schmidt theory, the level that planets

located today was the equator of the protosun.  The

planets-forming materials rotated around the Sun.

They scattered in form of cloud-like material at the

mentioned level. 

Planets’ formation is divided into two stages;

1.Formation of medium size bodies from primary

cloud-like material bearing dimensions of about

asteroids.

2.Formation of planets from emerging the first stage

celestial bodies.

If it is assumed that the primary conglomerate of

solid particles and gas in form of a cloud bearing

disc shape located in the equatorial section of the

Sun, then, solid particles accumulate at the middle

part of the disc.  These materials were condensed by

gravitational force.  After a while, solid bodies were

formed in different parts of the disc by accumulation

of solid particles.

By particles’collision to each other and their

crushing, a lot of bodies were produced.  Then, second

stage of planets’ formation from asteroids

commenced.  Certain planet-like celestial bodies

bearing bigger mass and less crushing traces were the

“embryo” of today planets.