Origin of the Earth
Origin of the Earth
There are dozens of theories about the origin of the Earth. In general, the theories of the origin of the Solar System or earth can be divided into two groups: (i) Evolutionary theories (ii) Catastrophic Theories.
Evolutionary Theories: The theories which suggest that planets are formed during the evolution of the sun, are called ”Evolutionary Theories“. The nebular Hypothesis is an example of these theories.
Catastrophic Theories: ”Catastrophic Theories” are those which imagine that planets are formed by some special accident or catastrophe, such as the close approach of two stars or by the collision of two stars. However, as the stars are so far apart in the galaxy, the possibility of such a catastrophe is extremely rare. examples of Catastrophic Theories are the planetesimal and gaseous tidal hypotheses.
The best-known hypothesis for the origin of the Earth and the other planets of the solar system are as follows:
The Nebular Hypothesis was put forward by Kant, the German philosopher in 1755 and Laplace, the French mathematician in 1796. This hypothesis suggests that the sun and planets including the Earth have formed from a disc-shaped rotating nebula. A vast cloud of hot gas is called ”Nebula”. The Nebular Hypothesis may be summarized as follows-.
- Originally there was a large, hot, gaseous nebula, which rotated along its axis.
- As the gas lost energy to radiation, it became cooler. As a result, the nebula contracted inward and its speed of rotation about its axis increased to conserve angular momentum. Due to this the centrifugal force in the equatorial zone also increased thereby causing the nebula to bulge out in the equatorial zone.
- The cooling and contraction of Nebula continued and ultimately a stage came when the centrifugal force became greater than the gravitational attraction acting inward. As a result, a gaseous ring was separated out.
- The above process was repeated and successive rings of gaseous material were thrown off from the central mass.
- In the final stages, the rings condensed into planets. Planetoids were formed when one such ring broke into many small fragments.
- The central mass of the Nebula continued to shrink and finally formed the sun.
Flaws in Nebular Hypothesis
The Nebular Hypothesis was not favoured because it had the following defects.
- This Hypothesis could not explain the energy distribution within the solar system. The Sun which possesses most of the mass (99.85%) of the solar system, should have gathered maximum angular momentum. However, 98% of the angular momentum is concentrated in the planets and the remaining 2% is present in the sun. In other words, the sun does not rotate fast enough. It should have a much higher speed of rotation.
- There was not enough mass in the rings to provide the gravitational attraction for condensation into individual planets.
- Some of the Stars orbit in the opposite direction their host star (sun) is rotating. If the entire solar system, Sun and planets, were created from the same spinning cloud, then there is no physical reason for why certain planets have orbits opposed to the Sun’s, such are Venus and Uranus. As well as planets observed in other solar systems.
The system TYC 8241 2652 had an alleged proto-planetary disk. This disk glowed brightly in the infrared when discovered in 1983, but as of 2 ½ years ago has stopped glowing in the infrared.
This system falsifies the idea that disks create Earth-sized objects because the proto-planetary disk model absolutely requires that the disk be present for millions of years, meaning that the duration of the infrared event was much shorter than expected.
This is because the infrared glowing is simply the result of a series of giant collision events that create trillions of tons of star shrapnel known as asteroids, meteorites, and small moon-like objects that are
Therefore TYC 8241 2652 is not evidence of star/planet formation but star/planet destruction caused by objects clearing their path for more stable orbits.
Mainstream has this process backward and is exceedingly clueless because their definitions are
unnecessarily complex and arbitrary.
The collision events recorded as infrared light is NOT a proto-planetary disc, as was once suggested since such a disc would have existed for millions of years in order to create planets.
What the Scientists actually observed was the initial destructive push of solar wind, clearing the heliosphere after the birth of star TYC 8241 2652, not collisions between proto-planets.
Planetesimal Hypothesis about the origin of the earth
The planetesimal hypothesis was proposed by Chamberlin and Moulton in 1904. The main points of the hypothesis are as follow:
- The sun existed before the formation of the planets. A large passing star approached very close to the sun.
- Due to the disruptive forces of the sun and the strong gravitational pull of the passing star, giant masses of gas were torn from the surface of the pre-existing sun.
- The giant mass of the gas broke into a large number of small chunks which on cooling gave rise to solid particles, called ”Planetesimals”.
- The planetesimal started flying as cold bodies into orbits around the sun in the plane of the passing star. By collision and gravitational attraction, the large planetesimal swept up the smaller pieces and thus planets were formed.
Flaws in Planetesimal Hypothesis
The main flaws in the planetesimal hypothesis are as follow:
- Most of the material which was ejected by the explosive action of the sun would come from the interior. t would be so hot that the gasses would disperse in space rather than condense into planets.
- Although the angular momentum imparted to the planets by a passing star would be greater than that produced the rotation of a nebula, the amount is still less than that.
- The space is vast and therefore the probability of a close approach of two stars is extremely unlikely.
Gaseous tidal hypothesis
This hypothesis was proposed by Jeans and Jeffreys in 1925. The gaseous tidal hypothesis may be summarized as follows.
- A very huge star progressively approached the sun. Due to the gravitational pull of the star, a gaseous tide was raised on the surface of the sun. As the star came nearer, the tide increased in size.
- when the star began to move away, the gaseous tide was detached from the sun. Its shape was like a spindle being the thickest in the middle.
- The spindle-shaped gaseous mass soon broke into ten pieces, nine of which condensed into planets, and the remaining one which further broke into small pieces formed the group of planetoids.
Flaws in the gaseous tidal hypothesis:
- the passing star is unable to impart proper angular momentum to the detached gaseous masses.
- the hot gaseous mass pulled away from the sun would not form solid planets but would dissipate into space.
Rotational and Tidal Theory
A scientist named Rossguna put forward this theory which is termed as Rotational and Tidal Theory. Actually, this theory is a combination of the basic principles contained in the theories of James Jeans and Laplace. According to Rossguna, a large star approached a fast rotating star. As a result, tidal action deshaped both the stars which separated later on leaving behind a mass of tidal protuberance. Planets were formed from this mass. Professor A.C, Bannerjee has disagreed with Rossguna’s Theory that a star can approach a fast-moving original star (Sun).
Binary Star Hypothesis
This hypothesis was proposed by Lyttleton in 1938. Before the formation of planets, the sun had a companion star. Another star approached close to these double stars and dragged the companion star away. A gaseous filament was torn from the companion star and it remained close to the sun. The planet was originated from this gaseous filament in the same way as described in the gaseous tidal hypothesis.
Recent Theories about the origin of Earth
Since 1943 there has been a tendency to swing back in theories of the Laplacian type. These theories seem to explain well the observed variations in the chemical compositions and densities of the planets. The objection to Laplacian theory, that the Sun’s angular momentum is too small, has been removed. The main points of recent theories are:
- There was a disc-shaped cloud of gas and dust around the sun.
- The planets were formed by the gradual aggregation of the dispersed matter in the cloud.
- Close to the sun where temperatures were highest, only those materials condensed which had high melting points such as metals and rock-forming compounds. Hence the denser planets grew in the hot region lying closer to the sun.
- Volatile materials such as water, methane, and ammonia were blown away. They condensed in the cold outer zone of the solar system thereby forming low-density planets.
3. The primitive sun had a considerable magnetic field. It acted as a rotating magnet and accelerated the hydrogen ions present in the dust cloud. Due to this acceleration, the gases moved outwards away from the sun carrying the fine dust with them and leaving only larger solid masses in the region of the inner planets. Thus there was the transfer of momentum from the sun to the gas ions which slowed down the sun’s rotation. This process also explains how the dust cloud was divided into two regions, an inner gas-free region of solid particles and an outer region rich in gases.