The Big Bang Theory is one of the most important theories in astronomy. The basics of the theory are fairly simple. All of the current and past matter in the universe became into existence at the same time. At a point in time, about 13.7 billion years ago, everything was compacted into a very small ball with infinite density, and intense heat, called singularity. Suddenly, that singularity began to expand and the universe came into being. It is still expanding today.