Most of you one time or the other must have wondered about the birth of the universe- how the world that we live in was created? What was the starting point? Birth of the universe? Birth of life? Well, the Big Bang Theory is the leading explanation about how the universe began. The Theory explains how the universe expanded from an initial state of extremely high density and high temperature by offering a detailed explanation of observed phenomena, radiation, an abundance of light elements, and large-scale structures.
The Big Bang Theory states that the universe began to cool down sufficiently in order to allow the formation of particles that would later become atoms after its initial phase of expansion. Primordial elements – Hydrogen, Helium, and Lithium – condensed through gravity that formed early stars and galaxies. In simpler terms, it can be stated that the universe inflated into the cosmic system 13.8 billion years ago to form the galaxy and the solar system as we know it.
The current version of Big Bang Theory-- the one used most by modern cosmologists-- is called the Lambda-CDM model. It postulates that our universe began at a specific instant, expanded to be flat (i.e., has zero curvature) and is made up of 5% baryons (i.e., the matter that makes up everything we see-- galaxies, stars, planets, people), 27% cold dark matter (hence the “CDM” of the theory’s name) and 68% dark energy.
It adds to a concept of Big Crunch, at some point of time, the universe would reach a maximum size and then begin to collapse. It would become denser and hotter again, ending with a state similar to that in which it started — a Big Crunch, the death of the universe.
While the majority of the astronomical community accepts the theory, there are some theorists, who have alternative explanations besides the Big Bang-- such as eternal inflation or an oscillating universe.
The Big Bang was not the event that caused our universe. Rather, it was the event that gave birth to the universe. While we can understand how the universe we see came to be, it’s possible that the Big Bang was not the first inflationary period the universe experienced. Some scientists believe we live in a cosmos that goes through regular cycles of inflation and deflation, and that we just happen to be living in one of these phases.
