The Earth is a member planet of the Universe which consists of numerous stellar systems. The Earth is a member of the Solar System.
The age of the Earth is about ten thousand million years or ten billion years. Before this huge age, gaseous matter filled the universe. In this gaseous state of matter, a disturbance occurred and as a result condensation was started. As a result of condensation the latent heat was released and it increased the temperature from 500 degrees to 5000 degrees.
Numerous theories have been advanced with regard to the composition, rotation, and condensation of the spiral nebulae. Although some believed that the nebulae were composed of solid meteorites but this is no longer subscribed and all the authorities agree on one point that the spiral nebulae were a gaseous mass.
Age of the Earth
Modern scientific methods have been employed only during the last 200 years. Scientists think that the age of the Earth may range between two to five billion years.
This theory is devised by German philosopher Immanuel Kant. Later, Mathematician Laplace revised it in 1796. According to this hypothesis, the planets were moulded out of a cloud of material associated with a young sun, which was slowly rotating.
This point of view considered a companion to the sun to have coexisted.
Revised Nebular Hypothesis
Revised Nebular Hypothesis was given by Otto Schmidt in Russia and Carl Weizascar in Germany. They regarded that the sun was encircled by solar nebula comprising of mostly hydrogen and helium along with what may be called dust. The friction and collision of particles led to the creation of a disk-shaped cloud and the planets were formed through the process of accretion.
Big Bang Theory
It is also known as the expanding universe hypothesis. In the beginning, all matter establishing the universe existed in one place in the form of a tiny ball with an unimaginably small volume, infinite temperature, and infinite density. It is now commonly acknowledged that the event of the big bang took place 13.7 billion years before the present. At the Big Bang. the so-called tiny ball blasted violently and steered to a huge expansion. The expansion continues even to the present day.
Formation of Planets
The following are considered to be the stages in the development of planets:
- The stars are contained lumps of gas within a nebula.
- The gravitational force within the lumps leads to the creation of a core to the gas cloud and a huge rotating disc of gas and dust develops around the gas core.
- In the subsequent stage, the gas cloud began getting condensed and the matter around the core changes into small rounded objects.
- These small-rounded substances by the process of cohesion progress into what is called planetesimals.
- Larger bodies start forming by collision, and gravitational attraction causes the material to stick together.
- In the final stage, these large number of small planetesimals accumulate to form fewer large bodies in the form of planets.