Emmanue Kant, the German Philosopher claimed that his Gaseous Hypothesis of the origin of the earth was based on the sound principles of Newton’s laws of gravitation and rotatory motion. In the beginning his hypothesis acclaimed world-wide appreciation, but, later on it was disproved as it was based on enormous concepts and wrong application on Newton’s law of gravitation. In-spite of severe criticism the hypothesis was considered a great step forward in the field of cosmogony.
The nebular Theory of Laplace
Marquis de Laplace propounded his well-known nebular hypothesis in 1796. In fact, it is a modified version of Kant's hypothesis. He rectified Kant's error by assuming that the primordial matter present in the space was already a hot and rotating gaseous nebula.
The Primordial matter existed in the form of a gaseous mass called ‘nebula’. This mass started cooling down and in the process lost some of its volume. Because of a reduced size, the rotational speed of the nebula increased. This had a cascading effect as the centrifugal force of its mass also increased. As a result, the mass of the nebula started concentrating along its equator. This mass was, on the other hand, being pulled inwards by a gravitational pull. But, as the centrifugal force increased further, some of the mass from the equator separated from the main nebula in the form of a ring which was also rotating. This ring, when cooled down and condensed, gave rise to planets and sub-planets, as it got broken into many smaller rings. The remaining mass became the sun.
Chamberlain-Moulton’s Planetesimal Hypothesis (1904)
According to this theory, the plantets were born out of two nebulae. The sun, with its very high temperatures projects hot material called the ‘prominences’, thousands of kilometers away from it. Another nebula, passing by the sun, attracted some of this projected material through its gravitational pull, which now started revolving around it instead of around the sun. The particles of this material got coalesced to form the planets. A lot of heat was generated in the process. Partly out of the gas particles attracted from the material floating around and partly acquired from the volcanic eruption, the atmosphere around the earth was formed.
The tidal Hypothesis of Jeans and Jeffreys
This hypothesis was put forward by a British scientist sir James jeans in 1919 and was later modified by another British scientist Harold jeffreys in 1929. Thus the credit for this hypothesis goes to both the scientists and it is popularly known as Tidal hypothesis of Jeans and Jeffreys.
A huge star came so close to sun that its gravitational pull created ‘tides’ on the surface of the sun and a part of the sun’s material got ejected. This material, so separated, began revolving around the sun and acquired an inflated, cigar shapes because of the bipolar force being exerted on it- from the sun and the star. This force was in the form of the gravitational pull. The gaseous material in the cigar-shaped mass-swollen in the middle and thinner towards the end- cooled down and got condensed into solid sphere which became the planets in our solar system, the large ones in the middle and the smaller ones towards the ends. A similar process involving the gravitational pull of the sun created sub-planets out of these planets. In this case too, the large sub-planets occupy the middle position.
Inter-Stellar Dust Hypothesis of Otto Schmidst
The Soviet scientist Otto Schmidt propounded an altogether new hypothesis in 1943 to explain the origin of the solar system which was based on the nebular hypothesis of Kant and Laplace.
According to this new hypothesis large quantities of gas and dust particles were found scattered in the universe which are known as gas and dust cloud. The sun was able to capture some gases and dust particles by the force of its gravitation. The cloud of gas and dust started revolving around the sun. They were revolving around the sun in an irregular way. At a later stage, the heavier particle of gas cloud and dust particles were combined and collected near the cloud heap and the cloud cover took the form of a vast flat saucer. This difference in the angular velocities of the sun and the planets is due to the difference in the angular velocities of gas and dust particles at the time of their condensation. Further, the inner planets of the solar system are composed of heavier elements such as, silicon, iron, aluminum etc., while the outer planets contain lighter elements, i.e. hydrogen, helium and methane etc.
Fasenkov’s Hypothesis 1951
According to Fasenkov. Originally there existed cloud of dust and gas which got consolidated into the sun, the planets and the sub-planets. This theory explains the different angular momentums of the sun and the planets , but fails to explain the varying composition of different planets – some with heavy elements and some with light ones.
Binary Star Hypothesis by Russel and Littleton
H.N. Russell, an American astronomer, propounded his Binary Star Hypothesis in the year 1937 to remove the shortcomings of tidal hypothesis of sir James Jeans. According to this theory, the sun existed in “binary companionship” with a “companion star”. A third star happened to pass by this binary arrangement. This star and the sun exerted a bipolar gravitational pull on the companion star. A tidal situation occurred and some material got separated from the companion star which began to revolve round the star. This revolving material gave rise to the planets.
Nova Hypothesis by Hoyle and Littleton
The Super-nova theory based on nuclear physics was put forward by F. Hoyle, the British astronomer, in 1946. He attempted to find a solution to certain unsolved problems in connection with the origin of the earth and the solar system. Certain stars in the universe increase their brightness several times suddenly. These stars are known as nova. A supernova contracts very rapidly; this increases its speed tremendously. Due to contraction, the temperature of the supernova increases to a very high level and in the presence of large amount of energy, the lighter elements change into higher ones. Because of its small size, rotational speed of the supernova increased and a centrifugal force came into play. The sun had such a supernova as its companion star and its attracted the material ejected from the supernova due to the centrifugal force. This material started revolving around the sun and got transformed into the planets on condensation.