Question:What is The Big Bang Theory?
The Big Bang Theory is the most widely accepted model of the evolution of the Universe that currently exists.
The Big Bang Theory does not explain the origin of the Universe itself, just how the Universe has changed over time.
Georges Lemaître, a Catholic priest, first proposed what would become the Big Bang Theory in what he called his article, "Hypothesis of the Primeval Atom".
In 1931, Lemaître suggested that the evident expansion of the universe, if projected back in time, meant that the further in the past the smaller the universe was, until at some finite time in the past all the mass of the Universe was concentrated into a single point, a "primeval atom" where and when the fabric of time and space came into existence.