What is the Big Bang?

       The Big Bang is the dominant theory of the origin of the universe. General relativity resulted in an expanding universe. Although Einstein called it the biggest blunder of his life. There was already evidence of an expanding universe. How do we know that we still aren't wrong? We also discovered that "Nebula's" were actually galaxies in their own right. 

        In 1927 the Roman Catholic priest and physicist Georges Lemaitre found that there was a correlation between the distance of the galaxies and the amount of red-shift in that galaxy's light. A philosophical side-note states that the universe has always existed, and the big bang theory was seen as "too religious" by people. George Gamow used CMB radiation and later on Robert Wilson noticed it and won the Nobel Peace Prize for the discovery. 

        The inflation theory also ties in with this. Inflation theory brings together ideas from quantum physics and particle physics. The problem with this is that once it started, it would never stop. Again, no real clear certainty is stated about this theory either.