Big bang theory

The Big bang is one of the theories developed to explain the origin of universe. According to it the universe starts from a big hot ball which is million million times hotter than the sun. The particles are in the state of plasma where there are no atoms. The burst of this hot ball lead to the formation of universe. But this does not explain all the phenomena in the universe it's just a good attempt to explain the formation of universe. No one knows what is before the Big bang as all the law of physics General Law of relativity itself fails in the singularity of the Big Bang (Its theory of relativity which predicted the Big Bang)