A Review Work on Origin and Evolution of the Universe through the Big Bang Theory and Inflation Theory
The universe began as an infinitely dense cosmic singularity which began its expansion in the event called the Big Bang, which can be described as the beginning of time. The history of the universe can be divided into many eras- today the matter density of the universe dominates its gravity completely, we live in the matter era. Density also changes with time, becoming ever higher as we look toward earlier times; but the variation with scale factor is different for matter density and for radiation energy density. Hence there was a time in the past when radiation was more important than ordinary matter in determining the evolution of the universe. This high-temperature epoch defines the early universe. The Cosmological Principle states that the Universe appears the same in every direction from every point in space. Recent observations made by the COBE and WMAP satellites observing this background radiation have effectively, in many scientists' eyes, transformed cosmology from a highly speculative science into a predictive science, as these observations matched predictions made by a theory called Cosmic Inflation, which is a modification of the standard Big Bang Model. This has led many to refer to modern times as the "Golden age of Cosmology". The Steady-state theory explained microwave background radiation as the result of light from ancient stars that has been scattered by galactic dust. Cosmic Inflation is the idea that the very early universe went through a period of accelerated, exponential expansion during the first 10-35 of a second before settling down to the more sedate rate of expansion we are still experiencing, so that all of the observable universe originated in a small causally-connected region. Inflation also solves the flatness problem because of the exponential growth. The Cosmological Principle also says that the cosmological theories are based on the idea on the large scales of the universe look like. This paper explains that an origin and evolution of a universe through the Big Bang theory and Inflation theory.
Keywords - Cosmic Singularity, Big Bang, Cosmological Principle, Cosmic Inflation